JP7748735B2 - Fluid density fluid displacement for storing or generating electricity - Google Patents

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Application No. 17/214,100, filed March 26, 2021, which is a continuation-in-part of U.S. Application No. 16/932,429, filed July 17, 2021. This application also claims priority to U.S. Application No. 63/117,355, filed November 23, 2020, U.S. Application No. 63/132,778, filed December 31, 2020, and U.S. Application No. 63/139,157, filed January 19, 2021. All of the foregoing applications are incorporated by reference herein in their entirety.

Solar, wind, and other intermittent energy sources account for an increasingly large proportion of global power generation capacity. Due to the intermittency of solar and wind energy, power grids and other infrastructure that may be quickly dominated by high proportions of wind and solar power generation will require storage to match power supply with power demand. The required storage capacity will generally increase with the increasing penetration of intermittent renewable energy sources, particularly solar- or wind-dominated power grids and power grids with limited geographic distribution. The required duration of storage capacity also generally increases with the increasing penetration of intermittent renewable energy. For example, power grids with a large proportion of solar-generated power may have insufficient power generation at night, and therefore may require storage with a duration of 10 to 16 hours to support nighttime grid power needs. In the United States, 80% solar and wind energy penetration may be achievable with a duration of 12 hours of storage. In particular, 100% solar and wind energy penetration is only feasible with storage durations of at least three weeks due to wind and/or solar events tending to occur at less than expected rates at least once a year and/or due to seasonal variations in solar and/or wind energy. Prior art energy storage technologies are too expensive and/or geographically limited to meet the large number of terawatt-hours of long-duration storage required for high penetration rates of solar and wind power worldwide.

Energy storage technologies are compared with respect to various factors. Levelized cost, i.e., levelized cost of electricity (LCOE) or levelized cost of storage (LCOS), is generally considered the primary or most important factor. Energy storage customers, such as project developers, electric utilities, and other customers, typically employ levelized cost as their primary metric for comparing energy storage technologies, where the lower the levelized cost, the more economically desirable the energy storage technology is relative to other options. A levelized cost calculation may include values including, but not limited to, one or more or combinations of the following variables: capital cost, or cost of capital, or discount rate, or capacity utilization rate, or round-trip energy efficiency, or cost of land, or power capacity degradation rate, or energy storage capacity degradation rate, or balance of plant, or land use, or geographic limitations, or end-of-life cost, or cost per MW of power capacity, or cost per MWh of storage capacity. Prior art energy storage technologies generally have high levelized costs due to shortcomings of one or more of the aforementioned variables or a combination of these variables. For example, lithium-ion batteries have high capital costs, significant power capacity degradation, significant energy capacity degradation, land use requirements, and high end-of-life costs. For example, compressed air energy storage has low round-trip energy efficiency and geographic limitations. For example, pumped hydro storage has high land use requirements and geographic limitations. For example, hydrogen energy storage has low round-trip energy efficiency, a high cost per MW of power capacity, and a high power capacity degradation rate.

Other factors may include, but are not limited to, one or more or a combination of the following: environmental impact of manufacturing, environmental impact of land use, material constraints, end of life disposal, recyclability, labor use, local labor values, local economic impact, and required maintenance.
For example, lithium-ion batteries have the following drawbacks related to the factors mentioned above:
o Adverse environmental impacts of manufacturing, including manufacturing of material inputs o Material constraints of lithium, cobalt, nickel, and graphite o Short life and end-of-life disposal challenges.
○ Lithium-ion batteries are not currently recyclable. ○ Local labor value is generally minimal, particularly for high-cost material inputs, including lithium, nickel, and cobalt. ○ Unethical labor practices and downstream environmental impacts, particularly in the mining and refining of required metals and materials, including cobalt and graphite. ○ Local job creation and associated economic impact is minimal, as the majority of costs and labor occur at large-scale manufacturing and mining operations that are generally located far from the renewable energy or energy storage project site.
○ Maintenance needs are high due to the need for thermal regulation, balance of plant, and expansion. Expansion is the installation of additional new lithium-ion batteries to compensate for the loss of energy storage and/or power capacity that naturally occurs in lithium-ion battery energy storage facilities over time. At large lithium-ion battery energy storage sites, significant "expansion" typically occurs at least once every five years.

For example, conventional pumped storage hydropower generation has the following drawbacks related to the factors mentioned above:
● Large-scale land use and significant geographical constraints ● Significant environmental damage and permanent environmental alteration ● Earthquake and landslide risks, including the risk of significant economic and/or human disaster in the event of a significant earthquake or landslide, or both.

Another challenge in the renewable energy industry is the availability of land for the development of renewable energy and/or energy storage projects. In many cases, local, regional, national, and international stakeholders strongly oppose the development of undeveloped or "untouched" land, including the development of renewable energy sources such as wind and solar. Stakeholders often oppose such development due to environmental, visual, or noise pollution during the construction and/or operation of wind and/or solar projects. This opposition makes it increasingly difficult to explore new land, obtain permits, and develop solar and wind projects, significantly increasing development timelines. As a result, renewable energy developers have become increasingly interested in developing offshore renewable energy projects in oceans and other large bodies of water. The visual impact of near-shore wind farms has also led developers to increasingly look farther out to sea and deeper underwater. Interconnecting power transmission from offshore wind to the onshore power grid presents significant challenges due to the intermittency of wind power and the large volume of wind power that requires interconnection. One potential solution is long-duration energy storage. Most prior art power storage technologies are not suitable for the marine environment. For example, lithium-ion batteries are considered unsuitable or undesirable for the marine environment due to the corrosive nature of the marine environment and the flammability of lithium in water, even in the absence of air or oxygen. There is a significant need for low-cost, scalable, environmentally friendly, low land or water use, long-duration, high round-trip energy efficiency, and long-duration energy storage technology suitable for the offshore environment.

Additionally, due to the increasingly common occurrence of extreme and abnormal weather events resulting from climate change, the need for power generation and storage technologies to reliably, consistently, and long-termly generate electricity as needed is becoming increasingly critical. Prior art energy storage technologies are unable to provide additional power beyond their nameplate storage capacity in the event of an emergency, which contributed to the high-profile power outages in California and across the United States in recent years. For example, if a lithium-ion battery or pumped hydroelectric power plant is rated at 1,000 MWh and the 1,000 MWh is fully used or fully discharged, the lithium-ion battery or pumped hydroelectric power plant will be unable to provide more power, even if more power is needed.

There is a significant need for energy storage technology that can function as both a high round trip efficiency (>70%) short, medium or long duration energy storage system and, as needed, a multi-day, multi-week or multi-month energy storage system. There is a significant need for energy storage technology that can function as both a high round trip efficiency (>70%) greater than 8 hour duration energy storage system and, as needed, a multi-day, multi-week or multi-month energy storage system. There is a significant need for energy storage technology that can function as both a high round trip efficiency (>70%) greater than 8 hour duration energy storage system and, as needed, a multi-day, multi-week or multi-month energy storage system.

The present invention relates to systems and methods for energy storage, energy generation, or a combination thereof.

Some embodiments may be applicable to energy storage devices, for example. Some embodiments may include a storage area below the surface of a body of water or liquid and a storage area near or above the surface of the body of water or liquid. To "charge" the energy storage device, a lower-density fluid, such as a relatively lower-density liquid or gas, may be pumped into the storage area, displacing a higher-density fluid, such as water. To discharge the energy storage device, the higher-density fluid may be allowed to displace the lower-density fluid, generating electricity due to the flow of the lower-density fluid through a generator.

Some embodiments may address one or more or all of the shortcomings of prior art energy storage systems. For example, some embodiments include one or more or a combination of the following:
• Low capital cost relative to the cost per MWh of energy storage capacity and the cost per MW of generating capacity; • High round trip efficiency, such as one or more or a combination of the following round trip efficiencies: 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 95%, or 99%.
● No power capacity degradation over each charge-discharge cycle ● No energy storage capacity degradation over each charge-discharge cycle ● No land use ● Minimal water surface area usage ● Minimal geographical restrictions, as 40% of the world's population lives within 100 km of the coast ● Long lifespan such as 20 years, or 25 years, or 30 years, or 35 years, or 40 years, or 45 years, or 50 years, or 55 years, or 60 years, or any combination thereof ● Recyclability of most or all components at "end of life" ● Reusability of most or all components at "end of life", which may include, but is not limited to, extending the lifespan or reusing for other uses.
● Minimal environmental impact of manufacturing and building materials ● Minimal environmental impact of construction, installation, and operation ● Significant positive impact on local economy ● Requires oil and gas workers to transition to the renewable energy industry For example, some embodiments employ substantially similar equipment, such as pipes, vessels, pumps, and materials, such as steel and cement, and skills, except for, for example, energy storage systems to store renewable electricity.
Designed for and/or applicable to aquatic, marine, or offshore environments

Some embodiments may be applicable to systems that provide high round-trip efficiency power storage and can supply fuel and/or electricity for days, weeks, months, or years, or any combination thereof, as needed. For example, some embodiments may store energy by displacing a high-density liquid with a low-density liquid, where the low-density liquid, the high-density liquid, or both, may contain chemicals that can alternatively be employed as fuel. For example, some embodiments may involve storing power by displacing a high-density liquid with a low-density liquid, where the displacing energy storage mechanism may store enough energy to provide power at maximum system power capacity for 1 hour, or 2 hours, or 4 hours, or 6 hours, or 8 hours, or 10 hours, or 14 hours, or 16 hours, or 18 hours, or 20 hours, or 25 hours, or 30 hours, or 35 hours, or 40 hours, or 45 hours, or 50 hours, or 75 hours, or 100 hours, or any combination thereof, or more. For example, some embodiments may involve storing electricity by displacing a high density liquid with a low density liquid, where the displacing energy storage mechanism may store enough energy to provide power at maximum system power capacity for less than 50 hours, and the low density liquid, or the high density liquid, or both, may include fuel and may be capable of providing power for more than 50 hours, or more than 75 hours, or more than 100 hours, or more than a week, or more than a month, as needed. For example, some embodiments may involve storing electricity by displacing a high density liquid with a low density liquid, where the displacing energy storage mechanism may store enough energy to provide power at maximum system power capacity for a first duration, and the low density liquid, or the high density liquid, or both, may include fuel and may be capable of providing power for a second duration, as needed. For example, some embodiments may involve storing electricity by displacing a high density liquid with a low density liquid, where the displacing energy storage mechanism may store enough energy to provide power at maximum system power capacity for a first duration, and where the low density liquid, the high density liquid, or both may include a fuel and may be capable of providing power as needed for a second duration, the second duration being greater than the first duration.

Some embodiments may be applicable to ensure that a submersible tank is in pressure equilibrium with seawater adjacent to, surrounding, or at the same elevation as the submersible tank. Some embodiments may be applicable to minimize the pressure difference between the pressure of a fluid inside a submersible tank and the pressure of external water or other fluid adjacent to, surrounding, or at the same elevation as the submersible tank. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from one fluid and transfer the excess pressure or power to another fluid. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a less dense fluid and transfer the excess pressure or power to a more dense fluid. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a more dense fluid and transfer the excess pressure or power to a less dense fluid. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a higher density fluid and transfer the excess pressure or power to a lower density fluid. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a higher pressure fluid and transfer the excess pressure or power to a lower pressure fluid. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a higher pressure fluid and transfer the excess pressure or power to a lower pressure fluid, where the excess pressure may be less than or equal to the pressure difference between the higher pressure fluid and water adjacent to, surrounding, outside of, or at least a portion of the submersible tank. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a first fluid and transfer the excess pressure or power to a second fluid, where the excess pressure may be less than or equal to the pressure difference between the first fluid and water or other fluid adjacent to, around, outside of, or level with at least a portion of the submersible tank. For example, some embodiments may relate to the use of a pressure or power exchanger to extract excess pressure or power from a second fluid and transfer the excess pressure or power to the first fluid, where the excess pressure may be less than or equal to the pressure difference between the second fluid and water or other fluid adjacent to, around, outside of, or level with at least a portion of the submersible tank. For example, some embodiments may relate to a pressure balancing device for enabling or ensuring pressure equilibrium with water or other fluid adjacent to, surrounding, external to, or at the same elevation as at least a portion of a submersible tank. For example, some embodiments may relate to a pressure sensor, or a valve, or any combination thereof. For example, some embodiments may relate to systems and methods for minimizing or preventing hydraulic rams or minimizing or preventing the potential adverse effects of hydraulic rams. Some embodiments may include an energy storage system in which the denser liquid has a density greater than water or seawater. Some embodiments may include an energy storage system in which at least one reservoir is located at an elevation above the elevation of the surface of a body of water, or sea level, or both.

Some embodiments may be applicable to energy storage systems in which the lower density liquid, the higher density liquid, or both, are volatile or have a low boiling point. For example, some embodiments may be applicable to using pressurized tanks or tanks that are resilient to pressure differentials. For example, some embodiments may be applicable to positioning tanks at depths or hydrostatic pressures where the pressure differential between the pressurized fluid inside the tank and the fluid outside, surrounding, or adjacent to the tank is less than if the tank were on land or surrounded by atmospheric pressure, or both. For example, some embodiments may be applicable to refrigerating, semi-refrigerating, cooling, passive cooling, active cooling, thermal management, or any combination thereof, lower density liquids, higher density liquids, or both. For example, some embodiments may relate to ensuring that the lower density liquid, the higher density liquid, or both, are stored in a liquid state. For example, some embodiments may relate to ensuring that low-density liquids, high-density liquids, or both are stored in a liquid state, a supercritical state, a slurry state, or any combination thereof. For example, some embodiments may relate to systems and methods for heat exchange and/or heat storage to minimize energy use and/or maximize energy efficiency and/or utility of the lower-density liquids, the higher-density liquids, or both for refrigeration, semi-refrigeration, cooling, passive cooling, active cooling, thermal management, or any combination thereof. For example, some embodiments may be applicable to enabling the use of cryogenic liquids. For example, some embodiments may be applicable to enabling simultaneous storage of energy and power generation from ocean thermal energy conversion, or from the temperature difference of an ocean or body of water temperature gradient, or the temperature difference between air and water, or any combination thereof.

Some embodiments may relate to a tank applicable to storing low-density fluids underwater. For example, some embodiments may relate to a rigid structure or a flexible structure. For example, some embodiments may relate to a tank or storage area containing a porous solid medium, where a low-density fluid may be stored in the pores of the porous medium. For example, some embodiments may relate to a tank or storage area containing a porous solid medium, where a low-density fluid is stored in the porous medium by pumping or otherwise directing the low-density fluid into the porous medium to displace a higher-density fluid stored in the porous medium. For example, some embodiments may employ a storage reservoir including a porous medium, where the density or weight of the porous medium may reduce the buoyancy of the storage reservoir. For example, some embodiments may employ a storage reservoir including a porous medium, the presence of which prevents the reservoir from substantially collapsing, for example, when the pressure inside the reservoir is less than the pressure outside, adjacent to, surrounding, or at the same elevation as the reservoir. For example, some embodiments may employ a storage reservoir including a porous medium, the presence of which prevents the reservoir from substantially collapsing, for example, when fluid is pumped out of or removed from the storage reservoir at a volumetric rate greater than the volumetric rate at which fluid is added to or pumped into the storage reservoir. For example, some embodiments may employ a storage reservoir including a porous medium, the presence of which prevents the reservoir from substantially collapsing, for example, when fluid is pumped out of or removed from the storage reservoir without the simultaneous addition of another fluid to the reservoir. Substantial collapse may include a reduction in the total volume of the storage reservoir by the following or more, one or more of the following, or a combination of the following: 1 percent, 5 percent, 10 percent, 15 percent, 20 percent, 25 percent, 30 percent, 35 percent, 40 percent, 45 percent, 50 percent, 55 percent, 60 percent, 65 percent, 70 percent, 75 percent, 80 percent, 85 percent, 90 percent, or 95 percent.

Some embodiments may be applicable to simultaneous energy storage systems and tidal power systems. For example, some embodiments may enable storage of electricity while generating power from tidal changes in water level within the same system. Some embodiments may be applicable, for example, to tidal power energy generation systems that generate energy from tidal changes in water level. Some embodiments may involve generating energy, such as electricity, using the displacement of air or other fluid from a storage area due to a tidal rise in water level. Some embodiments may involve generating power using the movement of air or other fluid into a storage area due to a tidal decrease in water level. If desired, moving parts for such tidal power systems, such as pumps and generators, may be located entirely above the surface of the body of water or liquid.

Some embodiments may be applicable to inhibiting or preventing growth formation or fouling buildup on structures in a liquid environment on marine structures, which may include, but are not limited to, marine structures designed for energy storage, or tidal power generation, or combinations thereof. Some embodiments may be applicable to inhibiting or preventing growth formation or fouling buildup on structures in a liquid environment, which may include aqueous and/or non-aqueous environments. Some embodiments described herein may inhibit, eliminate, or prevent growth formation or fouling buildup without the need for coatings, painting, manual cleaning/scrubbing, or other methods described in the art. Growth formation may include, but is not limited to, one or more, or a combination of marine growths, fouling buildup, marine organisms, marine animals, inorganic scaling, organic scaling, barnacles, mussels, bivalves, oysters, worms, shrimp, crustaceans, biofilms, algae, bacteria, fungi, or amoebas. Moving parts of the embodiments related to inhibiting or preventing growth or fouling or corrosion of structures in a liquid environment, such as pumps and generators, may be located entirely above the surface of the body of water or liquid, if desired.

Some embodiments may be applicable to increasing or decreasing the height of a floating structure, such as a dock. Some embodiments described herein may involve increasing the height of a floating structure above the surface of a liquid by pumping air into the floating structure or into a recessed area below the floating structure such that the air or other gas or other low-density fluid at least partially replaces a portion of the water in the recessed area. Similarly, the height of a floating structure above the surface of a liquid may be decreased by allowing gas to escape from the recessed area or by pumping gas out of the recessed area. Air or other gas may be transported into or out of the recessed area using one or more tubes. The recessed area may be open to water or other liquid. Where advantageous, the pumping or release of gas may be performed entirely outside the body of water or liquid using a moving part. By having moving parts outside of and not in contact with the water or liquid, the moving parts (e.g., air pump) may comprise lower cost equipment, may be less susceptible to fouling, and may have a longer lifespan.

It is important to note that the embodiments described herein may be combined, and the systems and methods described herein may overlap or have multiple simultaneous applications.

An exemplary structure having a recessed area "gas pocket" ("3") under each floating body or pontoon. (Above): An exemplary structure with a recessed area "gas pocket" ("3") under each float or pontoon with interconnected air pumps and tubes. An exemplary embodiment having an extended "wall" that may be employed to prevent air or gas loss in the event of, for example, waves, turbulent water, or a significant change in the angle of the dock. An exemplary embodiment in which varying the volume of gas in the gas pocket adjusts the height and/or angle above the water level of a floating structure, such as a dock. Figure 4 may show an increase in height. An exemplary embodiment in which varying the volume of gas in the gas pocket adjusts the height and/or angle above the water level of a floating structure, such as a dock. Figure 5 may show a decrease in height. 1 is an exemplary simplified setup of an embodiment employing a lower density liquid and a higher density liquid. Step 1: FIG. 7 may show an energy storage embodiment in the process of charging. Step 2: Figure 8 may show the energy storage embodiment in a relatively charged state. Step 3: Figure 9 may show an embodiment of energy storage during discharge. Step 4: Figure 10 may show the energy storage embodiment in a relatively discharged state. FIG. 11 may show an exemplary embodiment in which the LDL and/or HDL storage area above the high side head elevation or surface is located on a platform or floating platform. FIG. 12 may show an exemplary embodiment in which the LDL and/or HDL storage area above the high side head elevation or surface is located on land. FIG. 13 may illustrate an exemplary embodiment in which multiple subsurface storage regions are employed for energy and/or chemical storage. Step 1 FIG. 14 may show an embodiment during power generation. Step 2 Figure 15 may show an embodiment in which the storage area is nearly filled with water. Step 3 FIG. 16 may illustrate an embodiment in which power generation is occurring when the water level of the surrounding body of water is relatively low compared to the water level inside the storage area. Step 4 Figure 17 may show an embodiment in which the storage area has been nearly emptied of water. Step 4 Alternative: Figure 18 may show an embodiment in which the storage area has been completely emptied of water. Step 5 (Undertow, pump residual water out): Figure 19 may show an embodiment in which air is pumped into the storage area to remove or replace residual water. Step 1 (Upwelling, Filling, Power Generation): Figure 20 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material. Step 2 (High Tide, Cavity Full): Figure 21 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material. Step 3 (Underflow, Empty, Generate Power): Figure 22 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material. Step 4 (Undertide, Empty): Figure 23 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material. Step 1 (Rise, Fill, Generate Power): Figure 24 shows an exemplary embodiment where the water/air cavity or storage area is located on or within a body of water. Step 2 (High Tide, High Tide): Figure 25 shows an exemplary embodiment where the water/air cavity or storage area is located on or within the body of water. Step 3 (Undertide, Empty): Figure 26 shows an exemplary embodiment where the water/air cavity or storage area is located on or within the body of water. Alternative Step 3 (low tide, empty, depending on tide and location): Figure 27 shows an exemplary embodiment where the water/air cavity or storage area is located on or within the body of water. Step 4 (Undertide, Empty): Figure 28 shows an exemplary embodiment where the water/air cavity or storage area is located on or within the body of water. FIG. 29 shows an exemplary embodiment with a floating pump or floating generator station. FIG. 30 shows an energy storage system in which the first storage reservoir is located on land and the pump and/or generator is located on land. FIG. 31 shows an energy storage system in which the first storage reservoir is located on land and the pump and/or generator is located on land. FIG. 32 illustrates an energy storage system in which the first storage reservoir is located near, at, or below the surface of the body of water, and/or the pump and/or generator is located near, at, or below the surface of the body of water. FIG. 33 illustrates an energy storage system in which the first storage reservoir is located near, at, or below the surface of the body of water, and/or the pump and/or generator is located near, at, or below the surface of the body of water. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. 1 is an embodiment of a low density fluid displacement. A process for energy storage that stores electricity by replacing a high density liquid with a low density liquid and employing auxiliary cold and warm thermal storage. A process for energy storage that generates electricity by displacing a low density liquid with a high density liquid and employing auxiliary cold and warm thermal storage. A process for energy storage that stores electricity by replacing a high density liquid with a low density liquid and employing cold and warm auxiliary thermal storage and refrigeration systems. A process for energy storage that generates electricity by displacing a low density liquid with a high density liquid and employing cold and warm auxiliary thermal storage and cooling systems. A process for energy storage that stores electricity by replacing a high density liquid with a low density liquid and employing a heat storage and cooling system. A process for energy storage that generates electricity by displacing a low density liquid with a high density liquid and employing a heat storage and cooling system. A process for energy storage that stores electricity by replacing a high density liquid with a low density liquid and employing a heat storage and cooling system. A process for energy storage that generates electricity by displacing a low density liquid with a high density liquid and employing a heat storage and cooling system. A process for energy storage that stores electricity by replacing a high density liquid with a low density liquid and employing a heat storage and cooling system. A process for energy storage that generates electricity by displacing a low density liquid with a high density liquid and employing a heat storage and cooling system. A process for energy storage that generates electricity by displacing a low density liquid with a high density liquid and employing a heat storage and cooling system. A process for energy storage that stores electricity by replacing a high density liquid with a low density liquid and employing a heat storage and cooling system. A process for energy storage using a higher elevation reservoir located on land and a lower elevation reservoir located underwater. A process for energy storage using a higher elevation reservoir located on land and a lower elevation reservoir located underwater. A process for energy storage using a higher elevation reservoir located underwater near or on the seabed and a lower elevation reservoir located underwater near or on the seabed. A process for energy storage using a higher elevation reservoir located underwater near or on the seabed and a lower elevation reservoir located underwater near or on the seabed. A process for energy storage using a higher elevation reservoir located above water as a semi-submersible or fully submersible or combination thereof vessel and a lower elevation reservoir located underwater near or on the seabed. A process for energy storage using a higher elevation reservoir located above water as a semi-submersible or fully submersible or combination thereof vessel and a lower elevation reservoir located underwater near or on the seabed. A process for energy storage using a higher elevation reservoir including a floating vessel and a lower elevation reservoir located underwater near or on the seabed. A process for energy storage using a higher elevation reservoir including a floating vessel and a lower elevation reservoir located underwater near or on the seabed. A process for energy storage using underwater and/or lower elevation reservoirs above and/or on the seabed. A process for energy storage using underwater and/or lower elevation reservoirs above and/or on the seabed. A process for energy storage using underwater and/or lower elevation reservoirs above and/or on the seabed. A process for energy storage using underwater and/or lower elevation reservoirs above and/or on the seabed. A process for energy storage using lower elevation reservoirs that are underwater and/or underground below the seabed, or buried, or a combination thereof. A process for energy storage using lower elevation reservoirs that are underwater and/or underground below the seabed, or buried, or a combination thereof. A process for energy storage using lower elevation reservoirs that are underwater and/or underground below the seabed, or buried, or a combination thereof. A process for energy storage using lower elevation reservoirs that are underwater and/or underground below the seabed, or buried, or a combination thereof. A process for energy storage using underground lower elevation reservoirs. A process for energy storage using underground lower elevation reservoirs. A process for energy storage using underground lower elevation reservoirs. A process for energy storage using underground lower elevation reservoirs. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation. A process for energy storage configured to store both a low density liquid and a high density liquid in a higher elevation reservoir, the higher elevation reservoir being a floating structure. A process for energy storage configured to store both a low density liquid and a high density liquid in a higher elevation reservoir, the higher elevation reservoir being a floating structure. A process for energy storage configured to store both a low density liquid and a high density liquid in a higher elevation reservoir, the higher elevation reservoir being a floating structure. A process for energy storage configured to store both a low density liquid and a high density liquid in a higher elevation reservoir, the higher elevation reservoir being a floating structure. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing thermal storage. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing thermal storage. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing thermal storage. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing thermal storage. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing thermal storage. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing thermal storage. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing a thermal storage and thermal management system. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing a thermal storage and thermal management system. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation at exemplary flow rates. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation at exemplary flow rates. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing cooling from chilled water or seawater or deep seawater. A process for energy storage configured to store both low density and high density liquids in a reservoir at a higher elevation and employing cooling from chilled water or seawater or deep seawater. A process for energy storage using a pressure exchanger that uses heat management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger that uses heat management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger without thermal management, cooling, or refrigeration. A process for energy storage using a pressure exchanger that uses heat management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger that uses heat management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger without thermal management, cooling, or refrigeration. A process for energy storage using a pressure exchanger housed in one unit that uses thermal management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger housed in one unit without thermal management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger housed in one unit that uses thermal management, or cooling, or refrigeration. A process for energy storage using a pressure exchanger housed in one unit without thermal management, or cooling, or refrigeration. A process for energy storage that employs a mechanism for removing or separating a portion of a lower density liquid present in a higher density liquid. A process for energy storage using a countercurrent heat exchanger. A process for energy storage using a countercurrent heat exchanger. A process for energy storage using a countercurrent heat exchanger and additional auxiliary cooling. A process for energy storage using a first reservoir, a second reservoir, and a third reservoir, wherein the elevations of the first reservoir and the third reservoir are greater than the elevation of the second reservoir, and the elevation of the first reservoir is different from the elevation of the third reservoir. A process for energy storage using a first reservoir, a second reservoir, and a third reservoir, wherein the elevations of the first reservoir and the third reservoir are greater than the elevation of the second reservoir, and the elevation of the first reservoir is different from the elevation of the third reservoir. A process for energy storage using a first reservoir, a second reservoir, and a third reservoir, wherein the elevations of the first reservoir and the third reservoir are greater than the elevation of the second reservoir, and the elevation of the first reservoir is different from the elevation of the third reservoir. A process for energy storage using a first reservoir, a second reservoir, and a third reservoir, wherein the elevations of the first reservoir and the third reservoir are greater than the elevation of the second reservoir, and the elevation of the first reservoir is different from the elevation of the third reservoir. Subsea, underwater or submerged tanks, including rigid tanks and pressure balancing devices. Subsea, underwater or submerged tanks, including rigid tanks and pressure balancing devices. A process for energy storage using a pressure exchanger. A process for energy storage using a pressure exchanger. A process for energy storage using a pressure exchanger. A process for energy storage using a pressure exchanger. A process for energy storage that uses a pump to provide auxiliary pressure. A process for energy storage that uses a pump to provide auxiliary pressure. A process for energy storage using a pressure exchanger. A process for energy storage using a pressure exchanger. A process for energy storage using a pressure exchanger and a second reservoir at a different elevation than a third reservoir. A process for energy storage using a pressure exchanger and a second reservoir at a different elevation than a third reservoir. A process for energy storage using a lower elevation reservoir that includes separate storage for a higher density liquid in addition to a lower density liquid, where at least a portion of the displacement is provided by a pressure exchanger. A process for energy storage using a lower elevation reservoir that includes separate storage for a higher density liquid in addition to a lower density liquid, where at least a portion of the displacement is provided by a pressure exchanger.

Overview of Exemplary Energy Storage Embodiments: Systems and methods for energy storage and/or simultaneous oil or chemical storage are introduced. In some embodiments, energy is stored via a hydrostatic pressure difference between one or more insoluble or sparingly soluble fluids, which may be driven by a density difference between the one or more fluids. This technology may, for example, employ the depth of a body of water to enable this hydrostatic pressure. One embodiment may, for example, include a relatively high-density liquid and a relatively low-density liquid or fluid, which may have a lower density than the relatively high-density liquid. The end-to-end technology may be a closed system, or may be closed at least below the surface of the body of water. In some embodiments, all or nearly all moving parts are above the surface of a body of water, such as an ocean or lake, or advantageously have no moving parts underwater or deep water, or have no substantial moving parts, or have no relatively expensive moving parts, or have no moving parts at depths greater than 250 feet underwater, or have no moving parts at depths greater than 1000 feet underwater. It may be beneficial for the system to be a closed system, with the internal fluids, e.g., high-density and low-density liquids, in direct contact with each other. The internal fluids may be isolated from the surrounding body of water or may not be in substantial contact with the surrounding body of water. Simply employing water in a body of water may ensure that pressure, e.g., liquid pressure, is balanced between the internal fluid and the surrounding or external body of water. Equilibrating pressure between the outside and inside of the container may, for example, allow for the use of lower-cost materials, for example, because at least a portion of the material may not need to resist a pressure differential or substantial differential. Energy may be stored in a hydrostatic pressure difference between media (e.g., liquids) inside the container, e.g., where one or more media have a higher hydrostatic pressure than another one or more media. The hydrostatic pressure difference may be driven by the difference in hydrostatic pressure of liquids of different densities at the same head height. Embodiments may include a medium containing two or more immiscible or low-solubility liquids with different densities. The density difference between two or more liquids at the same or similar height may drive the hydrostatic pressure difference. Advantageously, the process can operate at reciprocating efficiencies of over 70% or 80% due to the incompressibility of liquids and the high efficiency of hydroelectric generators.

Embodiments may use liquid, solid, gas, supercritical fluid, or other medium phases. One or more phases may be advantageously employed, for example, because the integrated system may be a closed system. For example, in a closed system, contamination by surrounding bodies of water may not be an issue, unless there is a leak, for example.

In one embodiment, a liquid reservoir of a higher density liquid (e.g., water) and a liquid reservoir of a lower density liquid (e.g., butane) are positioned at a relatively higher head height than one or more separate liquid-liquid interface vessels. The relatively higher head height may include, but is not limited to, one or more of the following combinations: located at a smaller depth within the surface of the body of water, located at the surface of the body of water, located above the surface of the body of water, floating on the surface of the body of water, located on land adjacent to the body of water, or located on another body of water, or located on land. It may be desirable for the higher density liquid to have the same or similar density as the surrounding body of water at the same depth. For example, if a pipe or container containing high-density and low-density liquids is in the ocean, the higher density liquid may include a liquid with the same, similar, or relatively close density to the surrounding body of water or other surrounding medium. Alternatively, the higher density liquid may have a significantly different density than the surrounding body of water or other surrounding medium, as a pressure differential resistant material may be required in such embodiments. One or more separate liquid-liquid interface storage vessels may be located at a lower head elevation than the liquid storage vessel. The one or more liquid-liquid interface storage vessels may be connected to one or more liquid storage vessels at a higher head elevation using one or more tubes. The tubes may be employed to transport a lower density liquid, a higher density liquid, or a combination thereof. The one or more tubes may be connected to one or more valves or pumps, or a sealed connection joint. For example, a lower density liquid may be connected to one or more liquid tubes, which may be connected to one or more pumps or generators, or a reservoir of the lower density liquid, or a combination thereof. For example, a higher density liquid may be connected to one or more liquid tubes, which may be connected to one or more pumps or generators, or a reservoir of the higher density liquid, or a combination thereof.

Storing energy may involve, for example, pumping a lower density liquid into one or more tubes and transferring at least a portion of a higher density liquid from the one or more tubes and one or more submerged containers to a reservoir of higher density liquid, or alternatively, transferring the higher density liquid to a surrounding body of water. For example, as the lower density liquid is pumped into the tubes or storage container, it overcomes the hydrostatic pressure of the higher density liquid, developing a head, and energy may be stored due to the difference in hydrostatic pressure between the lower density liquid and the higher density liquid at the same head height. When the storage device stops charging, a valve may be employed to prevent one or more liquids from undesirably reversing flow direction.

Check valves may be employed during pump operation to prevent the low-density liquid from reversing the pumping direction. In the absence of leaks, energy storage may be infinite. During discharge, one or more valves may open to allow the pressurized low-density liquid to be at least partially displaced, allowing the low-density liquid to power a generator. Valves, pumps, generators, and other moving parts may be located at the surface, just below the surface, on land, or a combination thereof, as this may reduce capital, operating, and/or maintenance costs.

In another embodiment, the process may be an open system, with the denser fluid comprising one or more liquids or fluids in a body of water, such as water, brine, oil, or a relatively inexpensive liquid. For charging, a lower-density liquid may be pumped into one or more vessels to replace the denser water or liquid in the vessels. The process may contaminate the water in the bay, but this may be minimized by, but is not limited to, minimizing mixing, preventing contaminant levels, such as low-density liquid levels, from approaching or exceeding the edges of the vessels, using a combination of liquids or media with low solubility or insolubility, using a non-hazardous or inexpensive low-density liquid, or a combination thereof. In this embodiment, a storage vessel for the dense liquid is not required, potentially reducing capital costs and complexity. A version of this embodiment may include an upside-down barrel with a tube opening inside the closed, upward-facing face of the barrel and a port open to the surrounding body of liquid (e.g., a body of water, ocean, or lake) on the downward-facing face of the barrel. A version of this embodiment may include an inverted barrel with a tube connected to a liquid-tight port connected to the upward-facing surface of the barrel and a port on the downward-facing surface of the barrel that is open to a surrounding body of liquid (e.g., a body of water, ocean, or lake). A version of this embodiment may not include a liquid-tight port, and the tube may be routed to the open side of the inverted container or barrel and attached to the lower part of the container or barrel's interior (inside the upper part of the barrel, since it is inverted). Advantages of this alternative embodiment include, but are not limited to, a simplified configuration, higher pressure resistance, reduced chance of leaks or contamination, and lower cost. One or more containers or barrels may be further connected to a weight or anchor, and the upper region of the barrel may be connected to buoyancy to maintain the one or more containers or barrels in a desired position (e.g., in an upside-down position). One or more tubes may be further connected to a pump or generator, which may be further connected to one or more low-density fluid storage containers. The one or more lower density liquid (or other fluid, such as gas) storage vessels may be located at a higher head elevation, e.g., near, at, or above the surface of the body of water. During charging, the lower density liquid (or other fluid, such as gas) may be pumped into the vessels to displace the higher density liquid. During discharging, the lower density liquid may be pumped into the vessels to displace the higher density liquid.

Pressure of a low density liquid:
The pressure of the lower density liquid when displacing the higher density liquid may be higher than the surrounding body of water, as in the case of energy storage, and the pressure difference between the lower density liquid and the surrounding body of water increases as depth decreases. At the interface between the lower density liquid and the higher density liquid, the pressures of the two liquids may be equal or nearly equal. As the depth of the lower density liquid decreases (or the higher the lower density liquid is above the liquid-liquid interface), the lower density liquid deviates more in pressure from the higher density liquid, or the net pressure of the lower density liquid is greater. As a result, tubes or other containers transporting the lower density liquid over depths or head heights may need to be pressure-resistant, and the pressure-resistant requirements may increase as the depth decreases (or the head height from the liquid-liquid interface or deepest point increases). The pump or point of production may contain the highest pressure in an embodiment. One way to explain this phenomenon is as follows:

When an open tube is placed vertically in a body of water, the water inside the tube, even though isolated, is primarily at the same pressure as the surrounding body of water at any given depth because the water pressure exerted by the water inside the tube above a given point in the tube is the same as the water surrounding the tube. Similarly, when liquids of different densities, such as lower or higher density, are placed in a closed lower vessel outdoors, the liquid pressure at any given point may be equivalent to the liquid pressure exerted by the liquid above the point in the liquid. At the same height or depth, the lower density liquid may have a significantly lower gravity-induced pressure than the higher density liquid. When the lower density liquid is displacing the higher density liquid where it is subjected to gravity (e.g., due to the application of an external force), the net pressure or pressure differential experienced by the lower density liquid at any given height above the liquid-liquid interface or deepest point of the lower density liquid is:
P _Net = P _HD - P _LD
During the ceremony,
• "P _Net " may be the net pressure in the less dense liquid at a given height above the minimum depth of the less dense liquid or liquid-liquid interface.
● "P _HD " can be the hydrostatic head of the less dense liquid or the more dense liquid at a height above the minimum depth of the liquid-liquid interface. ● "P _LD " can be the hydrostatic head of the less dense liquid or the less dense liquid at a height above the minimum depth of the liquid-liquid interface.

Figure 6: Figure 6 shows an exemplary simplified configuration of an embodiment employing a lower-density liquid and a higher-density liquid. The two boxes with black text are storage vessels for the higher-head height liquid. The higher-head height liquid storage area is connected to one or more separate storage vessels via tubing or piping. In Figure 6, the tubing is connected to a single storage vessel at a head height below the surface of the body of liquid (such as a body of water), located at a head height below the higher-head height liquid storage vessel, and the single storage vessel may be referred to as the lower-head height storage vessel. The higher-density liquid tubing or piping is connected to one or more ports at the bottom of the lower-head height storage vessel. The lower-density liquid tubing or piping is connected to one or more ports at the top of the lower-head height storage vessel. The location of the placement of ports on the lower head height storage vessel may not be important, and the ports may be placed, including, but not limited to, adjacent to each other, vertically opposite each other, horizontally opposite each other, randomly, or in another configuration, or combinations thereof. It may be important that the ports be liquid-tight. An exception may be, for example, when a heavy liquid port is open to the surrounding water basin, potentially eliminating the need for a liquid-tight port for the denser liquid and potentially eliminating the need for a pipe or storage vessel for the denser liquid. The region within the lower head height vessel where the denser liquid and the less dense liquid meet may be referred to as a fluid-fluid interface or liquid-liquid interface. The liquids may be in direct contact, in which case it may be desirable for the liquids to be immiscible. The liquids may also be spaced apart, separated, or constitute discontinuous liquids by separators, or drums, including, but not limited to, drums or floating drums. When a floating drum is employed to separate a more dense liquid from a less dense liquid, it may be desirable for the floating drum to be less dense than the more dense liquid and more dense than the less dense liquid. A liquid-liquid separator or drum may be employed, for example, to reduce liquid-liquid mixing (particularly important for soluble liquids) or to reduce environmental contamination when open water is the more dense liquid of the more dense liquid. Energy may be stored by pumping the less dense liquid into a tube or pipe of the less dense liquid, thereby displacing the more dense liquid from the lower head height storage vessel. The stored energy may be released by allowing the displaced water to enter the lower head height vessel, thereby displacing the lower head height liquid and generating electricity. In the configuration shown in FIG. 1 , a pump/generator is shown connected to the pipe or tube of the less dense liquid, which may allow for high pump efficiency. The pump may be above the water surface, allowing for no moving parts to be submerged. The less dense liquid can be pressurized during charging and discharging.

A pump/generator may be connected to the denser liquid. One potential challenge with directly pumping a denser liquid is that charging may require the creation of a partial vacuum, which may be less efficient, and even a pure vacuum may not be enough driving force to remove enough denser liquid from a vessel at a lower head height. For example, if the pump or generator is in direct contact with or pumping a denser liquid, it may be desirable for the pump or generator to be below the water line.

The liquid storage area may include a tank or reservoir storing a lower density liquid or a higher density liquid. Substantially immiscible or insoluble may mean a liquid that is soluble in the other liquid at less than 50 weight percent (wt%), or less than 40 wt%, or less than 30 wt%, or less than 20 wt%.

It may be advantageous for the storage area of the denser liquid to be below the water line or at a depth equal to, similar to, or lower than the liquid-liquid interface or lowest point of the liquid. This may be advantageous, for example, when the denser liquid has the same density as the body of liquid, such as a body of water, surrounding the energy storage device. The storage area of the denser liquid may include, for example, a storage device such as a floatation bladder that is in pressure equilibrium with the surrounding body of liquid, such as a body of water. The storage area of the denser liquid may include, for example, a storage device with a floating or retractable roof that is in pressure equilibrium with the surrounding body of liquid, such as a body of water.

A lower head height vessel may be pressure differential resistant. The pressure resistance required by a lower head height vessel may increase with the vertical distance from the liquid-liquid interface or the lowest point of the lower density liquid. It may be advantageous to minimize the vertical height of the vessel and minimize the pressure differential experienced by a lower head height vessel compared to the lower density liquid. This may allow more or most of the pressure differential of the lower density liquid to be transferred to the pipe/tube. It may be advantageous to gradually increase the reinforcement of a lower head height vessel with increasing vertical distance from the liquid-liquid interface or the lowest point of the lower density liquid. For example, a structure with gradually increasing reinforcement of a lower head height vessel may be similar to a water tower, with vessels being gradually more pressure resistant and reinforced with higher hydrostatic pressures.

The higher density liquid reservoir and the lower density liquid reservoir may be located below the surface, floating above the surface, or on land, for example. In some embodiments, the higher density liquid reservoir may include the surrounding body of water. In some embodiments, the higher density liquid reservoir may be in a different location than the lower density liquid reservoir. For example, the higher density liquid reservoir may be a swim bladder-like expandable and contractible volumetric storage area below the surface of the body of water, while the lower density liquid storage area may be located on land.

An energy storage device may undergo charging or discharging of its storage capacity at any time. For example, if the device is at least partially charged, the device may be discharged. For example, if the device is at least partially discharged, the device may be charged. For example, if the device is fully charged, the device may not have the capacity to charge further. For example, if the device is fully discharged, the device may not have the capacity to discharge further.

Exemplary step-by-step instructions:
FIG. 7: Step 1: FIG. 7 may show an energy storage device in the process of charging. A liquid pump may pressurize and pump a lower density liquid (LDL) into a pipe connected to a lower head height storage area, allowing the LDL to displace a higher density liquid (HDL) in the lower head height storage. As the HDL is displaced by the LDL, gravitational potential energy may be stored. FIG. 7 may show the HDL being transferred to an HDL storage area above the lower head height storage area. The HDL storage area may be located elsewhere, for example, below the surface of the liquid body, at the same height or depth as the lower head region, or below the depth of the liquid-liquid interface, for example, if the HDL storage area contains a fluid that is in hydrostatic equilibrium with the surrounding liquid or a liquid of the same density as the surrounding liquid. One or more pumps may be powered by work, such as electrical work, hydraulic work, or mechanical work.

The LDL may be a volatile liquid (such as propane or butane), and the LDL storage area may be closed. Whether the LDL is volatile or not, the LDL storage area may be closed to the atmosphere. If the LDL is sufficiently volatile, the headspace gas within the LDL may contain LDL in the vapor phase. If the LDL has a sufficiently high partial pressure (e.g., propane or butane), the LDL storage area may be pressure-resistant, and appropriate safety precautions may be taken.

The HDL may be a volatile liquid. The HDL may include water. It may be desirable for the HDL storage area not to be open to the atmosphere, as biofouling agents and other contaminants may enter. Instead, the headspace of the HDL storage area may contain, for example, filtered or treated air.

Figure 8: Step 2: Figure 8 may show the energy storage device in a relatively charged state. A check valve may be employed to prevent liquid from entering the LDL tank in a charged or discharged state, or during charging or steady state.

For example, during overcharge when the HDL storage region is located at a higher elevation relative to the LDL, it may not be advantageous to force the LDL into the denser liquid region. If this were to occur, for example, when the HDL storage region is located at a higher elevation relative to the LDL liquid-liquid interface, the LDL may float to the surface of the HDL storage region. This can be remedied, for example, by removing the LDL from the HDL, for example, using one or more or a combination of the following: decanting, cyclones, coalescers, filters, or other means of phase or liquid-liquid separation. If the LDL forms a gas phase at the conditions in the HDL storage region, the LDL can be separated, for example, by one or more or a combination of the following, including, but not limited to, removing the LDL gas from the headspace, compressing the headspace gas, cooling the headspace gas, gas separation methods, pressure swing adsorption, pressure swing absorption, membranes, distillation, combustion, absorption, or adsorption.

Figure 9: Step 3: Figure 9 may show the energy storage device discharging. HDL may displace LDL in the subsurface storage area, which may result in high pressure LDL passing through a generator to generate electricity and into an LDL storage tank, for example.

Figure 10: Step 4: Figure 10 may show the energy storage device in a relatively discharged state. A check valve may be employed to prevent liquid from entering the LDL tank when in a discharged or charged state, or when charging, or at steady state.

Figure 11: Figure 11 may show an exemplary embodiment in which the LDL and/or HDL storage area above the high-side head elevation or surface is located on a platform or floating platform. If desired, the only direct interconnection between the energy storage device and land may be a medium for transporting electricity, such as an electric cable.

Figure 12: Figure 12 shows an exemplary embodiment in which the LDL and/or HDL storage area, located at head height or above the surface of the upper side, may be located on land, for example, on a beach or island.

Figure 13: Figure 13 may show an exemplary embodiment in which multiple subsurface storage areas are employed for energy storage. If there are two or more subsurface storage areas, the subsurface storage areas may be interconnected, which may minimize the number of pipes between one or more storage areas at higher head elevations and one or more storage areas at lower head elevations or subsurface.
Exemplary Installation of Exemplary Embodiments:
1. Connect the tubing (lower density liquid tubing and higher density liquid tubing) to two ports of a liquid-tight container. The tubing can be wound in a roll or another storage configuration.
a. Port location can be important, e.g., located to minimize mixing. For example, ports can be located near the top of the vessel for tubing connections of lower density liquids and near the bottom of the vessel for tubing of higher density liquids.
b. The tubing may be connected to one or more rolls of tubing.
c. The tubes or containers may need to be pressure resistant, but in some embodiments, only the tubes transporting the less dense liquids need to be able to withstand substantial pressure differentials.
2. Fill the container and/or tube with a liquid of the same or similar density as the surrounding body of water (e.g., in the case of the ocean, a density of seawater could be salt water or an aqueous solution containing a high density organic additive such as glycerol or ethylene glycol or propylene glycol. It may be desirable for the liquid to be free of biofouling deposits, scaling agents, or agents that cause corrosion or degradation). Alternatively, the liquid may contain biofouling deposits, scaling agents, or agents that cause corrosion or degradation, such as raw seawater or lake water, or crude oil storage liquid, or raw wastewater or other raw liquid. The liquid that fills the container and/or tube in this step may be considered a denser liquid.
3. Attach the tubing to the desired storage tank and generator/pump 4. To ensure the vessel remains in the desired position (e.g., upright, etc.) and to prevent tangling of the tubing, implementations may include attaching one or more weights or anchors near the bottom of the vessel and attaching one or more buoyant floating objects near the top of the vessel. The vessel float or near the top of the vessel, or a combination thereof, may be further attached to a line that may be connected by a detachable mechanism such as a clip, or a connector with a remotely detachable clip.
5. Allow the vessel to sink to the desired depth, e.g., near or at the bottom of the body of water. As the vessel sinks, unwind the tubes and lines (e.g., float lines and guide lines).
6. Once the vessel reaches its desired depth (eg, the depth at which the weight or anchor reaches the bottom), the guide line can be removed or attached to a float designating the location.
7. To charge, a lower density liquid is pumped into the liquid tube or container, displacing the higher density liquid, which travels through adjacent tubes to a storage container. During charging, the lower density liquid may displace the higher density liquid in the tube or container, or a combination thereof.
8. To discharge, open the valve to provide the pressurized low density liquid (e.g., from step 8) to a generator (e.g., which may be another generator or a pump that can be reversibly used as a generator).
Potential benefits of the energy storage technologies described herein:
●>80% round trip efficiency ○Liquid pumps and generators achieve high efficiency and low thermodynamic losses ●Unlimited available land area (located under a body of water or ocean)
Unlimited storage time Unlimited charge/discharge cycles No moving parts in the ocean No degradation or corrosion No reagents in contact with the ocean (a body of water such as the ocean is simply used to create a depth/head height with the same ambient hydrostatic pressure)
Not affected by marine or aquatic growths (e.g. barnacles, sludge)
Completely closed system. Cost per kWh - butane costs about $300 per cubic ^meter of liquid. Energy density (1 cubic ^meter of butane-water at 1000 m is about 1 kWh of electricity).
No environmental impact Closed system Non-toxic reagents (if leaks occur)
Abundant, non-toxic, non-volatile reagents and building materials Simple, low-cost construction Hydrostatic pressure inside the technology can be the same as its surroundings, allowing for the use of low-cost, low-pressure-resistant building materials. (Note: Tubing connected to low-density liquids may require higher pressure resistance.)
o No moving parts underwater o An embodiment may include three tanks (two on the surface and one on the seabed), two pipes and one pump/generator.

It may be desirable for the high density liquid (HDL) to have a density similar to that of the liquid in the surrounding body of water. This may allow for similar hydrostatic pressures within the vessel(s) and/or pipe as those surrounding the vessel(s) and/or pipe, potentially allowing for the use of lower cost, lower pressure resistant materials.

To maximize the energy density of the storage device implemented, potentially desirable properties include, but are not limited to, a large net density difference (i.e., density of the "high density liquid" minus density of the "low density liquid") and low-pressure or low-temperature driven liquid compression (e.g., water compresses minimally under high pressure). Examples of this include, but are not limited to, propane (LDL) and water (HDL).

To enable effective functionality of the introduced storage device, potentially desirable properties include, but are not limited to, two or more reagents being substantially insoluble or immiscible. It may be desirable for a high density liquid and a low density liquid to be substantially insoluble or immiscible with each other.

To minimize capital costs, potentially desirable properties include, but are not limited to, low-cost reagents, low density liquids, and/or low-corrosion or non-corrosive reagents. For example, butane and propane are low-cost, liquids that operate at higher pressures.

To minimize capital costs, potentially desirable features include, but are not limited to, employing materials that are compatible with the internal reagents of the integrated process. For example, polypropylene or HDPE are inexpensive, abundant, corrosion-resistant, and compatible with water, seawater, butane, and propane.

The energy storage device may also be a means for storing hydrocarbon liquids or chemicals or volatile hydrocarbons. For example, LDL storage areas and lower head height storage areas may include storage of hydrocarbons, such as, but not limited to, crude oil, gasoline, diesel, kerosene, ethane, propane, butane, hexane, octane, cyclopropane, or decane, or combinations thereof. The hydrocarbon liquids are stored in small, medium, or large quantities before being used or transported for various applications, such as polymer production, fuel, or other uses. By employing the energy storage device as a concurrent storage device for relatively low-density liquids, capital costs for the hydrocarbon liquids may be avoided. For example, oil and gas companies, hydrocarbon transportation companies, oil traders, commodity traders, chemical companies, and other users of hydrocarbons or other relatively low-density liquids may employ the energy storage device as a hydrocarbon liquid storage device. For example, the owner or operator of the energy storage device may receive compensation for storing, servicing, or storing the relatively low-density liquids. Although relatively low density liquids may be purchased, in this embodiment, the relatively low density liquids may not be advantageously purchased by the owner or operator of the energy storage device. Instead, the owner or operator of the energy storage device may be compensated for accurately storing the relatively low density liquids. This may eliminate the need to incur capital expenses for purchasing hydrocarbon liquids and may also develop new revenue streams for storing hydrocarbon liquids.

High density liquids may include higher density liquids with limited solubility in water, such as propylene carbonate (density of about 1.2 g/cm3) or ethylene glycol diacetate (density of about 1.128 g/cm3). With such higher density liquids with limited solubility in water, water may be employed as the low density liquid. Such high density liquids may be low cost, non-volatile, and relatively non-toxic, allowing for the use of large quantities of such high density liquids in aquatic or marine environments. Aquatic and marine are used interchangeably herein.
Ridged storage areas or containers may be employed for one or more storage areas located below the surface of water. Such storage areas may include, but are not limited to, storage containers employed herein for storing crude oil or chemicals below the surface of the ocean or other body of water. Storage areas, including non-ridged or ridged storage areas or containers, may be located outside of a body of water or liquid. Alternatively or additionally, the storage area may be located in a strategic petroleum reserve, oil reservoir, natural gas reservoir, liquid reservoir, saline aquifer, geological system, or oil and gas well. One or more storage areas subject to hydrostatic pressures greater than atmospheric pressure may be desirable in an environment that exerts similar or supporting pressures to minimize the strength requirements and potential costs of the storage area or container. In the case of solid environments, such as geological systems such as salt caverns, the geological system or an artificially constructed geological system may function to directly contain or store the liquids and may itself function as a storage area.
Illustrative exemplary embodiments:
An energy storage device,
Contains two or more storage areas,
at least one storage area is at a greater pressure than another storage area,
An energy storage device in which energy is stored using the pressure difference between a less dense liquid and a more dense liquid at the same head height or depth. An energy storage device comprising:
Contains two or more storage areas,
at least one storage area is at a greater pressure than another storage area,
the energy storage device is charged by pumping a relatively less dense liquid into the storage area to displace a relatively more dense liquid;
an energy storage device that is discharged by allowing a relatively higher density liquid to displace a relatively lower density liquid and allowing the flow of the lower density liquid to power an electrical generator or hydraulic turbine; an offshore oil or chemical storage facility that simultaneously functions as a large-scale energy storage device,
Contains two or more storage areas,
at least one storage area is at a greater pressure than another storage area,
an energy storage device in which energy is stored using the pressure difference between a lower density liquid and a higher density liquid at the same head height or depth; an undersea oil or chemical storage facility that simultaneously functions as a large-scale energy storage device,
Contains two or more storage areas,
at least one storage area is at a greater pressure than another storage area,
the energy storage device is charged by pumping a relatively less dense liquid into the storage area to displace a relatively more dense liquid;
an energy storage device that is discharged by allowing a relatively more dense liquid to displace a relatively less dense liquid and allowing the flow of the less dense liquid to power an electrical generator or hydraulic turbine; a process for storing energy while simultaneously storing natural gas, comprising:
storing natural gas in gas bags or storage areas below the surface of a body of water;
compressing or pumping natural gas into the gas bag or storage area, which may expand the volume of the storage area;
discharging or generating electricity by allowing the natural gas to leave the gas bag or storage area and pass through a generator or turbine;
The storage area is connected to a surface natural gas pipeline or LNG facility or natural gas facility through one or more tubes or pipes.
● Energy is stored in the displacement of a higher density liquid with a lower density liquid under conditions where the pressure head due to gravity of the higher density liquid exceeds the hydrostatic head of the lower density liquid ● The pump can reversibly function as a generator ● One storage area is located below the surface of the body of water and another storage area is located near or above the surface of the body of water ● The storage areas act as a reservoir for oils or chemicals ● The low density liquid or the high density liquid or both are the oils or chemicals requiring storage ● The storage area below the surface of the body of water constitutes a higher pressure, lower head height storage area, while the storage area above the surface of the body of water constitutes a lower pressure, higher head height area.
● The pump or generator is located near or above the surface of the body of water ● The storage area below the surface of the body of water includes a recessed area having an opening near the bottom of the recessed area that is open to the surrounding body of water ● The drum or separator separates or is located between the low density liquid and water from the surrounding body of water ● The storage area below the surface of the body of water includes an inflatable, deflatable or flexible structure such as a bladder or bag or balloon that can expand and fill with the low density liquid during charging, or that can deflate, deflate or empty during discharging.
- The storage area includes an expandable or contractible or flexible structure that can displace water around the storage area.
• The dense liquid comprises the water or body of water surrounding the storage area.
The storage area below the surface of the body of water may be moored or anchored to the ground near the bottom of the body of water.
● The pump or generator is in contact with the less dense liquid ● The pump or generator is in contact with the more dense liquid ● The pump or generator is located below the water surface ● The pump or generator is in contact with the more dense liquid and is located at the lower head level, near the higher pressure storage area ● During filling, the more dense liquid is pumped out of the storage area and the less dense liquid displaces it.
• One or more storage areas are employed for storage of one or more chemicals • A low density liquid or a high density liquid or both contains the chemicals being stored.
- Low density liquid or high density liquid or both can be added to or removed from the system.
● The storage facility or energy storage device is located near an oil platform or chemical facility. ● A treatment unit is employed to separate the remaining high density liquids from the low density liquids, or vice versa, before using one or more of the liquids or before transporting them after removal from the storage area.
● The storage unit may be employed for oil or chemical storage when excess storage is required ● The storage unit may contain, or be filled with, or be nearly completely filled with, a larger amount of lower density liquid to be employed, for example, on a temporary, semi-permanent or permanent basis for oil or chemical storage when such storage is required ● The storage unit may contain, or be filled with, or be nearly completely filled with, or be filled with a larger amount of higher density liquid to be employed, for example, on a temporary, semi-permanent or permanent basis for oil or chemical storage when such storage is required ● The system may be optimized to prioritize or balance energy storage or oil storage or chemical storage or a combination thereof, for example, depending on, but not limited to, one or more or a combination of the following:
○ The quantity of chemicals or oils requiring storage ○ The market rate/price for chemical or oil storage ○ The market rate/price for energy storage in the power grid ○ The arbitrage value available for energy storage ○ The arbitrage value available for chemical storage ● Low density liquids are low density fluids ● The low density fluids include gases ● The low density fluids or gases may include natural gas ● The natural gas may be employed in the system for power generation and oil and natural gas storage ● Natural gas may be stored in the form of compressed natural gas (CNG) or liquid natural gas (LNG) ● The storage area is connected to a surface natural gas pipeline or LNG facility or natural gas facility through one or more tubes or pipes ● A process for storing energy/electricity while simultaneously storing natural gas,
storing natural gas in gas bags or storage areas below the surface of a body of water;
compressing or pumping natural gas into the gas bag or storage area, which may expand the volume of the storage area;
discharging or generating electricity by allowing the natural gas to leave the gas bag or storage area and pass through a generator or turbine;
the storage area is connected to a surface natural gas pipeline or LNG facility or natural gas facility through one or more tubes or pipes,

The lower head height, the higher pressure storage area, can be equivalent to the storage area below the surface of the body of water.

Liquid Densities The following table shows the densities of various exemplary liquids that may be employed in the technology introduced herein.

The low density liquid or the high density liquid may be sourced, for example, from a waste material. For example, the low density liquid or the high density liquid may be sourced, for example, from one or more or a combination of, but not limited to, the following: waste cooking oil, waste plastic, waste plastic converted to liquid, waste plastic converted to fuel oil, waste glycerol, waste alcohol, waste coolant, waste antifreeze, waste lubricant, waste fuel, contaminated oils, contaminated chemicals, or expired goods.

Further Discussion of Second Description of Embodiments Overview of Additional Energy Storage Embodiments The present invention relates to a system for storing energy. The present invention stores energy in the hydrostatic pressure difference between a less dense liquid and a more dense liquid over the same head or depth.

The present invention may involve storing energy by displacing water or other more dense liquid with a less dense liquid. The displacing water with the less dense liquid may involve pumping the less dense liquid to a greater depth below the surface of the body of water or other liquid. The pumping may consume power, such as electricity, which may be converted into energy stored in gravitational potential energy and/or hydrostatic pressure differential. The stored energy may be converted back into power by allowing the less dense liquid to be released from the greater depth below the surface of the body of water or other liquid to a lesser depth below the surface of the body of water or other liquid, passing through a generator in the process.

FIG. 30: FIG. 30 may illustrate an energy storage system in which a first storage reservoir is located on land and a pump and/or generator is located on land. The second storage reservoir is located below the surface of the body of water at a greater hydrostatic pressure and/or a greater depth below the surface of the body of water than the first storage reservoir. The first storage reservoir, pump and/or generator, and second storage reservoir may be connected using pipes. FIG. 30 may illustrate the energy storage system in the process of charging. Charging may involve storing power by pumping a low-density liquid from the first storage reservoir to the second storage reservoir. The storage reservoir may include an expandable and/or collapsible or collapsible tank. For example, during charging, the first storage reservoir may contract or collapse to a smaller volume as liquid is pumped from the first storage reservoir to the second storage reservoir. For example, during charging, the second storage reservoir may expand to a larger volume as liquid is pumped from the first storage reservoir to the second storage reservoir.

Figure 31: Figure 31 may show an energy storage system in which a first storage reservoir is located on land and a pump and/or generator is located on land. The second storage reservoir is located below the surface of the body of water at a greater hydrostatic pressure and/or a greater depth below the surface of the body of water than the first storage reservoir. The first storage reservoir, pump and/or generator, and second storage reservoir may be connected using pipes. Figure 31 may show the energy storage system in the process of discharging. Discharging may involve releasing stored energy by allowing a less dense liquid to be released from the first storage reservoir to the second storage reservoir, and in the process generating electricity by allowing the less dense liquid to pass through a generator. The storage reservoir may include an expandable and/or contractible or collapsible tank. For example, during discharging, the first storage reservoir may expand to a larger volume as liquid is released from the second storage reservoir into the first storage reservoir. For example, during discharge, the second storage reservoir may contract or collapse to a smaller volume as liquid is released from the second storage reservoir into the first storage reservoir.

Figure 32: Figure 32 may show an energy storage system in which a first storage reservoir is located near, at, or below the surface of the body of water, and/or a pump and/or generator is located near, at, or below the surface of the body of water. The second storage reservoir is located below the surface of the body of water, at a greater hydrostatic pressure and/or at a greater depth below the surface of the body of water than the first storage reservoir. The first storage reservoir, pump and/or generator, and second storage reservoir may be connected using pipes. Figure 32 may show the energy storage system in the process of charging.

Figure 33: Figure 33 may show an energy storage system in which a first storage reservoir is located near, at, or below the surface of the body of water, and/or a pump and/or generator is located near, at, or below the surface of the body of water. The second storage reservoir is located below the surface of the body of water, at a greater hydrostatic pressure and/or at a greater depth below the surface of the body of water than the first storage reservoir. The first storage reservoir, pump and/or generator, and second storage reservoir may be connected using pipes. Figure 33 may show the energy storage system in the process of discharging.

Illustrative figure legend

Exemplary Step-by-Step Description Charging: Low density liquid is pumped from reservoir "1" to reservoir "2" using pump "3". Electricity is stored in the gravitational potential energy and/or hydrostatic pressure difference of the low density liquid stored in reservoir "2" relative to reservoir "1".

Discharge: Low density liquid is released from reservoir "2" and transferred to reservoir "1" to generate electricity using generator "3." Power is generated by releasing the gravitational potential energy and/or energy stored in the hydrostatic pressure difference of the low density liquid stored in reservoir "2" relative to reservoir "1."

Exemplary Calculations The following table shows key metrics regarding the energy density and cost of butane in the present gravitational potential energy storage device. The cost figures use an exemplary butane commodity price of $0.60 USD per gallon.

Note: Electricity can be transferred between power grids or applications that require or provide electricity.

Note: Electricity may be transported using, for example, subsea, underground, or above ground power lines, or a combination thereof.

Note: The lines/arrows between "1" and "3" and between "3" and "2" may represent the transfer of low density liquid between these process elements. The liquid may be transferred using, for example, a pipe or a transport vehicle. If the liquid is transferred using a pipe, it may be desirable for the pipe to be one or more or a combination of, but not limited to, located on the surface of the ground, or suspended above the surface of the ground, or located below the ground, or including an underwater pipeline, or including an underground pipeline, or including a pipeline below the water and above the ground, or including a pipeline below the ground and below the water, or including a pipeline above the water and above the ground.

Note: An expandable or collapsible reservoir may include a liquid storage container whose volume can expand or contract to allow for the storage of more or less liquid, respectively. The pressure inside the reservoir may be close to or equal to the pressure surrounding the reservoir. The reservoir may include, but is not limited to, an expandable or collapsible liquid storage device, including one or more or combinations of the following, but not limited to: a pillow tank, or an onion tank, or a balloon tank, or a bladder tank, or a fabric tank, or a swim bladder tank, or a collapsible tank, or a flexible tank, or a bellows tank, or an accordion tank, or a liner tank.

Note: This invention may include an LPG storage facility, or an oil storage facility, or a strategic LPG reserve, or a strategic petroleum reserve.

Note: The present invention may be employed to store fuel or other commodity chemicals while simultaneously employing the fuel or other commodity chemical as a gravity storage medium. This may allow the facility owner or operator to have an additional revenue stream (storage or discharge) in addition to revenue from the storage of fuel or other commodity chemicals. By employing the present invention as a storage facility, instead of purchasing or leasing low-density liquids, the facility owner may be paid a storage fee for storing low-density liquids, which may further improve the economics of the facility. A portion of the low-density liquid storage within the facility may be available for "commodity storage," while a portion of the low-density liquid storage within the facility may be intended for permanent or semi-permanent storage. The portion of the low-density liquid storage available for "commodity storage" versus the portion of the low-density liquid storage intended to be permanent or semi-permanent within the facility may vary by facility and may depend on multiple economic factors and facility priorities.

Note: "Commodity storage" may include flexible or semi-flexible storage and may include a portion of a storage facility's stored low-density liquids that may be periodically removed or added for market needs, such as those of commodity traders or other entities involved in commodity markets. If desired, the corresponding low-density liquid storage capacity devoted to "commodity storage" may include a portion of low-density liquids that may be added or removed without substantially affecting the performance, capacity, or capability of the storage. The threshold for "substantially affecting" may vary from facility to facility based on economic factors and facility priorities. "Semi-permanent storage" may include long-term storage or storage that may be utilized periodically or infrequently. For example, semi-permanent storage uses may include, but are not limited to, storage for commodity asset-backed funds, storage for commodity asset-backed ETFs or ETNs, or storage for strategic reserves. Permanent storage may encompass low-density liquids intended to remain within the facility and/or may be necessary for the proper operation of the facility.

Note: The stored low-density liquids may be employed as stored assets or physical assets backing a commodity-tracking ETF or other fund. The owner or operator of a low-density liquid storage facility may generate revenue from the electricity market as an energy storage service, as well as from management fees generated by the ETF for storing the low-density liquids backing the ETF. The ability to have these two revenue streams may allow the owner or operator of the facility to generate more revenue from the facility, or may allow for a lower CAPEX for the facility, or may allow for lower management fees for the ETF, or a combination thereof. To ensure that the assets backing the ETF or ETN are sufficiently readily available or transferable, a portion of the low-density liquids may be stored in storage reservoir "1" at all times to meet short-term low-density liquid needs.

Note: The temperature of ocean water below a certain depth may be relatively stable. The liquid in storage reservoir "2" is cooled or heated by the ambient seawater temperature, depending on the ambient temperature conditions surrounding reservoir "1" and the ambient conditions surrounding reservoir "2". For example, the ambient conditions surrounding reservoir "2" may be cooler than the ambient conditions surrounding reservoir "1". In such an embodiment, the relatively cool temperature of the liquid transferred from reservoir "2" to reservoir "1" may be utilized to provide cooling to one or more applications requiring cooling. An exemplary application requiring cooling may be a pump or generator "3". For example, the ambient conditions surrounding reservoir "2" may be warmer than the ambient conditions surrounding reservoir "1". In such an embodiment, the relatively warm temperature of the liquid transferred from reservoir "2" to reservoir "1" may be utilized to provide heat or enthalpy to one or more applications requiring heat or enthalpy. The specified depth may include less than, greater than, one or more of, or a combination of, the following: 300 meters, or 400 meters, or 500 meters, or 600 meters, or 700 meters, or 800 meters, or 900 meters, or 1000 meters, or 1100 meters, or 1200 meters, or 1300 meters, or 1400 meters, or 1500 meters, or 1750 meters, or 2000 meters.

Note: Due to the low density liquid being a liquid and the liquid being essentially incompressible compared to gas, the round trip efficiency of the present pressure and/or gravity energy storage devices may have significantly greater round trip efficiencies than energy storage devices employing pressurized gas. For example, the round trip efficiency of the present invention may be 40% or greater, or 50% or greater, or 60% or greater, or 70% or greater, or 75% or greater, or 80% or greater, or 85% or greater, or 90% or greater, or 95% or greater.

Note: A low-density liquid may have a low viscosity, e.g., a viscosity close to, equal to, or less than that of water. For example, butane has a kinematic viscosity of approximately 0.2 cP at 1°C, compared to water's kinematic viscosity of 1.73 cP at 1°C. Other low-density liquids other than, or in addition to, butane may have a viscosity less than that of water. Low viscosity may be advantageous because, for example, a lower-viscosity liquid may allow for smaller pipe diameters, lower CAPEX, lower pump energy losses, greater reciprocating efficiency, and a greater distance between reservoir "1" and reservoir "2."

Notes: Compatibility with low density liquids, compatibility with water or seawater, biofouling, pressure compatibility. For pipes transporting low density liquids, the pressure difference between the low density liquid in the pipe and the water surrounding the pipe increases with decreasing depth below the water surface. For example, to minimize CAPEX, the pressure rating of the pipe may be increased with a greater pressure difference. For example, pipes near reservoir "2" may have a lower pressure rating (and/or may be less expensive), and pipes near reservoir "1" may have a greater pressure rating (and/or may be more expensive).

Note: Reservoir "2" and/or reservoir "1" may be moored or connected or secured or anchored to land above the underlying body of liquid (e.g., a body of water).

Note: The storage reservoir or tank may include one or more or combinations of the following, but is not limited to: pillow tank, or onion tank, or balloon tank, or bag tank, or fabric tank, or swim bladder tank, or collapsible tank, or flexible tank, or bellows tank, or accordion tank, or liner tank, or rigid tank, or piston tank, or actuator tank, or valve tank, or basin tank, or cement tank, or wooden tank, or plastic tank, or ceramic tank, or fiber tank, or composite tank, or rubber tank, or flexible tank.

Note: Pipe materials may include one or more or combinations of the following, but are not limited to: plastic pipe, composite pipe, metal pipe, fiber pipe, resin pipe, wooden pipe, cement pipe, flexible pipe, rubber pipe, rigid pipe.

Note: It may be desirable to attach the first and/or second reservoirs to a denser material to reduce the buoyancy of the reservoirs. In the case of the first reservoir, the distance between the reservoir and land below the body of water is large enough to justify attaching a denser material to the first reservoir to reduce the cost of the tether cable. A tether cable may be employed to counteract the buoyancy of the reservoir and/or ensure that the reservoir is in the appropriate location relative to the other reservoir(s). In some embodiments, the distance between the first reservoir and land below the body of water may be large enough that attaching a denser material to the first reservoir is less costly than reducing the cost of the tether cable.

Note: In some embodiments, the location of the first reservoir may be maintained using a dynamic positioning system. The dynamic positioning system may employ various sensors, or GPS, or radar, or other positioning equipment, to notify the operating system of changes in current location and/or changes in the position of the first reservoir, and/or external thrust vectors such as currents. If the position of the first reservoir changes and/or a thrust vector is detected, aquatic or marine engines may be employed to offset the external thrust vector and/or position change to ensure the first reservoir maintains a desired position. If desired, attachment of a denser material to the first reservoir may make the first reservoir similar or neutral in density relative to the surrounding body of water. If desired, the first reservoir may employ a mechanism for dynamically adjusting the density of the first reservoir, for example, using the addition of a higher density material, the addition of a lower density material (e.g., a low density liquid or a gas such as air), the release of a higher density material, or the release of a lower density material. The mechanism(s) for dynamically adjusting density may also be incorporated into a dynamic positioning system. A dynamic positioning system may also be employed for the second reservoir.

Note: Collapsible or collapsible can include structures or containers or tanks whose occupied volume or storage capacity can be reversibly reduced.

Note: Inflatable can include a structure or container or tank that can reversibly increase its occupied volume or storage capacity.

Note: The lower density liquid may be soluble or partially soluble in the higher density liquid. Advantageously, the lower density liquid may be separated from the higher density liquid by a physical barrier, which may prevent dissolution of the lower density liquid into the higher density liquid. For example, the physical barrier may include a storage tank liner, or a wall, or a pipe, or a combination thereof.

Note: In some cases, one or more low-density liquids, having a density less than that of water, may have a boiling point near or below the temperature of ambient air or water and/or may have a large vapor pressure at ambient air or water temperature. In such cases, it may be desirable for the first reservoir to be a pressurized or rigid tank. For example, the pressurized or rigid storage tank may allow the low-density liquid to remain in the liquid phase while the low-density liquid is at a temperature above the atmospheric boiling point of the low-density liquid. In such cases where a rigid or pressurized tank is employed in the first storage reservoir, when a liquid, such as a low-density liquid, is removed from the first storage reservoir, the total volume of the rigid or pressurized tank may remain the same. The volume within the tank previously occupied by the low-density liquid in its liquid phase may instead be occupied by the low-density liquid in its vapor phase. The low-density liquid in its vapor phase may reside in a headspace above a liquid phase within the tank, such as a low-density liquid in its liquid phase. When a liquid, such as a low-density liquid, is added to the first storage reservoir, the total volume of the rigid or pressurized tank may remain the same. The volume within the tank previously occupied by the low-density liquid in its gas phase may instead be occupied by the low-density liquid in its liquid phase. Exemplary low-density liquids that may be applicable may include, but are not limited to, liquefied petroleum gas (LPG), propane, butane, diethyl ether, dimethyl ether, methoxypropane, methanol, acetone, pentane, hexane, petroleum ether, methoxyethane, liquid natural gas (LNG), gasoline, diisopropyl ether, an alkane, an alkene, an alkyne, a cycloalkane, or a combination thereof.

○Note: The present invention may employ devices for leak detection and/or leak prevention. Additionally, the present invention may employ methods for minimizing loss or damage caused by leaks. For example, a containment mechanism, including, but not limited to, a liner, blanket, tarp, fabric, funnel, floating object, or other containment mechanism, or combinations thereof, may be placed or suspended above the second reservoir and/or pipe and/or pipe connection. In the event of a leak, low-density liquid may rise from the leak and be captured or caught by the containment mechanism. The containment mechanism may be effective because low-density liquids tend to float and the containment mechanism may cover a portion or the entire surface area of the second reservoir and/or pipe and/or pipe connection above the second reservoir and/or pipe and/or pipe connection. The low-density liquid captured by the containment mechanism may be funneled into the containment mechanism, if desired, or may be transported to the surface using a return pipe, where the low-density liquid may be collected. When the low-density liquid contacts a portion of the containment vessel or pipe, one or more sensors may be triggered to alert a system operator to the need to repair the leak. For example, the sensor may include a mechanism for measuring the increased buoyancy of the containment mechanism due to the capture or containment of the leaked low-density liquid. For example, the sensor may include a mechanism for measuring the flow rate of liquid in the return pipe, and the presence of at least a certain liquid flow rate may indicate the presence of a low-density liquid leak. For example, the sensor may include a mechanism for detecting the low-density liquid using spectroscopy, or density or molecular weight measurements, or a combination thereof. For example, the sensor may include measuring a change in mass, pressure, or volume in a container connected to the return pipe. For example, the sensor may include measuring a change in mass or volume of the first or second reservoir, which may include a change in mass or energy storage capacity when the process is at steady state, or an unexplained change in mass or energy storage capacity. The first reservoir may employ the containment mechanism and/or sensor. For example, the first reservoir and/or pump and/or generator may employ the containment mechanism and/or sensor, e.g., if the first reservoir and/or pump and/or generator are located below the surface of the body of water.

○Note: The low density liquid or the pipe or the container or the reservoir or combination thereof may contain a medium that reacts when a leak occurs or at the site of a leak. For example, if the low density liquid begins to leak, material in the walls of the pipe or the container or the reservoir may react with the low density liquid. The reaction may inhibit, block or prevent the leak. The reaction may include one or more or a combination of the following, but is not limited to: an absorption reaction, or a swelling reaction, or a foaming reaction, or an expansion reaction, a reaction to form a solid, a reaction to form a viscous liquid, or a combination thereof. Alternatively or additionally, the low density liquid or the walls of the pipe or the container or the reservoir or combination thereof may contain a reagent that, upon exposure to water or air, reacts with water, air, or salts in the water. The reaction may inhibit, block or prevent the leak. The reaction may include one or more or a combination of the following, including, but not limited to, an absorption reaction, or a swelling reaction, or a foaming reaction, or an expansion reaction, a reaction to form a solid, a reaction to form a viscous liquid, or a combination thereof. The reaction may include forming a material that is more easily or readily trapped, or a more environmentally friendly material, or a material that may prevent further leaks, or a material that may simplify or facilitate the process of leak detection, or a material that may reduce the cost or damage associated with leaks. For example, the reaction may include forming a liquid of a particular color, or the reaction may include a tracing reagent.

○Note: The low density liquid or pipe or vessel or reservoir, or combinations thereof, may contain a tracer chemical or reagent that may facilitate leak detection. For example, a part or component of the pipe or vessel or reservoir may contain a material that, when exposed to water, salt water, low density liquid, air, or combinations thereof, may change one or more properties to facilitate detection of leaks, abrasion, or other forms of damage or exposure. For example, such properties may include, but are not limited to, color, electrical conductivity, electrical resistivity, thermal conductivity, surface texture, surface morphology, absorbance spectrum, vibration frequency, flexibility, temperature, density, stiffness, or combinations thereof.

○Note: The temperature below a body of water may be different from the temperature above it. In addition, the body of water itself may have various temperature ranges that may correlate with depth. The temperature of a body of water relative to its depth may be known as the thermocline of the body of water. In very deep bodies of water, such as oceans or lakes, water is generally most dense at about 4°C, so temperatures below about 1000 meters, or below about 1250 meters, or below about 1500 meters range from about 3-8°C. For example, in the ocean, even if the temperature of the water at the surface is warm, e.g., above 15°C or above 20°C, the temperature of the water below 1500 meters is generally near 4°C. In the present invention, the second reservoir may be located at a different depth than the first reservoir. The temperature of the water surrounding the second reservoir may be relatively constant or stable, for example, if the second reservoir is located at a depth below a body of water of more than 100 meters, or 200 meters, or 300 meters, or 500 meters, or 700 meters, or 900 meters, or 1000 meters, or 1250 meters, or 1500 meters. The temperature of the air or water adjacent to the first reservoir or surrounding the second reservoir may differ from the temperature of the water surrounding the second reservoir. The temperature difference between the second reservoir and the first reservoir may be beneficially utilized or may be put to use. For example, if the temperature of the second reservoir is less than the temperature of the first reservoir or objects adjacent to the first reservoir, electricity may be generated from the temperature difference between the liquid returning from the second reservoir and the surrounding ambient temperature near the first reservoir, or the temperature inside the first reservoir, or another heat or warm source or enthalpy source. For example, if the temperature of the second reservoir exceeds the temperature of the first reservoir or objects adjacent to the first reservoir, electricity may be generated from the temperature difference between the liquid returning from the second reservoir and the surrounding ambient temperature near the first reservoir, or the temperature inside the first reservoir, or another cold or warm source or heat or enthalpy sink. For example, if the temperature of the second reservoir is less than the temperature of the first reservoir or objects adjacent to the first reservoir, the liquid from the second reservoir may be employed as a cooling medium or source of cooling, or in district cooling to provide valuable or useful cooling to one or more applications requiring cooling. For example, if the temperature of the second reservoir exceeds the temperature of the first reservoir or objects adjacent to the first reservoir, liquid from the second reservoir may be employed as a heating medium or heat source, or in district heating to provide valuable or useful heating for one or more applications requiring heating. For example, if the temperature of the second reservoir is less than the temperature of the first reservoir or objects adjacent to the first reservoir, liquid from the second reservoir may be employed as a cooling source to power or facilitate a desalination process or a process for removing water from a gas stream or air. For example, if the temperature of the second reservoir is less than the temperature of the first reservoir or objects adjacent to the first reservoir, it may be desirable to insulate the first reservoir or one or more pipes. The insulator may allow the first reservoir to remain cooler, which may be advantageous, for example, if the low-density liquid has a low boiling point or is volatile, and minimizing the temperature in the first reservoir minimizes the pressure in the first reservoir. The insulator may also prevent condensation from forming on the tank.

Note: The present invention may also be employed as a means for Ocean Thermal Energy Conversion (OTEC).

Note: If desired, one or more components of the present invention may be heated, cooled, temperature controlled, or a combination thereof.

○Note: The low-density liquid may have a freezing point below that of water, which may be used to advantage. For example, the first reservoir may be employed as a cold or heat storage unit, e.g., to provide cooling for a refrigeration or frozen storage facility. Such cold storage may be employed, e.g., to optimize energy consumption or for grid load shifting or load reduction. For example, the first reservoir may be employed as a cryogenic cold or heat storage unit. Alternatively or additionally, the cold, low-density liquid may be employed as a low-temperature heat transfer fluid and/or as a low-temperature heat storage medium. For example, the low-density liquid may be employed in applications requiring cooling, which may include, but are not limited to, district cooling, or cooling for a desalination facility, or cooling for a power plant, or cooling for an air separation unit, or cooling for a liquefaction facility, or cooling for an HVAC system. For example, an LNG gasification facility may generate large amounts of waste cooling. An LNG gasification facility may employ a low-density liquid in or from the first reservoir as a heat or enthalpy source, cooling the low-density liquid in the process. Due to its potentially lower freezing point, the low-density liquid may be cooled to a lower temperature than water while remaining in the liquid phase, enabling heat transfer or large-scale heat storage, or both, at temperatures near, at, or below the freezing point of water. Additionally, because the first reservoir is interconnected to a second reservoir and the second reservoir may be at a relatively consistent "cold" temperature, the "warm" low-density liquid may be near 4°C or otherwise below ambient temperature. Advantageously, because the "warm" low-density liquid may be significantly below ambient temperature, more energy may be recovered from the "cold source" than if the low-density liquid were near or at ambient temperature.

Note: Low density liquids or high density liquids or both may be employed as heat transfer fluids or as heat storage fluids, or in ocean thermal energy conversion.

Illustrative exemplary embodiments:
1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low density fluid in the first storage reservoir into the second storage reservoir to displace water adjacent to the second storage reservoir, and to generate or discharge electricity by allowing the low density fluid in the second storage reservoir to return to the first storage reservoir;
Water and a fluid having a density lower than that of water are both in liquid form in the system.
2. The system of embodiment 1, wherein the second storage reservoir is expandable, contractible, or collapsible.
3. The system of embodiment 1, wherein the second storage reservoir is a pillow tank, an onion tank, a balloon tank, a bladder tank, a fabric tank, a swim bladder tank, a collapsible tank, a flexible tank, a bellows tank, an accordion tank, or a liner tank.
4. The system of embodiment 1, wherein the second storage reservoir includes a recessed region having an opening near a bottom of the recessed region, the opening being open to a body of water.
5. A system for storing and generating electricity, comprising:
a first storage reservoir configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water, the second storage reservoir being at a greater depth below the surface of the body of water than the first storage reservoir;
A pump and
a generator;
The pump, the generator, and the first and second reservoirs
(1) storing electricity by pumping a low-density fluid in a first storage reservoir to a second storage reservoir to displace water; (2) generating or discharging electricity by allowing a low-density fluid in the second storage reservoir to return to the first storage reservoir; or (3) both (1) and (2);
Water and a fluid having a density lower than that of water are both in liquid form in the system.
6. The system of embodiment 5, wherein the displaced water is in a second storage reservoir.
7. The system of embodiment 5, wherein the displaced water is water within a body of water, and the displaced water is adjacent to the second storage reservoir.
8. The system of embodiment 5, wherein the water pump and the generator are the same unit.
9. The system of embodiment 5, wherein the first storage reservoir, the second storage reservoir, or both, comprise an expandable, contractable, or collapsible structure.
10. The system of embodiment 5, wherein the first storage reservoir, the second storage reservoir, or both comprise a pillow tank, an onion tank, a balloon tank, a bladder tank, a fabric tank, a swim bladder tank, a collapsible tank, a flexible tank, a bellows tank, an accordion tank, or a liner tank.
11. The system of embodiment 5, wherein the second storage reservoir includes a recessed region having an opening near a bottom of the recessed region that is open to the body of water.
12. The system of embodiment 5, wherein the second storage reservoir is anchored beneath the body of water.
13. The system of embodiment 5, wherein the fluid having a density lower than that of water comprises a hydrocarbon liquid.
14. The system of embodiment 5, further comprising a dynamic positioning system for maintaining or adjusting the position of the first reservoir, the second reservoir, or both.
15. The system of embodiment 5, further comprising an operative connection to a power grid or power transmission infrastructure.
16. The system of embodiment 5, wherein the second storage reservoir is configured to store a fluid having a density lower than water.
17. The system of embodiment 5, wherein the first and second reservoirs are connected by one or more pipes.
18. The system of embodiment 5, wherein the pump and generator comprise a single unit.
19. The system of embodiment 5, wherein the first reservoir is configured to be located below the surface of the body of water.
20. The system of embodiment 5, wherein the fluid having a density lower than water comprises propane, butane, LPG, pentane, hexane, or a mixture thereof.
21. The system of embodiment 5, wherein the fluid having a density lower than water comprises an alcohol, an ether, an ester, or a mixture thereof.
22. The system of embodiment 5, wherein the fluid having a density lower than water comprises methanol, ethanol, propanol, acetone, dimethyl ether, diethyl ether, or a mixture thereof.
23. The system of embodiment 9, wherein the second reservoir is configured to collapse or contract during discharge.
24. The system of embodiment 26, wherein the collapsing or contracting is due to water adjacent to the second reservoir displacing a fluid having a lower density than water.
25. The system of embodiment 9, wherein the second reservoir expands during charging.
26. The system of embodiment 25, wherein the expansion is due to the fluid having a lower density than the water entering the second reservoir and displacing water adjacent to the second reservoir.
27. The system of embodiment 19, wherein the first reservoir is configured to be secured beneath a body of water.
28. The system of embodiment 19, wherein the first reservoir is configured to be attached to a material having a density greater than water to reduce buoyancy.
29. The system of embodiment 19, wherein the first reservoir is attached to a material having a density greater than water and configured to be neutrally buoyant, and wherein the first reservoir is configured such that the position of the first reservoir is maintained or adjusted by a dynamic positioning system.
30. The system of embodiment 5, wherein the second reservoir is attached to a material having a density greater than water to reduce buoyancy.

Overview of Additional Liquid Displacement Embodiments The present invention relates to systems and methods for storing or generating electricity. Some embodiments relate to systems or methods for storing energy by displacing a higher density liquid with a lower density liquid. Some embodiments relate to systems or methods for facilitating electricity storage or generation. Some embodiments relate to environmental, health, and safety mechanisms. Some embodiments relate to systems and configurations for enabling energy storage in specific geographic types. Some embodiments relate to systems and configurations for enabling energy storage using low density liquid working fluids with various levels of volatility or vapor pressure. Some embodiments relate to ensuring optimal energy storage performance.

Exemplary definitions:
Condensable gas: A chemical or mixture of chemicals that undergoes a reversible phase transition from liquid to gas, or gas to vapor, or both, or has a boiling point, or a combination thereof, under the following conditions:
○ Vapor pressure less than 2.5 atmospheres, or less than 5 atmospheres, or less than 10 atmospheres, or less than 15 atmospheres, or less than 20 atmospheres ○ Vapor pressure greater than 0.1 atmospheres, or greater than 0.2 atmospheres, or greater than 0.3 atmospheres, or greater than 0.4 atmospheres, or greater than 0.5 atmospheres, or greater than 0.6 atmospheres, or greater than 0.7 atmospheres, or greater than 0.8 atmospheres, or greater than 0.9 atmospheres, or greater than 1.0 atmospheres ○ Temperatures in the range of 230 Kelvin to 380 Kelvin ● Partially discharged or partially charged: A condition in which the energy storage system contains stored energy, but the stored energy is less than the total energy storage capacity of the energy storage system. For example, when a surface LDL storage tank contains an amount of LDL that is above its minimum capacity and less than its maximum capacity. For example, when a submerged LDL storage tank contains an amount of LDL that is above its minimum capacity and less than its maximum capacity.
● Maximum capacity: Maximum capacity may include the maximum amount of HDL or water, and/or the maximum amount of LDL, or both, that can be stored in a given storage tank, or in a region of an energy storage device, or in general. For example, the maximum capacity of LDL in a subsea tank may include the maximum amount of LDL that can be stored in the subsea tank before the LDL is compromised or can or enters a pipeline designed to transfer water. For example, the maximum capacity of HDL in a subsea tank may include the maximum amount of water or HDL that can be stored in the subsea tank before the HDL is compromised or can or enters a pipeline designed to transfer LDL. For example, the maximum capacity of LDL in a subsea tank may include the maximum amount of LDL that can be stored in the subsea tank before the LDL is compromised or can or enters a surface HDL or water tank. For example, the maximum capacity of HDL in a subsea tank may include the maximum amount of HDL that can be stored in the subsea tank before the HDL is endangered or can or enters a surface LDL tank.
Minimum Capacity: Minimum capacity may include the smallest amount of HDL or water, and/or the largest amount of LDL, or both, that can be stored in a given storage tank, or in a region of an energy storage device, or in general. For example, a minimum capacity of a tank of LDL or HDL may include the tank containing no LDL or HDL, or containing very little LDL or HDL. For example, a minimum capacity of LDL in a subsea tank may include the smallest amount of LDL that can be stored in the subsea tank before the HDL is endangered or can or enters a pipeline designed to transport the LDL. For example, a minimum capacity of HDL in a subsea tank may include the smallest amount of water or HDL that can be stored in the subsea tank before the LDL is endangered or can or enters a pipeline designed to transport the HDL. For example, the minimum volume of LDL in a subsea tank may include the smallest amount of LDL that can be stored in the subsea tank before the HDL is compromised or can or enters the surface LDL or water tank. For example, the minimum volume of HDL in a subsea tank may include the smallest amount of water or HDL that can be stored in the subsea tank before the LDL is compromised or can or enters the surface HDL or water tank. The minimum volume or amount of LDL in a floating submersible tank may include the smallest amount of LDL needed to ensure the floating submersible tank is buoyant.
Pump and Generator, or Pump and Generator: The pump and generator may include a combined pump/generator unit, which may include, but is not limited to, a Hydro Power Recovery Turbine (HPRT). Alternatively or additionally, some embodiments may employ a separate pump and a separate generator.
● First reservoir: The first reservoir may include one or more or a combination of tanks configured to store a low density liquid and may be located at a higher elevation than the second reservoir or at an elevation greater than the second reservoir.
Second reservoir: The second reservoir may include one or more or a combination of tanks configured to store a low-density liquid and may be located at a lower elevation than the first reservoir or at a lower elevation than the first reservoir. The second reservoir may be configured to store both the low-density liquid and water. The second reservoir may be configured to store both the low-density liquid and water in a manner where the low-density liquid and the water exchange volume or pressure while preventing mixing or direct physical contact between the water and the low-density liquid.
Third reservoir: The third reservoir may be interconnected to or include the ocean. The third reservoir may include a water tank or storage vessel. The water tank or storage device may be on the surface, above water, underwater, or a combination thereof. The submersible water reservoir may include a tank or storage vessel or reservoir or body of water containing water interconnected to the second reservoir via a pipe. If desired, at least a portion of the water tank or storage vessel, the third reservoir, or the water interconnected to the third reservoir, may have a pressure similar to or equilibrium with the hydrostatic pressure of the ocean. If the liquid within the third reservoir has the same density as seawater, the third reservoir may be located at any elevation between the elevations of the first and second storage reservoirs, or at any elevation underwater.
Storage vessel: A storage vessel or tank may comprise a barrier for containing a material such as a liquid, solid, or gas. The storage vessel or tank may comprise a variety of configurations or materials, including, but not limited to, storage tanks, or vessels adapted to store liquids or multiphase media, or combinations thereof, as known in the art.
Treated Seawater: Treated seawater may include water or aqueous solutions derived from seawater that are less corrosive than seawater, or have a lower dissolved oxygen concentration than seawater, or are less susceptible to the formation of biofouling or scaling than seawater, or a combination thereof. It may be desirable for the treated seawater to have a density similar to seawater.
Tether: A tether may include a cable or line or connector connecting a floating or buoyant structure to another structure, which may include, but is not limited to, the seabed, a mooring, a vessel, another tank, or an anchor, or any combination thereof.
Configured to store water and fluids having a lower density than water: This term may describe a reservoir or storage designed for the storage of water and lower density liquids. This term may include configuring storage that prevents water and lower density liquids from reacting, dissolving, or forming new phases. This term may include configuring storage that ensures that water and lower density liquids are physically separated while being stored in the same storage vessel.
Low density liquid: A liquid that is less dense than a more dense liquid. A liquid that is less dense than the density of water. A liquid that is less dense than liquid water at temperatures above 3°C and/or below 50°C.
● Substantial low density liquid-water hydrates: "Substantial" may mean an amount or location or combination thereof of low density liquid-water hydrates such that the low density liquid-water hydrates interfere with or disrupt the operation of the energy storage system.
● Close to or approximately the same as: "Close to or approximately the same as" may describe a value that is within 10% of another value.
Sub-tanks: Sub-tanks may include tanks located within another tank, or within an enclosed structure, or within a recessed structure, or a combination thereof, or a tank located inside any of the above.
Rigid Containment Structure: A rigid containment structure may include an enclosure or cover that holds a subtank or one or more other structures. The rigid containment structure may capture or collect low density liquids and/or debris in the event of a failure of the subtank or one or more other structures.
Mechanically Isolated: A submersible tank that is mechanically isolated from ambient or adjacent seawater may include a tank in which the contents within the tank are isolated from or operate under a pressure independent of the pressure of the contents surrounding the tank. A mechanically isolated tank may be a tank that does not exchange pressure with fluids or materials outside or surrounding the tank. For example, a submersible tank may have a pressure within the tank that is different from the pressure of the water surrounding the submersible tank, and the shape and/or volume of the tank may remain unchanged. In some embodiments herein, the pressure within the submersible tank may be close to or approximately equal to the hydrostatic pressure of water at the same depth as the tank, but the contents within the tank may not exchange pressure with seawater adjacent to or surrounding the tank. Achieving a pressure within the tank that is similar to the pressure outside the tank without exchanging pressure between the interior and exterior of the tank may involve one or more or a combination of engineering design systems and/or methods. For example, the engineered head space gas or condensable head space gas may be engineered to have a vapor pressure in the hydrostatic pressure range of seawater at the same depth as the tank at temperatures within the range of temperatures inside the tank and/or the temperature of the water surrounding or adjacent to the tank. By achieving a pressure inside the tank similar to that outside the tank without exchanging pressure between the inside and outside of the tank, a submersible or submersible rigid tank may be manufactured, for example, from fewer or less expensive materials or a combination thereof.
Defects: Defects may include breaks, leaks, disconnections, or accidental releases that may result in the release of internal liquids, which may include, but are not limited to, low density liquids and/or water.

Detailed Diagram Description and Explanation of Exemplary Embodiments Figure 34: This diagram may illustrate an energy storage system that stores electricity by pumping a lower density liquid from a tank at a higher elevation to a tank at a lower elevation to displace water in the tank at the lower elevation. This diagram may illustrate charging or storage of this embodiment. The tank at the higher elevation with the lower density liquid may comprise a first reservoir. The tank at the lower elevation with the lower density liquid and water may comprise a second reservoir. The tank at the higher elevation with water may comprise a third reservoir or surface water tank. The density of the water in the surface water tank may be close to or equal to the density of seawater. The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the depth of the second reservoir.

Figure 35: This figure may include the same embodiment as Figure 34. This figure may show this embodiment in a nearly fully charged state.

Figure 36: This figure may include the same embodiment as Figure 34. This figure may show this embodiment discharging or generating electricity.

Figure 37: This figure may include the same embodiment as Figure 34. This figure may show this embodiment in a nearly fully discharged state.

Figure 38: Legend for Figures 34, 35, 36, and 37.

Figure 39: An energy storage system that charges by pumping a low-density liquid from a first reservoir ("1") near the surface to a second reservoir ("2") underwater, displacing the seawater surrounding the second reservoir. This diagram shows an energy storage system that charges by pumping a low-density liquid from a first reservoir to a second reservoir, displacing the water surrounding the second reservoir. The first reservoir ("1") near the surface can be at an elevation greater than the elevation of the second reservoir ("2"). The first reservoir can be above water on land, can remain floating on water, or can be underwater. In this diagram, the second reservoir floats above the seabed. In this diagram, the second reservoir may be suspended above the seabed and may be buoyant. In this illustration, the second reservoir may be anchored and/or moored to the seabed. In this illustration, the second reservoir may be surrounded by seawater. The second reservoir may include a piston tank. The second reservoir may include an inflatable or collapsible structure such as an onion tank, swim bladder tank, pillow tank, or storage bag. In this illustration, the internal pressure of the second reservoir may be close to or approximately equal to the hydrostatic pressure of the water in contact with the bottom of the second reservoir.

Figure 40: An energy storage system that stores electricity by pumping a low-density liquid from a first reservoir ("1") near the surface to a second reservoir ("2") underwater, displacing the seawater surrounding the second reservoir. This diagram shows the energy storage system fully charged at steady state. The first reservoir ("1") near the surface can be at an elevation greater than the elevation of the second reservoir ("2"). The first reservoir can be above water on land, can remain afloat on the water, or can be submerged. In this diagram, the second reservoir is floating above the seabed. In this diagram, the second reservoir may be suspended above the seabed and may be buoyant. In this diagram, the second reservoir may be anchored and/or moored to the seabed. In this diagram, the second reservoir may be surrounded by seawater. The second reservoir may include a piston tank. The second reservoir may include an inflatable or collapsible structure such as an onion tank, swim bladder tank, pillow tank, or storage bag. In this illustration, the internal pressure of the second reservoir may be close to or approximately equal to the hydrostatic pressure of the water in contact with the bottom of the second reservoir.

Figure 41: An energy storage system that stores electricity by pumping a low-density liquid from a first reservoir ("1") near the surface to a second reservoir ("2") underwater, displacing the seawater surrounding the second reservoir. This diagram shows the energy storage system discharging or generating electricity by displacing the low-density liquid inside the second reservoir with the water surrounding the second reservoir ("2"), passing it through a pipe to a generator, generating electricity, and transferring it back into the first reservoir ("1"). The first reservoir ("1") near the surface can be at an elevation greater than the elevation of the second reservoir ("2"). The first reservoir can be above water on land, floating on water, or submerged. In this diagram, the second reservoir is floating above the seabed. In this diagram, the second reservoir may be suspended above the seabed and may be buoyant. In this illustration, the second reservoir may be anchored and/or moored to the seabed. In this illustration, the second reservoir may be surrounded by seawater. The second reservoir may include a piston tank. The second reservoir may include an inflatable or collapsible structure such as an onion tank, swim bladder tank, pillow tank, or storage bag. In this illustration, the internal pressure of the second reservoir may be close to or approximately equal to the hydrostatic pressure of the water in contact with the bottom of the second reservoir.

Figure 42: An energy storage system that stores electricity by pumping a low-density liquid from a first reservoir ("1") near the surface to a second reservoir ("2") underwater, displacing the seawater surrounding the second reservoir. This diagram shows the energy storage system in a fully discharged state. The first reservoir ("1") near the surface can be at an elevation greater than the elevation of the second reservoir ("2"). The first reservoir can be above water on land, can remain afloat on the water, or can be submerged. In this diagram, the second reservoir is floating above the seabed. In this diagram, the second reservoir may be suspended above the seabed and may be buoyant. In this diagram, the second reservoir may be anchored and/or moored to the seabed. In this diagram, the second reservoir may be surrounded by seawater. The second reservoir may include a piston tank. The second reservoir may include an inflatable or collapsible structure, such as an onion tank, swim bladder tank, pillow tank, or storage bag. In this illustration, the internal pressure of the second reservoir may be close to or approximately equal to the hydrostatic pressure of the water in contact with the bottom of the second reservoir.

Figure 43: Figure 43 is an energy storage system with a labeled tether or anchor or tie-down tether. "C" is the labeling of the tether or anchor or tie-down. The tether or anchor or tie-down may be employed to connect a submersible tank (e.g., "2") to the seabed, thereby allowing the submersible tank (e.g., "2") to float above the seabed.

Figure 44: Figure 44 shows a water or HDL storage tank with a condensable gas in the head space. The storage tank can be rigid in construction. "A" is the labeling of the yellow layer (lighter than black and white). "A" represents a practically insoluble condensed liquid containing the condensable gas in a condensed (i.e., liquid) state. The insoluble condensed liquid can have the same composition as at least a portion of the gas in head space "B" and/or the vapor pressure of the insoluble condensed liquid can be in equilibrium or equilibrium with the head space gas. "B" represents the gas occupying the head space. "A" contains less liquid in Figure 44 than in Figure 45 because more condensable gas is in the condensed liquid state in Figure 45 compared to Figure 44. "6" can represent a third reservoir. The condensable head space gas may allow the water tank to evacuate water while maintaining a relatively stable pressure within the tank or without substantially reducing the pressure within the water tank. The condensable head space gas may allow the interior of the submerged rigid water tank to have an internal pressure that approaches the hydrostatic pressure of seawater at the submerged rigid tank's depth while remaining mechanically isolated from seawater at the submerged rigid tank's depth. The condensable head space gas may have an engineered vapor pressure or boiling point that is compatible with a design pressure range within a design temperature range.

Figure 45: Figure 45 shows a water or HDL storage tank with condensable gas in the head space. The storage tank can be rigid in construction. "A" is the labeling of the yellow layer (lighter than black and white). "A" represents a practically insoluble condensed liquid containing the condensable gas in a condensed (i.e., liquid) state. The insoluble condensed liquid may have the same composition as at least a portion of the gas in head space "B" and/or the vapor pressure of the insoluble condensed liquid may be in equilibrium or equilibrium with the head space gas. "B" represents the gas occupying the head space. "A" contains more liquid in Figure 45 compared to Figure 44 because more condensable gas is in the condensed liquid state, which may be due to the water occupying a larger percentage of the volume in Figure 45. "6" may represent a third reservoir. The condensable head space gas may allow the water tank to evacuate water while maintaining a relatively stable pressure within the tank or without substantially reducing the pressure within the water tank. The condensable head space gas may allow the interior of the submerged rigid water tank to have an internal pressure that approaches the hydrostatic pressure of seawater at the submerged rigid tank's depth while remaining mechanically isolated from seawater at the submerged rigid tank's depth. The condensable head space gas may have an engineered vapor pressure or boiling point that is compatible with a design pressure range within a design temperature range.

Figure 46: An energy storage system that stores electricity by pumping a low-density liquid into a rigid submersible tank to displace water within the rigid tank, which is then transferred to an external submersible water reservoir. This diagram shows, for example, this embodiment in a charging state, e.g., powering a pump ("4") to transfer low-density liquid from a near-surface reservoir ("1") to a submersible reservoir ("2"), whereby the low-density liquid displaces water within the submersible reservoir. The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the submersible depth of the second reservoir.

Figure 46: An energy storage system that stores electricity by pumping a low-density liquid into a rigid, submersible tank to displace water inside the rigid tank, which is then transferred to an external, submerged water reservoir. This figure shows this embodiment in a fully charged, steady state. The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the submerged depth of the second reservoir.

Figure 48: An energy storage system that stores electricity by pumping a low-density liquid into a rigid, underwater tank to displace water within the rigid tank, which is then transferred to an external underwater water reservoir. This diagram shows this embodiment in a power generation or discharge state. For example, a valve ("5") may be opened to allow water within the underwater reservoir ("2") to displace the low-density liquid from the underwater reservoir through a pipe ("3") to generate electricity through a generator ("4") or discharge stored electricity into the near-surface reservoir ("1"). The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 49: An energy storage system that stores electricity by pumping a low-density liquid into a rigid submersible tank to displace water inside the rigid tank, which is then transferred to an external submersible water reservoir. This figure shows this embodiment in a fully discharged steady state. The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the submerged depth of the second reservoir.

Figure 50: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank (second reservoir) to displace water within the second reservoir, which is then transferred to an external submersible water reservoir (third reservoir). This diagram shows the embodiment in a fully discharged, steady-state state. "2" may represent a rigid submersible tank that may include the second reservoir. "S" may represent a separator or barrier that may be located between the low-density liquid and the water, or that may physically separate, prevent, or minimize direct contact between the low-density liquid and the water. The separator or barrier may prevent direct contact between the low-density liquid and the water and/or provide physical separation between the low-density liquid and the water. The separator or barrier may, for example, allow the low-density liquid to displace the water while preventing or minimizing direct contact between the water and the low-density liquid. "8" may represent an external water reservoir or a third reservoir. In this illustration, the external reservoir may be located underwater. In this illustration, the external reservoir may be underwater at a similar depth as the second reservoir. "9" may represent a water pipe interconnecting the external reservoir to the second reservoir. In this illustration, the external water reservoir, or the pipe interconnecting the external water reservoir to the second reservoir, or a combination thereof, may have an internal pressure that is close to the hydrostatic pressure of seawater at or near the depth of the second reservoir. The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 51: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank (second reservoir) to displace water within the second reservoir, which is then transferred to an external submersible water reservoir (third reservoir). This diagram shows, for example, the embodiment in a charging state, e.g., powering a pump ("4") to transfer low-density liquid from a near-surface reservoir ("1") to a submersible reservoir ("2"), whereby the low-density liquid displaces water within the submersible reservoir. "2" may represent a rigid submersible tank that may contain the second reservoir. "S" may represent a separator or barrier that may be located between the low-density liquid and the water, or that may physically separate, prevent, or minimize direct contact between the low-density liquid and the water. The separator or barrier may prevent direct contact between the low-density liquid and water and/or may provide physical separation between the low-density liquid and water. The separator or barrier may, for example, allow the low-density liquid to displace water while preventing or minimizing direct contact between the water and the low-density liquid. "8" may represent an external water reservoir or a third reservoir. In this diagram, the external reservoir may be located underwater. In this diagram, the external reservoir may be underwater at a similar depth as the second reservoir. "9" may represent a water pipe interconnecting the external reservoir to the second reservoir. In this diagram, the external water reservoir, or the pipe interconnecting the external water reservoir to the second reservoir, or a combination thereof, may have an internal pressure that approximates the hydrostatic pressure of seawater at or near the depth of the second reservoir. The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 52: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank (second reservoir) to displace water within the second reservoir, which is then transferred to an external submersible water reservoir (third reservoir). This diagram shows the embodiment in a fully charged, steady-state state. "2" may represent a rigid submersible tank that may include the second reservoir. "S" may represent a separator or barrier that may be located between the low-density liquid and the water, or that may physically separate, prevent, or minimize direct contact between the low-density liquid and the water. The separator or barrier may prevent direct contact between the low-density liquid and the water and/or provide physical separation between the low-density liquid and the water. The separator or barrier may, for example, allow the low-density liquid to displace the water while preventing or minimizing direct contact between the water and the low-density liquid. "8" may represent an external water reservoir or a third reservoir. The physical separation or barrier may include a membrane. In this illustration, the external reservoir may be located underwater. In this illustration, the external reservoir may be underwater at a similar depth as the second reservoir. "9" may represent a water pipe interconnecting the external reservoir to the second reservoir. In this illustration, the external water reservoir, or the pipe interconnecting the external water reservoir to the second reservoir, or a combination thereof, may have an internal pressure that approaches the hydrostatic pressure of seawater at or near the depth of the second reservoir. The pressure inside the second reservoir may approach or be approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 53: An energy storage system that stores electricity by pumping a low-density liquid into a submerged tank (second reservoir) to displace water within the second reservoir, which is then transferred to an external submerged water reservoir (third reservoir). This diagram shows the embodiment in a power generation or discharge state. For example, a valve ("5") may be open to allow water within the submerged reservoir ("2") to displace the low-density liquid from the submerged reservoir through a pipe ("3") to generate electricity through a generator ("4") or discharge stored electricity into a reservoir near the surface ("1"). "2" may represent a rigid submerged tank that may include the second reservoir. "S" may represent a separator or barrier that may be located between the low-density liquid and the water, or that may physically separate, prevent, or minimize direct contact between the low-density liquid and the water. The separator or barrier may prevent direct contact between the low-density liquid and water and/or may provide physical separation between the low-density liquid and water. The separator or barrier may, for example, allow the low-density liquid to displace water while preventing or minimizing direct contact between the water and the low-density liquid. "8" may represent an external water reservoir or a third reservoir. In this diagram, the external reservoir may be located underwater. In this diagram, the external reservoir may be underwater at a similar depth as the second reservoir. "9" may represent a water pipe interconnecting the external reservoir to the second reservoir. In this diagram, the external water reservoir, or the pipe interconnecting the external water reservoir to the second reservoir, or a combination thereof, may have an internal pressure that approximates the hydrostatic pressure of seawater at or near the depth of the second reservoir. The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 54: An energy storage system that stores electricity by pumping a low-density liquid into a submerged tank (second reservoir) and displacing the water within the second reservoir into a separate water reservoir. The third reservoir may include a tank at a higher elevation than the second reservoir, and/or a tank at a lower elevation than the second reservoir, and/or a rigid tank mechanically isolated from the water submerging the tank, and/or a tank on or above the surface of a body of water, and/or a tank located on land. This figure shows the embodiment at or near a fully discharged steady state. "2" may include a submerged second reservoir that may contain a low-density liquid and water within the submerged tank. Within the second reservoir, the low-density liquid may be physically separated from the water by a physical barrier or separator ("S"). The physical barrier or separator may allow the low-density liquid to exchange pressure with the water while ensuring that the water and the low-density liquid are physically separated or do not come into direct contact. The physical barrier or separator may be rigid, flexible, or a combination thereof. The physical separation or barrier may include a membrane. The physical barrier or separator may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. The separator or barrier may prevent direct contact between the low-density liquid and the water and/or provide physical separation between the low-density liquid and the water. The separator or barrier may, for example, allow the low-density liquid to displace the water while preventing or minimizing direct contact between the water and the low-density liquid. "6" may include a third reservoir, which in this illustration includes a reservoir for displaced water and may be located on land. "1" may include a first reservoir, which may contain a store of low-density liquid and may be located at an elevation above the second reservoir. Electricity may be stored by powering a pump ("4") to pump low-density liquid from the first reservoir through a pipe ("3") to a second reservoir ("2") and transferring water from the second reservoir through a pipe ("7") to a third reservoir ("6"). Electricity may be generated or discharged by allowing the low-density liquid in the second reservoir to be replaced by water from a third reservoir, which passes the low-density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it into the first reservoir. The pump and generator may include the same unit(s) that may reversibly function as a pump and generator, which may include a hydraulic power recovery turbine (HPRT). The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 55: An energy storage system that stores electricity by pumping a low-density liquid into a submerged tank (second reservoir) and displacing the water within the second reservoir into a separate water reservoir. The third reservoir may include a tank at a higher elevation than the second reservoir, and/or a tank at a lower elevation than the second reservoir, and/or a rigid tank mechanically isolated from the water submerging the tank, and/or a tank on or above the surface of a body of water, and/or a tank located on land. This figure shows the embodiment in a storage or charging state, where electricity may be stored by powering a pump to transfer the low-density liquid from the first reservoir to the second reservoir and displacing the water in the second reservoir. "2" may include a submerged second reservoir that may contain a low-density liquid and water within the submerged tank. Within the second reservoir, the low-density liquid may be physically separated from the water by a physical barrier or separator (“S”). The physical barrier or separator may allow the low-density liquid to exchange pressure with the water while ensuring that the water and the low-density liquid are physically separated or do not come into direct contact. The physical barrier or separator may be rigid, flexible, or a combination thereof. The physical barrier or separator may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. The separator or barrier may prevent direct contact between the low-density liquid and the water and/or may provide physical separation between the low-density liquid and the water. The separator or barrier may, for example, allow the low-density liquid to displace the water while preventing or minimizing direct contact between the water and the low-density liquid. "6" may include a third reservoir, which in this illustration includes a reservoir for displaced water and may be located on land. "1" may include a first reservoir, which may include a storage for low-density liquid and may be located at an elevation above the second reservoir. Electricity may be stored by powering a pump ("4") to pump low-density liquid from the first reservoir through a pipe ("3") to a second reservoir ("2") and by transferring water from the second reservoir through a pipe ("7") to a third reservoir ("6"). Electricity may be generated or discharged by allowing the low-density liquid in the second reservoir to be replaced by water from the third reservoir, which passes the low-density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it back into the first reservoir. The pump and generator may include the same unit(s) that can reversibly function as a pump and generator, which may include a hydropower recovery turbine (HPRT). The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 56: An energy storage system that stores electricity by pumping a low-density liquid into a submerged tank (second reservoir) and displacing the water within the second reservoir into a separate water reservoir. The third reservoir may include a tank at a higher elevation than the second reservoir, and/or a tank at a lower elevation than the second reservoir, and/or a rigid tank mechanically isolated from the water submerging the tank, and/or a tank on or above the surface of a body of water, and/or a tank located on land. This figure shows the embodiment at or near a fully charged steady state. "2" may include a submerged second reservoir that may contain a low-density liquid and water within the submerged tank. Within the second reservoir, the low-density liquid may be physically separated from the water by a physical barrier or separator ("S"). The physical barrier or separator may allow the low-density liquid to exchange pressure with the water while ensuring that the water and the low-density liquid are physically separated or do not come into direct contact. The physical barrier or separator may be rigid, flexible, or a combination thereof. The physical barrier or separator may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. The separator or barrier may prevent direct contact between the low-density liquid and the water and/or provide physical separation between the low-density liquid and the water. The separator or barrier may, for example, allow the low-density liquid to displace the water while preventing or minimizing direct contact between the water and the low-density liquid. "6" may include a third reservoir, which in this illustration includes a reservoir for displaced water and may be located on land. "1" may include a first reservoir, which may contain a store of low-density liquid and may be located at an elevation above the second reservoir. Electricity may be stored by powering a pump ("4") to pump low-density liquid from the first reservoir through a pipe ("3") to a second reservoir ("2") and transferring water from the second reservoir through a pipe ("7") to a third reservoir ("6"). Electricity may be generated or discharged by allowing the low-density liquid in the second reservoir to be replaced by water from a third reservoir, which passes the low-density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it into the first reservoir. The pump and generator may include the same unit(s) that may reversibly function as a pump and generator, which may include a hydraulic power recovery turbine (HPRT). The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 57: An energy storage system that stores electricity by pumping a low-density liquid into a submerged tank (second reservoir) and displacing the water within the second reservoir into a separate water reservoir. The third reservoir may include a tank at a higher elevation than the second reservoir, and/or a tank at a lower elevation than the second reservoir, and/or a rigid tank mechanically isolated from the water submerging the tank, and/or a tank on or above the surface of a body of water, and/or a tank located on land. This figure shows the embodiment in a generating or discharging state. Electricity may be generated by allowing the low-density liquid to be transferred from the second reservoir, through a pipe, into a generating generator, and into the first reservoir. The low-density liquid in the second reservoir may be allowed to be replaced by water. This allowing may include opening a valve ("5") on the low-density liquid pipe. "2" may include a submerged second reservoir that may contain a low-density liquid and water within the submerged tank. Within the second reservoir, the low-density liquid may be physically separated from the water by a physical barrier or separator ("S"). The physical barrier or separator may allow the low-density liquid to exchange pressure with the water while ensuring that the water and the low-density liquid are physically separated or do not come into direct contact. The physical barrier or separator may be rigid, flexible, or a combination thereof. The physical barrier or separator may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. The separator or barrier may prevent direct contact between the low-density liquid and the water and/or provide physical separation between the low-density liquid and the water. The separator or barrier may, for example, allow the lower density liquid to displace the water while preventing or minimizing direct contact between the water and the lower density liquid. "6" may include a third reservoir, which in this illustration includes a reservoir for the displaced water and may be located on land. "1" may include a first reservoir, which may include a storage for the lower density liquid and may be located at an elevation above the second reservoir. Electricity may be stored by powering a pump ("4") to pump the lower density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2") and by transferring water from the second reservoir through a pipe ("7") to the third reservoir ("6"). Electricity may be generated or discharged by allowing the low-density liquid in the second reservoir to be replaced by water from the third reservoir, which passes the low-density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it back into the first reservoir. The pump and generator may include the same unit(s) that can reversibly function as a pump and generator, which may include a hydropower recovery turbine (HPRT). The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Figure 58: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank ("2") (second reservoir) and displacing the water within the second reservoir into a separate water reservoir. The second reservoir may include a submersible rigid tank that can contain both the low-density liquid and water. Within the second reservoir, the low-density liquid may be stored in a sub-reservoir or sub-tank ("10") that may include an inflatable or collapsible structure such as a bladder tank or a piston or combination thereof. The sub-tank may be employed to prevent direct contact between the low-density liquid and the water in the second reservoir. In the event of a breach or leak of the internal sub-tank, the leaked low-density liquid may remain within this rigid tank or rigid containment structure, preventing exposure of the low-density liquid to the surrounding environment. The sub-tank may be considered a physical barrier or separator and may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. This figure shows this embodiment in a nearly fully discharged state. A third reservoir, which may be connected to the second reservoir using a pipe, may include nearby seawater, a water tank in pressure equilibrium with the ocean, a rigid water tank mechanically isolated from the nearby ocean and at a pressure similar to the hydrostatic pressure of the nearby ocean, a water tank on or near the ocean surface, or a land-based water tank. The third reservoir may be located at any elevation relative to the second reservoir, provided that it is in pressure equilibrium with the surrounding ocean and/or the density of the liquid within the third reservoir is close to that of seawater. For example, the third reservoir may be located at the same or a similar elevation as the second reservoir, as shown in this figure. For example, the third reservoir may be located at a greater depth or at a lower elevation than the second reservoir. For example, the third reservoir may be located at a shallower depth or at a higher elevation than the second reservoir. For example, the third reservoir may be located on land. Electricity may be stored by powering a pump ("4") to pump a low-density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2") and by transferring water from the second reservoir through a pipe ("7") to the third reservoir ("6"). Electricity may be stored by powering a pump ("4") to pump low density liquid from the first reservoir through a pipe ("3") to a second reservoir ("2"), specifically to the low density liquid second reservoir sub-tank ("10"), and by transferring water from the second reservoir through a pipe ("9") to a third reservoir ("8"). Electricity may be generated or discharged by allowing the low density liquid in the second reservoir, specifically in the low density liquid second reservoir sub-tank ("10"), to be replaced with water from the third reservoir, which passes the low density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it into the first reservoir ("1"). The pump and generator may include the same unit(s) that may reversibly function as a pump and generator, which may include a hydraulic power recovery turbine (HPRT). The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

An energy storage system having a surface tank ("1"), a submersible rigid tank ("2"), a bladder sub-tank ("10") configured to store a low density liquid, and an interconnected external bladder tank ("8") configured to store water.

In this embodiment, the battery is in an almost completely discharged state.

Figure 59: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank ("2") (second reservoir) and displacing the water inside the second reservoir into a separate water reservoir. The second reservoir may include a submersible rigid tank that can contain both the low-density liquid and water. Within the second reservoir, the low-density liquid may be stored in a sub-reservoir or sub-tank ("10") that may include an inflatable or collapsible structure such as a bladder tank or a piston or combination thereof. The sub-tank may be employed to prevent direct contact between the low-density liquid and the water in the second reservoir. In the event of a breach or leak of the internal sub-tank, the leaked low-density liquid may remain inside this rigid tank or rigid containment structure, preventing exposure of the low-density liquid to the surrounding environment. The sub-tank may be considered a physical barrier or separator and may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. This diagram shows this embodiment storing or "charging" electricity, where a low density liquid is pumped from a first reservoir to a second reservoir, displacing water from the second reservoir to a third reservoir. The third reservoir, which may be connected to the second reservoir using a pipe, may include nearby seawater, or a water tank in pressure equilibrium with the ocean, or a rigid water tank mechanically isolated from the nearby ocean and at a pressure similar to the hydrostatic pressure of the nearby ocean, or a water tank on or near the ocean surface, or a water tank on land. The third reservoir may be located at any elevation relative to the second reservoir, provided that the third reservoir is in pressure equilibrium with the surrounding ocean and/or the density of the liquid within the third reservoir is close to that of seawater. For example, the third reservoir may be located at the same elevation or a similar elevation as the second reservoir, as shown in this figure. For example, the third reservoir may be located at a greater depth or at a lower elevation than the second reservoir. For example, the third reservoir may be located at a shallower depth or at a higher elevation than the second reservoir. For example, the third reservoir may be located on land. Electricity can be stored by powering a pump ("4") to pump low density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2") and to transfer water from the second reservoir through a pipe ("7") to the third reservoir ("6"). Electricity can be stored by powering a pump ("4") to pump low density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2"), specifically to the low density liquid second reservoir sub-tank ("10"), and to transfer water from the second reservoir through a pipe ("9") to the third reservoir ("8"). Electricity may be generated or discharged by allowing the low-density liquid in the second reservoir, specifically the low-density liquid second reservoir sub-tank ("10"), to be replaced by water from the third reservoir, which passes the low-density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it into the first reservoir ("1"). The pump and generator may include the same unit(s) that can reversibly function as a pump and generator, which may include a hydropower recovery turbine (HPRT). The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Power storage ("charging") in this embodiment. Low-density liquid is pumped ("4") from the surface tank ("1") through a pipe ("3") into the submerged rigid tank ("2"), displacing the water in the submerged rigid tank ("2"). The displaced water travels through a pipe ("9") into the external swim bladder tank ("8").

Figure 60: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank ("2") (second reservoir) and displacing the water inside the second reservoir into a separate water reservoir. The second reservoir may include a submersible rigid tank that can contain both the low-density liquid and water. Within the second reservoir, the low-density liquid may be stored in a sub-reservoir or sub-tank ("10") that may include an inflatable or collapsible structure such as a bladder tank or a piston or combination thereof. The sub-tank may be employed to prevent direct contact between the low-density liquid and the water in the second reservoir. In the event of a breach or leak of the internal sub-tank, the leaked low-density liquid may remain inside this rigid tank or rigid containment structure, preventing exposure of the low-density liquid to the surrounding environment. The sub-tank may be considered a physical barrier or separator and may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. This figure shows this embodiment in a nearly fully charged state. A third reservoir, which may be connected to the second reservoir using a pipe, may include nearby seawater, a water tank in pressure equilibrium with the ocean, a rigid water tank mechanically isolated from the nearby ocean and at a pressure similar to the hydrostatic pressure of the nearby ocean, a water tank on or near the ocean surface, or a land-based water tank. The third reservoir may be located at any elevation relative to the second reservoir, provided that it is in pressure equilibrium with the surrounding ocean and/or the density of the liquid within the third reservoir is close to that of seawater. For example, the third reservoir may be located at the same or a similar elevation as the second reservoir, as shown in this figure. For example, the third reservoir may be located at a greater depth or at a lower elevation than the second reservoir. For example, the third reservoir may be located at a shallower depth or at a higher elevation than the second reservoir. For example, the third reservoir may be located on land. Electricity may be stored by powering a pump ("4") to pump a low-density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2") and by transferring water from the second reservoir through a pipe ("7") to the third reservoir ("6"). Electricity may be stored by powering a pump ("4") to pump low density liquid from the first reservoir through a pipe ("3") to a second reservoir ("2"), specifically to the low density liquid second reservoir sub-tank ("10"), and by transferring water from the second reservoir through a pipe ("9") to a third reservoir ("8"). Electricity may be generated or discharged by allowing the low density liquid in the second reservoir, specifically in the low density liquid second reservoir sub-tank ("10"), to be replaced with water from the third reservoir, which passes the low density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it into the first reservoir ("1"). The pump and generator may include the same unit(s) that may reversibly function as a pump and generator, which may include a hydraulic power recovery turbine (HPRT). The pressure within the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

In this embodiment, the battery is almost fully charged.

Figure 61: An energy storage system that stores electricity by pumping a low-density liquid into a submersible tank ("2") (second reservoir) and displacing the water within the second reservoir into a separate water reservoir. The second reservoir may include a submersible rigid tank that can contain both the low-density liquid and water. Within the second reservoir, the low-density liquid may be stored in a sub-reservoir or sub-tank ("10") that may include an inflatable or collapsible structure such as a bladder tank or a piston or combination thereof. The sub-tank may be employed to prevent direct contact between the low-density liquid and the water in the second reservoir. In the event of a breach or leak of the internal sub-tank, the leaked low-density liquid may remain within this rigid tank or rigid containment structure, preventing exposure of the low-density liquid to the surrounding environment. The sub-tank may be considered a physical barrier or separator and may be removable, replaceable, adjustable, or a combination thereof, which may facilitate operation, maintenance, efficiency, system life, cost, or a combination thereof. This figure illustrates that this embodiment generates power or "discharges." For example, discharging may include allowing a low-density liquid in the second reservoir to be replaced by water in a third reservoir, which enters a pipe, enters a generator, generates power, and is transferred back into the first reservoir. The third reservoir, which may be connected to the second reservoir using a pipe, may include nearby seawater, or a water tank in pressure equilibrium with the ocean, or a rigid water tank mechanically isolated from the nearby ocean and at a pressure similar to the hydrostatic pressure of the nearby ocean, or a water tank on or near the ocean surface, or a water tank on land. The third reservoir may be located at any elevation relative to the second reservoir, provided that the third reservoir is in pressure equilibrium with the surrounding ocean and/or the density of the liquid within the third reservoir is close to that of seawater. For example, the third reservoir may be located at the same elevation or a similar elevation as the second reservoir, as shown in this figure. For example, the third reservoir may be located at a greater depth or at a lower elevation than the second reservoir. For example, the third reservoir may be located at a shallower depth or at a higher elevation than the second reservoir. For example, the third reservoir may be located on land. Electricity can be stored by powering a pump ("4") to pump low density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2") and to transfer water from the second reservoir through a pipe ("7") to the third reservoir ("6"). Electricity can be stored by powering a pump ("4") to pump low density liquid from the first reservoir through a pipe ("3") to the second reservoir ("2"), specifically to the low density liquid second reservoir sub-tank ("10"), and to transfer water from the second reservoir through a pipe ("9") to the third reservoir ("8"). Electricity may be generated or discharged by allowing the low-density liquid in the second reservoir, specifically the low-density liquid second reservoir sub-tank ("10"), to be replaced by water from the third reservoir, which passes the low-density liquid from the second reservoir through a pipe ("3") to a generator ("4"), generating electricity and transferring it into the first reservoir ("1"). The pump and generator may include the same unit(s) that can reversibly function as a pump and generator, which may include a hydropower recovery turbine (HPRT). The pressure inside the second reservoir may be close to or approximately equal to the hydrostatic pressure of the ocean at the underwater depth of the second reservoir.

Power generation ("discharge") in this embodiment. Water in the external swim bladder tank ("8") is allowed to displace low-density liquid in the submerged rigid tank ("2"). The displaced low-density liquid travels through a pipe ("3"), through a generator ("4"), and to the surface tank ("1").

Figure 62: This diagram may include an embodiment similar to Figures 58-61. This diagram may show this embodiment in a nearly fully discharged state. This diagram may employ a third reservoir containing nearby seawater or open ocean water. The sub-tank within the second reservoir ("10"), the second reservoir, and the external water pipe ("11") connected to the second reservoir may be configured so that when a lower density liquid is pumped into "10," displaced water from the second reservoir exits the second reservoir in a manner that prevents the lower density liquid from exiting the second reservoir in the event of a release or leak of the lower density liquid. For example, this configuration may include configuring the pipes and/or tank such that the liquid or material exiting the tank must have a density equal to or greater than that of water, or close to that of water. For example, the configuration may include the external water pipes "11" having an outlet or external outlet facing towards the seabed or a downward bend, for example, the configuration may include the external water pipes "11" having an upward bend and/or a pipe facing upward and/or towards the sea surface and/or away from the seabed and/or with an upward opening inside the submersible tank. For example, the configuration may include the external water pipe containing a chemical or reagent or material that, when present with or in contact with the low-density liquid, will cause the low-density liquid to swell, absorb, or react with the low-density liquid, which may occur, for example, in the event of a leak or release of the low-density liquid from the sub-tank, which may cause a valve inside the pipe to close, or the pipe to be passively blocked or closed, or a combination thereof, in the event of a leak or release of the low-density liquid from the sub-tank. "11" may be removable or replaceable. The sub-tank inside the second reservoir, or the external water pipe, or the third reservoir (if it includes a tank), or a combination thereof, may be removable or replicable. For example, while the second storage reservoir continues to operate, a sub-tank within the second reservoir, or an external water pipe, or a third reservoir (if it includes a tank), or a combination thereof, can be removed or replaced. For example, a sub-tank within the second reservoir, or an external water pipe, or a third reservoir (if it includes a tank), or a combination thereof, can be removed or replaced while the second storage reservoir continues to be installed. For example, a sub-tank within the second reservoir, or an external water pipe, or a third reservoir (if it includes a tank), or a combination thereof, can be removed, replaced, or maintained while one or more components continue to be installed and/or operating, which may include one or more of the components described herein or other parts of the present invention.

An energy storage system having a surface tank ("1"), a submerged rigid tank ("2"), and a float bladder sub-tank configured to store a low-density liquid ("10"). The submerged rigid tank ("2") is in direct fluid communication with adjacent deep seawater by a pipe ("11").

In this embodiment, the battery is in an almost completely discharged state.

Figure 63: This diagram may include the embodiment described in the description of Figure 62. This diagram shows the embodiment in a "charging" or energy storage or charge accumulation state. Charging may involve pumping a low-density liquid from a first reservoir to a second reservoir to replace water in the second reservoir. Water may exit the second reservoir during the replacement such that the low-density liquid may remain in the second reservoir even if the low-density liquid leaks from an internal sub-tank within the second reservoir.

Power storage ("charging") in this embodiment. Low-density liquid is pumped ("4") from the surface tank ("1") through a pipe ("3") into the submerged rigid tank ("2"), displacing seawater from the submerged rigid tank ("2"). The displaced seawater travels through a pipe ("11") into the ocean adjacent to the submerged rigid tank ("2").

Figure 64: This figure may include the embodiment described in the description of Figure 62. This figure shows this embodiment in a nearly fully charged state.

Figure 65: This diagram may include the embodiment described in the description of Figure 62. This diagram shows the embodiment in a "discharging" or energy or power generation state. Discharging may involve allowing a low density liquid to be transferred from a second reservoir into a pipe and into the first reservoir through a generator generating electricity. The displacement may involve seawater passing through a pipe ("11") into the second reservoir. Water may exit the second reservoir during the displacement such that the low density liquid may remain in the second reservoir even if the low density liquid leaks from an internal sub-tank within the second reservoir.

Power generation ("Discharge") in this embodiment. Seawater adjacent to the submerged rigid tank ("2"), which is in direct fluid communication with the submerged rigid tank ("2") through pipe ("11"), allows for the displacement of low-density liquid within the submerged rigid tank ("2"). The displaced low-density liquid travels through pipe ("3"), through the generator ("4"), and to the surface tank ("1").

Figure 66: Energy storage embodiment having a second reservoir and/or a third reservoir with a containment cover or barrier ("CB" or "CCB"). The CB may include a cover positioned over or above one or more components of the system. The CB may include a cover positioned over or above a component of the system that may hold or contain a low-density liquid. If the low-density liquid flows out of the second reservoir, the low-density liquid may float and be captured by the CB, for example, due to the low-density liquid being less dense than water.

Figure 67: Energy storage embodiment having a second reservoir and/or a third reservoir with a containment cover or barrier ("CB" or "CCB"). The CB may include a cover that covers or is positioned over one or more components of the system. The CB may include a cover that covers or is positioned over a component of the system that may hold or contain a low-density liquid. If the low-density liquid flows out of the second reservoir, the low-density liquid may float and be captured by the CB, for example, due to the low-density liquid being less dense than water.

Figure 68: Energy storage embodiment having a second reservoir and/or a third reservoir with a containment cover or barrier ("CB" or "CCB"). The CB may include a cover that covers or is positioned over one or more components of the system. The CB may include a cover that covers or is positioned over a component of the system that may hold or contain a low-density liquid. If the low-density liquid flows out of the second reservoir, the low-density liquid may float and be captured by the CB, for example, due to the low-density liquid being less dense than water.

Figure 69: Energy storage embodiment having a second and/or third reservoir with a containment cover or barrier ("CB" or "CCB"). The CB may include a cover that covers or is positioned over one or more components of the system. The CB may include a cover that covers or is positioned over a component of the system that may hold or contain a low-density liquid. If the low-density liquid flows out of the second reservoir, the low-density liquid may float and be captured by the CB, for example, due to the low-density liquid being less dense than water. In this figure, "S" may include a separator or barrier that may prevent or minimize physical or direct contact between the low-density liquid and the water in the second reservoir.

Figure 70: An energy storage system that stores electricity by pumping a low-density liquid into a sub-tank ("5") in a second reservoir ("2") to displace water therein. The second reservoir may comprise a rigid tank or rigid containment structure that may surround or contain a sub-tank ("5") configured to store the low-density liquid. The sub-tank may include an expandable or collapsible tank. The sub-tank may be located above a water port, hole, pipe, outlet, or combination thereof to ensure that the low-density liquid remains within the second reservoir, for example, in the event of a leak or accidental release of the low-density liquid. The water port, hole, pipe, outlet, or combination thereof may be employed to allow displaced water to exit the second reservoir during "storage" of electricity and/or to allow water to enter the second reservoir to displace the low-density liquid during discharge or generation of electricity. The sub-tank may include a membrane or membrane-like structure. A rigid tank or rigid containment structure may surround the sub-tank and/or cover an upper portion of the sub-tank. Exemplary characteristics of the rigid tank or rigid containment structure may include the ability to control the ingress or egress of water or other liquids or substances to or from the second reservoir, including, but not limited to, the ability to open or close valves or ports that may enable or disable, or both, the inflow or egress of water or other liquids or other substances to or from the second reservoir. This figure illustrates "charging" this embodiment. Such charging may involve pumping a lower density liquid from the first reservoir to the second reservoir to replace water from the second reservoir with the lower density liquid.

Figure 71: An energy storage system that stores electricity by pumping a low-density liquid into a sub-tank ("5") in a second reservoir ("2") to displace water therein. The second reservoir may comprise a rigid tank or rigid containment structure that may surround or contain a sub-tank ("5") configured to store the low-density liquid. The sub-tank may include an expandable or collapsible tank. The sub-tank may be located above a water port, hole, pipe, outlet, or combination thereof to ensure that the low-density liquid remains within the second reservoir, for example, in the event of a leak or accidental release of the low-density liquid. The water port, hole, pipe, outlet, or combination thereof may be employed to allow displaced water to exit the second reservoir during "storage" of electricity and/or to allow water to enter the second reservoir to displace the low-density liquid during discharge or generation of electricity. A rigid tank or rigid containment structure may surround the sub-tank and/or cover an upper portion of the sub-tank. Exemplary characteristics of the rigid tank or rigid containment structure may include the ability to control the ingress or egress of water or other liquids or substances to or from the second reservoir, including, but not limited to, the ability to open or close valves or ports that may enable or disable, or both, the inflow or egress of water or other liquids or other substances to or from the second reservoir. This figure shows this embodiment in a nearly fully charged state.

Figure 72: An energy storage system that stores electricity by pumping a low-density liquid into a sub-tank ("5") in a second reservoir ("2") to displace water therein. The second reservoir may comprise a rigid tank or rigid containment structure that may surround or contain a sub-tank ("5") configured to store the low-density liquid. The sub-tank may include an expandable or collapsible tank. The sub-tank may be located above a water port, hole, pipe, outlet, or combination thereof to ensure that the low-density liquid remains within the second reservoir, for example, in the event of a leak or accidental release of the low-density liquid. The water port, hole, pipe, outlet, or combination thereof may be employed to allow displaced water to exit the second reservoir during "storage" of electricity and/or to allow water to enter the second reservoir to displace the low-density liquid during discharge or generation of electricity. The rigid tank or rigid containment structure may surround the sub-tank and/or cover an upper portion of the sub-tank. Exemplary characteristics of the rigid tank or rigid containment structure may include the ability to control the ingress or egress of water or other liquids or substances to or from the second reservoir, including, but not limited to, the ability to open or close valves or ports that may enable or disable, or both, the inflow or egress of water or other liquids or other substances to or from the second reservoir. This figure illustrates discharge or power generation in this embodiment. Discharge or power generation may involve transferring a low-density liquid from the second reservoir into the first reservoir by piping it through a generator to generate electricity. Transfer of the low-density liquid from the second reservoir may be enabled by opening a valve near or within the pump or generator, or a valve near or within the second reservoir tank, or a combination thereof. Replacing the low-density liquid in the second reservoir may include water entering the second reservoir and displacing the low-density liquid in the second reservoir.

Figure 73: An energy storage system that stores electricity by pumping a low-density liquid into a sub-tank ("5") in a second reservoir ("2") to displace water therein. The second reservoir may comprise a rigid tank or rigid containment structure that may surround or contain a sub-tank ("5") configured to store the low-density liquid. The sub-tank may include an expandable or collapsible tank. The sub-tank may be located above a water port, hole, pipe, outlet, or combination thereof to ensure that the low-density liquid remains within the second reservoir, for example, in the event of a leak or accidental release of the low-density liquid. The water port, hole, pipe, outlet, or combination thereof may be employed to allow displaced water to exit the second reservoir during "storage" of electricity and/or to allow water to enter the second reservoir to displace the low-density liquid during discharge or generation of electricity. A rigid tank or rigid containment structure may surround the sub-tank and/or cover an upper portion of the sub-tank. Exemplary characteristics of the rigid tank or rigid containment structure may include the ability to control the ingress or egress of water or other liquids or substances to or from the second reservoir, including, but not limited to, the ability to open or close valves or ports that may enable or disable, or both, the inflow or egress of water or other liquids or other substances to or from the second reservoir. This figure shows this embodiment in a nearly fully discharged state.

Figure 74: This diagram illustrates charging or storing power in this embodiment. This diagram illustrates an embodiment in which a first reservoir ("1") and/or pump ("4") and/or generator ("4") are located underwater at a higher elevation or lesser depth than the second reservoir. The first reservoir may include a rigid tank or a swim bladder tank. In this diagram, the first reservoir is shown as a rigid tank. In this embodiment shown in this diagram, a subsea power cable ("15") connects the pump and/or generator ("4") to a power source and/or power demand and/or power grid. The power source and/or power demand and/or power grid, which may include power transmission infrastructure, may be represented in this diagram by "13" and "14" and may be located on land or underwater. The subsea power cable may interconnect the energy storage system with offshore power sources, including, but not limited to, offshore wind, offshore solar, and offshore rigs, offshore power plants, or other power sources. The subsea power cable may interconnect the energy storage system with offshore demand sources, including, but not limited to, offshore pipelines, offshore power transmission stations, offshore compression stations, offshore drilling, heated flowlines, offshore oil rigs, offshore production systems, hydrogen production, ammonia production, _CO2 conversion, gas processing facilities, and/or other energy consumption sources. A subsea power cable may interconnect the energy storage system with onshore energy demands and onshore power sources, including industrial electricity demands, commercial electricity demands, residential electricity demands, transportation electricity demands, renewable power sources, residential power sources, power grid load balancing, power grid services, onshore solar power plants, onshore wind power, onshore hydroelectric power, onshore combustion power generation, hydrogen production, storage of excess renewable electricity, and discharge during peak demand or when intermittent renewable energy is short of power production. The diagram may show an energy storage system that stores electricity by pumping a low density liquid into a sub-tank ("5") in a second reservoir ("2") to replace the water inside the second reservoir.

The present embodiment takes advantage of several aspects of the technical limitations of offshore technology and the geography of many offshore regions.
• The offshore seafloor in most of the world is relatively shallow, within 10 miles, or 20 miles, or 30 miles, or 40 miles, or 50 miles, or 60 miles, or 70 miles, or 80 miles, or 90 miles, or 100 miles from the coast, or any combination thereof. Relatively shallow depths can include water depths of less than 1,000 meters, or less than 900 meters, or less than 800 meters, or less than 700 meters, or less than 600 meters, or less than 500 meters, or less than 400 meters, or less than 300 meters, or less than 200 meters, or less than 100 meters, or any combination thereof. Furthermore, in most terrains, the relatively shallow waters eventually meet on a steep rocky or continental shelf that descends to depths of 1,500 meters, or 2,000 meters, or 2,500 meters, or 3,000 meters, or even greater. This embodiment places the first reservoir and/or pump and generator close to the rock or continental shelf, which may minimize the length of the pipeline from the first reservoir to the second reservoir, which improves round trip energy efficiency and reduces capital costs.
In this embodiment, the pump and/or generator may be interconnected to a power source or a power demand or a power grid or a combination thereof by a subsea power cable. Subsea power cables are cheapest and/or easiest to install in relatively shallow and/or relatively flat terrain. The subsea cable herein may be installed in relatively shallow and/or relatively flat undersea terrain.
Modern offshore wind farms require relatively shallow water depths, typically less than 1,000 meters, to be economically viable. This embodiment allows the present invention to be integrated with current offshore wind farms by being located relatively close to shallow waters that are ideal for offshore wind farms. Also, by being able to coexist with offshore wind, offshore solar, offshore rigs, or a combination thereof, the present invention may integrate with existing or pre-planned subsea power cables or transmission infrastructure. Alternatively or additionally, by being able to coexist with offshore wind, offshore solar, offshore rigs, or other offshore technologies, the present invention may improve the economics of that and other technologies, facilitating the construction of subsea power infrastructure and/or the present invention. For example, Virginia, North Carolina, Delaware, and Maryland (all locations where offshore wind farms are proposed) have shallow water and nearby steep rock shelves and/or continental shelves.
● Due to the first reservoir and/or generation being located "offshore," the only "cross-shore infrastructure" in this embodiment may be subsea power cables and associated transmission interconnections and infrastructure. The minimal "cross-shore" and "onshore" infrastructure of this embodiment may reduce required permits and/or approvals and/or timelines and/or regulatory agencies. Additionally, the lack of tanks or generators onshore may allow this embodiment to occupy less land area onshore and/or allow this embodiment to be less visually obtrusive and/or may make this embodiment more visually attractive.
In this embodiment, the first reservoir and/or pump and/or generator may be located at a depth deep enough to minimize exposure to ocean waves and/or marine weather. In this embodiment, the first reservoir and/or pump and/or generator may be located at a depth shallow enough to allow a significant elevation difference between the first and second reservoirs. For example, a significant elevation difference may include an elevation or depth difference of 500 meters or more, or 1,000 meters or more, or 1,500 meters or more, or 2,000 meters or more. In this embodiment, it may be advantageous for the first reservoir and/or pump and/or generator to be located at a depth shallow enough to allow access or convenient access for professional divers and/or professional diving vessels for monitoring and/or maintenance.
This embodiment has a virtually unlimited land area and/or geographic region for energy storage. The amount of undersea seabed with suitable geographic conditions far exceeds the land area of the seabed required for multi-hour, multi-day, or even multi-month storage using this embodiment.

Figure 75: This figure includes the same embodiment as Figure 74. This figure shows this embodiment in a nearly fully charged state.

Figure 76: This figure includes the same embodiment as Figure 74. This figure shows the discharge or generation of electricity in this embodiment.

Figure 77: This figure includes the same embodiment as Figure 74. This figure shows this embodiment in a nearly fully discharged state.

Figure 78: This diagram illustrates charging or storage in this embodiment. This diagram illustrates an embodiment in which the first reservoir ("1") and/or pump ("4") and/or generator ("4") are located within a floating vessel ("16"). The floating vessel may include a carrier, a carrier modified to allow for greater offloading or loading flow rates than conventional carriers, a specially designed carrier, or a combination thereof. The carrier may include, for example, a vessel such as an LPG carrier. The floating vessel may be interconnected to a subsea power cable and/or a subsea low-density liquid pipeline using, or facilitated by, one or more buoys. For example, this diagram may illustrate a low-density liquid pipeline interconnection buoy as an "L" and a subsea cable electrical interconnection buoy as an "X." One or more, or a combination of, a subsea pipeline, a floating vessel, a buoy, a subsea tank, or a subsea tank may be employed.

Floating vessels may be connectable or disconnectable, or both. Floating vessels may be connectable or disconnectable to each other. Floating vessels may be connectable to a floating buoy or disconnectable from a floating buoy. For example, floating vessels may be added or removed (connected or disconnected) if more or less energy storage or power capacity, or both, is needed. Floating vessels may be transferred between one or more facilities or businesses to, for example, optimize needed resources. For example, some areas may require more storage or power capacity during certain periods or seasons, and/or less storage or power capacity during certain other periods or seasons. Floating vessels may be transferred or added to some areas during periods of greater demand. Floating vessels may be disconnected and/or transferred during periods of less demand. Floating vessels may be transferred from areas of less demand to areas of greater demand as needed. For example, a forward market or a spot market, or both, may be created to lease the floating vessel. The floating vessel may be employed as an LPG carrier or other form of carrier when demand for energy storage is low. In some cases, it may be desirable for one or more of the floating vessel and/or the low density liquid and/or a portion of the low density liquid to be leased by the utility operator or owner, for example, instead of being owned outright.

Floating vessels may be disconnected to avoid severe weather such as hurricanes. Floating vessels may be disconnected for maintenance. Floating vessels may be updated or replaced over time. For example, new technological advances or application or performance needs may be integrated into the floating vessel as a retrofit, or a new floating vessel may be constructed, or both. Floating vessels may be disconnected or connected due to changes in demand.

Floating vessels may exist in multiple forms. For example, a floating vessel may include a storage unit for low-density liquid. For example, a floating vessel may include both a storage unit for low-density liquid and a pump and/or generator. For example, a floating vessel may include a pump and/or generator. Multiple forms of floating vessels may be combined or integrated as needed. Floating vessels may be variously modified, replaced, or integrated, or may have updated configurations, or combinations thereof, which may be easy to implement, for example, in response to changing needs from one or more applications.

The floating vessel attachment buoy may include an anchor attachment or similar device to allow the floating vessel to remain in a general location without a dynamic positioning system or with minimal need for a dynamic positioning system.

The use of floating vessels may enable virtually unlimited energy storage capacity. For example, floating vessels may be interconnected to increase energy storage capacity, power capacity, or both. This embodiment may benefit from the current global capability to construct and ship large-scale floating carriers for LPG and other hydrocarbons, and/or the availability of floating carriers currently used to transport, for example, hydrocarbons or offshore floating storage or both.

The use of a floating vessel for the first reservoir and/or pump and/or generator may minimize permits and/or approvals required due to, for example, existing permits for the carrier vessel.

The floating vessel may be connected to the buoy by a turret and swivel stack that may be located on the floating vessel. The turret and swivel stack may allow the vessel to rotate into the wind or otherwise move while interconnecting low-density liquid pipelines and/or subsea electrical cables.

Figure 79: This figure includes the embodiment of Figure 78. This figure shows this embodiment in a nearly fully charged state.

Figure 80: This figure includes the embodiment of Figure 78. This figure shows the discharge or power generation of this embodiment.

Figure 81: This figure includes the embodiment of Figure 78. This figure shows this embodiment in a nearly fully discharged state.

Figure 82: This figure shows an embodiment in which the first reservoir ("1") and/or pump ("4") and/or generator ("4") are located within the floating vessel ("16"). This figure may show an embodiment in which the floating vessel can be connected to a subsea low-density liquid pipeline ("3") and a subsea electrical cable ("15") by an associated buoy ("LX"). The associated buoy may be able to connect to and/or disconnect from the floating vessel. The associated buoy may simplify the connection and/or disconnection process between the floating vessel and the associated buoy. In this figure, the associated buoy may be shown disconnected from the floating carrier.

Figure 83: This figure may include the same embodiment as Figure 82. In this figure, the combined buoy may be shown connected to a floating carrier.

Figure 84: Energy storage system having a surface low-density liquid tank ("1"), a submersible rigid tank ("2"), a swim bladder sub-tank ("10") configured to store low-density liquid, and a surface water tank ("6").

In this embodiment, the battery is in an almost completely discharged state.

Figure 85: This embodiment includes the embodiment of Figure 84.

Power storage ("charging") in this embodiment: Low density liquid is pumped ("4") from the surface low density liquid tank ("1") through a pipe ("3") into the submerged rigid tank ("2"), displacing water from the submerged rigid tank ("2"). The displaced water travels through a pipe ("7") to the surface water tank ("6").

Figure 86: This embodiment includes the embodiment of Figure 84. This embodiment is in a nearly fully discharged state.

Figure 87: This embodiment includes the embodiment of Figure 84.

Power generation ("discharge") of the storage system. Water in the surface water tank ("6") is transferred through a pipe ("7") to the submerged rigid tank ("2"), where it is allowed to displace the low-density liquid in the submerged rigid tank ("2"). The displaced low-density liquid travels through a pipe ("3"), through a generator ("4"), and to the surface tank ("1").

FIGURE LEGENDS Please note: the drawings or figures are not drawn to scale.

Additional Description: High Vapor Pressure Low-Density Liquid and/or Subsea First Reservoir. Locating the first reservoir underwater may have key advantages. For example, by locating the first reservoir underwater, a low-density liquid with a high vapor pressure may be employed as the low-density liquid working fluid. The system may be designed such that the underwater first reservoir is located at a depth where the hydrostatic pressure of water is close to the vapor pressure of the low-density liquid at seawater temperatures. By locating the tank at a depth where the vapor pressure inside the underwater first reservoir is similar to the pressure of the water surrounding the first reservoir, the installed tank may need to withstand a smaller pressure difference and may have relatively thin walls or be less expensive than a tank storing the same liquid on the surface. Also, advantageously, the temperature of the water below the ocean may be relatively consistent depending on the climate and location, which may allow for easier prediction of the vapor pressure of the low-density liquid and/or design of tank pressure requirements and/or design depth. Also, advantageously, the temperature of the water below the ocean may be relatively consistently below a certain temperature range, which may allow for easier prediction of vapor pressure of low density liquids and/or design of tank pressure requirements and/or design depth.

As an example, liquid ethane has a vapor pressure of 2807 kPa at 280°K and 4357 kPa at 300°K, which is equivalent to the hydrostatic pressure of water at depths of approximately 286 meters and 445 meters, respectively. The first reservoir and/or pump and/or generator may be located, for example, at a depth greater than 150 meters and less than 500 meters. The ethane remains in a liquid phase rather than a supercritical phase, which is below ethane's critical point of 305.322°K. Advantageously, even in equatorial regions, the temperature of ocean water at depths greater than 150 meters is generally consistently below 300°C, which may ensure that the ethane remains in a liquid phase rather than a supercritical phase. In its liquid phase, ethane has a density of 304 kg/ ^m3 at 300°K and 383 kg/ ^m3 at 280°K. This embodiment may be configured similarly to the configuration of FIG. 74. Alternatively or additionally, this embodiment may be configured similarly to FIG. 55 except that "1,""6," and/or "4" are located underwater, albeit at a higher elevation than "2." Alternatively or additionally, this embodiment may be configured similarly to other figures herein, but the first reservoir, or the third reservoir, or the pump/generator, or a combination thereof, may be located below the ocean, in figures where the first reservoir, or the third reservoir, or the pump/generator, or a combination thereof may be shown above the ocean or on land adjacent to the ocean. Advantageously, liquid ethane may be more abundant and/or less expensive than other low-density liquid options. Advantageously, liquid ethane may have a lower density than other low-density liquid options.

Liquid-Liquid Displacement The present embodiments relate to an energy storage device employing a low-density liquid and a high-density liquid. Electricity is stored by displacing a high-density liquid with a low-density liquid, and electricity is generated by allowing a high-density liquid to displace a low-density liquid. In the present embodiments, the displacement occurs in a submerged storage reservoir configured to store both the low-density liquid and the high-density liquid. An exemplary high-density liquid may include, but is not limited to, water. An exemplary low-density liquid may include, but is not limited to, propane, butane, ethane, or LPG. In some embodiments, the submerged storage reservoir may include a rigid storage tank. In some embodiments, the low-density liquid includes hydraulic fluid employed in pumps and generators to generate electricity.

In some embodiments, a lower density liquid floats above a higher density liquid within the underwater storage reservoir. The lower density liquid may include hydraulic or working fluids employed in pumps or generators. There are several advantages that result from allowing the lower density liquid to float or sit above the higher density liquid within the underwater storage reservoir. These advantages may include, but are not limited to:
By allowing the lower density liquid to float above the higher density liquid, the present invention may employ a rigid submersible tank. A rigid submersible tank or structure may be employed to contain or store at least a portion of the lower density liquid. A rigid submersible tank may have numerous advantages, which may include, but are not limited to, a longer lifespan, reduced risk of leaks or breakage, and resilience to the elements.
In the event of a catastrophic failure or leak or rupture of the underwater storage area, one or more or a combination of the following beneficial outcomes may occur:
o The energy storage system may continue to operate. o The low density liquid may be safely removed and/or recoverable by allowing the low density liquid to be transferred from the underwater reservoir to a reservoir near the surface, allowing the storage system to generate power or "discharge."
○ Low density liquids may remain within the underwater storage area ○ Low density liquids may not leak or flow out of the underwater storage area ● Low density liquids may be contained within rigid areas of the underwater storage tank, which may have longer term or safer storage characteristics.
Low density liquids and water may directly replace each other while being physically separated The present embodiment may employ density-based methods for passive risk mitigation, error correction, and emergency response, which may include, but are not limited to:
For example, this embodiment may employ a floating plug having a density greater than the low density liquid and less than water. The plug may stop the flow of liquid into the low density liquid pipe when the water level in the second reservoir exceeds a predefined level. The plug may prevent water from entering the low density liquid pipe. The plug may be employed to ensure that a predefined minimum volume of low density liquid is present in the underwater storage reservoir.
o If the barrier or separator is broken, in or o During filling, the lower density liquid may displace water downwards and out of the submersible tank through the lower port in the submersible tank.

In some embodiments, the lower density liquid may be prevented from direct contact with the higher density liquid by physical separation.
- The physical separation may involve a liquid that is insoluble in both the low density liquid and the high density liquid, but has a density greater than the low density liquid and less than the high density liquid.
- The physical separation may include solids.
- The physical separation may include a barrier having a density greater than the low density liquid and less than the high density liquid.
- The physical separation may include an impermeable material such as a synthetic fabric or liner.
- Such physical separation may be employed to prevent hydrate formation.
- The physical separation can be below a low density liquid and above water in a submersible storage reservoir or rigid submersible storage tank.
- The physical separation may be located in an underwater storage reservoir.
- The physical separation may be in a tank that includes a rigid structure that may contain an underwater storage reservoir.

Containment Cover or Containment Barrier or Containment Boundary ("CB" or "CCB")
The present invention may include a containment cover, boundary, or barrier (CB or CBB) over an underwater storage reservoir. The CB may capture low-density liquid in the event of a leak or accidental release of the low-density liquid. The CB may be located on or above the underwater storage reservoir. The CB may include a liner, fabric, or solid, or sheet, or a combination thereof. The CB may be configured to funnel low-density liquid (if captured) into specific areas of the CB, for example, to facilitate recovery of LDL. In the event of an accidental release or leak of LDL, LDL or LDL hydrate or LDL compositions may rise to the top of the underwater reservoir and be captured by the CB or float within the CB. The CB may float above the underwater reservoir or be moored to the seabed. The CB may be less dense than seawater, which may facilitate floating. Alternatively or additionally, the CB itself may be suspended or floating due to float(s) attached to the CB. In some embodiments, the CB may cover or be above a surface area equal to or greater than the surface area of the underwater reservoir and/or the underwater valve or connection. In some embodiments, the CB may cover or be above only a specific section of the underwater reservoir, e.g., covering only the surface area above a connection or port. There may be more than one CB. For example, there may be a CB above a specific connection or port. In some embodiments, there may be redundant CBs. For example, a CB may cover a specific port, while another CB may cover the entire port and/or section of the underwater reservoir.

The CB may include a material that has an affinity for water and/or LDL. The CB may include a material that repels both water and LDL. The CB may include a hydrophobic material that absorbs LDL.

The CB may include a sensor, system, or mechanism for determining whether there is an LDL leak or whether LDL is being trapped by the CB. For example, the sensor may include measuring buoyancy acting on the CB. As LDL is released and floats within the CB, the buoyancy acting on the CB increases, which may be measured by one or more sensors. For example, the sensor or indicator may include a hydrophobic material that absorbs LDL. When LDL contacts the hydrophobic material, the LDL may be absorbed, which may trigger the sensor and/or provide an indication that an LDL leak or accidental release has occurred. For example, the sensor may include spectroscopy, which may provide an indication of the presence of a new liquid other than seawater, such as LDL. For example, the sensor may include a float that is less dense than water but greater in density than LDL. If a sufficient amount of LDL leaks and collects within the CB, the float may begin to sink into the LDL layer that may form. Other sensor mechanisms may include, but are not limited to, conductivity, spectroscopy, spectroscopic measurements, visible color, absorbance, viscosity, pH, solubility, polarity, dielectric constant, or combinations thereof.

Systems may be employed to notify a system operator of the occurrence of an LDL release. Passive and/or active systems may be employed to correct the problem, shut down the system, undergo predefined procedures, or undergo new procedures, or combinations thereof, autonomously, semi-autonomously, or in the presence of a human system operator, or combinations thereof.

Rigid Tank with Interconnected Water Reservoir An exemplary embodiment or configuration may include a rigid tank having an internal swim bladder tank for storing an LDL. The remaining storage volume not occupied by the LDL swim bladder tank may be occupied by water. The water may be interconnected to or may include the surrounding or adjacent ocean. The water may include water from an interconnection to a water reservoir. The reservoir may include a surface water reservoir or a submerged reservoir. The submerged water reservoir may include a tank containing water interconnected to the rigid tank via a pipe. The water reservoir may have a pressure similar to or in equilibrium with the hydrostatic pressure of the ocean.

The following are some characteristics and attributes of exemplary embodiments:
The LDL port in the rigid tank and/or the LDL bladder in the rigid tank may be located in the upper portion of the rigid tank and/or away from the water port.
The water port may be located at the bottom or bottom portion of the rigid tank and/or away from the LDL and/or LDL port.
The water tank may contain fresh water or deionized water if desired, which may be advantageous to prevent corrosion on the inside of the submersible rigid tank.
In the event of a break or rupture of one or all of the inflatable/swim bladder containment devices, the LDL will remain within the rigid tank. The LDL can be safely removed through the LDL port, which may involve the same procedure typically employed for electrical discharge/power generation in the present invention.
Because the LDL port is near the top of the rigid tank and/or the LDL is stored near the top of the tank, the LDL may rise to the top of the rigid tank, which may prevent the LDL from leaking and/or spilling into surrounding bodies of water, or may ensure that the LDL is contained within the system, or may ensure that the LDL is salvageable to the system.
If LDL were to mix with water inside the underwater rigid tank, LDL hydrates could form, which may be significantly denser than LDL. If the underwater tank is filled with LDL, the underwater reservoir could be designed to ensure that the rigid tank water port is blocked by LDL hydrates, preventing LDL from exiting the water port. Such designs could include, but are not limited to, filters or screens within the port that can intentionally block or collect solids if LDL hydrates form.
- When LDL hydrates form, they may sink to the bottom of the tank or float at the interface between the water and the LDL.
In the event of a leak or rupture or detection of hydrate formation, one or more valves may close. For example, a water pipe or water port may have a valve that closes. Similarly, an LDL port or LDL pipe may have a valve that closes.
This embodiment has multiple redundancies. This embodiment may allow the LDL to remain contained within a rigid structural object or rigid tank, which may ensure that if one or more swim bladders or barriers fail, rupture, or break, the LDL will not be released into the surrounding ocean and/or that the LDL is salvageable and recoverable and/or that the process is functional. Additionally, this embodiment may allow the interior of the rigid tank to come into contact with water that has less corrosive species than seawater.

Floating bladder tank:
The present invention may relate to a gravity energy storage system involving the displacement of water with a low density liquid, where a submersible storage tank floats above the seabed. The floating submersible storage tank may be buoyant due to the floating submersible storage having a lower density or a lower average density than the surrounding seawater.

Illustrative exemplary embodiments:
Low Density Liquid-Water Reservoir with a Physical Barrier or Separation Between the Low Density Liquid and the Water Exemplary Embodiments 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be located at the higher elevation and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located at a lower elevation and configured to store water and a fluid having a density lower than water;
a third storage reservoir configured to store water; and
A pump and
a generator;
the pump, the generator, and the first, second, and third reservoirs are operatively connected to store electricity by pumping a low-density fluid in the first storage reservoir into the second storage reservoir, thereby displacing water within the second storage reservoir into the third reservoir;

A system in which water in a third reservoir generates or discharges electricity by allowing a low-density fluid in a second storage reservoir to displace into the first storage reservoir.

Exemplary Embodiment 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;

A system in which the second storage reservoir is configured to store water and a low-density liquid.

Exemplary Embodiment 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;
The system wherein the second storage reservoir is a rigid tank configured to store water and low density liquids.

Illustrative Exemplary Embodiments 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a low density liquid;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low density liquid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low density liquid in the second storage reservoir to return to the first storage reservoir;

The system wherein the second storage reservoir is configured to store water and a low density liquid, the low density liquid having a density less than the density of liquid water.
Exemplary Sub-Embodiment 2. The system of exemplary embodiment 1, wherein the second storage reservoir comprises a rigid tank.
3. The system of Exemplary Embodiment 1, wherein the lower density liquid is located above the water inside the second reservoir.
4. The system of Exemplary Embodiment 1, wherein the less dense liquid floats above the water inside the second reservoir.
5. The system of exemplary embodiment 1, wherein the system further comprises a hydraulic fluid in the pump, the hydraulic fluid being the same as the low density liquid.
6. The system of Exemplary Embodiment 1, wherein the pump, the generator, and the first and second reservoirs are operably connected by a pipe.
7. The system of Exemplary Embodiment 6, wherein a low-density liquid is transferred between the first reservoir and the second reservoir using the pipe.
8. The system of exemplary embodiment 1, further comprising a physical barrier in the second reservoir to separate the low density liquid from the water in the second reservoir.
9. The system of exemplary embodiment 8, wherein the second reservoir is configured to prevent leakage of the low density liquid in the event of damage to the physical barrier.
10. The system of Exemplary Embodiment 8, wherein the physical barrier comprises a material having an average density less than that of liquid water and greater than that of a low-density liquid at a temperature greater than 3° C. and less than 50° C. at the same hydrostatic pressure.
11. The system of exemplary embodiment 8, wherein at least a portion of the physical barrier is located above the water and at least a portion of the physical barrier is located below the less dense liquid.
12. The system of exemplary embodiment 8, wherein the physical barrier comprises a liquid.
13. The system of exemplary embodiment 8, wherein the physical barrier comprises a solid.
14. The system of Exemplary Embodiment 8, wherein the physical barrier is configured to prevent (1) substantial dissolution of the low density liquid in water, (2) substantial dissolution of water in the low density liquid, (3) formation of substantial low density liquid-water hydrates, or a combination thereof.
15. The system of Exemplary Embodiment 1, further comprising a barrier positioned over at least a portion of the second reservoir.
16. The system of Exemplary Embodiment 15, wherein the barrier is configured to contain a low density liquid, a low density liquid-water composition, or a combination thereof, in the event of a failure of the second reservoir.
17. The system of Exemplary Embodiment 15, wherein the barrier comprises an instrument for detecting low density liquids.
18. The system of exemplary embodiment 15, wherein the barrier is configured to funnel low density liquids to facilitate recovery.
19. The system of exemplary embodiment 15, wherein the barrier is suspended above at least a portion of the second reservoir.
20. The system of exemplary embodiment 19, wherein the barrier is suspended by a tether connected to a mooring, an anchor, the seabed, or a combination thereof.
21. The system of exemplary embodiment 15, wherein the barrier is buoyant, connected to a buoyant floating object, or a combination thereof.
22. The system of Exemplary Embodiment 1, wherein the second reservoir is buoyant, connected to a buoyant floating body, or a combination thereof.
23. The system of exemplary embodiment 22, wherein the second reservoir is floating or suspended above the seabed.
24. The system of exemplary embodiment 23, wherein the second reservoir is suspended by a tether connected to a mooring, an anchor, the seabed, or a combination thereof.
25. The system of Exemplary Embodiment 1, further comprising a third reservoir, the third reservoir operably connected to transfer water displaced by the lower density liquid during charging from the second reservoir to the third reservoir.
26. The system of exemplary embodiment 25, wherein the water has a density that is within ±5% of the density of seawater at a temperature above 3° C. and below 40° C. under the same hydrostatic pressure.
27. The system of exemplary embodiment 25, wherein at least a portion of the third reservoir comprises seawater.
28. The system of exemplary embodiment 25, wherein at least a portion of the third reservoir contains treated seawater.
29. The system of exemplary embodiment 26, wherein at least a portion of the third reservoir has a pressure within ±10 atmospheres of the hydrostatic pressure of seawater at the depth of the second reservoir.
Exemplary Sub-Embodiment 2. The system of embodiment 1, wherein a fluid having a density less than water is located above the water inside the second reservoir. 3. The system of embodiment 1, wherein a fluid having a density less than water floats above the water inside the second reservoir. 4. The system of embodiment 1, wherein a hydraulic or working fluid in the pump and generator comprises a fluid having a density less than water. 5. The system of embodiment 4, wherein the pump, generator, and first and second reservoirs are operably connected by a pipe. 6. The system of embodiment 5, wherein a fluid having a density less than water is transferred between the first reservoir and the second reservoir using the pipe. 7. The system of embodiment 1, wherein a fluid having a density less than water and the water in the second reservoir are separated by a physical barrier. 8. The system of embodiment 7, wherein the physical barrier is floating. 9. The system of embodiment 7, wherein the physical barrier has an average density less than water and greater than that of the fluid having a density less than water. 11. The system of embodiment 7, wherein at least a portion of the physical barrier is located above water and below a fluid having a density lower than water. 12. The system of embodiment 7, wherein the physical barrier comprises a liquid. 13. The system of embodiment 7, wherein the physical barrier comprises a solid. 14. The system of embodiment 7, wherein the physical barrier prevents dissolution of water into a fluid having a density lower than water in water, dissolution of water into a fluid having a density lower than water, formation of a fluid-water hydrate having a density lower than water, or a combination thereof. 15. The system of embodiment 1, wherein a containment cover or barrier is located above one or more portions of the second reservoir. 16. The system of embodiment 14, wherein the containment cover or barrier captures or recovers a fluid having a density lower than water or a derivative of this fluid in the event of a leak, breach, or accidental release. 17. The system of embodiment 14, wherein the containment cover or barrier includes a system for detecting capture of a fluid having a density lower than water. 18. The system of embodiment 14, wherein the containment cover or barrier is configured to funnel a fluid having a density lower than water or a derivative of this fluid to facilitate capture or recovery. 19. The system of embodiment 14, wherein the containment cover or barrier is suspended above at least a portion of the second reservoir, the third reservoir, or both. 20. The system of embodiment 18, wherein the suspension is by a tether connected to a mooring, or an anchor, or the seabed, or a combination thereof. 21. The system of embodiment 14, wherein the containment cover or barrier is buoyant, or connected to a buoyant floating object, or a combination thereof. 22. The system of embodiment 1, wherein the second reservoir is buoyant, or connected to a buoyant floating object, or a combination thereof. 23. The system of embodiment 21, wherein the second reservoir floats above the seabed. 24. The system of embodiment 22, wherein the second reservoir is suspended above the seabed. 25. The system of embodiment 23, wherein the suspension is by a tether connected to a mooring, or an anchor, or the seabed, or a combination thereof. 26. The system of embodiment 1, wherein the third reservoir contains a liquid having the same density as seawater. 26. The system of embodiment 1, wherein the third reservoir contains a liquid having a density that is within ±0.5%, or within ±1%, or within ±2%, or within ±3%, or within ±4%, or within ±5%, or within ±6%, or within ±7%, or within ±8%, or within ±9%, or within ±10% of the density of seawater. 27. The system of embodiment 1, wherein the third reservoir comprises a liquid having a density that is within ±0.5%, or within ±1%, or within ±2%, or within ±3%, or within ±4%, or within ±5%, or within ±6%, or within ±7%, or within ±8%, or within ±9%, or within ±10% of the density of seawater, and the liquid may be a liquid at a temperature above 3°C and below 40°C at the same hydrostatic pressure. 28. The system of embodiment 1, wherein the third reservoir comprises at least a portion of seawater. 29. The system of embodiment 26, wherein the liquid is less corrosive than seawater, or less likely to form biofouling or scaling than seawater, or a combination thereof. 30. The system of embodiment 26, wherein the liquid comprises treated seawater. 31. The system of embodiment 26, wherein at least a portion of the liquid is at a pressure that has the hydrostatic pressure of 10 atmospheres of seawater near the second reservoir.

1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be located at the higher elevation and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located at a lower elevation;
a third storage reservoir configured to store water; and
A pump and
a generator;
The pump, the generator, and the first, second, and third reservoirs store electricity by pumping a low-density fluid in the first storage reservoir into the second storage reservoir, thereby transferring water within the second storage reservoir into the third storage reservoir;
the water in the third reservoir is operably connected to generate or discharge electricity by allowing the lower density fluid in the second storage reservoir to transfer to the first storage reservoir;
The second storage reservoir is configured to store water and a low density liquid.

1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be located at the higher elevation and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located at a lower elevation and configured to store low density liquid and water;
a third storage reservoir configured to store water; and
A pump and
a generator;
The pump, the generator, and the first, second, and third reservoirs store electricity by pumping a low-density fluid in the first storage reservoir into the second storage reservoir, thereby transferring water within the second storage reservoir into the third storage reservoir;
A system wherein the water in the third reservoir is operably connected to generate or discharge electricity by allowing a lower density fluid in the second storage reservoir to displace into the first storage reservoir.

1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;

A system in which the second storage reservoir is configured to store water and a low-density liquid.

1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;
the second storage reservoir is configured to store water and a low density liquid;
Low density liquids include hydraulic fluids in pumps and generators;
2. System 2, wherein the low-density liquid is located above the water inside the second storage reservoir. 3. System 3, wherein the low-density liquid is located above the water inside the second reservoir. 4. System 4, wherein the low-density liquid floats above the water inside the second reservoir. 5. System 4, wherein the hydraulic or working fluid in the pump and generator comprises a low-density liquid. 6. System 5, wherein the pump, generator, and first and second reservoirs are operably connected by a pipe. 7. System 5, wherein the low-density liquid is transferred between the first reservoir and the second reservoir using the pipe. 8. System 1, wherein the water and the low-density liquid in the second reservoir are separated by a physical barrier. 9. System 7, wherein the physical barrier is floating. 10. System 7, wherein the physical barrier has an average density less than that of water and greater than that of the low-density liquid. 11. The system of embodiment 7, wherein the physical barrier is located above water and below the low-density liquid. 12. The system of embodiment 7, wherein the physical barrier comprises a liquid. 13. The system of embodiment 1, wherein the physical barrier prevents dissolution of the low-density liquid in water, dissolution of water in the low-density liquid, formation of low-density liquid-water hydrates, or a combination thereof. 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;
the second storage reservoir is configured to store water and a low density liquid;
The water and the low density liquid are separated by a physical barrier.
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;
the second storage reservoir is configured to store water and a low density liquid;
The water and the low density liquid are separated by a floating physical barrier. System 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;
The water and the low density liquid in the second storage reservoir are in direct contact at a water-low density liquid liquid-liquid interface.
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the low-density fluid in the first storage reservoir into the second storage reservoir to displace water within the second storage reservoir, and to generate or discharge electricity by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir;
The second storage reservoir is a system containment cover or containment barrier ("CB" or "CCB") that includes a low density liquid-water liquid-liquid interface:
Floating/buoyancy tanks:
1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to be near the surface of the body of water and configured to store a fluid having a density lower than water;
a second storage reservoir configured to be located below the surface of the body of water and configured to store a fluid having a density lower than water;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping a low density liquid in the first storage reservoir into the second storage reservoir to displace water adjacent the second storage reservoir, and to generate electricity by allowing the low density fluid in the second storage reservoir to return to the first storage reservoir;
Water and fluids having a density lower than that of water are both in liquid form,
The system wherein the second storage reservoir is floating.

2. The system of embodiment 1, wherein the floating object is moored below the ocean. 3. The system of embodiment 1, wherein the floating object is suspended above the ocean below. Condensable gas in the surface water tank:
Exemplary Interconnected Rigid Tank with Pressure Equalization 1. An energy storage system comprising:
It includes surface tanks, subsea tanks, pipes, pumps, and generators.
storing electricity by displacing water in said subsea tank using a low density liquid;
1. An energy storage system that generates electricity by allowing water to displace a low-density liquid in a subsea tank, comprising: a surface tank, a subsea tank, pipes, a pump, and a generator; storing energy by pumping a low-density liquid into the subsea tank to displace the water in the subsea tank; 2. The pressure in the subsea tank is in equilibrium with the hydrostatic pressure of the surrounding water; 3. The subsea tank includes a water-low-density liquid interface; 4. The water inside the subsea tank is in direct contact with the low-density liquid; 5. The water inside the subsea tank is separated from the low-density liquid by a floating barrier; 1. a rigid tank having a low-density liquid and water, configured to store the LDL and water; and a float bladder tank configured to store the water; 2. The float bladder tank is located at the same elevation as the rigid tank; 3. The swim bladder tank is located at a different elevation than the rigid tank. Note: The location of the swim bladder tank relative to the rigid tank and the elevation of the swim bladder tank can be at virtually any elevation below the body of water, since the water inside the tank has the same density as the water in the surrounding body of water.

Notes: Note: The float bladder tank may be submerged as a fully collapsed tank and connected to the rigid tank, for example, via a pipe. The rigid tank is submerged by flooding the rigid tank. As the water in the rigid tank is displaced by the LDL, the displaced water fills the float bladder tank. The float bladder tank may be floating or rest on the seabed.
● Note: The energy storage system may be charged when in a partially charged state.
●Note: The energy storage system can be charged when in a fully discharged state.
• Note: An energy storage system can be discharged when it is in a partially charged or partially discharged state.
●Note: The energy storage system can be discharged when in a fully charged state.
Note: It may be desirable for the pressure of water being transferred to or from the surface water tank ("internal water") to be equal to the gravitational hydrostatic pressure of the water surrounding the pipe ("external water"). Alternatively or additionally, the pressure of the internal water may be less than or greater than the external water, depending on the pressure tolerances of the subsea tank, or one or more components or parts in contact with the internal water, or a combination thereof. An exemplary method for ensuring that the pressures of the internal and external water are similar is to place a valve or pressure regulator between the surface water tank(s) and the subsea tank(s). For example, the valve or pressure regulator may be attached to or inside a pipeline connecting the surface water tank(s) and the subsea tank(s).
Note: It may be desirable for the pressure within the second reservoir to be the same as the hydrostatic pressure surrounding or adjacent to the second reservoir. The pressure within the second reservoir may differ from the hydrostatic pressure surrounding or adjacent to the second reservoir by less than 10 PSI, or less than 15 PSI, or less than 20 PSI, or less than 1 atmosphere, or less than 2 atmospheres, or less than 3 atmospheres, or less than 4 atmospheres, or less than 5 atmospheres, or less than 6 atmospheres, or less than 7 atmospheres, or less than 8 atmospheres, or less than 9 atmospheres, or less than 10 atmospheres, or less than 11 atmospheres, or less than 12 atmospheres, or less than 15 atmospheres, or less than 20 atmospheres, or less than 30 atmospheres, or less than 40 atmospheres, or less than 50 atmospheres, or less than 60 atmospheres, or less than 70 atmospheres, or less than 80 atmospheres, or less than 90 atmospheres, or less than 100 atmospheres.
Note: Within the underwater storage reservoir, a low-density liquid or a high-density liquid may be enclosed in a bladder tank within the rigid submersible tank. For example, water may be enclosed within a bladder tank within the rigid submersible tank, while a low-density liquid may float above the bladder tank. For example, a low-density liquid may be enclosed within a bladder tank within the rigid submersible tank, while water may sink or reside below the bladder tank. The water within the rigid submersible tank may contain, be fluidly connected to, or be in hydrostatic equilibrium with adjacent or surrounding seawater.
Note: In some embodiments, the separator or physical barrier may comprise a layer of solid hydrate of a low-density liquid. The solid hydrate may have a density greater than that of the low-density liquid and less than that of water. The solid hydrate layer may inhibit further mixing or formation of hydrates.
Note: The pump/generator in the present invention may include a hydraulic power recovery turbine (HPRT). HPRTs may currently be employed as pump/generators in industries including, but not limited to, hydrocarbon transportation, processing, and refining. HPRTs are known to be more energy efficient using lower viscosity working fluids. The present invention may employ ultra-low viscosity liquids, such as liquid propane, liquid butane, or LPG, which may have viscosities substantially lower than water, allowing the HPRT to have reciprocating efficiencies that exceed those associated with water.
Note: A surface water tank or a third reservoir configured to store water on the surface or at a higher elevation than the second reservoir may include a rigid tank or a swim bladder tank or a combination thereof. For example, a third reservoir configured to store water and/or located near, on, or above the ocean surface may include a swim bladder tank, which may be at a pressure equilibrated with the pressure outside or adjacent to the third reservoir.
Note: Fluid properties affect HPRT efficiency in the same way as centrifugal pumps, with more viscous fluids reducing efficiency. The fact that propane and some other exemplary LDLs have lower viscosities than water means that some LDLs may have greater energy/round trip efficiency in HPRT than water.
Note: HPRTs can operate most efficiently within a certain range of volume utilization (flow rate) and pressure head. HPRTs are generally most efficient closer to their maximum volume utilization and pressure head. For example, when employing HPRTs, there are several ways to ensure near maximum pump/generator efficiency, which may include, but are not limited to, one or more or a combination of the following:
○ Multiple smaller HPRTs may be employed, with those operating at maximum or near maximum efficiency and/or maximum or near maximum capacity (highest efficiency is near the highest or highest capacity). If the demand for storage changes, the number and/or capacity of HPRTs paralleled or "turned on" for storage may be adjusted. If the demand for generation changes, the number and/or capacity of HPRTs paralleled or "turned on" for generation may be adjusted.
If the energy that needs to be stored is less than the capacity of the HPRT, there are several options:
Designing a system with additional lower capacity HPRTs (e.g., two or three or four or five or more HPRTs, each a fraction of the total capacity of each of the larger HPRTs), each of which can operate near maximum efficiency and/or capacity during operation.
For a small number of lower capacity HPRTs or charging variants that are a fraction of the capacity of the lowest capacity HPRT, a flywheel or capacitor or lithium ion battery or other standard energy storage device may be employed to meet this relatively smaller storage need. The "other standard energy storage device" may be discharged to charge liquid displacement energy storage technology by powering a pump (such as an HPRT) when desired, or may directly supply electricity to the grid or an application or a combination thereof.
Note: Floating subsea tanks may be rigid or collapsible/inflatable or a combination thereof. Floating subsea tanks may be suspended above the seabed by tethers or anchors or attachment lines or other mechanisms.
Note: In the event of a subsea landslide or other catastrophic event, the floating subsea tank may be designed to disconnect from the floating subsea tank's tether(s) and/or pipeline(s) as part of an emergency disconnection system that may allow the subsea tank to float to the surface, thereby allowing the subsea tank to avoid rupture or other catastrophic failure that may otherwise occur due to debris from the underwater landslide or other catastrophic event.
• Note: Floating subsea tanks may make it easier to implement tanks, for example, where the seabed is uneven or steep or otherwise difficult to place the tank on the seabed surface.
Note: The installation of floating submersible tanks may involve, for example:
○1) Sinking the completely collapsed float tank to the seabed ○2) Attaching the float tank tether and/or anchor to the seabed and/or mooring or sinker. Attaching the LDL pipeline to the float tank.
o 3) Using the LDL pipeline to add LDL to the float tank, resulting in the float tank becoming buoyant. The float tank may be floating above the seabed and/or may be suspended above the seabed due to one or more or a combination of the following, but not limited to: tethers or anchors.
Note: The LDL pipeline may be placed or sunk on the seabed while containing or filled with LDL. The LDL pipeline may be weighted or attached to anchors or weights or a combination thereof, for example to prevent the LDL pipeline from floating to the surface.
Note: The LDL pipeline may be located or sunk on the seabed. The LDL pipeline may be flooded with seawater during the sunk process. Once on the seabed or in place, the water in the LDL pipeline may be displaced with LDL by pumping the LDL into the pipeline and/or by allowing the displaced seawater to exit the pipeline. The displaced seawater may exit the pipeline and, for example, into the surrounding ocean or into a separate containment tank. The separate containment tank, if employed, may be temporary or permanent. When the pipeline is sufficiently filled with LDL, one or more valves may be closed, for example, to prevent the escape of LDL into the surrounding ocean and/or to prevent seawater from entering the LDL pipeline. Alternatively or additionally, for example, when the pipeline is sufficiently filled with LDL, the pipeline may be attached to a submersible tank or a floating submersible tank. The LDL pipeline may be weighted or attached to anchors or weights or a combination thereof, for example, to prevent the LDL pipeline from floating up on the sea surface.
• Note: The minimum volume or amount of LDL in a floating submersible tank may include the minimum amount of LDL required to ensure that the floating submersible tank is buoyant.
Note: One or more or a combination of the components of the present invention may be located underground or partially underground. For example, a first storage reservoir, which may comprise a land or underwater rigid tank, may be located underground. For example, one or more or portions or combinations of pipes, or valves, or pumps, or generators may be located underground or partially underground. For example, a second reservoir, which may comprise a submerged rigid tank, may be located underground.
Note: Locating one or more tanks or other components underground may hide the tank from public view, thereby increasing safety and/or reducing the tank's potential eyesore. Locating one or more tanks or other components underground may increase the tank's useful life. Locating one or more tanks or other components underground may increase the system's resilience to severe weather, natural disasters, or man-made risks.
Note: An "8" may be buoyant or neutrally buoyant, or may be denser than the surrounding waters, or a combination thereof. For example, the density of a subsea tank may vary depending on the volume or amount of liquid stored in the tank.
Note: LPG, propane, butane, or other liquefied gases that may be employed as low density liquids may be semi-refrigerated or partially refrigerated or refrigerated in surface storage tanks. By employing semi-refrigerated storage, the surface storage tank, floating storage tank, or first reservoir may be able to have a greater conveying capacity, or may have a lower capital cost, or a combination thereof.
• Note: The low density liquid may be stored at ambient temperature and/or at a temperature that matches or is close to the temperature of the surrounding water in the second storage reservoir, and/or may be stored under pressure.
Note: Due to butane's higher boiling point and lower vapor pressure than propane, and the possibility of constructing larger, less expensive pressure vessels, it may be desirable to employ butane or butane-propane mixtures or combinations thereof.
Note: A refrigerated or semi-refrigerated or partially refrigerated or cooled container may contain temperatures up to one or more or combinations of the following: 50°C, or 40°C, or 30°C, or 20°C, or 10°C, or 5°C, or 0°C, or -10°C, or -20°C, or -30°C, or -40°C, or -50°C.
Note: A configuration including a subsea rigid tank configured to store water and LDL and a separate or interconnected float bladder tank configured to store water may be advantageous due to, for example, but not limited to, one or more or a combination of the following:
o No need for a water pipeline to the surface or a tank above the surface o Underwater swim bladder tank stores primarily water instead of LDL.
- A swim bladder tank may have a longer service life or lifetime in water compared to an LDL - A swim bladder tank configured for water may be less expensive or may include less expensive materials than a swim bladder tank configured for an LDL - In the event of a rupture or catastrophic failure of the swim bladder tank, a valve on the pipe connecting the swim bladder tank to the rigid tank may close, which may include an emergency shut-off procedure. If the valve fails to close, the LDL within the rigid tank will naturally remain within the rigid tank; for example, the LDL may remain within the rigid tank due to the location or configuration of the pipe connecting the rigid tank to the swim bladder tank. Advantageously, in the event of a catastrophic failure or rupture of the swim bladder tank, the pressure inside the rigid tank is likely to remain constant, and the composition of the water inside the rigid tank may remain constant.
A swim bladder tank allows a rigid submersible tank to be subjected to a pressure inside the tank that is the same as the pressure outside the tank, or the surrounding hydrostatic pressure.
*Note: Some embodiments may include a floating separator that separates the water from the LDL in the submersible tank.
Note: The round trip electrical efficiency can be 30% or more, or 40% or more, or 50% or more, or 60% or more, or 70% or more, or 80% or more, or 90% or more.
• Note: The present invention may include multiple pipelines, surface tanks, subsea tanks, HPRT units or pump-generator units, valves, other components, or combinations thereof.
Note: A rigid tank or rigid containment structure may enclose at least a portion or an upper portion of an internal sub-reservoir or sub-tank, which may include a flexible structure or an inflatable or collapsible structure, such as a floatation bladder. The rigid structure may include a steel tank or a composite tank or a combination thereof. In the event of a breach or leak of the internal sub-tank, the leaked low-density liquid may remain inside the rigid tank or rigid containment structure, preventing exposure of the low-density liquid to the surrounding environment. Alternatively or additionally, the internal sub-tank may store water, while the low-density liquid may be stored within the rigid tank. Alternatively or additionally, the low-density liquid and water are stored in an internal sub-tank inside the rigid tank or rigid containment structure. The "rigid containment structure" may also or alternatively be a flexible structure.
Note: Dashed lines in the diagram may indicate labeling lines. Dashed lines or dashed boxes may indicate labels only. Dashed lines or dashed boxes may not themselves be process elements.
* Note: The boxes with dashed lines in the figures and the dashed lines in the figures are labels only and are not themselves components of the figures.
●Note: Numbers may not be to scale. For example, the depth of the second reservoir may be greater than or equal to one or more or combinations of the following: 200 meters, or 300 meters, or 400 meters, or 500 meters, or 600 meters, or 700 meters, or 800 meters, or 900 meters, or 1,000 meters, or 1,100 meters, or 1,200 meters, or 1,300 meters, or 1,400 meters, or 1,500 meters, or 1,600 meters, or 1,700 meters, or 1,800 meters, or 1,900 meters, or 2,000 meters, or 2,100 meters, or 2,200 meters, or 2,300 meters, or 2,400 meters, or 2,500 meters, or 2,600 meters, or 2,700 meters, or 2,800 meters, or 2,900, or 3,000 meters. Note:
The water reservoir may contain a liquid that is the same density as, and in pressure equilibrium with, the surrounding or adjacent seawater.
It may be desirable to prevent mixing between the water in the water reservoir and the surrounding seawater. To prevent this mixing, it may be desirable to employ a flexible barrier between the water reservoir and the surrounding seawater, which may be classified as a reservoir boundary layer.
If the reservoir were to break or suffer a catastrophic failure, or were at risk of breaking or catastrophic failure, a valve on the pipe interconnecting the water reservoir with the rigid tank could close, if desired. The valve could prevent the low-density liquid, or other contents of the rigid tank or end-to-end system, from spilling into or contaminating the surrounding ocean. If the valve were to fail to close, the rigid tank and pipe could be configured to allow the low-density liquid to naturally remain within the tank and/or to minimally spill or leak from the rigid tank. For example, the low-density liquid could float above the water in the second reservoir, and the pipe interconnecting the water reservoir with the rigid tank could be located below the liquid-liquid interface of the low-density liquid and the water.
Note: A reservoir may include multiple interconnected reservoirs or tanks or storage vessels, or multiple interconnected process elements, or a combination thereof. For example, a submersible storage reservoir may include multiple interconnected submersible tanks.
Note: The third reservoir may be less corrosive than seawater or may have biofouling-resistant properties while allowing the same hydrostatic pressure as seawater. For example, the third reservoir may include seawater treated with an oxygen scavenger to remove dissolved oxygen and/or prevent corrosion. For example, the third reservoir may include seawater treated with a biocide or a non-corrosive or non-oxidizing biocide. For example, the third reservoir may include an aqueous solution having the same or similar density as seawater, except that it includes a different mixture or salt composition and/or a reagent other than seawater, which may be less corrosive than seawater or have other advantageous properties. For example, the third reservoir may include an aqueous solution having the same or similar density as seawater, except that it includes a reagent that inhibits the formation of low-density liquid-water hydrates. For example, the third reservoir may include deep-sea seawater, which may include a low dissolved oxygen concentration and may be less corrosive than surface seawater.
Note: The separator or flexible tank or bladder inside the rigid tank may be removable or replaceable. This allows the separator or flexible tank or bladder inside the rigid tank to undergo maintenance or be replaced near its end of life or end-of-life.
Note: Low density liquids may include, but are not limited to, one or more or combinations of the following: propane, butane, ethane, pentane, hexane, LPG, gas liquids, oils, or other low density liquids described herein or in the art.
Note: The temperature of ocean water generally ranges from -2°C to 40°C. Deep ocean water is generally around 4°C.
Note: A low density liquid has a density less than that of water over a temperature range of at least 3°C and/or less than 40°C.
Note: If the third reservoir is located underwater, the condensable gas in the head space may ensure that the pressure inside the third reservoir is close to the hydrostatic pressure of the ocean at the same underwater depth, which may be beneficial, for example, if the third reservoir is a rigid tank. The vapor pressure of the condensable head space gas may be adjusted or engineered to ensure that it matches or is close to the hydrostatic pressure of the ocean at the same underwater depth at the expected operating temperature. The expected operating temperature may range from -2°C to 50°C, depending, for example, on the body of water, depth, time of year, surface temperature, microclimate, water temperature surrounding or in contact with one or more components of the system, other conditions, or a combination thereof.
Note: The pipe connection between the submersible tank and the pipe may be designed to allow for safe disconnection and/or reconnection. The submersible tank may be disconnected from the pipe for maintenance, replacement, expansion, or monitoring of the submersible tank, the submersible pipe, other submersible components, or a combination thereof. In some cases, the submersible tank or the pipe, or both, may contain a low-density liquid during disconnection. The submersible tank may be disconnected from the pipe for maintenance or replacement. In some cases, the submersible tank or the pipe, or both, may contain a low-density liquid during disconnection. In some cases, the low-density liquid may be removed from the submersible tank before disconnecting the submersible tank. A safe disconnection may include minimal or no leakage of the low-density liquid. Some embodiments of the present invention may be designed to allow for replacement or maintenance of the submersible tank. Some embodiments of the present invention may be designed to allow for transport of the submersible tank to the surface and/or return of the submersible tank to its original location. Some embodiments of the present invention may allow for the removal, replacement, or maintenance of one or more components or subcomponents of a submersible tank or other underwater component, if desired. Some embodiments of the present invention may allow for the addition of one or more tanks underwater while integrating with existing underwater and/or surface infrastructure. For example, a separator or a flexible tank or bladder inside a rigid tank may be removable or replaceable.
• Removability or replaceability may encompass the ability to remove or replace a component while maintaining operation or with minimal interruption to operation.

Additional notes:
Exemplary Cost Drivers • Larger scale results in lower cost per kWh of energy storage capacity and lower cost per kW of power capacity.
Deeper water depths provide greater energy density and require smaller tank volumes and pipe diameters per kWh and kW of storage capacity. To ensure the project can accommodate pipelaying technology and subsea services, the project may initially employ water depths of 3,000 meters or less. As pipelaying technology and subsea services advance, water depths greater than 3,000 meters may be employed.
● The more hours of energy storage (i.e., the more energy storage capacity relative to power capacity), the lower the cost per kWh ○ Pipe diameter is driven by energy density and the required "power capacity" ○ Tank capacity is driven by energy density and the required "energy storage capacity" ● Distance to power grid and power grid transmission equipment, and/or power grid infrastructure modifications ● Proximity to onshore and offshore EPC assets, and logistics for delivery and installation of equipment and materials Exemplary revenue drivers (maximizing revenue and ROI)
● The price per kWh of electricity in the local electricity market and expected power purchase agreement prices/terms ● The demand for grid services due to the intermittency of renewable energy in the electricity grid ● The solar or wind potential of the location ● The structure of the electricity market and its relationship to the electricity grid and/or local utility ● Economic model: solar plus storage project (PPA) versus grid services

Additional notes:
Propane gas, or LPG, or refrigerant, or a boiling point liquid at about room temperature, or a liquid condensable at room temperature, or a combination thereof, in the headspace of a rigid water tank on the surface.

Exemplary purposes for the condensable gas in the water tank are: 1) to allow the tank to remain rigid without creating a vacuum when the water leaves, and 2) to allow the water to not release any propane into the air. Due to the high pressure in the water which allows for some propane solubility, dilute concentrations of propane can exist in the water. This embodiment is closed/not open to the air, so the propane cannot be released into the air.

Note: The head space may be occupied by a hydrocarbon refrigerant that boils near room temperature; for example, a combination of butane and pentane. As the water fills the tank, the refrigerant is compressed and condenses into a liquid (greatly reducing the amount of compression required). The condensed refrigerant forms a floating layer on top of the water. As the water exits, the refrigerant boils on top of the water.

Note: Once the water has filled the tank, propane or butane gas can be removed from the tank headspace to allow the water to occupy space without compressing the propane. Propane gas can be removed by compression into a separate tank.

Note: Gas within the water tank or in the headspace of a water tank that is compressed as the water enters the tank. If desired, the gas may be at least partially condensed.

Flywheel compensates for start-up pauses

It may be desirable for the near-room-temperature boiling liquid to be non-flammable. The near-room-temperature boiling liquid may include a refrigerant or combination of refrigerants. For example, the near-room-temperature boiling liquid may include a fluorinated hydrocarbon.

Overview: This invention can store electricity by replacing water with low density liquid (LDL). Electricity can be stored in the form of gravitational potential energy from the gravitational hydrostatic pressure difference between the LDL and the water.
Step-by-step overview:
1. Charge: The valve at the surface is opened (5). The LDL in the rigid LDL surface tank (1) is pumped (4) through a pipe (3) into the submerged rigid tank (2). As the LDL fills the submerged rigid tank, it displaces the water inside the tank. The displaced water travels through a water pipe (7) to the surface water tank (6). When charging is complete, the valve at the surface (5) is closed.
2. Power Generation: The surface valve (5) is opened. Water inside the surface water tank (6) travels through the water pipe (7) and naturally displaces the LDL inside the submerged rigid tank (2). The displaced LDL travels through the LDL pipe (3) and enters the generator (4) at the surface to generate electricity and allow the LDL to flow into the rigid LDL surface tank. When charging is complete, the surface valve (5) is closed.
Exemplary Definitions Auxiliary Thermal Storage: Auxiliary thermal storage may include a process or system for storing and/or recovering thermal energy from a low-density liquid, a high-density liquid, or a combination thereof. Recovered thermal energy may include, for example, thermal energy held at the "cold" temperature of a refrigerated or cooled low-density liquid. Auxiliary thermal storage may be required to enable efficient operation in systems having various system components operating at different temperatures. Auxiliary thermal storage may be required to enable efficient operation in systems having a cooled or refrigerated high-side elevation low-density liquid reservoir that may operate at temperatures below the temperature of surface seawater or ground or air or a combination thereof.
• Parasitic energy: Energy consumption that reduces the performance or efficiency or both of a system.
Non-parasitic energy: Energy consumption that has a non-negligible impact, no impact, a positive impact, or a combination thereof on the performance or efficiency or both of a system.
Reservoir or Tank: A reservoir or tank may include an apparatus or device for storing materials such as low-density liquids or high-density liquids or both. Reservoir or tank may be used interchangeably. It is important to note that in some cases, reservoir may be used broadly to describe the general storage of fluids within an area, or zone, or depth, or range, or combinations thereof. It is important to note that in some cases, tank may be used broadly to describe the general storage of fluids within an area, or zone, or depth, or range, or combinations thereof. It is important to note that in some cases, tank may be used narrowly to describe an individual storage unit for the storage of one or more fluids within an area, or zone, or depth, or range, or combinations thereof. It is important to note that in some cases, reservoir may be used narrowly to describe an individual storage unit for the storage of one or more fluids within an area, or zone, or depth, or range, or combinations thereof.
• High-side elevation reservoir: A liquid reservoir located at a higher elevation than the elevation of a lower-side elevation reservoir within the same storage system.
• Low-elevation reservoir: A liquid reservoir located at an elevation lower than that of a higher-elevation reservoir within the same storage system.
Low density liquid or lower density liquid or LDL: A working fluid that has a lower density than a dense liquid. A working fluid that has a lower density than the different working fluid with which it exchanges pressure.
High density liquid or higher density liquid or HDL or higher density liquid: A working fluid that has a higher density than a low density liquid. A working fluid that has a density in g/mL greater than a low density liquid. A working fluid that has a higher density than the different working fluid it is exchanging pressure with.
Cooling or "refrigerating": The removal of heat from a fluid or system or both, for example using heat transfer, heat exchange, a refrigeration cycle, radiative cooling, or other heat removal, or a combination thereof.
Partially refrigerated: A reservoir and/or working fluid that is cooled to a temperature below at least some ambient temperature. A reservoir and/or working fluid that is cooled to a temperature below at least some ambient temperature, but the working fluid may require pressure above atmospheric pressure to be stored in the liquid phase.
• Working fluid: A liquid or gas or both employed in a system to store potential energy or heat or both.
- One or more heat storage media or liquids: materials that store or transfer heat, or a combination thereof.
One or more "cold" thermal storage media: materials that are cooler than one or more "warm" thermal storage media. The one or more "cold" thermal storage media may be at or near the temperature of a refrigerated or cooled low-density liquid, or at or near the temperature of a low-density liquid in a refrigerated or refrigerated or semi-refrigerated upper elevation low-density liquid reservoir. For example, the one or more "cold" thermal storage media may be the temperature of a refrigerated or cooled low-density liquid plus or minus heat exchanger losses and other potential losses.
One or more "warm" thermal storage media: materials that are warmer than one or more "cold" thermal storage media. The one or more "warm" thermal storage media may be at a temperature above the temperature of a refrigerated or cooled low-density liquid, or may be at a temperature above the temperature of a low-density liquid in a cooled or refrigerated or semi-refrigerated high-side elevation low-density liquid reservoir.
"Cold": A temperature of a medium that is below the temperature of the same medium at a "warm" temperature. In some embodiments, a "cold" temperature can be a temperature below ambient air temperature, or below ambient water temperature, or below ambient soil temperature, or a combination thereof. In some embodiments, a "cold" temperature can be close to or at or below the temperature or temperature range of a cooled, refrigerated, or semi-refrigerated reservoir of low-density liquid.
"Warm": The temperature of a medium that is above the temperature of the same medium at a "warm" temperature. In some embodiments, a "warm" temperature can be a temperature above ambient air temperature, or ambient water temperature, or ambient soil temperature, or a combination thereof. In some embodiments, a "warm" temperature can be near or at the temperature or temperature range of a cooled, refrigerated, or semi-refrigerated reservoir of low-density liquid.
"Cold" low density liquid: A low density liquid that is at a temperature below the temperature of a "warm" low density liquid. In some embodiments, a "cold" low density liquid can be a low density liquid temperature where the low density liquid has a vapor pressure close to or below the pressure limit or pressure rating of a cooled or refrigerated or semi-refrigerated high-side low density liquid reservoir.
"Warm" low density liquid: A low density liquid at a temperature above that of a "cold" low density liquid. In some embodiments, a "warm" low density liquid may be a temperature of a low density liquid at which the low density liquid has a vapor pressure that is close to or above the pressure limit or pressure rating of a cooled or refrigerated or semi-refrigerated high-side low density liquid reservoir.
Thermal Management: A process for removing, adding, or otherwise transferring heat. A process that may monitor and/or adjust the temperature of one or more or a combination of fluids or components and may automatically, monitor, or both, adjust, or add or remove heat, or a combination thereof.
Low boiling point, low density liquid, or high vapor pressure, low density liquid: a liquid that has a vapor pressure of about 1 atmosphere or greater at potential ambient temperature conditions. In some embodiments, a low boiling point liquid can include a liquid that has a vapor pressure of about 1 atmosphere or greater at temperatures below 60°C, or below 50°C, or below 40°C, or a combination thereof. In some embodiments, a low boiling point liquid can include a liquid that has a vapor pressure of about 1 atmosphere or greater at temperatures below 100°C, or below 90°C, or below 80°C, or below 70°C, or below 60°C, or below 50°C, or below 40°C, or below 30°C, or a combination thereof.
Increased density denser liquid: in some embodiments, a liquid having a density greater than that of water, or seawater, or the water of a body of water, or a combination thereof. In some embodiments, a solution comprising a solvent and a reagent having a density greater than that of the solvent.
Insoluble or limited solubility: A reagent or liquid or combination thereof that has a solubility in another reagent or liquid of less than 99%, or less than 90%, or less than 80%, or less than 70%, or less than 60%, or less than 50%, or less than 40%, or less than 30%, or less than 20%, or less than 10%, or less than 5%, or less than 1%.
Parasitic Load: A demand for energy or material, or a combination thereof, from a process that reduces the performance or efficiency of a system, but which may be required or useful or desired for the operation of that system.
• Ocean: may include an ocean, or a body of water, or a lake, or a body of water containing dense liquid, or a combination thereof.
• Denser or high density liquid: A liquid that has a density greater than that of a low density liquid. A liquid that has a density greater than that of a low density liquid in the same energy storage system or process. A liquid that has a density less than that of the high density liquid it replaces in an energy storage system or process.
● Lower density liquid or higher density liquid: A liquid that has a density less than that of a higher density liquid. A liquid that has a density less than that of a higher density liquid in the same energy storage system or process. A liquid that has a density less than that of the higher density liquid it replaces in an energy storage system or process.

Illustrative Diagram Description Figure 88: Process for energy storage by displacing a higher elevation low density liquid with a lower density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low density liquid reservoir, a refrigeration system for cooling the higher elevation low density liquid reservoir, a cold auxiliary thermal storage reservoir, a warm auxiliary thermal storage reservoir, a heat exchanger, a pump and/or generator, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment storing energy, such as electricity, which may also be referred to as going through a state of charge.

Figure 89: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a refrigeration system for cooling the higher elevation low-density liquid reservoir, a cold auxiliary thermal storage reservoir, a warm auxiliary thermal storage reservoir, a heat exchanger, a generator and/or pump, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment generating energy, such as electricity, which may also be referred to as undergoing a state of discharge.

Figure 90: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a refrigeration system for cooling the higher elevation low-density liquid reservoir, a higher elevation high-density liquid reservoir, a cold auxiliary thermal storage reservoir, a warm auxiliary thermal storage reservoir, a heat exchanger, a generator and/or pump, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment storing energy, such as electricity, which may also be referred to as going through a state of charge.

Figure 91: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a refrigeration system for cooling the higher elevation low-density liquid reservoir, a higher elevation high-density liquid reservoir, a cold auxiliary heat storage reservoir, a warm auxiliary heat storage reservoir, a heat exchanger, a pump and/or generator, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment generating energy, such as electricity, which may also be referred to as undergoing a state of discharge.

Figure 92: A process for energy storage that stores electricity by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a refrigeration system for cooling the higher elevation low-density liquid reservoir, an auxiliary thermal storage reservoir that may have a temperature layer or temperature gradient, a heat exchanger, a pump and/or generator, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment storing energy, such as electricity, which may also be referred to as going through a state of charge.

Figure 93: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a refrigeration system for cooling the higher elevation low-density liquid reservoir, an auxiliary thermal storage reservoir that may have a temperature layer or temperature gradient, a heat exchanger, a generator and/or pump, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment generating energy, such as electricity, which may also be referred to as going through a state of discharge.

Figure 94: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a cooling system for cooling the higher elevation low-density liquid reservoir, a higher elevation high-density liquid reservoir, an auxiliary thermal storage reservoir that may have a temperature layer or temperature gradient, a heat exchanger, a pump and/or generator, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment storing energy, such as electricity, which may also be referred to as going through a state of charge.

Figure 95: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a refrigeration system for cooling the higher elevation low-density liquid reservoir, a higher elevation high-density liquid reservoir, an auxiliary thermal storage reservoir that may have a temperature layer or temperature gradient, a heat exchanger, a generator and/or pump, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment generating energy, such as electricity, which may also be referred to as going through a state of discharge.

Figure 96: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or a combination of the following: a higher-elevation reservoir of lower-density liquid, a cooling system for cooling the higher-elevation reservoir of lower-density liquid, a heat exchanger, a pump and/or generator, a lower-elevation reservoir, and interconnecting piping. This diagram may show this embodiment storing energy, such as electricity, which may also be referred to as going through a state of charge.

Figure 97: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher-elevation reservoir of lower-density liquid, a cooling system for cooling the higher-elevation reservoir of lower-density liquid, a heat exchanger, a generator and/or pump, a lower-elevation reservoir, and interconnecting piping. This diagram may show this embodiment producing energy, such as electricity, which may also be referred to as undergoing a state of discharge.

Figure 98: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or combinations of the following: a higher elevation low-density liquid reservoir, a cooling system for cooling the higher elevation low-density liquid reservoir, a higher elevation high-density liquid reservoir, an auxiliary thermal storage reservoir that may have a temperature layer or temperature gradient, a heat exchanger, a generator and/or pump, a lower elevation reservoir, and interconnecting piping. This diagram may show this embodiment generating energy, such as electricity, which may also be referred to as going through a state of discharge.

Figure 99: A process for energy storage by displacing a higher-density liquid with a lower-density liquid. This embodiment may include, but is not limited to, one or more or a combination of the following: a higher-elevation reservoir of lower-density liquid, a cooling system for cooling the higher-elevation reservoir of lower-density liquid, a heat exchanger, a pump and/or generator, a lower-elevation reservoir, and interconnecting piping. This diagram may show this embodiment storing energy, such as electricity, which may also be referred to as going through a state of charge.

Figure 100: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir of lower density liquid that is a higher elevation reservoir, and a lower elevation reservoir, where the higher elevation reservoir may be located on land and the lower elevation reservoir may be located underwater.

Figure 101: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located on land and the lower elevation reservoir may be located underwater.

Figure 102: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located underwater near or on the seabed, and the lower elevation reservoir may be located underwater near or on the seabed.

Figure 103: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located underwater near or on the seabed, and the lower elevation reservoir may be located underwater near or on the seabed.

Figure 104: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located underwater as a semi-submersible or fully submerged vessel or a combination thereof, and the lower elevation reservoir may be located underwater near the seabed or on the seabed.

Figure 105: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located underwater as a semi-submersible or fully submerged vessel or a combination thereof, and the lower elevation reservoir may be located underwater near the seabed or on the seabed.

Figure 106: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located underwater as a floating vessel and the lower elevation reservoir may be located underwater near or on the seabed.

Figure 107: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a higher elevation reservoir of lower density liquid and a lower elevation reservoir, where the higher elevation reservoir may be located underwater as a floating vessel and the lower elevation reservoir may be located underwater near or on the seabed.

Figure 108: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir underwater and/or at a lower elevation above and/or on the seabed.

Figure 109: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir underwater and/or at a lower elevation above and/or on the seabed.

Figure 110: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir underwater and/or at a lower elevation above and/or on the seabed.

Figure 111: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir underwater and/or at a lower elevation above and/or on the seabed.

Figure 112: A process for energy storage by replacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a lower elevation reservoir that is underwater and/or underground below the sea floor, buried, or a combination thereof.

Figure 113: A process for energy storage by replacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a lower elevation reservoir that is underwater and/or underground below the sea floor, buried, or a combination thereof.

Figure 114: A process for energy storage by replacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a lower elevation reservoir that is underwater and/or underground below the sea floor, buried, or a combination thereof.

Figure 115: A process for energy storage by replacing a higher density liquid with a lower density liquid. This diagram may show embodiments with lower elevation reservoirs that are underwater and/or underground below the sea floor, buried, or a combination thereof.

Figure 116: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir at a lower elevation underground.

Figure 117: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir at a lower elevation underground.

Figure 118: A process for energy storage by displacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir at a lower elevation underground.

Figure 119: A process for energy storage by replacing a higher density liquid with a lower density liquid. This diagram may show an embodiment with a reservoir at a lower elevation underground.

Exemplary Figure Legends Figures 88 and 89:
Figures 90 and 91:
Figures 92 and 93:
Figures 94 and 95:
Figures 96 and 97:
Figures 98 and 99:

Example diagram walkthrough Figure 88:
charging:
1) A "cold" low density liquid may be transferred from a refrigerated or cooled high-side high density low density liquid reservoir to a heat exchanger. The heat exchanger may involve heat exchanging the "cold" low density liquid with a "warm" thermal storage medium to form a "warm" low density liquid and a "cold" thermal storage medium. The "cold" thermal storage medium may be stored in a "cold" thermal storage reservoir. The "warm" low density liquid is transferred to "2)".
2) A "warm" low-density liquid is pumped to a reservoir at a lower elevation using one or more pumps, where the low-density liquid displaces a high-density liquid. The pumps may be powered by energy, such as electricity, which may be stored during the displacement of the high-density liquid with the low-density liquid.

Figure 89:
Discharge:
1) A lower density liquid in a lower elevation reservoir may be allowed to be displaced by a higher density liquid. The displaced lower density liquid may be piped to a generator to generate electricity. Upon reaching the portion of the higher elevation that may contain the generator, the lower density liquid may be "warm," which may mean that the lower density liquid is hotter than the lower density liquid in the cooled or refrigerated higher elevation reservoir.
2) The "warm" low density liquid may enter a heat exchanger that may involve heat exchange of the "warm" low density liquid with a "cold" heat storage medium to form a "cold" low density liquid and a "warm" heat storage medium. The "warm" heat storage medium may be stored in a "warm" heat storage reservoir. The "cold" low density liquid may be transferred to a refrigerated or cooled high-side low density liquid reservoir.

Figure 90:
charging:
1) A "cold" low density liquid may be transferred from a refrigerated or cooled high-side high density low density liquid reservoir to a heat exchanger. The heat exchanger may involve heat exchanging the "cold" low density liquid with a "warm" thermal storage medium to form a "warm" low density liquid and a "cold" thermal storage medium. The "cold" thermal storage medium may be stored in a "cold" thermal storage reservoir. The "warm" low density liquid is transferred to "2)".
2) A "warm" low-density liquid is pumped using one or more pumps to a reservoir at a lower elevation where it displaces a high-density liquid. The pumps may be powered by energy, such as electricity, which may be stored during the displacement of the high-density liquid with the low-density liquid. The displaced high-density liquid may be transported through a pipe to a reservoir of high-density liquid at a higher elevation.

Figure 91:
Discharge:
1) It may allow for the replacement of a lower density liquid in a lower elevation reservoir with a higher density liquid in a higher elevation reservoir. The higher density liquid from the higher elevation reservoir may be piped to the lower elevation reservoir to replace the lower density liquid in the lower elevation reservoir. The displaced lower density liquid may be piped to a generator to generate electricity. Upon reaching the portion of the higher elevation that may contain the generator, the lower density liquid may be "warm," which may mean that it is hotter than the lower density liquid in the cooled or refrigerated higher elevation reservoir.
2) The "warm" low density liquid may enter a heat exchanger that may involve heat exchange of the "warm" low density liquid with a "cold" heat storage medium to form a "cold" low density liquid and a "warm" heat storage medium. The "warm" heat storage medium may be stored in a "warm" heat storage reservoir. The "cold" low density liquid may be transferred to a refrigerated or cooled high-side low density liquid reservoir.

Figure 92:
charging:
1) A "cold" low density liquid can be transferred from a refrigerated or cooled high-side reservoir of high density low density liquid to a heat exchanger. The heat exchanger can include heat exchanging the "cold" low density liquid with a "warm" thermal storage medium to form a "warm" low density liquid and a "cold" thermal storage medium. The "cold" thermal storage medium can be stored in a thermal storage reservoir. The "warm" low density liquid can be transferred to "2)".
2) A "warm" low-density liquid can be pumped to a reservoir at a lower elevation using one or more pumps, where the low-density liquid displaces the high-density liquid. The pumps can be powered by energy, such as electricity, and the energy can be stored during the displacement of the high-density liquid with the low-density liquid.

Figure 93:
Discharge:
1) A lower density liquid in a lower elevation reservoir may be allowed to be displaced by a higher density liquid. The displaced lower density liquid may be piped to a generator to generate electricity. Upon reaching the portion of the higher elevation that may contain the generator, the lower density liquid may be "warm," which may mean that the lower density liquid is hotter than the lower density liquid in the cooled or refrigerated higher elevation reservoir.
2) The "warm" low density liquid may enter a heat exchanger that may involve heat exchange of the "warm" low density liquid with a "cold" heat storage medium to form a "cold" low density liquid and a "warm" heat storage medium. The "warm" heat storage medium may be stored in a heat storage reservoir. The "cold" low density liquid may be transferred to a refrigerated or cooled high-side low density liquid reservoir.

Figure 94:
charging:
1) A "cold" low density liquid may be transferred from a refrigerated or cooled high-side high density low density liquid reservoir to a heat exchanger. The heat exchanger may involve heat exchanging the "cold" low density liquid with a "warm" thermal storage medium to form a "warm" low density liquid and a "cold" thermal storage medium. The "cold" thermal storage medium may be stored in a thermal storage reservoir. The "warm" low density liquid is transferred to "2)".
2) A "warm" low-density liquid is pumped using one or more pumps to a reservoir at a lower elevation where it displaces a high-density liquid. The pumps may be powered by energy, such as electricity, which may be stored during the displacement of the high-density liquid with the low-density liquid. The displaced high-density liquid may be transported through a pipe to a reservoir of high-density liquid at a higher elevation.

Figure 95:
Discharge:
1) It may allow for the replacement of a lower density liquid in a lower elevation reservoir with a higher density liquid in a higher elevation reservoir. The higher density liquid from the higher elevation reservoir may be piped to the lower elevation reservoir to replace the lower density liquid in the lower elevation reservoir. The displaced lower density liquid may be piped to a generator to generate electricity. Upon reaching the portion of the higher elevation that may contain the generator, the lower density liquid may be "warm," which may mean that it is hotter than the lower density liquid in the cooled or refrigerated higher elevation reservoir.
2) The "warm" low density liquid may enter a heat exchanger that may involve heat exchange of the "warm" low density liquid with a "cold" heat storage medium to form a "cold" low density liquid and a "warm" heat storage medium. The "warm" heat storage medium may be stored in a heat storage reservoir. The "cold" low density liquid may be transferred to a refrigerated or cooled high-side low density liquid reservoir.

Figure 96:
charging:

The "cold," low-density liquid is pumped using one or more pumps to a reservoir at a lower elevation, where it displaces the high-density liquid. The pumps may be powered by energy, such as electricity, which may be stored during the displacement of the high-density liquid with the low-density liquid.

Figure 97:
Discharge:

A lower-density liquid in a lower-elevation reservoir may be displaced by a higher-density liquid. The displaced lower-density liquid may be piped to a generator to generate electricity. Upon reaching the higher-elevation portion, which may include the generator, the lower-density liquid may be "warm," which may mean that the lower-density liquid is at a higher temperature than the lower-density liquid in the cooled or refrigerated higher-elevation reservoir. The "warm" lower-density liquid may undergo cooling before, during, or after entering the cooled or refrigerated higher-elevation reservoir of the lower-density liquid, or a combination thereof.

Figure 98:
charging:

A "cold," low-density liquid is pumped using one or more pumps to a reservoir at a lower elevation, where it displaces a high-density liquid. The displaced high-density liquid can be transferred by pipe to a reservoir of high-density liquid at a higher elevation. The pumps can be powered by energy, such as electricity, and the energy can be stored during the displacement of the high-density liquid with the low-density liquid.

Figure 99:
Discharge:

A lower-density liquid in a lower-elevation reservoir may be displaced by a higher-density liquid in a higher-elevation reservoir. The higher-density liquid from the higher-elevation reservoir may be piped to the lower-elevation reservoir to displace the lower-density liquid in the lower-elevation reservoir. The displaced lower-density liquid may be piped to a generator to generate electricity. Upon reaching the portion of the higher-elevation that may include the generator, the lower-density liquid may be "warm," which may mean that the lower-density liquid is at a higher temperature than the lower-density liquid in the cooled or refrigerated higher-elevation reservoir. The "warm" lower-density liquid may undergo cooling before, during, or after entering the cooled or refrigerated higher-elevation reservoir, or a combination thereof.

Description: In some embodiments, a low-density liquid may have a low boiling point. In some embodiments, the external or ambient pressure surrounding a reservoir of a low-density liquid may be less than the vapor pressure of the low-density liquid when the low-density liquid is stored at ambient temperature. If the pressure of the low-density liquid inside a reservoir exceeds the pressure surrounding or adjacent to the reservoir, the reservoir may be "pressurized" and must be able to withstand that pressure to ensure safety and prevent rupture. Pressurized reservoirs, such as ASME pressurized tanks, may be utilized and employed for the storage of butane, propane, LPG, and other volatile liquids in the art. To enable pressurization and pressure resistance, pressurized tanks may require thicker walls, stronger reinforcement, stronger materials, or a combination thereof, compared to non-pressurized tanks. As a result, pressurized tanks are generally more expensive than non-pressurized tanks for storing the same mass of volatile liquid. Additionally, the higher the pressure rating or pressure resistance of a pressurized tank, the more expensive the tank generally is.

In some embodiments, one or more low-density liquid reservoirs may be cooled, actively cooled, or subjected to some form of thermal management. For example, in some embodiments, the higher elevation low-density liquid reservoir may be cooled or refrigerated. Cooling or "refrigeration" may be used interchangeably and may simply describe the active removal of heat. For example, in some embodiments, the higher elevation low-density liquid storage reservoir may be cooled or refrigerated to reduce the required pressure resistance of the higher elevation low-density liquid storage reservoir, or to allow the higher elevation low-density liquid storage reservoir to be unpressurized, or a combination thereof. Refrigerated storage tanks are available in the art and may be employed to store butane, propane, LPG, and other volatile liquids.

Active refrigeration or cooling may require an energy input, which may be parasitic. The energy required to refrigerate or cool a low-density liquid may reduce the overall round-trip energy efficiency. Minimizing the energy required to refrigerate or cool a low-density liquid storage reservoir may be advantageous for maximizing the round-trip energy efficiency of the energy storage system.

In some embodiments, the higher elevation low density liquid storage reservoir may be refrigerated. Refrigerated or cooled storage reservoirs may allow for lower capital costs due to, for example, the ability to use non-pressurized or low-pressurized tanks.

In some embodiments, a refrigerated high-side elevation low-density liquid storage reservoir may be employed with integrated auxiliary thermal storage. Auxiliary thermal storage may be employed to minimize the parasitic energy requirements associated with refrigerating or cooling the low-density liquid storage reservoir. Auxiliary thermal storage may be employed to minimize the cooling or refrigeration capacity, or "cooling tonnage," required to refrigerate or cool the low-density liquid storage reservoir, thereby minimizing the capital cost or energy demand of the cooling equipment, or a combination thereof. Auxiliary thermal storage may be integrated to recover the "cold" stored in the specific heat capacity of the low-density liquid before it is transferred to the low-density liquid reservoir during energy storage system storage or "charging." Auxiliary thermal storage may be integrated to cool the low-density liquid before it is transferred to the refrigerated or cooled high-side elevation low-density liquid storage reservoir during energy storage system power generation or "discharging."

There are various systems, methods, and configurations for integrating auxiliary thermal storage.

For example, in some embodiments, the integrated auxiliary thermal storage system may include a thermal storage reservoir, a thermal storage medium, a heat transfer medium, and a heat exchanger. In this example, the thermal storage medium and the heat transfer medium may comprise the same medium, and may include a high heat capacity liquid, such as, but not limited to, water, water with a freezing point depressant, salt water brine, aqueous brine, or a liquid-liquid phase change liquid. In this example, the thermal storage reservoir may include one or more storage tanks that store the thermal storage medium. In some embodiments, the thermal storage reservoir may include a single tank with a temperature gradient or thermocline. In some embodiments, the thermal storage reservoir may include two tanks, one tank for a "cold" thermal storage medium and one tank for a "warm" thermal storage medium. This example may be a thermal storage reservoir that includes two tanks, one tank for a "cold" thermal storage medium and one tank for a "warm" thermal storage medium. In this embodiment, the heat exchanger may include a heat exchanger that facilitates heat transfer between the thermal storage medium and the low-density liquid. This embodiment may employ normal butane as the low-density liquid, although other low-density liquids may be employed if desired. This embodiment may store electricity or energy by pumping the low-density liquid from a higher elevation reservoir to a lower elevation reservoir to displace water in the lower elevation reservoir. This embodiment may generate electricity or energy by piping the low-density liquid to a generator to generate electricity or generate energy and transfer it back into the higher elevation reservoir.
In this embodiment, during power storage or "charging," the lower density liquid leaving or after leaving the refrigerated higher elevation storage reservoir may pass through a heat exchanger where the "cold" lower density liquid may exchange heat with a "warm" thermal storage liquid, resulting in the formation of a "warm" lower density liquid and a "cold" thermal storage liquid. The cold thermal storage liquid may be transferred to the thermal storage reservoir. The "warm" lower density liquid may be transferred in a pipe to the lower elevation reservoir. The heat exchange may occur before, during, or after the pumping step. For example, this embodiment may include a first pump that increases the pressure of a "cold," low-density liquid to a pressure above the vapor pressure of the low-density liquid in the "warm" temperature range, and then, after heat exchange in a heat exchanger, the resulting "warm," low-density liquid may undergo a subsequent pumping step that increases the pressure of the low-density liquid to a pressure sufficient to transfer the low-density liquid to a reservoir at a lower elevation. For example, this embodiment may include pumping a "cold," low-density liquid to a pressure sufficient to transfer the low-density liquid to a reservoir at a lower elevation, then heat exchanging the "cold," low-density liquid with a "warm" heat transfer liquid and transferring the resulting "warm," low-density liquid to a reservoir at a lower elevation. In some embodiments, the heat exchange may occur before or during the transfer of the low-density liquid to the reservoir at a lower elevation. In some embodiments, the heat exchanger may include one or more or combinations of the following, including but not limited to: a shell in tube heat exchanger, or a plate heat exchanger, or a pipe of low density liquid, a coil wrapped around a thermally conductive low density liquid pipe segment, or one or more heat exchange methods known in the art.
In this example, during power generation or "discharge," the low density liquid before, during, or after entering the generator, or a combination thereof, may pass through a heat exchanger where the "warm" low density liquid may exchange heat with a "cold" heat storage liquid, resulting in the formation of a "cold" low density liquid and a "warm" heat storage liquid. The warm heat storage liquid may be transferred to a heat storage reservoir. The "cold" low density liquid may be transferred to a higher elevation reservoir, including a cooled or refrigerated higher elevation reservoir. In some embodiments, the "cold" low density liquid resulting from the heat exchange may be near, equal to, or below the temperature of the refrigerated or refrigerated higher elevation low density liquid reservoir. This embodiment may involve generating electricity from a high pressure warm, low density liquid, which may be depressurized to a pressure above the vapor pressure of the low density liquid at the "warm" temperature, and then, after heat exchange in a heat exchanger, the resulting "cold," low density liquid may enter a second generator or depressurization step, which may reduce the pressure of the "cold," low density liquid to a pressure suitable for transfer to a cooled or refrigerated low density liquid storage reservoir. This embodiment may involve generating electricity from a high pressure warm, low density liquid, then heat exchanging the warm, low density liquid to form a cold, low density liquid, and then transferring the cold, low density liquid to a low density liquid storage reservoir at a higher elevation. In some embodiments, the warm, low-density liquid entering the heat exchanger may be at a pressure equal to or greater than the vapor pressure of the low-density liquid at the "warm" temperature, and the "cold," low-density liquid exiting the heat exchanger may be at a pressure sufficient for transfer to a reservoir of cooled or refrigerated high-side elevation low-density liquid. In some embodiments, the warm, low-density liquid entering the heat exchanger may be at a pressure equal to or greater than the vapor pressure of the low-density liquid at the "warm" temperature, and the "cold," low-density liquid exiting the heat exchanger may require further pressure reduction before transfer into a reservoir of cooled or refrigerated high-side elevation low-density liquid. In some embodiments, the warm, low-density liquid entering the heat exchanger may be at a pressure equal to or greater than the vapor pressure of the low-density liquid at the "warm" temperature, and the "cold," low-density liquid exiting the heat exchanger may require further pressure reduction before transfer into a reservoir of cooled or refrigerated high-side elevation low-density liquid. In some embodiments, the heat exchanger may include one or more or combinations of the following, including but not limited to: a shell in tube heat exchanger, or a plate heat exchanger, or a pipe of low density liquid, a coil wrapped around a thermally conductive low density liquid pipe segment, or one or more heat exchange methods known in the art.
In some embodiments, the pump and generator may comprise the same unit, such as a reversible pump/generator or a water recovery turbine.
• In some embodiments, the same heat exchanger employed during discharging may be employed during conversion.

In embodiments employing a storage tank of cooled or refrigerated low density liquid, auxiliary thermal storage may be beneficial to maximize the round trip efficiency of the system. Calculations for an exemplary system are shown below:
In this exemplary system, liquid normal butane may be provided as an exemplary low density liquid.
In this example, the exemplary outside ambient temperature is 30°C.
This example includes 1 GWh of energy storage.
With the lower elevation reservoir located at a depth of approximately 3,000 meters and the higher elevation reservoir located at an elevation of approximately 0 meters, this example requires approximately 235,294 cubic meters of liquid normal butane, or approximately 134,823 tons of liquid normal butane at a density of 573 kg per cubic meter.
●Liquid normal butane has a boiling point of approximately -1°C at atmospheric pressure.
The liquid butane of this embodiment can be stored in a refrigerated high elevation reservoir at approximately -3°C when steady state or when emptied, and at -1°C when the high elevation reservoir is full.
This embodiment stores (charges) electricity by pumping a lower density liquid from a higher elevation reservoir to a lower elevation reservoir, displacing the water in the lower elevation reservoir.
This embodiment generates (discharges) electricity by allowing water to displace a lower density liquid in a reservoir at a lower elevation, pipe the displaced lower density liquid to a generator, generate electricity, and transfer it into a reservoir at a higher elevation.
For purposes of this example, the temperature of the low density liquid entering at least one higher elevation portion of the system during discharge (which may include, but is not limited to, the high elevation pipe segments, generators, tanks, reservoirs, and/or any heat exchangers) may be ambient temperature, which in this example is 30°C. In practice, the temperature of the low density liquid entering at least one higher elevation portion of the system during discharge may be lower than ambient temperature due to the lower temperatures of the deep ocean (typically about 0-5°C) and the generally cooler temperatures of the oceans (temperatures in most of the world's oceans, including surface water depths, are generally below 30°C for most of the year).
This example shows a complete charge/discharge cycle, where the high-side elevation reservoir is substantially emptied during charging and substantially filled during discharging. In practice, the energy storage system may operate in various charge and discharge states and may undergo charging or discharging or a combination thereof when the high-side elevation reservoir is partially full, empty, full, or a combination thereof.
The heat exchanger temperature difference between the heat exchanged fluids is assumed to be approximately 1°K.
The "warm" heat storage liquid is assumed to be at an exemplary ambient temperature, or 30° C. In practice, the "warm" heat storage liquid may be at a temperature below ambient, for example, due to, but not limited to, a low density liquid returning during discharge being at a temperature below ambient, or due to a thermal management system, or a combination thereof.
The specific heat capacity of liquid normal butane is 2.275 J/g°K. The heat capacity of 134,823 metric tons of liquid normal butane is 306,722 MJ/°K. As shown in the example with calculations below, an exemplary embodiment having a refrigerated or cooled high-side elevation low-density liquid reservoir with supplemental thermal storage may require significantly less cooling energy or parasitic cooling than an exemplary embodiment having a refrigerated or cooled high-side elevation low-density liquid reservoir without supplemental thermal storage. As shown in the example with calculations below, an exemplary embodiment having a refrigerated or cooled high-side elevation low-density liquid reservoir without supplemental thermal storage may require a reduction in parasitic load or round-trip efficiency of approximately 14-28% for cooling. As shown in the example with calculations below, an exemplary embodiment having a refrigerated or cooled high-side elevation low-density liquid reservoir with supplemental thermal storage may require a reduction in parasitic load or round-trip efficiency of approximately 1-3% for cooling. Clearly, an auxiliary thermal storage system may be advantageous for maximizing round trip efficiency of embodiments employing a refrigerated high-side elevation low-density liquid reservoir. Additionally, an auxiliary thermal storage system may be advantageous for minimizing CAPEX due to the smaller cooling capacity requirements of embodiments employing a refrigerated high-side elevation low-density liquid reservoir with auxiliary thermal storage compared to embodiments employing a refrigerated high-side elevation low-density liquid reservoir without auxiliary thermal storage.

A version of this embodiment using auxiliary heat storage:
○ Steps 1) Charging: During charging from 0% to 100%, 134,823 tons of "cold" liquid normal butane at a temperature of -3°C leaves the refrigerated or cooled upper elevation reservoir and is heat exchanged with "warm" thermal storage liquid. The "cold" thermal storage liquid at -2°C and the "warm" liquid normal butane at a temperature of 29°C exit the heat exchanger. The "warm" low density liquid may be transferred to the lower elevation reservoir. The thermal storage liquid may be stored in the thermal storage reservoir. In some embodiments, the "cold" thermal storage liquid in the thermal storage reservoir may be maintained at or near the design "cold" temperature. Such maintenance may include, for example, but not limited to, refrigeration, other forms of cooling, insulation, radiative cooling, or other forms of thermal management.
2) Discharge: During discharge from 100% to 0%, 134,823 metric tons of "warm" liquid normal butane enters heat exchange with "cold" heat storage liquid. For this example, the "warm" liquid normal butane is at 30°C and the "cold" heat storage liquid is at -2°C. The "warm" heat storage liquid exits the heat exchange with a temperature of 29°C and "cold" liquid normal butane at a temperature of -1°C. The "cold" liquid normal butane is transferred to a refrigerated or cooled reservoir of lower density liquid at a higher elevation. The "warm" heat storage liquid is transferred into the heat storage reservoir.

Cooling Energy Consumption - In this example, it may be desirable to cool normal liquid butane to a design storage temperature or design emptying temperature. In this example, normal liquid butane in a refrigerated or cooled high elevation low density liquid storage reservoir may be cooled to a temperature of -1°C to -3°C. The cooling may occur during filling, during storage, during emptying, or a combination thereof.
With a heat capacity of 306,722 MJ/°C, cooling from -1°C to -3°C requires the removal of 613,444 MJ of heat.
Using a refrigeration cycle or cooling system with a coefficient of performance of 6, cooling would require 102,241 MJ of electricity or 28.4 MWh of electricity. Since the energy storage system of this example stores 1 GWh of electricity, 28.4 MWh of electricity is a 2.84% cooling parasitic load or reduces the overall round trip efficiency of the energy storage system by approximately 2.84%.
Using a refrigeration cycle or cooling system with a coefficient of performance of 15, which may use deep ocean water as a heat sink or lower ambient temperature or lower wet bulb temperature or a combination thereof, cooling would require 40,896 MJ of electricity or 11.36 MWh of electricity. Since the energy storage system of this example stores 1 GWh of electricity, 11.36 MWh of electricity is a cooling parasitic load of 1.136%, or reduces the overall round trip efficiency of the energy storage system by approximately 1.136%.
o Note: In some embodiments, the cold thermal storage may be cooled to a design temperature below the design low density liquid storage temperature before, during, or after heat exchange with the "cold" low density liquid, or a combination thereof.

A version of this embodiment without auxiliary heat storage:
Steps: 1) Charging: During charging from 0% to 100%, 134,823 tonnes of "cold" liquid normal butane at a temperature of -3°C leaves the refrigerated or cooled higher elevation reservoir. The "cold", low density liquid is transferred directly to the lower elevation reservoir.
2) Discharge: During discharge from 100% to 0%, 134,823 metric tons of "warm" liquid normal butane enters the upper elevation portion. In this example, the "warm" liquid normal butane is at ambient temperature, which is 30°C in this example. In practice, the "warm" low-density liquid may be cooler than ambient temperature, warmer than ambient temperature, or both. In this example, the "warm" liquid butane must be cooled from 30°C to -3°C, or at least -1°C, before entering the refrigerated or cooled low-density liquid upper elevation reservoir.

Cooling Energy Consumption: In this example, the "warm" liquid butane must be cooled from 30°C to -3°C, or at least -1°C. This cooling can occur during filling, or during storage, or during emptying, or a combination thereof.
With a heat capacity of 306,722 MJ/°C, cooling from 30°C to -3°C requires the removal of 10,121,826 MJ of heat.
Using a refrigeration cycle or cooling system with an average coefficient of performance of 10, cooling would require 1,012,183 MJ of electricity or 281.2 MWh of electricity. Since the energy storage system of this example stores 1 GWh of electricity, 281.2 MWh of electricity is a 28.12% cooling parasitic load or reduces the overall round trip efficiency of the energy storage system by approximately 28.12%.
Using a refrigeration cycle or cooling system with a coefficient of performance of 20, which may use deep ocean water as a heat sink or lower ambient temperature or lower wet bulb temperature or a combination thereof, cooling would require 506,091 MJ of electricity or 140.58 MWh of electricity. Since the energy storage system of this example stores 1 GWh of electricity, 140.58 MWh of electricity is a cooling parasitic load of 14.058%, or reduces the overall round trip efficiency of the energy storage system by approximately 14.058%.

In some embodiments, the "cold" thermal storage medium may be maintained at a temperature equal to or lower than the temperature of the low-density liquid in the refrigerated or cooled low-density liquid storage reservoir. Such maintenance may include some form of thermal management. For example, such thermal management may include systems and methods for cooling or temperature control or temperature monitoring, or combinations thereof, described herein or known in the art. In some embodiments, the thermal management system employed for the "cold" thermal storage medium may overlap with or be integrated with the thermal management system employed in cooling the refrigerated low-density liquid storage reservoir. In some embodiments, the thermal management system employed for the "cold" thermal storage medium may be separate from the thermal management system employed in cooling the refrigerated low-density liquid storage reservoir.

Additional systems and methods for minimizing parasitic energy consumption associated with cooling or refrigerating a reservoir of low density liquid may include, but are not limited to:
● Reservoir insulation ● Efficient refrigeration ● Employing evaporation or boiling of a low density liquid inside a low density liquid reservoir to cool the low density liquid in the reservoir. The resulting low density liquid vapor can be internally recirculated, for example, by condensing the vapor to a liquid by compression, cooling, or both. The condensed low density liquid vapor can contain the liquid low density liquid and can be returned to the low density liquid reservoir in the liquid phase. Alternatively or additionally, the low density liquid vapor can be used for another purpose, including, but not limited to, as a fuel, or an industrial feedstock, or a chemical feedstock, or a refrigerant, or a combination thereof.
● Use of evaporative cooling ● Use of water-based evaporative cooling ● Use of cold deep ocean temperatures for cooling or as a heat transfer medium ● Radiative cooling ● OTEC
10. The energy storage system of claim 10, further comprising: seawater cooling; seawater as a heat sink for a refrigerator or chiller; cold, deep seawater as a heat sink for a refrigerator or chiller; reflective, non-light, or heat absorbing colors or coatings on the tanks; thermal storage; and high density liquid and/or water that may be located in the energy storage system as the system working fluid, as a "heat" sink to cool the refrigerated or cooled low density liquid reservoir and/or auxiliary thermal storage reservoir. In some embodiments, high density liquid and/or water in a lower elevation reservoir is transferred to a higher elevation reservoir during charging. The transferred high density liquid and/or water may be at a temperature lower than ambient temperature, for example, due to the potentially relatively lower temperature of the deep ocean than some ambient temperatures and/or heat exchange with the deep ocean. For example, the displaced high density liquid and/or water may be heat exchanged with a refrigerated or cooled low density liquid reservoir and/or an auxiliary thermal storage reservoir to cool the reservoir, For example, the displaced high density liquid and/or water may be employed as a heat sink in a refrigeration cycle employed to cool or remove heat from a refrigerated or cooled low density liquid reservoir and/or an auxiliary thermal storage reservoir to cool the reservoir.

In some embodiments, a refrigerated high-side elevation storage tank may be employed in the absence of supplemental thermal storage. When the cooling or refrigeration method is non-parasitic in nature, requires minimal energy, is passive, or a combination thereof, the round-trip efficiency of an embodiment having a refrigerated or chilled low-density liquid reservoir, such as a high-side elevation reservoir of refrigerated or chilled low-density liquid, may be similar to the round-trip efficiency of an embodiment having an unrefrigerated or unrefrigerated low-density liquid reservoir. When the cooling or refrigeration method is parasitic in nature, the round-trip efficiency of an embodiment having a refrigerated or chilled low-density liquid reservoir, such as a high-side elevation reservoir of refrigerated or chilled low-density liquid, may be less than the round-trip efficiency of an embodiment having an unrefrigerated or unrefrigerated low-density liquid reservoir. Some embodiments employing refrigerated or chilled tanks without supplemental thermal storage may have lower capital costs than embodiments employing refrigerated or chilled tanks with supplemental thermal storage, for example, due to the ability to use unpressurized or low-pressurized tanks and/or the lack of supplemental thermal storage and associated heat exchangers. Some embodiments employing refrigerated or chilled tanks without supplemental thermal storage may have higher capital costs than embodiments employing refrigerated or chilled tanks with supplemental thermal storage, for example, due to higher cooling capacity requirements in embodiments employing refrigerated or chilled tanks without supplemental thermal storage than in embodiments employing refrigerated or chilled tanks with supplemental thermal storage.

In some embodiments, energy is stored by pumping a lower density liquid to displace a higher density liquid in a lower elevation reservoir; energy is stored by allowing the higher density liquid to displace the lower density liquid in the lower elevation reservoir. In some of the described embodiments, the lower elevation reservoir may be underwater, under liquid, underground, or both. In some embodiments, when the lower elevation reservoir is underwater or under liquid, it may be desirable for the higher density liquid to have a density similar to or equal to the density of the fluid or liquid surrounding or adjacent to the lower elevation reservoir, which may result in hydrostatic balance and/or minimized pressure differentials between the interior and exterior of the lower elevation reservoir. In some embodiments where the lower elevation reservoir is underground, for example, an increased density of the denser liquid may be employed due to the ability of the earth to exert an isostatic pressure regardless of the density of the denser liquid.

In some embodiments where the lower elevation reservoir is subsurface, the lower density liquid may be in direct contact with the higher density liquid in the lower elevation reservoir. When the lower density liquid is in direct contact with the higher density liquid, it may be desirable for the lower density liquid to be insoluble or have limited solubility in the higher density liquid and/or it may be desirable for the lower density liquid to be a non-hydrate that forms the lower density liquid.

It is important to note that lower density liquids may have inherent advantages over compressed air, in addition to the inherently greater round-trip efficiency of using a lower density liquid to displace a higher density liquid. For example, unlike air, lower density liquids may be in direct contact with water, regardless of pressure or depth or a combination thereof, allowing for virtually unlimited potential energy density and subsurface depth. Ultra-energy dense embodiments may be envisioned that may include, but are not limited to, depths underground or underwater or under liquid or combinations thereof, or elevation differences of 1,000 meters or more, or 2,000 meters or more, or 3,000 meters or more, or 4,000 meters or more, or 5,000 meters or more, or 6,000 meters or more, or 7,000 meters or more, or 8,000 meters or more, or 9,000 meters or more, or 10,000 meters or more, or 11,000 meters or more, or 12,000 meters or more, or 13,000 meters or more, or 14,000 meters or more, or 15,000 meters or more, or 20,000 meters or more, or 25,000 meters or more, or 30,000 meters or more, or 35,000 meters, or 40,000 meters, or 45,000 meters, or 50,000 meters or more. The elevation difference may include the elevation difference between a reservoir at a higher elevation and a reservoir at a lower elevation, or between a first reservoir and a second reservoir, or between a first reservoir and a third reservoir, or any combination thereof. On the other hand, air, particularly the nitrogen in air, forms gas hydrates at pressures above 173 bar (approximately 1,730 meters of hydrostatic head), limiting the energy density and depth of the system based on the displacement of water with air. Additionally, the solubility of air or other gases increases in water with pressure due to Henry's law. Unlike air, the solubility of some low-density liquids in water may not increase substantially or practically with pressure. Additionally, air forms a supercritical fluid at pressures above approximately 30 bar. Unlike air, liquids generally remain liquid regardless of pressure as long as the pressure exceeds the boiling point pressure of the liquid at its temperature.

In some embodiments, the denser liquid may include a density enhancer, or may include a liquid having a density greater than water, or both. Increasing the density of the denser liquid, decreasing the density of the less dense liquid, or both, increases the energy density of the energy storage system. In embodiments where the denser liquid and the less dense liquid are in a closed system and the lower elevation reservoir is underground, surrounded by solids, or both, maximizing the density of the denser liquid may be particularly advantageous. For example, the denser liquid or enhanced denser liquid may include one or more or combinations of the following, but are not limited to: aqueous salt solution, aqueous brine, liquid salt, halogen, heavy liquid, liquid metal, concentrated aqueous solution, urea ammonium nitrate solution, frac water, concentrated frac water, desalinated brine, or mining brine.

In some embodiments, the reservoir at a lower elevation may be located in a region having a different temperature than the reservoir at a higher elevation. Additionally, pipes transporting liquid between reservoirs may traverse regions where the temperature differs from that of the reservoir at the higher elevation, the reservoir at the lower elevation, or both. In some embodiments, the temperature difference may be utilized and/or exploited. For example, the temperature difference may be utilized and/or exploited for cooling, heating, or both. For example, the temperature difference may be utilized and/or exploited to generate electricity, desalinate water, facilitate separation, freeze, boil water, or perform other valuable work or activities.

The temperature differential may be utilized and/or exploited during or as an auxiliary advantage to the process operation.
For example, the lower elevation reservoir may be located in a region of water whose temperature is substantially different from the temperature of the region of the higher elevation reservoir. For example, the temperature of the water surrounding or adjacent to the lower elevation reservoir may be less than 10° C. or less than 5° C., and the temperature of the environment surrounding or adjacent to the higher elevation reservoir may be greater than 5° C. or greater than 10° C. In embodiments where the higher elevation low-density liquid reservoir is partially refrigerated or refrigerated or cooled, it may be desirable to take advantage of or utilize the potentially lower-than-ambient temperature of the low-density liquid displaced from the lower elevation reservoir to reduce cooling or refrigeration energy consumption. In embodiments where the higher elevation reservoir of low-density liquid is partially refrigerated or refrigerated or cooled, it may be desirable to utilize or take advantage of the potentially cooler than ambient temperatures of the lower-density liquid and/or higher-density liquid displaced from the lower elevation reservoir to reduce refrigeration or refrigeration energy consumption. In some embodiments, it may be desirable to utilize and/or take advantage of the potentially cooler than ambient temperatures of the lower-density liquid and/or higher-density liquid displaced from the lower elevation reservoir to provide process cooling, district cooling, air-conditioning cooling, power plant cooling, or other cooling needs. In some embodiments, it may be desirable to utilize and/or take advantage of the potentially cooler than ambient temperatures of the lower-density liquid and/or higher-density liquid displaced from the lower elevation reservoir to generate electricity. The lower density liquid or higher density liquid, or both, displaced from the lower elevation reservoir may be heat exchanged with a process that utilizes or takes advantage of the potentially lower ambient temperatures before, during, or after storing the lower density liquid or higher density liquid, or both, in the higher elevation reservoir, or a combination thereof.
For example, a lower elevation reservoir may be located underground in an area where the temperature is substantially different from the temperature of the area of the higher elevation reservoir. For example, the temperature surrounding or adjacent to the lower elevation reservoir may be greater than 10° C., or greater than 20° C., or greater than 30° C., or greater than 40° C., or greater than 50° C., and the temperature surrounding or adjacent to the higher elevation reservoir may be less than 0° C., or less than 10° C., or less than 20° C., or less than 30° C., or less than 40° C., or less than 50° C. In some embodiments, it may be desirable to utilize or exploit the potentially higher-than-ambient temperatures of the low-density liquid or high-density liquid, or both, displaced from the lower elevation reservoir for district heating, process heating, or other heating needs. In some embodiments, it may be desirable to utilize and/or exploit the potentially above-ambient temperatures of the lower-density liquid and/or higher-density liquid displaced from the lower elevation reservoir for power generation. The lower-density liquid and/or higher-density liquid displaced from the lower elevation reservoir may be heat exchanged with a process that utilizes or exploits the potentially above-ambient temperatures before, during, or after storing the lower-density liquid and/or higher-density liquid in the higher elevation reservoir, or a combination thereof.

In some embodiments, the low density or high density liquid, or both, may comprise a heat storage medium. In some embodiments, the large or high calorific value of the stored liquid may be advantageous for use or dual use as a heat storage medium or a temperature buffer, or both. For example, the low density or high density liquid, or both, may be employed as a medium for cooling heat storage, or heating heat storage, or cooling, or heating, or heat transfer in HVAC, district heating systems, or district cooling systems, or process cooling, or process heating, or temperature stabilization, or a combination thereof.

In some embodiments, it may be desirable to employ a non-hydrate-forming, low-density liquid. A non-hydrate-forming, low-density liquid may include a liquid that does not form a solid hydrate or clathrate in the presence of water under pressure. It may be advantageous to employ a non-hydrate-forming, low-density liquid as the low-density liquid, for example, to enable direct contact between water and the low-density liquid. For example, a non-hydrate-forming, low-density liquid and/or direct contact between water and the low-density liquid may prevent or minimize the need for mechanical pressure exchange barriers, such as pistons, floating separators, or bladders, which may enable longer system life, lower costs, and fewer mechanical moving parts. For example, a non-hydrate-forming, low-density liquid may enable direct-contact pressure exchange with subsea seawater, which may reduce capital costs, reduce complexity, increase round-trip efficiency, increase system life, or a combination thereof. For example, in some embodiments, the non-hydrate-forming low-density liquid may allow direct contact between the low-density liquid and an aqueous high-density liquid, which may include, but is not limited to, a high-density liquid comprising water, or a high-density liquid comprising water and a density enhancer, or a density-enhancing reagent, or a combination thereof.

In some embodiments, a portion of the lower density liquid may dissolve in the higher density liquid. In some embodiments, a portion of the lower density liquid may dissolve in the higher density liquid even if the lower density liquid is slightly soluble or practically insoluble in the higher density liquid. In some embodiments in which a higher density liquid is displaced by a lower density liquid in a lower elevation reservoir and the displaced higher density liquid is transferred to a higher elevation reservoir of higher density liquid, the lower density liquid dissolved in the higher density liquid may create vapor pressure of the lower density liquid. If desired, the lower density liquid, the vapor of the lower density liquid, or the vapor pressure of the lower density liquid, or a combination thereof, may be removed or recovered before, during, or after storage of the higher density liquid in the higher elevation reservoir of higher density liquid, or a combination thereof. For example, the vapor of the lower density liquid from the higher density liquid may undergo compression, cooling, liquefaction, or a combination thereof to form the lower density liquid in the liquid phase and/or the lower density liquid in the liquid phase to a reservoir of lower density liquid at a higher elevation.

NOTES: In some embodiments, the heat storage medium and the heat transfer medium may comprise the same or different materials. For example, in some embodiments, the heat storage medium and the heat transfer medium may both comprise a liquid, or a liquid-liquid phase-change liquid, or both. For example, in some embodiments, the heat storage medium may comprise a solid-to-liquid phase-change material, or a solid-solid phase-change material, or a solid-liquid slurry, or a combination thereof, and/or the heat transfer medium may comprise a liquid phase material, or a liquid-liquid phase-change material, or a gas-to-liquid phase-change material, or a solid-liquid phase-change material, or a solid-liquid slurry, or a combination thereof.
Note: Water may be provided as an exemplary liquid. For example, water may be provided as an exemplary denser liquid. Other denser liquids may be employed instead of or in addition to water.
Note: The low density liquid pump may stop pumping when no more power needs to be stored. One or more valves may be closed to prevent low density liquid from unintentionally backing up into the low density liquid pump. The valves may be near the pump, or near the lower elevation reservoir, or both. Alternatively or additionally, a valve in contact with the high density liquid may be employed to prevent additional high density liquid from entering the lower elevation reservoir. The valve in contact with the high density liquid may be located near the lower elevation reservoir.
Note: In some embodiments, a dense liquid may comprise a solid-liquid slurry, emulsion, dispersion, pumpable solid, or combinations thereof. For example, a dense liquid may comprise a dispersion of dense nanoparticles in a solid. For example, a dense liquid may comprise a solid-liquid mixture comprising nanoparticles comprising a solid suspended in a liquid. For example, a dense liquid may comprise a ferrofluid. For example, a dense liquid may comprise a solid coated with a surfactant to prevent aggregation or allow the formation of a suspension in the liquid. For example, a dense liquid may comprise a solid coated with a surfactant to prevent aggregation or allow the formation of a suspension in a liquid such as an organic solvent or water, or both. For example, a dense liquid may comprise a colloidal liquid. For example, a dense liquid may comprise nanoscale ferromagnetic or ferrimagnetic particles suspended in a carrier fluid such as an organic solvent or water. For example, a dense liquid may comprise nanoscale particles suspended in a carrier fluid such as an organic solvent or water. For example, a dense liquid may comprise solid particles suspended in the liquid by Brownian motion. In some embodiments, ferrofluids or magnetic fluids may be employed as the dense liquid, the low-density liquid, or both, and power may be generated by passing the ferrofluid or magnetic fluid through magnets and/or coils. For example, the dense liquid may include nanoscale solid particles suspended in a carrier fluid, such as an organic solvent or water. For example, the dense liquid may include a slurry of solids and liquids, where turbulence, surfactants, Brownian motion, or a combination thereof, allows the solids to remain suspended in the liquid.
Note: In some embodiments, the low density liquid may comprise a solid-liquid slurry, or an emulsion, or a dispersion, or a pumpable solid, or a combination thereof. For example, in some embodiments, the low density liquid may comprise pumpable ice. For example, in some embodiments, the low density liquid may comprise a mixture of low density nanoparticles and a solvent, such as water, an organic solvent, an inorganic solvent, or a combination thereof.

Notes: Some embodiments may be configured with the lower elevation reservoir located underground.
No hydrate formation with non-hydrate-forming low density liquids. Air, and especially the nitrogen in air, forms solid hydrates with water at high pressures (pressures above 30 bar depending on temperature).
Non-hydrate-forming low-density liquids do not form solid hydrates with water regardless of pressure, allowing for higher energy density energy storage systems. Configurations with water and low-density liquids in an enclosed structure mechanically isolated from the ocean, where the water or other high-density liquid can be transferred into pipes interconnected to a reservoir at a higher elevation.
Water or a higher density liquid may be in direct contact with a lower density liquid, for example at a liquid-liquid interface in a lower elevation reservoir.
The low density liquid may include a liquid having a density less than the high density liquid.
• Allowing the lower density liquid to be displaced by the higher density liquid may involve opening one or more valves.
The pump may also function as a generator. For example, in some embodiments, the pump and generator may comprise the same unit. For example, the pump/generator may comprise a water power recovery turbine or HPRT.
• The cold low density liquid may undergo further cooling before, during, or after transfer to a refrigerated or cooled higher elevation low density liquid reservoir.
• It may be desirable for the water or high density liquid to have a density similar to that of the surrounding water or other liquid medium in the tank at the lower elevation.
- The low density liquid may be practically insoluble in water or other high density liquids, or may have limited solubility in water or other high density liquids.
The low density liquids may include liquids, including non-hydrate-forming low density liquids. Some gases and liquids form hydrates with water under high pressure and relatively low temperatures, some known as clathrates. Non-hydrate-forming low density liquids may include low density liquids with a molecular structure that forms non-hydrates or non-clathrates, or a molecular weight that is too large to form hydrates, or a combination thereof. Examples include, but are not limited to, one or more or a combination of the following:
Normal butane (n-butane) is a molecule that forms non-hydrates. In a calorimetric study of hydrates of pure isobutane and mixtures of isobutane and normal butane, Buleiko et al. stated, "The experimental measurements resulting from our study conclusively demonstrated that normal butane does not form hydrates in the studied field, but behaves like a non-hydrate-forming molecule." evaluated "the possibility of normal butane hydrate formation within the temperature range of 78-280 K and at pressures up to 15 MPa." 15 MPa is a pressure of 150 bar.
○ Butane, pentane, hexane, heptane, octane, nonane ○ Hydrocarbons ○ Hydrocarbon mixtures ○ Oils ○ Organic compounds ○ Low molecular weight organic compounds ○ Diesel ● In some embodiments, the low density liquid may be soluble in water, or may form hydrates, or a combination thereof.
Some embodiments employing water-soluble low-density liquids or hydrate-forming low-density liquids, or combinations thereof, may employ a barrier between the water and the water-soluble or hydrate-forming low-density liquid, which may include, but is not limited to, a floating barrier, a bladder, a bladder tank, mutually immiscible liquids at a liquid-liquid interface, a piston, a mechanical exchange, a hydraulic exchange, or combinations thereof.
Some embodiments employing low density liquids that are soluble in water, or low density liquids that form hydrates, or a combination thereof, may employ higher density liquids that are not water.
Some embodiments employing low density liquids that are soluble in water, or low density liquids that form hydrates, or combinations thereof, may employ water with hydrate formation inhibitors. Hydrate formation inhibitors are known in the art in the oil and gas industry. Hydrate formation inhibitors may include, but are not limited to, propylene glycol, methanol, ethylene glycol, alcohols, salts, or combinations thereof.
Some embodiments employing a low density liquid that is soluble in water or other high density liquid may operate with the high density liquid containing a saturating concentration of the dissolved liquid. Employing a high density liquid saturated with a low density liquid may only be possible in embodiments employing a low density liquid that has limited solubility or partial miscibility in the high density liquid.
Some embodiments using a low-density liquid that is soluble in water or other high-density liquid may employ a dissolution inhibitor that may reduce or inhibit the solubility of the low-density liquid in the high-density liquid compared to the solubility of the low-density liquid in the high-density liquid without the presence of the dissolution inhibitor. The dissolution inhibitor may be soluble in the low-density liquid, the high-density liquid, or both.
Some embodiments employing low density liquids that are hydrate formers may employ a hydrate formation inhibitor, which may be soluble in the low density liquid, the high density liquid, or both.
Some embodiments employing a low density liquid that is soluble in water or other high density liquids may employ a barrier between the low density liquid and the high density liquid, for example, in a reservoir at a lower elevation. For example, if the low density liquid is liquid ammonia, or a water soluble alcohol, or a combination thereof, and water is the high density liquid, a barrier between the low density liquid and the high density liquid may be required.
The water or higher density liquid may contain additives to provide certain advantageous properties, which may include, but are not limited to, one or more or a combination of the following:
The low density liquids may include additives to provide certain advantageous properties, which may include, but are not limited to, one or more or a combination of the following: ○ Anti-fouling agents ○ Anti-scalant agents ○ Corrosion inhibitors ○ Freezing point depressants ○ Density modifiers ○ Decomposition inhibitors ○ Hydrate formation inhibitors ○ Viscosity reducers ○ Oxygen scavengers ○ Tracers or tracer chemicals that facilitate the ability to track leaks (if a leak occurs) Low density liquids may include additives to provide certain advantageous properties, which may include, but are not limited to, one or more or a combination of the following:
10°F or -1°C at atmospheric pressure ● Heat exchange with a low density liquid may occur after the pump or before the generator ● Heat exchange with a low density liquid may occur before the pump or after the generator ● In some embodiments, the low density liquid may have a low boiling point. A low boiling point may include boiling within 10°K of temperatures feasibly achieved under ambient outdoor temperature conditions, or temperatures potentially reached on surfaces exposed to the sun. For example, a boiling point at atmospheric pressure of 30° C. or less, or 35° C. or less, or 40° C. or less, or 45° C. or less, or 50° C. or less, or 55° C. or less, or 60° C. or less, or combinations thereof, may comprise a low boiling point.
• Embodiments employing low boiling point, low density liquids may employ one or more or a combination of systems and methods to ensure safe liquid handling and storage.
For example, in embodiments where the higher elevation reservoir is located underwater, it may be desirable to locate the higher elevation reservoir at a depth where the hydrostatic pressure surrounding or adjacent to the higher elevation reservoir is equal to or greater than the vapor pressure of the lower density liquid.
For example, in embodiments where the air or water pressure surrounding or adjacent to a higher elevation reservoir is less than the vapor pressure of the low density liquid under ambient outdoor temperature conditions, it may be desirable to employ a pressure resistant tank or pressurized tank or ASME pressurized tank or combination thereof.
For example, in embodiments where the air or water pressure surrounding or adjacent to a reservoir at a higher elevation is less than the vapor pressure of the low-density liquid under ambient outdoor temperature conditions, it may be desirable to cool the low-density liquid to reduce the vapor pressure of the low-density liquid.
For example, a low density liquid can be cooled to a temperature below the boiling point of the low density liquid at atmospheric pressure.
For example, a low density liquid may be cooled to a temperature below the boiling point of the low density liquid at a desired pressure. For example, a low density liquid may be cooled to a temperature such that the vapor pressure of the low density liquid is suitable for storage in a desired tank.
For example, the temperature of the low density liquid in an insulated tank or a refrigerated tank or a temperature controlled tank or tanks or combinations thereof may be maintained within a desired temperature range.
Refrigerated or temperature controlled or chilled tanks may employ one or more or a combination of methods for thermal management. For example, the thermal management methods may include, but are not limited to, one or more or a combination of the following:
○ Refrigeration ○ Chillers ○ Vapour compression refrigeration cycle ○ Absorption based refrigeration cycle ○ Evaporative cooling ○ Water based evaporative cooling ○ Cooling resulting from boiling of a low density liquid. The resulting vapour may be called off-gassing.
It may be desirable to compress, liquefy, or otherwise reuse or recycle the off-gas.
It may be desirable to use the off-gas for fuel or other uses.
○Cooling ○Heat storage ○OTEC
○ Chilled seawater ○ Refrigeration from LNG vaporization, which may involve using the endothermic heat of vaporization of liquefied natural gas ○ Liquid-liquid phase refrigeration cycle ○ Gas-gas phase refrigeration cycle ○ Solid-solid phase refrigeration cycle ○ Solid-gas phase refrigeration cycle ● Butane or n-butane or normal butane may serve as an exemplary high vapor pressure, low density liquid. Other liquids may be employed instead of or in addition to butane. Butane may also refer to a solution that contains or includes butane.
Water may be provided as an exemplary high density liquid, low density liquid, or both. Other liquids may be employed instead of or in addition to water. Water may also refer to a solution that contains or includes water.
The one or more thermal storage media may include a liquid, a solid, a gas, or a supercritical fluid, or a combination thereof, which may be employed to store heat or "cold," or to transfer heat or "cold," or a combination thereof. The thermal storage media may include a phase change material, which may include, but is not limited to, a solid-liquid phase transition, a liquid-liquid phase transition, a liquid-gas phase transition, a liquid-solid phase transition, a solid-solid phase transition, a gas-gas phase transition, a chemical reaction, a reversible chemical reaction, or a combination thereof.
The heat storage liquid may comprise water, or an aqueous solution containing water or a freezing point depressant, or a non-aqueous liquid, or a liquid-liquid phase transition liquid, or a combination thereof.
The heat storage liquid may include water or an aqueous solution containing water and a freezing point depressant. For example, the heat storage liquid may include a solution of water and one or more or a combination of, but not limited to, the following:
o Water soluble organic compounds which may include one or more or combinations of the following, but are not limited to: propylene glycol, ethylene glycol, methanol, ethanol, propanol, isopropanol, acetone, ketones, alcohols, aldehydes, glycols, glycol polymers, polymers, sugars, sugar alcohols, sugar substitutes, molasses o Water soluble nitrogen compounds which may include one or more or combinations of the following, but are not limited to: ammonia, nitric acid, urea, or derivatives thereof o Ionic compounds which may include one or more or combinations of the following, but are not limited to: sodium chloride, calcium chloride, ammonium salts, sodium salts, calcium salts, magnesium salts, potassium salts, sea salt, alkali metal salts, alkaline earth metal salts, transition metal salts, chloride salts, sulfates, sulfites, carbonates, bicarbonate salts, surfactants o Ionic - liquid + aqueous solutions o Acids o Bases o Water soluble gases o Water soluble sulfur compounds which may include, but are not limited to, organic sulfur compounds Heat storage heat exchange may be employed to reduce cooling energy requirements.
Heat storage heat exchange can be employed to recover the "cold" stored in the specific heat capacity of liquid butane.
The thermal storage medium may be stored in one or more tanks.
The thermal storage medium may be stored in a tank with a temperature gradient, for example, a cooler thermal storage liquid forming one temperature layer and a warmer thermal storage liquid forming another temperature layer.
The thermal storage medium may be stored in two or more tanks, at least one tank for the "warm" liquid and at least one tank for the "cold" liquid.
Before charging or during filling, liquid butane can be heat exchanged with a "warm" thermal storage medium to form a "cold" thermal storage medium and to form "warm" butane. The heat exchange can occur when the butane is at a pressure equal to or greater than the vapor pressure of butane. For example, the heat exchange can occur after or during a liquid butane pumping or pressurization step. For example, the steps described can occur before or during butane transfer from a higher elevation reservoir to a lower elevation reservoir, which may be required when the energy storage device is storing power or in the process of "charging."
Before or during discharge, the liquid butane may be heat exchanged with a "cold" heat storage medium to cool the liquid butane to near or below the boiling point of butane at atmospheric pressure (or other desired pressure) and form a "hot" heat storage liquid. For example, the heat exchange may occur before or during the liquid butane hydropower generation stage or depressurization stage. For example, the described steps may occur before or during butane transfer from a lower elevation reservoir to a higher elevation reservoir, which may be required when the energy storage device is generating power or in the process of "discharging."
During installation and/or business set-up, low density liquids may be added to the system using one or more or a combination of processes.
For example, low density liquids can be added or removed by connecting flow lines from LPG or other hydrocarbon or low density liquid transport vessels to interconnection points on the low density liquid subsea pipeline within the energy storage system.
For example, low density liquids may be added or removed by connecting an LPG or other hydrocarbon or low density liquid transport vessel to a disconnectable buoy, which may be connected to one or more of a low density liquid tank or a subsea pipeline or a combination thereof.
For example, low density liquid may be added or removed by low density liquid transported from a pipeline.
For example, low density liquid may be added or removed by low density liquid transferred from rail cars.
For example, low density liquid may be added or removed by low density liquid transferred from a tanker truck, bullet tank, or a combination thereof.
If the reservoir of low density liquid is refrigerated or cooled, the low density liquid may be refrigerated or cooled before, during or after addition of the low density liquid to the refrigerated or cooled reservoir of low density liquid.
Liquid n-butane specific heat capacity: 2.275 J/g°C
• A "cold" heat storage medium may include a heat storage medium below the boiling point temperature of a low density liquid at a pressure of 1 bar (or another desired pressure range).
• The "cold" thermal storage medium may be stored in an insulated tank.
A "cold" thermal storage medium can be maintained at a sufficiently cold temperature using thermal management, which may include refrigeration or other cooling methods when the temperature of the thermal storage medium exceeds a certain temperature or temperature range, or as desired. A sufficiently cold temperature thermal storage medium can include a temperature at which, when heat exchanged with a "warm" low-density liquid, the resulting "cooled" low-density liquid has a vapor pressure at or below the design pressure rating of the higher elevation tank. In some embodiments, a sufficiently cold temperature thermal storage medium can include a temperature at which, when heat exchanged with a "warm" low-density liquid, the resulting "cooled" low-density liquid is at a temperature below the temperature of the "warm" low-density liquid. In some embodiments, the "cooled" low-density liquid can have a vapor pressure at or below the pressure rating of a higher elevation storage reservoir and can be transferred to the higher elevation storage reservoir. In some embodiments, the "chilled" low-density liquid may have a vapor pressure equal to or greater than the pressure rating of the higher elevation storage reservoir and may undergo further cooling before being transferred to the higher elevation storage reservoir. In some embodiments, the "chilled" low-density liquid may have a vapor pressure equal to or less than the pressure rating of the higher elevation storage reservoir and may undergo further cooling before being transferred to the higher elevation storage reservoir.
- Heat exchange with the low density liquid of the thermal storage medium can occur before, after or both the pump and/or generator steps.
Refrigerated or cooled high elevation reservoirs may require more parasitic cooling energy consumption when the energy storage system is partially or fully discharged. Partially or fully discharged conditions may include when high elevation or above land or water storage reservoirs are partially or completely filled with a low density liquid.
Some embodiments may include a closed system in which the displaced higher-density liquid is transferred from a lower-level reservoir to a higher-level reservoir. In some embodiments, the pipe transferring the higher-density liquid between the lower-level and higher-level reservoirs may be surrounded by or immersed in a liquid having a similar or equal density. For example, if the pipe is immersed in, surrounded by, or adjacent to a liquid having a similar or equal density, the higher-density liquid pipe may have an internal pressure that is close to or equal to the hydrostatic pressure outside the pipe. For example, if the pipe is immersed in, surrounded by, or adjacent to a liquid having a similar or equal density, the higher-density liquid pipe may be constructed using a pipe that requires a lower pressure resistance than the lower-density liquid pipe. The lower-pressure pipe may be lower cost or larger in diameter or both compared to one or more pipes employed for the lower-density liquid.
A refrigeration system for cooling a storage reservoir of a low-density liquid employs a backup generator. The backup generator may be utilized to power cooling or refrigeration equipment in the event of an emergency. The backup generator may be used, for example, when an energy storage system is fully discharged and no other power source is available. The backup generator may be powered by a low-density liquid, such as, but not limited to, butane or other low-density liquid or gas-to-liquid fuel. The backup generator may also be powered by other fuel sources if desired.
If desired, power smoothing or immediate response may employ lithium ion batteries, batteries, flywheels, capacitors, supercapacitors, or other energy storage systems.
Systems, methods, or controls may be employed to minimize or mitigate the potential intensity of hydraulic waves or "hydraulic hammer" that may have the potential to occur during changes in liquid flow rate or liquid pressure, or combinations thereof. Hydraulic hammer or hydraulic wave mitigation measures may be known in the art and may include, but are not limited to, gradual flow adjustments, start-up procedures, shut-off procedures, water towers, surge tanks, hydro-pneumatic shock absorbers, hydraulic shock absorbers, expansion tanks, pump pumping bypasses, pump flywheels, or combinations thereof.
Refrigerated or chilled tanks for storing low boiling point, low density liquids may be similar or the same as refrigerated tanks employed in the art, including, for example, but not limited to, one or more of the following or combinations thereof: LPG terminals, propane storage, butane storage, ammonia storage, NGL storage, LNG storage, or combinations thereof.
• Subsea tank construction materials may include one or more or combinations of the following, including but not limited to: metal, steel, aluminum, concrete, precast concrete, plastic, coated polyethylene, polypropylene, composites, fiberglass, rubber, fabric, aggregate.
• Low density liquids can experience changes in density with temperature and pressure.
Due to the relatively low temperature of deep ocean water (typically about 0-3°C), during discharge, the low-density liquid may return to the higher elevation reservoir at a temperature below the surrounding ambient temperature. If the low-density liquid may return to the higher elevation reservoir at a temperature below the surrounding ambient temperature due to cooling that occurs in the deep ocean, the low-density liquid may require less cooling or heat removal than is available in thermal storage, thereby further reducing the potential parasitic energy demand associated with storing refrigerated or cooled low-density liquid.
Seawater may be employed as a thermal storage fluid. Seawater may have a freezing point of approximately -2°C.
• Desalinated brine or reverse osmosis brine may be employed as the heat storage liquid.
Additives may be added to the heat storage liquid, which may include one or more or a combination of the following, but are not limited to: inhibitors, oxygen scavengers, freezing point depressants, other additives described herein, and other additives known in the art.
The present invention may include pumps, sensors, controls, pipes, valves, and/or other equipment or materials that may not be shown in the figures or described herein.
The thermal storage reservoir may include a rigid tank, or a swim bladder tank, or a combination thereof.
• The upper elevation reservoir and/or the lower elevation reservoir may comprise rigid tanks, or bladder tanks, or a combination thereof.
• The thermal storage reservoir may include a floating or solid or liquid material or a combination thereof barrier to separate or minimize mixing of one or more "warm" and "cold" thermal storage liquids.
• Tanks and reservoirs may include tanks and reservoirs known in the art for storing liquids, solids, gases, gas-liquids, or combinations thereof. For example, tanks and reservoirs may include, but are not limited to, one or more or combinations of the following: ASME pressurized tanks, semi-pressurized tanks, atmospheric pressure tanks, balanced pressure tanks, floating roof tanks, Horton spheres, bullet tanks, steel tanks, cement tanks, fiberglass tanks, composite tanks, plastic tanks, aluminum tanks, stainless steel tanks, titanium tanks, metal tanks, glass tanks, ceramic tanks, wooden tanks, floatation bladder tanks, rigid tanks, piston tanks, refrigerated tanks, cooled tanks, open air tanks, open air pits, open air ponds, liner ponds, flexible tanks, modular tanks, subsea tanks, pressure balanced tanks, hybrid tanks, moored tanks, density neutral tanks, ballasted tanks, tanks with support structures, subsea tanks, underground tanks, insulated tanks, mobile tanks, non-mobile tanks, cylindrical tanks, open bottom tanks, open port tanks, tanks with ports and valves, closed system tanks, open system tanks.

Illustrative Diagram Description: FIG. 120: A process for energy storage by displacing a higher density liquid with a lower density liquid. Energy can be stored in the gravitational potential energy difference between a higher density liquid and a lower density liquid at two different elevations. The embodiment shown in this figure can employ a higher elevation reservoir and a lower elevation reservoir, each of which can be designed to store both higher density and lower density liquids. Under conditions in which the system does not store gravitational potential energy, the higher elevation reservoir can store a lower density liquid and the lower elevation reservoir can store a higher density liquid. Energy can be stored when at least a portion of the lower density liquid displaces at least a portion of the higher density liquid in the lower elevation reservoir. In the embodiment shown in this diagram, the volume of liquid entering a reservoir can be equal to the volume of liquid leaving the reservoir, so the volumes of liquid in both the higher elevation reservoir and the lower elevation reservoir can remain relatively constant, if desired. For example, generally, when a volume of lower density liquid is pumped from the higher elevation reservoir into the lower elevation reservoir, a roughly equal volume of higher density liquid can be displaced from the lower elevation reservoir and transferred into the higher elevation reservoir. The diagram shows a higher elevation reservoir on land and a lower elevation reservoir underwater. The diagram shows an energy storage system that is stable in an almost fully "discharged" state.

Figure 121: Similar to Figure 120, except this figure shows an energy storage system that stores, charges, or "charges" energy.

Figure 122: Similar to Figure 120, except this figure shows an energy storage system that is stable at a nearly fully "charged" state.

Figure 123: Similar to Figure 120, except this diagram shows an energy storage system that is generating, producing, or "discharging" energy.

Figure 124: A process for energy storage by displacing a higher density liquid with a lower density liquid. Energy can be stored in the gravitational potential energy difference between a higher density liquid and a lower density liquid at two different elevations. The embodiment shown in this figure can employ a higher elevation reservoir and a lower elevation reservoir, each of which can be designed to store both a higher density liquid and a lower density liquid. Under conditions in which the system does not store gravitational potential energy, the higher elevation reservoir can contain a lower density liquid and the lower elevation reservoir can contain a higher density liquid. Energy can be stored when at least a portion of the lower density liquid displaces at least a portion of the higher density liquid in the lower elevation reservoir. In the embodiment shown in this figure, the volume of liquid entering the reservoir can be equal to the volume of liquid exiting the reservoir, so the volume of liquid in both the higher elevation reservoir and the lower elevation reservoir can remain relatively constant, if desired. For example, if a volume of lower density liquid is pumped from a higher elevation reservoir into a lower elevation reservoir, an equal volume of higher density liquid may be displaced from the lower elevation reservoir and transferred into the higher elevation reservoir. This diagram shows a higher elevation reservoir on a floating structure and a lower elevation reservoir underwater. This diagram shows an energy storage system stable in a nearly fully "discharged" state.

Figure 125: Similar to Figure 124, except this diagram shows an energy storage system that stores, charges, or "charges" energy.

Figure 126: Similar to Figure 124, except this figure shows an energy storage system stable in a nearly fully "charged" state.

Figure 127: Similar to Figure 124, except this diagram shows an energy storage system that generates, or generates, or "discharges" energy.

Figure 128: A process for energy storage by displacing a higher density liquid with a lower density liquid. Energy can be stored in the gravitational potential energy difference between a higher density liquid and a lower density liquid at two different elevations. The embodiment shown in this figure can employ a higher elevation reservoir and a lower elevation reservoir, each of which can be designed to store both higher density and lower density liquids. The embodiment shown in this figure can operate at a different temperature in the higher elevation reservoir than the lower elevation reservoir. For example, the higher elevation reservoir can be at a lower temperature than the lower elevation reservoir. The embodiment shown in this figure can efficiently allow the higher elevation reservoir to store liquid at a different temperature than the lower elevation reservoir, for example, by employing heat exchange and/or heat exchange with auxiliary heat storage between the lower and higher density liquids. For example, due to the difference in heat capacity between the low density liquid and the high density liquid, a portion of the high density liquid may be in heat exchange with the low density liquid, and another portion of the high density liquid may be in heat exchange with auxiliary thermal storage. This diagram shows that this embodiment has a thermal storage system that includes a "cold" thermal storage reservoir and a "warm" thermal storage reservoir. This diagram shows an energy storage system that stores, charges, or "charges" energy.

Figure 129: Similar to Figure 128, except this diagram shows an energy storage system that generates, or generates, or "discharges" energy.

Figure 130: Similar to Figure 128, except this figure shows this embodiment with a thermal storage system including a reservoir containing both "warm" and "cold" thermal storage, which may be separated within the tank due to one or more or a combination, including but not limited to, a thermal gradient, or swim bladder, or barrier, or other separator.

Figure 131: Similar to Figure 128, except this figure shows this embodiment with a thermal storage system including a reservoir containing both "warm" and "cold" thermal storage, which may be separated within the tank due to one or more or a combination, including but not limited to, a thermal gradient, or a swim bladder, or a barrier, or other separator.

Figure 132: A process for energy storage that stores electricity by displacing a higher density liquid with a lower density liquid. Energy can be stored in the gravitational potential energy difference between a higher density liquid and a lower density liquid at two different elevations. The embodiment shown in this figure can employ a higher elevation reservoir and a lower elevation reservoir, each of which can be designed to store both higher density and lower density liquids. The embodiment shown in this figure can operate at a different temperature in the higher elevation reservoir than the lower elevation reservoir. For example, the higher elevation reservoir can be at a lower temperature than the lower elevation reservoir. The embodiment shown in this figure can efficiently allow the higher elevation reservoir to store liquid at a different temperature than the lower elevation reservoir by employing a "warm" high density liquid storage reservoir, a low density liquid-high density liquid heat exchange, and a "cold" high density liquid storage reservoir. For example, due to the difference in heat capacity between the low-density liquid and the high-density liquid, a portion of the high-density liquid may be heat exchanged with the low-density liquid, and another portion of the high-density liquid may be stored in a "warm" high-density liquid storage reservoir. The embodiment shown in this figure may employ a "cold" high-density liquid storage reservoir. "Cool" high-density liquid transferred to and from a higher elevation reservoir designed to store both high-density and low-density liquids may be transferred to and from the "cold" high-density liquid storage reservoir. This figure shows an energy storage system that stores, charges, or "charges" energy.

Figure 133: Similar to Figure 132, except this diagram shows an energy storage system that generates, or generates, or "discharges" energy.

Figure 134: Similar to Figure 132, except this figure shows an energy storage system having a cooling or thermal management system that applies cooling or other thermal management to both a storage reservoir of "cold" high density liquid and a reservoir designed to store both low density and high density liquids.

Figure 135: Similar to Figure 134, except this diagram shows an energy storage system that generates, or generates, or "discharges" energy.

Figure 136: Similar to Figure 134, except showing an example calculation of flow rate.

Figure 137: Similar to Figure 135, except showing an example calculation of flow rate.

Figure 138: A process for energy storage by displacing a higher density liquid with a lower density liquid. Energy can be stored in the gravitational potential energy difference between a higher density liquid and a lower density liquid between two or more reservoirs at at least two or more different elevations. The embodiment shown in this figure can employ a higher elevation reservoir and a lower elevation reservoir, each of which can be designed to store both higher density and lower density liquids. The embodiment shown in this figure can operate at a temperature in the higher elevation reservoir similar to the lower elevation reservoir. The embodiment shown in this figure can operate with the higher elevation reservoir at a temperature different from the ambient temperature adjacent to or surrounding the higher elevation reservoir, or a relatively stable temperature, or a combination thereof. The embodiment shown in this figure may efficiently allow a higher elevation reservoir to store liquid at a different temperature than the ambient temperature adjacent to or surrounding the higher elevation reservoir by employing low density liquid-high density liquid heat exchange and by employing heat exchange with and/or cooling by "cold" seawater from the deep ocean ("cold deep seawater", which may be represented by "CW" in FIG. 138). This figure shows an energy storage system that stores, charges, or "charges" energy.

Figure 139: Similar to Figure 138, except showing an energy storage system that generates, produces, or "discharges" energy.

Illustrative Figure Legends Figures 120-123:
Figures 124-127:
Figures 128 and 129:

Please note: The legends in the diagrams above may define certain components within the context of a system in the process of storing or "charging." Some terms, such as "flow combiner," may include different terms, such as "flow divider," or the reverse application when the system is in the process of generating power or electricity or "discharging."

Figures 132-137:

Please note: The legends in the diagrams above may define certain components within the context of a system in the process of storing or "charging." Some terms, such as "flow combiner," may include different terms, such as "flow divider," or the reverse application when the system is in the process of generating power or electricity or "discharging."

Figures 138 and 139:

Please note: The legends in the diagrams above may define certain components within the context of a system in the process of storing or "charging." Some terms, such as "flow combiner," may include different terms, such as "flow divider," or the reverse application when the system is in the process of generating power or electricity or "discharging."

Additional Description: In some embodiments, the upper elevation and/or lower elevation reservoirs may be designed to store both low-density liquid and high-density liquid. Some embodiments may include storing low-density liquid and high-density liquid in at least a portion of the same tank or vessel. For example, some embodiments may include an upper elevation reservoir designed to store both low-density liquid and high-density liquid, where the low-density liquid and high-density liquid may be stored in the same tank or vessels. For example, some embodiments may include a lower elevation reservoir designed to store both low-density liquid and high-density liquid, where the low-density liquid and high-density liquid may be stored in the same tank or vessels.

In some embodiments, a tank may be designed to store both a low-density liquid and a high-density liquid. In some embodiments, the total volume of liquid stored in the tank may remain constant, while the relative volumes of the low-density liquid and the high-density liquid may vary depending on the state of charge (percentage of storage capacity) and/or other factors. For example, a higher elevation storage reservoir including at least one tank may include a tank designed to store both a low-density liquid and a high-density liquid. In this example, when a volume of the low-density liquid is transferred from the tank, an equal volume of the high-density liquid may be transferred into the tank. Similarly, in this example, when a volume of the high-density liquid is transferred from the tank, an equal volume of the low-density liquid may be transferred into the tank. For example, a lower elevation storage reservoir including at least one tank may include a tank designed to store both a low-density liquid and a high-density liquid. In this example, when a volume of the low-density liquid is transferred from the tank, an equal volume of the high-density liquid may be transferred into the tank. Similarly, in this example, when a volume of high density liquid is transferred from the tank, an equal volume of low density liquid can be transferred into the tank. The described embodiment can exhibit several advantages:
For example, the described embodiments may allow for the use of fewer tanks: a higher elevation area employing tanks designed to store both low density and high density liquids may require half the storage capacity as a higher elevation area that stores high density and low density liquids separately.
For example, the described embodiments may enable the use of rigid and/or fixed volume structures for storage tanks. The use of rigid and/or fixed volume structures for storage tanks may be enabled by the ability of the system to store the same volume of liquid in the tank regardless of the state of charge of the energy storage tank. Compared to floating roof tanks and/or bladder-type tanks, rigid or fixed volume tanks may last longer, cost less, require less maintenance, have fewer failure points, or a combination thereof.
For example, the described embodiments may enable the use of high-density liquids and/or low-density liquids as thermal storage media, thereby increasing the energy efficiency of systems that may require cooled, refrigerated, or temperature-controlled low-density (and/or high-density) liquids. In some embodiments, heat exchange to and from low-density and high-density liquids may enable heat recovery and significantly lower cooling parasitic loads. For example, in a higher elevation reservoir, during power storage or "charging," the low-density liquid may exit the higher elevation reservoir and be heat exchanged with the high-density liquid before or while the high-density liquid enters the higher elevation reservoir. For example, in a higher elevation reservoir, during power generation or "discharging," the high-density liquid may exit the higher elevation reservoir and be heat exchanged with the low-density liquid before or while the low-density liquid enters the higher elevation reservoir.
For example, the described embodiments may enable a system with a floating high-side elevation reservoir to have a floating vessel that continuously contains the same volume of stored liquid, which may allow for a floating high-side elevation reservoir that is fully ballasted or more stable during most or all states of charge.

In some embodiments, it may be desirable for the low density liquid and the high density liquid to be in direct contact at a liquid-liquid interface within the tank. For example, it may be desirable for the low density liquid and the high density liquid to be in direct contact at a liquid-liquid interface in embodiments including, but not limited to, one or more or combinations of the following: the low density liquid is practically insoluble in the high density liquid, or the low density liquid is completely saturated in the high density liquid, or the high density liquid is completely saturated in the low density liquid.

In some embodiments, it may be desirable for the low-density liquid and the high-density liquid to be separated within the tank. For example, in some embodiments, it may be desirable for the low-density liquid and the high-density liquid to be separated by a floating barrier, or a bladder, or a liner, or a pressure exchanger. For example, in some embodiments, it may be desirable for the low-density liquid and the high-density liquid to be separated by a floating barrier, or a bladder, or a liner, or a pressure exchanger due to one or more or a combination of the following, including, but not limited to: the low-density liquid is soluble in the high-density liquid; the low-density liquid is stored near or below the freezing point of the high-density liquid; the low-density liquid can form hydrates with the high-density liquid; or the low-density liquid reacts with the high-density liquid. In some embodiments, such separation within the tank may include an insulating barrier, which may allow the low-density liquid and the high-density liquid to be stored at different temperatures in the same tank. While some embodiments involve storing the low-density liquid and the high-density liquid at the same or similar temperatures, in some other embodiments, it may be advantageous to store the low-density liquid and the high-density liquid at different temperatures. For example, storing the low-density liquid and the high-density liquid at different temperatures may be desirable when one or more or a combination of the following occurs, including but not limited to: the low-density liquid is stored at, near, or below the freezing point of the high-density liquid; or the high-density liquid is stored at, near, or above a temperature that may result in the vapor pressure of the low-density liquid being too high.

In some embodiments, the low-density liquid and the high-density liquid may be stored, at least in part, in a higher elevation reservoir and/or a lower elevation reservoir designed to store both the low-density liquid and the high-density liquid. In some embodiments, storing or "charging" electricity may involve transferring the low-density liquid from the higher elevation reservoir into the lower elevation reservoir, which may involve transferring the high-density liquid from the lower elevation reservoir into the higher elevation reservoir. Similarly, in some embodiments, generating or "discharging" electricity may involve transferring the low-density liquid from the higher elevation reservoir into the lower elevation reservoir, which may involve transferring the low-density liquid from the lower elevation reservoir into the higher elevation reservoir. During filling, the volume of low-density liquid entering the lower elevation reservoir may be equal to the volume of high-density liquid exiting the lower elevation reservoir. During filling, the volume of high-density liquid entering the higher elevation reservoir may be equal to the volume of low-density liquid exiting the higher elevation reservoir. During discharging, the volume of high-density liquid entering the lower elevation reservoir may be equal to the volume of low-density liquid exiting the lower elevation reservoir. During discharging, the volume of low-density liquid entering the higher elevation reservoir may be equal to the volume of high-density liquid exiting the higher elevation reservoir. In some embodiments, one or more or a combination of the reservoirs may need to be heated, cooled, or both.

Heating or cooling, or both, may include ensuring that the low-density liquid and/or the high-density liquid are temperature controlled or within a design temperature range within a particular section of the system. For example, in some embodiments, a higher elevation reservoir may be "cooled" to ensure that the temperature of the low-density liquid is below a temperature range to ensure that the vapor pressure of the low-density liquid is below the design pressure of the storage tank. For example, in some embodiments, a lower elevation reservoir may be "heated" to ensure that the temperatures of the low-density liquid and the high-density liquid are above a temperature range to prevent the formation of solid hydrates. "Cooling" or "cooled" may include maintaining or storing the low-density liquid or the high-density liquid, or both, below a certain temperature range. "Cooling" or "cooled" may include storing the low-density liquid or the high-density liquid, or both, below the temperature of the environment external to the reservoir. "Heating" or "heated" can include maintaining or storing a low-density liquid or a high-density liquid, or both, at or above a certain temperature range. "Heating" or "heated" can include maintaining or storing a low-density liquid or a high-density liquid, or both, at or above the temperature of the environment external to the reservoir.

In some embodiments, the volume of low-density liquid entering and leaving the elevation region may be approximately the same as the volume of high-density liquid entering and leaving the elevation region. If the reservoir at a higher elevation operates at a different temperature than the reservoir at a lower elevation, or if the temperature of the liquid changes substantially during transfer, or a combination thereof, "heating" or "cooling" or both may be required to ensure each section of the system operates within its design temperature range. Heat recovery or heat storage or a combination thereof may be required to ensure that the "heating" or "cooling" or both is performed efficiently or with minimal parasitic loads associated with the "heating" or "cooling" or both. In some embodiments, one process for heat recovery may involve heat exchange of low-density liquid being transferred to one reservoir with high-density liquid being transferred to the opposite reservoir. In some embodiments, during charging or discharging, the volume or volumetric flow rate, or both, of the low-density liquid being transferred to one reservoir may be the same as the volume or volumetric flow rate, or both, of the high-density liquid being transferred to the opposing reservoir. While the volumes or volumetric flow rates, or both, may be the same, the heat capacities of the low-density liquid and the high-density liquid may differ. As a result, exchanging heat between an equal volume of the low-density liquid with an equal volume of the high-density liquid may result in incomplete heat recovery. There are embodiments that may address, benefit from, or exploit the difference in heat capacity between the low-density liquid and the high-density liquid, or a combination thereof. There are embodiments that may enable heat recovery and/or efficient operation of various sections of the system at various temperatures.

For example, some embodiments may involve heat exchanging only a portion of the high-density liquid with a low-density liquid transferred into an opposite reservoir. To allow only a portion of the high-density liquid to be heat exchanged with the low-density liquid, the high-density liquid may be split into two or more streams, for example, during storage or charging. One of the streams may contain a flow rate of high-density liquid such that the total heat capacity of the stream is approximately the same as the total heat capacity of the low-density liquid, allowing the low-density liquid and the high-density liquid to be heat exchanged with virtually complete heat recovery. The other high-density liquid stream may contain a portion of the high-density liquid in excess of the portion having the same total heat capacity as the low-density liquid. The other high-density liquid stream may be heat exchanged with auxiliary thermal storage. After heat exchange with the low-density liquid, the auxiliary thermal storage, or both, the two high-density liquid streams may be combined. When the system is in the process of storing or "charging," the two streams may be transferred to a reservoir at a higher elevation. When the system is in the process of generating power or "discharging," the two streams may be combined into a common pipe or pipes and transported to a reservoir at a lower elevation. An example of this embodiment may be seen in Figures 128 and 129. An exemplary example of this embodiment is described further below.
In this example, Figure 128 is used as a reference. "1" may represent a higher elevation reservoir designed to store both low and high density liquids. "2" may include a low density liquid transferred between the higher elevation reservoir and a heat exchanger. "3" may represent a heat exchanger that facilitates heat transfer between the low and high density liquids. "4" may represent a low density liquid transferred between a heat exchanger and a pump/generator or a hydropower recovery turbine (HPRT). "5" may represent a pump/generator or a hydropower recovery turbine (HPRT). "6" may represent a low density liquid transferred between a pump/generator and a lower elevation reservoir. "7" may represent a lower elevation reservoir designed to store both low and high density liquids. "8" may represent a high density liquid transferred between a lower elevation reservoir and a higher elevation region. "9" may represent a liquid flow divider that splits the high density liquid flow into two liquid streams (but may represent a flow merger during discharge). "10" may represent a high density liquid stream having a total heat capacity approximately equal to that of the low density liquid, and may represent the high density liquid transferred between the flow divider and a low density liquid-high density liquid heat exchanger. "11" may represent a high density liquid stream after heat exchange with the low density liquid, and may represent the high density liquid transferred between the low density liquid-high density liquid heat exchanger and a flow merger. "12" may represent a high density liquid stream transferred between a flow divider and a high density liquid-auxiliary heat storage heat exchanger. "13" may represent a high density liquid-auxiliary heat storage heat exchanger. "14" may represent the high density liquid flow after heat exchange with the auxiliary thermal storage. "15" may represent a flow combiner or flow combiner (but may represent a flow divider during discharge). "16" may represent the high density liquid transferred between the flow combiner and a higher elevation reservoir designed to store both low density and high density liquids. "17" may represent a "warm" auxiliary thermal storage reservoir. "18" may represent the heat storage or heat transfer medium transferred between the high density liquid-to-auxiliary thermal storage heat exchanger and the "warm" auxiliary thermal storage reservoir, or may represent the "warm" heat storage or heat transfer medium. "19" may represent the heat storage or heat transfer medium transferred between the high density liquid-to-auxiliary thermal storage heat exchanger and the "cold" auxiliary thermal storage reservoir, or may represent the "cold" heat storage or heat transfer medium. "20" may represent a "cold" auxiliary thermal storage reservoir. "21" may represent a cooling source or thermal management system or combination thereof to provide cooling or thermal management to a higher elevation reservoir or low density liquid or high density liquid or combination thereof, as needed. "22" may represent any heat transfer between a cooling source or thermal management system or combination thereof and a higher elevation reservoir or low density liquid or high density liquid or combination thereof.
An exemplary implementation of this embodiment may be a 50 MW (maximum power), 600 MWh (maximum storage capacity) system with a lower elevation reservoir in 3,000 meters of water depth and a floating higher elevation region. The low density liquid may include n-butane, and the higher density liquid may include seawater or an aqueous solution having a density similar to seawater. The energy density of the LDL replacing the HDL is approximately 3.56 kWh/m ³ , which may correspond to a 600 MWh energy storage system with the upper elevation reservoir and the lower elevation reservoir each having a liquid storage capacity of approximately 167,888 m ³ . At a total power capacity of 50 MW, the volumetric flow rate of the LDL is approximately 14,045 ^{m 3} /hr, and the volumetric flow rate of the HDL is approximately 14,045 ^{m 3} /hr. Below are additional exemplary specifications and calculations:
A high elevation reservoir designed to store both low and high density liquids may store low and high density liquids at a temperature of -2°C, which may be below the boiling point temperature of n-butane LDL at atmospheric pressure and above the freezing point of the aqueous HDL employed in this example.
Lower elevation reservoirs designed to store both low-density and high-density liquids shall store liquids at the same temperature as deep seawater, or approximately 2°C to 4°C.
In this example, the temperature of the low-density liquid and/or high-density liquid transported into the higher elevation region is assumed to be the same as the surface water temperature, which is a moderate assumption. In this example, the surface water temperature is assumed to be 30°C.
○ The specific heat capacity of the high density liquid is 3.9 J/g°C. ○ The specific heat capacity of liquid normal butane is 2.275 J/g°K. ○ The density of the high density liquid is 1030 kg per cubic meter. ○ The density of the low density liquid is 573 kg per cubic meter. ○ The total volumetric flow rate of the low density liquid at maximum power capacity is 14,045 ^m3 /hour. ○ The total volumetric flow rate of the high density liquid at maximum power capacity is 14,045 ^m3 /hour. ○ The total mass flow rate of the low density liquid at maximum power capacity is 8,048 metric tons per hour. ○ The total mass flow rate of the high density liquid at maximum power capacity is 14,466 metric tons per hour. ○ The total heat capacity of the low density liquid at maximum power capacity flow rate is 18,309 MJ per degree Kelvin per hour. ○ The total heat capacity of the high density liquid at maximum power capacity flow rate is 56,417 MJ per degree Kelvin per hour. ○ The volumetric flow rate of the portion of the high density liquid that has the same total heat capacity as the low density liquid is 4,558 m ³ /hr. ○ The percentage of the total flow of the high density liquid, including the portion of the high density liquid that has the same total heat capacity as the low density liquid, is 32.45%. ○ The volumetric flow rate of the portion of the high density liquid over the portion that has the same total heat capacity as the low density liquid is 9,487 m ³ /hr. ○ The percentage of the total flow of the high density liquid, including the portion of the high density liquid over the portion that has the same total heat capacity as the low density liquid, is 67.55%.

Below is a table with an example simplified flow overview of this example, using FIG. 128 as a reference.

Please note: Some temperatures shown in the table above may reflect ambient temperatures as a conservative estimate of temperature, rather than predicting temperature changes via transmission through pipes.

Please note: Some of the temperatures shown in the table above may not reflect the required temperature difference for heat transfer in the heat exchanger.

For example, some embodiments may involve heat exchanging only a portion of the high-density liquid with a low-density liquid transferred into an opposing reservoir. To allow only a portion of the high-density liquid to be heat exchanged with the low-density liquid, the high-density liquid may be split into two or more streams, for example, during storage or charging. One of the streams may contain a flow rate of high-density liquid such that the total heat capacity of the stream is approximately the same as the total heat capacity of the low-density liquid, which may allow the low-density liquid and the high-density liquid to be heat exchanged with virtually complete heat recovery. After heat exchange with the low-density liquid, the high-density liquid stream may be transferred to a "cold" high-density liquid storage reservoir. For example, during charging, the "cold" high-density liquid may be transferred from the "cold" high-density liquid storage reservoir into a storage reservoir designed to store both high-density and low-density liquids. The volume of high density liquid transferred into the storage reservoir designed to store both high density and low density liquids may be approximately the same as the volume of low density liquid transferred out of the storage reservoir designed to store both high density and low density liquids. The volume of high density liquid transferred into the storage reservoir designed to store both high density and low density liquids may be greater than the volume of high density liquid entering the "cold" high density liquid storage reservoir. The other high density liquid stream may include a portion of high density liquid in excess of the portion having the same total heat capacity as the low density liquid. The other high density liquid stream may be transferred to a "warm" high density liquid storage reservoir. Figures 132 and 133 may show an example of this embodiment. Illustrative examples of this embodiment are described further below.
In this example, Figure 132 is used as a reference. "1" may represent a higher elevation reservoir designed to store both low and high density liquids. "2" may include a low density liquid transferred between the higher elevation reservoir and a heat exchanger. "3" may represent a heat exchanger that facilitates heat transfer between the low and high density liquids. "4" may represent a low density liquid transferred between a heat exchanger and a pump/generator or a hydropower recovery turbine (HPRT). "5" may represent a pump/generator or a hydropower recovery turbine (HPRT). "6" may represent a low density liquid transferred between a pump/generator and a lower elevation reservoir. "7" may represent a lower elevation reservoir designed to store both low and high density liquids. "8" may represent a high density liquid transferred between a lower elevation reservoir and a higher elevation region. "9" may represent a liquid flow divider that splits the high density liquid flow into two liquid streams (but may represent a flow merger during discharge). "10" may represent a high density liquid stream transferred between a flow divider and a "warm" high density liquid storage reservoir. "11" may represent a "warm" high density liquid storage reservoir. "12" may represent a high density liquid stream having a total heat capacity approximately equal to that of the low density liquid, and may represent a high density liquid transferred between a flow divider and a low density liquid-high density liquid heat exchanger. "13" may represent a high density liquid stream after heat exchange with a low density liquid, and may represent a high density liquid transferred between a low density liquid-high density liquid heat exchanger and a "cold" high density liquid storage reservoir. "14" may represent a "cold" high density liquid storage reservoir. "15" may include "cold" high density liquid transferred between a "cold" high density liquid storage reservoir designed to store both low density and high density liquids and a higher elevation reservoir. "21" may represent a cooling source or thermal management system or combination thereof to provide cooling or thermal management to the higher elevation reservoir, or low density liquid, or high density liquid, or combination thereof, as needed. "22" may represent any heat transfer between a cooling source or thermal management system or combination thereof and a higher elevation reservoir, or low density liquid, or high density liquid, or combination thereof.
An exemplary implementation of this embodiment may be a 50 MW (maximum power), 600 MWh (maximum storage capacity) system with a lower elevation reservoir in 3,000 meters of water depth and a floating higher elevation region. The low density liquid may include n-butane, and the higher density liquid may include seawater or an aqueous solution having a density similar to seawater. The energy density of the LDL replacing the HDL is approximately 3.56 kWh/m ³ , which may correspond to a 600 MWh energy storage system with the upper elevation reservoir and the lower elevation reservoir each having a liquid storage capacity of approximately 167,888 m ³ . At a total power capacity of 50 MW, the volumetric flow rate of the LDL is approximately 14,045 ^{m 3} /hr, and the volumetric flow rate of the HDL is approximately 14,045 ^{m 3} /hr. Below are additional exemplary specifications and calculations:
A high elevation reservoir designed to store both low and high density liquids may store low and high density liquids at a temperature of -2°C, which may be below the boiling point temperature of n-butane LDL at atmospheric pressure and above the freezing point of the aqueous HDL employed in this example.
Lower elevation reservoirs designed to store both low-density and high-density liquids shall store liquids at the same temperature as deep seawater, or approximately 2°C to 4°C.
In this example, the temperature of the low-density liquid and/or high-density liquid transported into the higher elevation region is assumed to be the same as the surface water temperature, which is a moderate assumption. In this example, the surface water temperature is assumed to be 30°C.
○ The specific heat capacity of the high density liquid is 3.9 J/g°C. ○ The specific heat capacity of liquid normal butane is 2.275 J/g°K. ○ The density of the high density liquid is 1030 kg per cubic meter. ○ The density of the low density liquid is 573 kg per cubic meter. ○ The total volumetric flow rate of the low density liquid at maximum power capacity is 14,045 ^m3 /hour. ○ The total volumetric flow rate of the high density liquid at maximum power capacity is 14,045 ^m3 /hour. ○ The total mass flow rate of the low density liquid at maximum power capacity is 8,048 metric tons per hour. ○ The total mass flow rate of the high density liquid at maximum power capacity is 14,466 metric tons per hour. ○ The total heat capacity of the low density liquid at maximum power capacity flow rate is 18,309 MJ per degree Kelvin per hour. ○ The total heat capacity of the high density liquid at maximum power capacity flow rate is 56,417 MJ per degree Kelvin per hour. ○ The volumetric flow rate of the portion of the high density liquid that has the same total heat capacity as the low density liquid is 4,558 m ³ /hr ○ The percentage of the total flow of the high density liquid, including the portion of the high density liquid that has the same total heat capacity as the low density liquid, is 32.45% ○ The volumetric flow rate of the portion of the high density liquid beyond the portion that has the same total heat capacity as the low density liquid, is 9,487 ^{m 3} /hr ○ The percentage of the total flow of the high density liquid, including the portion of the high density liquid beyond the portion that has the same total heat capacity as the low density liquid, is 67.55% ● Below is a table with an exemplary simplified flow overview of this example, using Figure 132 as a reference.

Please note: Some temperatures shown in the table above may reflect ambient temperatures as a conservative estimate of temperature, rather than predicting temperature changes via transmission through pipes.

Please note: Some of the temperatures shown in the table above may not reflect the required temperature difference for heat transfer in the heat exchanger.

In some embodiments, cold, warm, deep sea water may be employed to cool low-density liquids and/or high-density liquids. By employing cold, warm, deep sea water as a cooling source, the described embodiments may involve less capital cost or complexity. The cold, warm, deep sea water may be utilized, for example, using pipes, water pumps, and heat exchangers capable of transporting water between the deep ocean and higher elevation areas. The cold, warm, deep sea water may be heat exchanged with a portion of the high-density liquid that exceeds the portion having the same total heat capacity as the low-density liquid.

For example, some embodiments may involve heat exchanging only a portion of the high-density liquid with a low-density liquid transferred into an opposing reservoir. To allow only a portion of the high-density liquid to be heat exchanged with the low-density liquid, the high-density liquid may be split into two or more streams, for example, during storage or charging. One of the streams may contain a flow rate of high-density liquid such that the total heat capacity of the stream is approximately the same as the total heat capacity of the low-density liquid, which may allow the low-density liquid and the high-density liquid to be heat exchanged with virtually complete heat recovery. The other high-density liquid stream may contain a portion of high-density liquid that exceeds the portion having the same total heat capacity as the low-density liquid. The other high-density liquid stream may be heat exchanged with "cold" deep seawater. After heat exchange with the low-density liquid, "cold" deep seawater, or both, the two high-density liquid streams may be combined. When the system is in the process of storing or "charging," the two streams can be transferred to a higher elevation reservoir designed to store both low density and high density liquids. An example of this embodiment can be seen in Figures 138 and 139. An exemplary example of this embodiment is described further below.
In this example, Figure 138 is used as a reference. "1" may represent a higher elevation reservoir designed to store both low and high density liquids. "2" may include a low density liquid transferred between the higher elevation reservoir and a heat exchanger. "3" may represent a heat exchanger that facilitates heat transfer between the low and high density liquids. "4" may represent a low density liquid transferred between a heat exchanger and a pump/generator or a hydropower recovery turbine (HPRT). "5" may represent a pump/generator or a hydropower recovery turbine (HPRT). "6" may represent a low density liquid transferred between a pump/generator and a lower elevation reservoir. "7" may represent a lower elevation reservoir designed to store both low and high density liquids. "8" may represent a high density liquid transferred between a lower elevation reservoir and a higher elevation region. "9" may represent a liquid flow divider that splits the high density liquid flow into two liquid streams (but may represent a flow merger during discharge). "10" may represent a high density liquid stream having a total heat capacity approximately equal to that of the low density liquid, and may represent the high density liquid transferred between the flow divider and a low density liquid-high density liquid heat exchanger. "11" may represent a high density liquid transferred between a low density liquid-high density liquid heat exchanger and a flow merger (but may represent a flow merger during discharge). "12" may represent a high density liquid stream transferred between a flow divider and a cooling heat exchanger. "13" may represent a cooling heat exchanger that may exchange cold deep seawater with the high density liquid. "14" may represent high density liquid transferred between the cooling heat exchanger and the flow combiner. "15" may represent the flow combiner (but may represent a flow combiner during discharge). "16" may represent "cold" high density liquid transferred between the flow combiner and a higher elevation reservoir designed to store both low density and high density liquids. "17" may represent "warm" cooling liquid or "warm" deep sea water returned to the ocean after heat exchange. "18" may represent "cold" cooling liquid or "cold" deep sea water transferred to the heat exchanger as a cooling medium. "21" may represent a cooling source or thermal management system, or combination thereof, to provide additional cooling or thermal management, if needed, to the higher elevation reservoir, or low density liquid, or high density liquid, or combination thereof. "22" may represent heat transfer between a cooling source or thermal management system or combination thereof and a higher elevation reservoir or low density liquid or high density liquid or combination thereof.
An exemplary implementation of this embodiment may be a 50 MW (maximum power), 600 MWh (maximum storage capacity) system with a lower elevation reservoir in 3,000 meters of water depth and a floating higher elevation region. The low density liquid may include n-butane, and the higher density liquid may include seawater or an aqueous solution having a density similar to seawater. The energy density of the LDL replacing the HDL is approximately 3.56 kWh/m ³ , which may correspond to a 600 MWh energy storage system with the upper elevation reservoir and the lower elevation reservoir each having a liquid storage capacity of approximately 167,888 m ³ . At a total power capacity of 50 MW, the volumetric flow rate of the LDL is approximately 14,045 ^{m 3} /hr, and the volumetric flow rate of the HDL is approximately 14,045 ^{m 3} /hr. Below are additional exemplary specifications and calculations:
o High elevation reservoirs designed to store both low density and high density liquids can store low density and high density liquids at temperatures of 5°C.
Lower elevation reservoirs designed to store both low-density and high-density liquids shall store liquids at the same temperature as deep seawater, or approximately 2°C to 4°C.
In this example, the temperature of the low-density liquid and/or high-density liquid transported into the higher elevation region is assumed to be the same as the surface water temperature, which is a moderate assumption. In this example, the surface water temperature is assumed to be 30°C.
○ The specific heat capacity of the high density liquid is 3.9 J/g°C. ○ The specific heat capacity of liquid normal butane is 2.275 J/g°K. ○ The specific heat capacity of seawater is 4 J/g°K. ○ The density of the high density liquid is 1030 kg per cubic meter. ○ The density of the low density liquid is 573 kg per cubic meter. ○ The density of seawater is 1030 kg per cubic meter. ○ The total volumetric flow rate of the low density liquid at maximum power capacity is 14,045 ^m3 /hour. ○ The total volumetric flow rate of the high density liquid at maximum power capacity is 14,045 ^m3 /hour. ○ The total mass flow rate of the low density liquid at maximum power capacity is 8,048 metric tons per hour. ○ The total mass flow rate of the high density liquid at maximum power capacity is 14,466 metric tons per hour. ○ The total heat capacity of the low density liquid at maximum power capacity is 18,309 MJ per degree K per hour. ○ The total heat capacity of the high density liquid at maximum power capacity flow rate is 56,417 MJ per °K per hour ○ The volumetric flow rate of the portion of the high density liquid having the same total heat capacity as the low density liquid is 4,558 m ³ /hour ○ The percentage of the total flow of the high density liquid, including the portion of the high density liquid having the same total heat capacity as the low density liquid, is 32.45% ○ The volumetric flow rate of the portion of the high density liquid beyond the portion having the same total heat capacity as the low density liquid, is 9,487 m ³ /hour ○ The percentage of the total flow of the high density liquid, including the portion of the high density liquid beyond the portion having the same total heat capacity as the low density liquid, is 67.55% ○ The total volumetric flow rate of the deep sea cooling water at maximum power capacity during charging is 9,250 m ³ /hour ● Below is a table with an exemplary simplified flow overview of this example, using Figure 138 as a reference.

Please note: Some temperatures shown in the table above may reflect ambient temperatures as a conservative estimate of temperature, rather than predicting temperature changes via transmission through pipes.

Please note: Some of the temperatures shown in the table above may not reflect the required temperature difference for heat transfer in the heat exchanger.

In some embodiments, semi-pressurized tanks may be employed. In some embodiments employing cold deep-sea water for cooling, semi-pressurized tanks may be employed due to the low density liquid having an atmospheric boiling point temperature below the temperature of cold deep-sea water. For example, n-butane may have a boiling point of -1°C to 1°C at atmospheric pressure, and cold deep-sea water may be approximately 5°C after transport to the ocean surface. At 5°C, n-butane has a vapor pressure of approximately 1.2 atmospheres. Semi-pressurized tanks may have a design pressure of 1.2 atmospheres or greater.

In some embodiments, "heated" or "heating" may include increasing the temperature of a liquid at an elevation and transferring the liquid to a different elevation once the desired temperature is reached. Similarly, in some embodiments, "cooled" or "cooling" may include decreasing the temperature of a liquid at an elevation and transferring the liquid to a different elevation once the desired temperature is reached. For example, a low-density liquid transferred from a reservoir at a higher elevation to a reservoir at a lower elevation may be heated in the higher elevation region before or during transfer to the reservoir at the lower elevation. For example, a high-density liquid transferred from a reservoir at a higher elevation to a reservoir at a lower elevation may be heated in the higher elevation region before or during transfer to the reservoir at the lower elevation. For example, a lower density liquid transferred from a lower elevation reservoir to a higher elevation reservoir may be cooled in the lower elevation region before or during transfer to the higher elevation reservoir. For example, a higher density liquid transferred from a lower elevation reservoir to a higher elevation reservoir may be heated in the lower elevation region before or during transfer to the higher elevation reservoir.

In some embodiments, "heated" or "heating" can include increasing the temperature of a liquid at an elevation and transferring the liquid into a reservoir at a similar or same elevation or within the same elevation region. Similarly, in some embodiments, "cooled" or "cooling" can include increasing the temperature of a liquid at an elevation and transferring the liquid into a reservoir at a similar or same elevation or within the same elevation region. In some embodiments, the cooling or heating or both can occur within the reservoir or can be applied directly to the reservoir.

In some embodiments, heating or cooling, or both, may occur at different elevations, at approximately the same elevation, within the reservoir, or applied directly to the reservoir, or a combination thereof.

"State of charge" may include the amount of energy stored in an energy storage system relative to the total actual or design energy storage capacity of the energy storage system. In some embodiments, the state of charge may be defined by the percentage of low-density liquid in the upper elevation reservoir.

Notes: In some embodiments, the denser liquid may have a freezing point lower than the boiling point of the less dense liquid at the pressure in the higher elevation reservoir. In some embodiments, the denser liquid may include seawater or a liquid having a density similar to or virtually the same as ocean water. Seawater, or a solution with a similar salt concentration to seawater, may have a freezing point low enough for some low-density liquids; for example, n-butane has a boiling point temperature at atmospheric pressure above the freezing point of seawater. In some embodiments, the denser liquid may have a freezing point lower than that of seawater. For example, a freezing point lower than that of seawater may be achieved by adding an antifreeze additive to water or an aqueous solution to create a solution with a similar density and a lower freezing point than seawater. Antifreeze additives may include one or more or combinations of the following, but are not limited to: water-soluble organic compounds, salts, glycols, ethylene glycol, propylene glycol, methanol, ethanol, glycerol, polyols, or isopropanol. For example, a lower freezing point than seawater may be achieved by combining an antifreeze additive that is less dense and/or more dense than seawater with water to create a solution that has a similar density and a lower freezing point than seawater. The antifreeze additive may include, but is not limited to, one or more or combinations of the following: water soluble organic compounds, salts, glycols, ethylene glycol, propylene glycol, methanol, ethanol, glycerol, polyols, or isopropanol.
Systems may be employed to minimize or prevent hydraulic ram that can occur in incompressible liquid systems during changes in liquid flow rate. Systems and methods for compensating for or minimizing hydraulic ram include, but are not limited to, one or more or combinations of the following: overpressure tanks, or charged tanks, or pressurized gas compensation, or water towers, or liquid towers, or gravity towers, or expansion tanks, or systems and methods known in the art.
In some embodiments, it may be desirable for the dense liquid to contain an additive that reduces the viscosity of the dense liquid. For example, ethanol, methanol, or propanol may be added in addition to an additive having a density greater than water to create a solution that has a lower viscosity than a solution having only an additive having a density greater than water, or a lower viscosity than seawater, or a combination thereof.
Some embodiments may employ subsea pumps or subsea generators or both or a combination thereof. Subsea pumps or subsea generators or both or a combination thereof may be desirable in some embodiments, for example, employing subsea cables.
• Some embodiments may employ a high density liquid as the heat storage medium.
Some embodiments may employ a heat exchanger that directly contacts a higher density liquid with a lower density liquid in a heat exchange. Directly contacting a higher density liquid with a lower density liquid in a heat exchange may result in one or more or a combination of, but not limited to, reducing the heat exchanger temperature differential required during the heat exchange, or increasing energy efficiency, or reducing the capital cost of the heat exchanger, or reducing the required size of the heat exchanger, or reducing pressure drop, or improving round trip energy efficiency, or reducing parasitic loads.
In some embodiments, the higher density liquid may be in direct contact with the lower density liquid at various points in the system. For example, in some embodiments, the higher density liquid is in direct contact with the lower density liquid in a lower elevation reservoir, a higher elevation reservoir, or a combination thereof. For example, in some embodiments, the thermal storage medium may have the same composition as the higher density liquid, or may include the higher density liquid. For example, in some embodiments, heat exchange between the lower density liquid and the higher density liquid may involve direct contacting of the higher density liquid with the lower density liquid. For example, in some embodiments, heat exchange between the lower density liquid and the higher density liquid may involve direct mixing and direct separation of the higher density liquid and the lower density liquid. For example, in some embodiments, heat exchange between the lower density liquid and the thermal storage medium may involve direct contacting of the thermal storage medium with the lower density liquid.
Some embodiments may employ two or more low density liquid pipes or risers and/or two or more high density liquid pipes or risers. Employing two or more pipes or risers may be desirable in some embodiments due to, for example, one or more or a combination of the following, including but not limited to, reducing installation costs, matching installation capacity, installation capacity limitations, reducing CAPEX, redundancy, increasing service life, connecting to two or more lower elevation tanks, connecting to two or more higher elevation tanks, connecting to two or more pumps or generators, or a combination thereof.
In some embodiments, low-density liquid and high-density liquid may be stored in a lower elevation reservoir and a higher elevation reservoir within at least a portion of the same tank. For example, during power storage or "charging," LDL may replace HDL in the lower elevation reservoir, and HDL may replace LDL in the higher elevation reservoir. For example, during power generation or "discharging," HDL may replace LDL in the lower elevation reservoir, and HDL may replace LDL in the higher elevation reservoir.
In some embodiments, the LDL in the higher elevation reservoir may contain a low-boiling, low-density liquid or may require cooling or storage at a temperature some distance below ambient temperature in the higher elevation reservoir. In some embodiments, such as those in which low-density and high-density liquids are stored in lower and higher elevation reservoirs within at least a portion of the same tank, it may be desirable for the HDL to function as a form of heat storage or heat storage medium. For example, during power generation or "discharge,""cold" HDL exiting the higher elevation reservoir may be heat exchanged with "warm" LDL entering the higher elevation reservoir, resulting in the "cold" LDL entering the higher elevation reservoir and the "warm" HDL being transferred to the lower elevation reservoir.
● In some embodiments, during energy storage (charging) or generation (discharging), the volumes of LDL and HDL entering and leaving the higher elevation region and the lower elevation region may be the same or similar, but it is important to note that the densities and specific heat capacities of HDL and LDL may differ. For example, HDL may have a higher density and/or a higher specific heat capacity than LDL. HDL may have a higher total heat capacity than LDL for the same volume of liquid. Exchanging heat between equal volumes of HDL and LDL may result in a larger temperature change in the LDL than in the HDL, resulting in incomplete heat recovery. There are several configurations that can be employed to more efficiently recover heat from the entry and exit of HDL or from the entry and exit of LDL. Such configurations may include, but are not limited to, one or more or combinations of the following summarized below:
In some embodiments, only a portion of the HDL is heat exchanged with the LDL during transfer of the LDL and HDL between the higher elevation reservoir and the lower elevation reservoir, and that portion may include an amount of HDL having a total heat capacity similar to or the same as the total heat capacity of the LDL exchanged with that portion of HDL.
In some embodiments, only a portion of the HDL is heat exchanged with the LDL during the transfer of the LDL and HDL between the higher elevation reservoir and the lower elevation reservoir. Another portion of the HDL may be heat exchanged with the auxiliary heat storage. This "portion" of HDL and the "other portion" or HDL may be combined in the same pipe or pipes before or during the transfer from the higher elevation portion to the lower elevation portion.
In some embodiments, only a portion of the HDL is heat exchanged with the LDL during transfer of the LDL and HDL between the higher elevation reservoir and the lower elevation reservoir.
During storage or "charging," the portion of HDL may be stored in a "cold" HDL storage tank after heat exchange. The "cold" HDL storage tank may transfer a volume of "cold" HDL to a tank designed to store both HDL and LDL. The volume of "cold" HDL transferred into a tank designed to store both HDL and LDL may contain approximately the same volume of HDL as the volume of LDL exiting the tank designed to store both HDL and LDL. The volume of "cold" HDL transferred into a tank designed to store both HDL and LDL may contain a volume of HDL greater than the volume of HDL in the "portion" of HDL. Another portion of the HDL, which may include HDL that is not heat exchanged with LDL during transfer of LDL and HDL between the higher elevation and lower elevation reservoirs, may be stored in a "warm" HDL storage tank.
During power generation or "discharge," a volume of "cold" HDL may be transferred from the tank designed to store both HDL and LDL to the "cold" HDL storage tank, and/or an equivalent volume of LDL may enter the tank designed to store both HDL and LDL. A portion of HDL may be transferred from the "cold" HDL storage tank and heat exchanged with LDL before or during transfer of the LDL into the tank designed to store both HDL and LDL. Additionally, HDL representing "another portion of HDL" may be transferred from the "warm" HDL storage tank. This "portion" and the "other portion" or HDL may be combined in the same pipe or pipes before or during transfer from a higher elevation to a lower elevation.
Electricity may be provided as an example of work that is stored, generated, or transferred, or a combination thereof. If desired, other forms of work may be stored, generated, or transferred, including, but not limited to, one or more or a combination of the following: hydraulic work, or pneumatic work, or mechanical work.
If the density of the high density liquid is practically the same as the density of the water surrounding the lower elevation reservoir, the pressure inside the lower elevation reservoir can be close to or practically the same as the pressure outside, surrounding, or adjacent to the lower elevation reservoir.
• In some embodiments, the HDL may include a heat storage medium.
Some embodiments may employ direct contact heat exchangers. For example, if the lower density liquid is insoluble in or completely saturated with the higher density liquid, the lower density liquid and the higher density liquid may be in direct contact during heat exchange. Direct contact heat exchange may have multiple advantages, which may include, but are not limited to, one or more or a combination of the following: lower heat exchange delta T, or lower CAPEX, or greater energy efficiency, or less corrosion, or smaller surface, or less fouling buildup, or lower pressure drop.
A possible direct contactor heat exchanger may include a column including a high density liquid input, a high density liquid output, a low density liquid input, and a low density liquid output. The low density liquid input may be located near the bottom of the column. The high density liquid input may be located near the top of the column. The low density liquid output may be located near the top of the column. The high density liquid output may be located near the bottom of the column. For example, the low density liquid may enter near the bottom of the column and float to the top of the column. For example, the high density liquid may enter near the top of the column and settle to the bottom of the column. During the flotation of the low density liquid and the settling of the high density liquid, the low density liquid and the high density liquid may exchange heat, and heat transfer may occur. If desired, the column may include packaging. If desired, the column may include agitation. If desired, one column or two or more columns may be employed.
In some embodiments, it may be desirable to store low-density liquids and high-density liquids at relatively high temperatures in an environment having a total pressure near or above the pressure required for hydrate formation. In some embodiments, the relatively high temperature may include a temperature above the hydrate formation temperature. In some embodiments, the environment having a total pressure near or above the pressure required for hydrate formation may include a lower-elevation reservoir, or a pipe, or a combination thereof. In some embodiments, it may be desirable to heat the low-density liquid, the high-density liquid, or both to the relatively high temperature before, during, or after transferring the low-density liquid or the high-density liquid from a higher-elevation reservoir to a lower-elevation reservoir. It may be desirable to employ the heated low-density liquid and/or the high-density liquid at a total pressure near or above the pressure required for hydrate formation to prevent hydrate formation, enable safe liquid handling, enable direct liquid-liquid contact, or a combination thereof. For example, it may be desirable for tanks, pipes, and/or other equipment to include at least a portion of insulation to minimize heat or "cold" losses and/or reduce parasitic heating and/or cooling loads. In some embodiments, it may be desirable to have low density liquids and high density liquids in countercurrent heat exchange or otherwise exchange heat during transport to enable heat and "cold" recovery and minimize parasitic heating and/or cooling energy demands. In some embodiments, it may be desirable to employ high temperature and/or low temperature auxiliary thermal storage.

ILLUSTRATIVE DIAGRAM DESCRIPTIONS FIG. 140A: The embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment employing a power exchanger (which may also be referred to as a pressure exchanger, or an energy recovery device or unit, or a power recovery device or unit). In this embodiment, the power exchanger may be located in a lower elevation region near a lower elevation reservoir. The power exchanger may recover a portion of hydraulic power from the lower density liquid stream and transfer the recovered portion of hydraulic power to the higher density liquid stream. For example, the power exchanger may include a turbine or pump or pressure exchanger ("5") on the lower density liquid stream, a mechanical, hydraulic, pneumatic, or electrical power transfer method ("10"), and/or a turbine or pump or pressure exchanger ("5") on the higher density liquid stream. For example, in this diagram, the power exchanger may transfer sufficient power or pressure from the low-density liquid stream to the high-density liquid stream to apply sufficient pressure to the high-density liquid stream to allow it to overcome the pressure differential or pressure drop or pressure loss in transferring the high-density liquid from the lower elevation reservoir to the higher elevation reservoir ("12"). For example, in this diagram, the power exchanger may provide pressure or power transfer between the low-density liquid and the high-density liquid while allowing the lower elevation reservoir ("7") to remain at a relatively stable or constant pressure or with minimized changes in the pressure of the lower elevation reservoir. This diagram may show that power can be recovered and transferred from the low-density liquid to the high-density liquid stream, or power can be recovered and transferred from the high-density liquid to the low-density liquid stream, or a combination thereof. The diagram may show an embodiment with a pressure balancing device and/or pressure sensor ("8") connected to a lower elevation reservoir ("7"). The diagram may show a higher elevation reservoir ("1") of low density liquid that may be thermally managed, cooled, refrigerated, or a combination thereof ("14" and "15"). The diagram may show this embodiment storing or "charging" electricity.

Figure 140B: This diagram may be the same as Figure 140A, but may show that a portion of the hydraulic power may be transferred from the low density liquid stream to the high density liquid stream upon storage or "charging."

Figure 140C: This figure may be the same as Figure 140A, but may show a higher elevation reservoir of low density liquid without thermal management, cooling, or refrigeration.

FIG. 141A: This diagram may be the same as FIG. 140A, but may show the embodiment generating or "discharging." In some embodiments, during discharge, higher density liquid may bypass the power exchanger ("11") and/or lower density liquid may bypass the power exchanger ("5") when the system is generating or "discharging." In some embodiments, an auxiliary pump may apply auxiliary pressure to the higher density liquid being transferred from the higher elevation reservoir to the lower elevation reservoir, for example, to overcome or compensate for pressure losses or drops during transfer from the higher elevation reservoir to the lower elevation reservoir, and/or to ensure that the pressure of the higher density liquid within the lower elevation reservoir is approximately the same as the pressure surrounding, adjacent to, or external to the lower elevation reservoir, and/or combinations thereof. The backing pump, which may not be shown in this diagram, may be located in the higher elevation area, the lower elevation area, elsewhere in the process, or a combination thereof.

Figure 141B: This diagram may be the same as Figure 140B, but may show that this embodiment generates or "discharges" power. This diagram may show that a portion of the hydraulic power may be transferred from the higher density liquid stream to the lower density liquid stream upon generation or "discharge."

Figure 141C: This figure may be the same as Figure 140A, but may show a higher elevation reservoir of low density liquid without thermal management, cooling, or refrigeration.

Figure 142A: This embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment employing a power exchanger. In this embodiment, the power exchanger may include a power recovery device or a pressure exchanger device that may be housed in one unit. The power exchanger may include hydraulic and/or mechanical power or pressure transmission. The power exchanger may include electrical power or pressure transmission. The power exchanger may include pneumatic power or pressure transmission. The diagram may show a power exchanger ("9") that recovers excess pressure or power from the low-density liquid stream ("4") before it enters the lower-elevation reservoir ("6") and transfers the excess pressure or power to the high-density liquid stream ("9"), resulting in a high-density liquid stream ("10") with sufficient pressure to overcome or compensate for the pressure drop or loss during transfer of the high-density liquid from the lower-elevation reservoir to the higher-elevation reservoir. The diagram may show an embodiment with a pressure balancing device and/or pressure sensor ("8") connected to the lower-elevation reservoir ("7"). The diagram may show a thermally managed, cooled, refrigerated, or combination thereof ("14" and "15") high-elevation reservoir of low-density liquid ("1"). This diagram may indicate that this embodiment stores or "charges" electricity.

Figure 142B: This embodiment shown in this figure may be the same as Figure 142A, but may show a higher elevation reservoir of low density liquid without thermal management, cooling, or refrigeration.

143A: This diagram may be the same as FIG. 140A, but may show the embodiment generating or "discharging." In some embodiments, during discharge, higher density liquid may bypass the power exchanger ("9") and/or lower density liquid may bypass the power exchanger ("9") when the system is generating or "discharging." In some embodiments, an auxiliary pump may apply auxiliary pressure to the higher density liquid being transferred from the higher elevation reservoir to the lower elevation reservoir, for example, to overcome or compensate for pressure losses or drops during transfer from the higher elevation reservoir to the lower elevation reservoir, and/or to ensure that the pressure of the higher density liquid within the lower elevation reservoir is approximately the same as the pressure surrounding, adjacent to, or external to the lower elevation reservoir, and/or combinations thereof. The backing pump, which may not be shown in this diagram, may be located in the higher elevation area, the lower elevation area, elsewhere in the process, or a combination thereof.

Figure 143B: This embodiment shown in this figure may be the same as Figure 143A, but may show a higher elevation reservoir of low density liquid without thermal management, cooling, or refrigeration.

Figure 144: The embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment that employs a mechanism ("11") for removing or separating a portion of the lower density liquid present in the higher density liquid prior to or during storage of the higher density liquid in a reservoir at a higher elevation. The removed or separated lower density liquid may be transferred to one or more sections of the process designed to store the lower density liquid.

Figure 145: The embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment with a higher elevation reservoir designed to store both a lower density liquid and a higher density liquid, and/or may be thermally managed, such as cooled or refrigerated. This figure may depict an embodiment that uses countercurrent heat exchange between a lower density liquid and a higher density liquid. This figure may depict the embodiment storing or "charging" electricity.

Figure 146: This figure may be the same as Figure 145, but may show that this embodiment generates or "discharges" electricity.

Figure 147: This figure may be the same as Figure 145, but may show additional auxiliary cooling of the high density liquid during "charging" after heat exchange with the low density liquid. For example, additional auxiliary cooling of the high density liquid may be required in some embodiments due to the greater heat capacity of the high density liquid for the same liquid volume as the low density liquid.

Figure 148: This embodiment shown in this figure may illustrate an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may illustrate an embodiment with a higher elevation lower density liquid reservoir located in a separate location from a higher elevation higher density liquid reservoir. For example, this figure may illustrate a higher elevation higher density liquid reservoir located on a floating structure and a higher elevation lower density liquid reservoir located on land. This figure may illustrate this embodiment in a discharged state.

Figure 149: This figure may be the same as Figure 148, but may show that this embodiment stores or "charges" electricity.

Figure 150: This figure may be the same as Figure 148, but may show the present embodiment in a charged state.

Figure 151: This figure may be the same as Figure 148, but may show that this embodiment generates or "discharges" electricity.

Figure 152: This diagram may show a rigid tank with a pressure balancing device. This diagram may include a reservoir at a lower elevation during the process of power storage or "charging." This diagram may include a reservoir at a higher elevation during the process of power generation or "discharging." The pressure balancing device may include, but is not limited to, a flow meter, a flow controller, a bladder tank ("6"), a valve, a connection/disconnection device, a pressure sensor, or combinations thereof. The pressure balancing device may mitigate pressure changes or pressure waves or overpressure events. The pressure balancing device may monitor the pressure inside the rigid tank relative to the pressure outside, surrounding, or adjacent to the rigid tank. The pressure balancing device may ensure that the pressure inside the rigid tank is similar to or equal to the pressure outside, surrounding, or adjacent to the rigid tank. The pressure balancing device may be isolable or removable from the rigid tank. It is important to note that the bladder tank of the pressure balancing device may have a volume substantially smaller than the volumetric capacity of the rigid tank. It is important to note that the volume of liquid in the bladder tank of the pressure balancing device may remain relatively constant during normal operation, including, for example, when the energy storage process is charging, discharging, or at steady state. The pressure balancing device may be employed to monitor the pressure inside the reservoir relative to the pressure outside the reservoir and communicate the pressure information to flow control devices (such as pumps, turbines, and valves) to mitigate the effects of potential under- or over-pressure events. The bladder tank may be replaced or supplemented with a piston or similar pressure-equalizing tank. In some embodiments, the pressure balancing device may comprise an expansion tank.

Figure 153: This diagram may show a rigid tank with a pressure balancing device. This diagram may include a reservoir at a higher elevation during the process of storing or "charging." This diagram may include a reservoir at a lower elevation during the process of generating or "discharging."

Figure 154: The embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment with a higher elevation reservoir configured to store both a lower density liquid and a higher density liquid, and a power exchanger near or within the lower elevation region. This figure may depict an embodiment that uses thermal management and/or heat exchange between the lower density liquid and the higher density liquid. This figure may depict the embodiment storing or "charging" power.

Figure 155: This figure may be the same as Figure 154, but may show that this embodiment generates or "discharges" electricity.

Figure 156: The embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment with a higher elevation reservoir configured to store both a lower density liquid and a higher density liquid, and a power exchanger near or within the lower elevation region. This figure may depict an embodiment that uses thermal management of the lower density liquid and/or the higher density liquid within the higher elevation reservoir. This figure may depict the embodiment storing or "charging" power.

Figure 157: This figure may be the same as Figure 156, but may show that this embodiment generates or "discharges" electricity.

Figure 158: This embodiment shown in this figure may depict an energy storage system that stores energy by displacing a higher density fluid with a lower density fluid. This figure may depict an embodiment having a pump fluidly connected to a higher density liquid in a lower elevation region. The pump may be employed to apply a supplemental pressure to the higher density liquid, the supplemental pressure being equal to or greater than the pressure differential, pressure drop, or pressure loss required to transfer the higher density liquid from the lower elevation region to the higher elevation region at a desired flow rate. The pump may be electrically powered. The pump may be powered by electricity provided by a subsea cable. The pump may be powered by electricity provided by a power exchanger. The pump may be electrically, hydraulically, mechanically, pneumatically, or a combination thereof. This figure may depict this embodiment storing or "charging" electricity.

Figure 159: This embodiment shown in this figure may depict an energy storage system that stores energy by displacing a denser fluid with a less denser fluid. This figure may depict an embodiment having a pump fluidly connected to a denser liquid in a higher elevation region. The pump may be employed to apply a supplemental pressure to the denser liquid that is equal to or greater than the pressure differential, pressure drop, or pressure loss required to transfer the denser liquid from the higher elevation region to the lower elevation region at a desired flow rate. The pump may be employed to apply a supplemental pressure to the denser liquid to ensure that the pressure of the denser liquid in a lower elevation reservoir, for example, during discharge or power generation, is approximately equal to or similar to the hydrostatic pressure outside or adjacent to the lower elevation reservoir. The pump may be electrically powered. The pump may be electrically, hydraulically, mechanically, pneumatically, or a combination thereof. This diagram may show this embodiment generating or "discharging" electricity.

Illustrative Figure Legends Figs. 140A-C, 141A-C:

Figures 142A-B, 143A-B:

Figure 144:

Figures 145 and 146:

Figure 147:

Figures 148-151:

Figures 152-153:

Figures 154 and 155:

Figures 156 and 157:

Figure 158:

Figure 159:

Additional Description: In some embodiments, a pressure exchanger, or pressure recovery, or power recovery turbine, or a combination thereof, may be employed, which may be referred to as a power exchanger or pressure exchanger. Note that power exchanger and pressure exchanger may be used interchangeably. In some embodiments, a power exchanger or pressure exchanger may be employed near the reservoir at a lower elevation.
A power exchanger may involve recovering power from one stream and transferring this power to another stream. For example, in some embodiments, during charging, excess pressure or power in a low-density liquid stream being transferred into a lower elevation reservoir may be harnessed by a power exchanger, and the harnessed power may be employed to power and/or facilitate the transfer of a higher-density liquid from the lower elevation reservoir to the higher elevation reservoir.
In some embodiments, energy is stored when a lower density liquid is piped from a reservoir at a higher elevation to a reservoir at a lower elevation to displace a higher density liquid in the reservoir at the lower elevation. In some embodiments, the displaced higher density liquid at the lower elevation is piped to the reservoir at the higher elevation. In some embodiments, the pressure of the lower density liquid during energy storage or "charging" must exceed the pressure of the higher density liquid in the reservoir at the lower elevation by a pressure difference equal to or greater than the pressure difference required for the displaced higher density liquid to be piped from the reservoir at the lower elevation to the reservoir at the higher elevation at a desired volumetric flow rate. The desired volumetric flow rate may include, for example, a volumetric flow rate equal to the volumetric flow rate of the lower density liquid being transferred into the reservoir at the lower elevation. Transferring a denser liquid through a pipe from a lower elevation reservoir to a higher elevation reservoir at a sufficient flow rate may require, for example, a pressure differential or some pressurization to overcome the pipeline pressure drop, which in some embodiments may be applied by the less dense liquid being transferred to the lower elevation reservoir.
In some embodiments, the pressure differential may be applied by a lower density liquid being transferred to a lower elevation reservoir, with the pressure differential being applied within the lower elevation reservoir to the higher density liquid in the lower elevation reservoir. Applying the pressure differential within the lower elevation reservoir may require the lower elevation reservoir to be designed to withstand a pressure equal to or greater than the pressure differential, particularly if, for example, the pressure within the lower elevation reservoir was approximately equal to the pressure surrounding, external to, or adjacent to the lower elevation reservoir prior to applying the pressure differential.
In some embodiments, the pressure differential can be powered by the lower-density liquid being transferred to the lower-elevation reservoir. For example, before entering the lower-elevation reservoir, the lower-density liquid can pass through a power exchanger, where a portion of the power and/or pressure is recovered from the lower-density liquid. The portion of the power and/or pressure recovered from the lower-density liquid can be employed to power the transfer of the higher-density liquid from the lower-elevation reservoir to the higher-elevation reservoir. "Powering the transfer of the higher-density liquid from the lower-elevation reservoir to the higher-elevation reservoir" can include providing pressure and/or power to a pump to a pressure differential equal to or greater than the pressure differential required to transfer the displaced higher-density liquid through a pipe from the lower-elevation reservoir to the higher-elevation reservoir at the desired volumetric flow rate. It may be desirable for the power exchange or pressure exchange, or both, to occur external to the lower-elevation tank or reservoir. For example, by performing at least a portion of the power and/or pressure exchange external to the lower elevation tank or reservoir, the lower elevation tank or reservoir may operate with minimal internal pressure changes during charging and discharging. For example, by performing at least a portion of the power and/or pressure exchange external to the lower elevation tank or reservoir, the lower elevation tank or reservoir may require less pressure differential tolerance or resistance, which may allow for the use of larger and/or less expensive tanks or other storage vessels.
In some embodiments, the power exchanger may function as a flow meter, or a flow controller, or a valve, or a combination thereof. For example, in some embodiments, the power exchanger may be in communication with a pressure sensor and/or a pressure balancing device inside the lower elevation reservoir, and the power exchanger may adjust the flow rate of the lower density liquid and/or the higher density liquid to ensure, for example, that the pressure inside the lower elevation reservoir is within a desired pressure range.
o In some embodiments, the power exchanger may function to power a process near the lower elevation reservoir, which may include, but is not limited to, a valve, a flow controller, a sensor, a monitoring device, a pump, a pressure exchanger, a turbine, a flow meter, a light, an instrument, a drone, an autonomous vehicle, a non-autonomous vehicle, a communication device, or a combination thereof.
The pressure of the low density liquid created by the pump during energy storage or "charging" can be, for example, greater than or equal to the sum of:
The gravitational or hydrostatic pressure of the denser liquid minus the gravitational or hydrostatic pressure of the less dense liquid at the elevation difference between the lower elevation reservoir and the higher elevation reservoir.
- Pressure difference or pressure loss of a low density liquid being transported in a pipeline between a reservoir at a higher elevation and a reservoir at a lower elevation at a desired volumetric flow rate. - Pressure difference or pressure loss of a high density liquid being transported in a pipeline between a reservoir at a lower elevation and a reservoir at a higher elevation at a desired volumetric flow rate.
Any pressure or power losses in the power or pressure exchange between a low density liquid and a high density liquid, for example to allow or encourage the low density liquid to displace the high density liquid in a reservoir at a lower elevation.
In some embodiments, a portion of the lower density liquid may dissolve in the higher density liquid. In some embodiments, a portion of the higher density liquid may dissolve in the lower density liquid. In some embodiments, a portion of the lower density liquid may dissolve in the higher density liquid due to the relative pressure of the lower density liquid and the higher density liquid in the lower elevation reservoir. In some embodiments, the lower density liquid may have a low boiling point or a high vapor pressure or both. In some embodiments, the lower density liquid may be present in the higher density liquid transferred from the lower elevation reservoir to the higher elevation reservoir. In some embodiments, a portion of the lower density liquid present in the higher density liquid may be removed from the higher density liquid before transferring the higher elevation liquid into the higher elevation reservoir. In some embodiments, a portion of the lower density liquid present in the higher density liquid may be removed from the higher density liquid while the higher elevation liquid is within the higher elevation reservoir. The removal of the portion of the lower density liquid from the higher density liquid may involve, for example, one or more or a combination of, but not limited to, the following: pressure reduction, liquid-liquid separation, gas-liquid separation, vacuum distillation, vacuum compression, degassing, agitation, heating, cooling, compression, membrane, or separator. The separated lower density liquid may be recovered, transferred to another part of the process, or transferred to another use. The separated lower density liquid may include a gas phase lower density liquid. The gas phase lower density liquid may be compressed and/or condensed and/or cooled before, during, or after transfer to another part of the process. Separation of the lower density liquid present in the higher density liquid may occur before, during, or after transferring the higher density liquid into a higher elevation reservoir, or a combination thereof.
In some embodiments, the low density liquid may be soluble in the high density liquid at a concentration of less than 30% by weight, or less than 20% by weight, or less than 10% by weight, or less than 5% by weight, or less than 4% by weight, or less than 3% by weight, or less than 2% by weight, or less than 1% by weight, or less than 0.5% by weight, or less than 0.1% by weight, or less than 0.01% by weight, or less than 0.01% by weight.
In some embodiments, the low-density liquid and/or the high-density liquid may be thermally managed to be stored in the higher elevation reservoir at a desired temperature range. For example, if the higher elevation reservoir is configured to store both a low-density liquid and a high-density liquid, the low-density liquid and the high-density liquid may be cooled, heated, or both to ensure the desired temperature range. For example, if the low-density liquid is liquid normal butane and the high-density liquid is seawater or an aqueous solution having a density similar to seawater, it may be desirable to store the low-density liquid or the high-density liquid, or both, at a temperature close to the temperature of deep seawater (e.g., below 6°C), or at the boiling point of the low-density liquid at atmospheric pressure (e.g., below 1°C or below -1°C), or both. For example, due to the large volumes of low-density and high-density liquids, and/or the low surface area to volume ratio of the large-volume tank, and/or the warm or cold temperatures of deep seawater, the temperatures of the low-density and high-density liquids may operate within a desired temperature range or with minimal temperature change during process operation. If the temperatures of the low-density and/or high-density liquids vary beyond the desired temperature range, a thermal management process may cool and/or heat the low-density and/or high-density liquids to within the desired temperature range.
• In some embodiments, the lower elevation area or lower elevation reservoir may comprise tanks in different locations.
In some embodiments, the higher elevation region or higher elevation reservoir may comprise tanks in different locations. For example, in some embodiments, the higher elevation low density liquid tank may be located on land, while the higher elevation high density liquid tank may comprise a floating structure. For example, in some embodiments, the higher side elevation low density liquid tank may comprise a rigid tank, while the higher side elevation high density liquid tank may comprise a bladder tank. For example, in some embodiments, the higher side elevation low density liquid tank may comprise a rigid tank, while the higher side elevation high density liquid tank may comprise a reservoir or basin. For example, in some embodiments, the higher side elevation high density liquid tank may comprise a floating structure.
In some embodiments, a rigid tank may be employed as the lower elevation reservoir. When the lower elevation reservoir is submerged, it may be desirable for the pressure inside the lower elevation reservoir to be similar to the pressure surrounding or external to the submerged reservoir. It may be desirable for the pressure inside the lower elevation reservoir to be similar to the pressure surrounding or external to the lower elevation reservoir, for example, to minimize the required pressure differential resistance or required pressure differential tolerance of the lower elevation reservoir tank, which may minimize the cost of the lower elevation reservoir tank. It may be desirable to be able to mitigate or minimize the effects of pressure or pressure wave changes due to, for example, changes in liquid flow, overpressure, water hammer, liquid hammer, or combinations thereof. For example, some embodiments may employ a pressure balancing device interconnected to the rigid tank of the lower elevation reservoir. The pressure balancing device may comprise a relatively small air bladder tank, and/or a piston, and/or a flow meter, and/or a pressure sensor, and/or a flow controller, and/or an actuator, and/or a pump, and/or a valve, and/or a pressure relief valve, and/or a pressure compensation valve, or a combination thereof.
o A pressure balancing device may ensure that the pressure inside the lower elevation reservoir is similar or nearly the same as the pressure outside, surrounding, or adjacent to the lower elevation reservoir.
The pressure balancing device may be fluidly connected to a high density liquid inside a reservoir at the lower elevation of the rigidity. Alternatively or additionally, the pressure balancing device may be fluidly connected to a low density liquid inside a reservoir at the lower elevation of the rigidity.
Where the pressure balancing device employs a bladder tank or piston or a combination thereof, it may be desirable for the volumetric capacity of the bladder tank or piston or a combination thereof to be 0.01% or less, or 0.05% or less, or 0.1% or less, or 0.5% or less, or 1% or less, or 5% or less, or 10% or less, or 15% or less, or 20% or less, or 25% or less of the volumetric capacity of the reservoir at the lower elevation of the rigidity.
o Pressure balancing devices may reduce or minimize the effects of changes in pressure or pressure waves.
The pressure balancing device may monitor the pressure inside the rigid tank relative to the pressure outside the rigid tank. For example, if liquid flows from the pressure balancing device into a reservoir at a lower elevation, the pressure inside the reservoir at the lower elevation may be less than the pressure outside the reservoir at the lower elevation. For example, if liquid flows from a reservoir at a lower elevation into the pressure balancing device, the pressure inside the reservoir at the lower elevation may exceed the pressure outside the reservoir at the lower elevation.
o The pressure balancing device may communicate with pumps, or power exchangers, or valves, or flow controllers, or other devices, or combinations thereof, which may be located in the lower elevation area, the higher elevation area, or any other point in the system, or combinations thereof. For example, the pressure balancing device may provide information regarding the pressure or relative pressure inside the lower elevation reservoir, which may allow other devices to make adjustments to ensure that the rigid lower elevation reservoir is at a desired pressure relative to the pressure surrounding, adjacent to, or external to the rigid lower elevation reservoir.
The bladder tank or piston or a combination of both of the pressure balancing device may be located at a location external to the rigid tank.
The bladder tank or piston or combination thereof of the pressure equalizing device may be configured such that the bladder tank or piston or combination thereof can be replaced or removed when desired. For example, the bladder tank or piston or combination thereof may be removed or replaced if damaged, or in need of maintenance, or due to an improved replacement, or combination thereof.
The bladder tank or piston or combination thereof of the pressure exchange device may be configured such that the bladder tank or piston or combination thereof is accessible to the undersea vessel or autonomous vehicle.
The bladder tank or piston or combination thereof of the pressure balancing device may be configured such that the bladder tank or piston or combination thereof is easily separable from the rigid tank. For example, the bladder tank or piston or combination of the pressure balancing device may be fluidly disconnected from the rigid tank by closing a valve. The bladder tank or piston or combination of the pressure balancing device may be fluidly disconnected, for example, including but not limited to, if a leak occurs, or if a potential risk of failure occurs, or if the pressure balancing device is undergoing maintenance, or if a part of the pressure balancing device is being replaced, or combinations thereof.
It may be desirable for the bladder and/or piston of the pressure balancing device to be at a partially utilized volume under normal operating conditions. This partially utilized volume may mitigate an overpressure event due to liquid flowing into the pressure balancing device due to reserve volume in the pressure balancing device. This partially utilized volume may mitigate an overpressure event due to liquid flowing from the pressure balancing device into a rigid tank at a lower elevation.
During normal operation of the energy storage process, it may be desirable for a relatively minimal amount of liquid to flow into or out of the bladder and/or piston of the pressure equalizer. For example, during a typical full charge/discharge cycle of the energy storage process, the volume of liquid stored in the bladder and/or piston of the pressure balancing device may vary by no more than +/- 1%, or no more than +/- 5%, or no more than +/- 10%, or no more than +/- 15%, or no more than +/- 20%, or no more than +/- 25%, or no more than +/- 30%, or no more than +/- 35%, or no more than +/- 40%, or no more than +/- 45%, or no more than +/- 50%, or no more than +/- 55%, or no more than +/- 60%, or no more than +/- 65%, or no more than +/- 70%, or no more than +/- 75%, or no more than +/- 80%, or no more than +/- 85%, or no more than +/- 90%, or no more than +/- 90%.
○ It may be desirable for the pressure balancing device to be fluidly connected only to the liquid in the lower elevation reservoir during over-pressure and/or under-pressure events. For example, in an over-pressure event, a pressure relief valve or similar valve may be opened to allow liquid to be transferred from the rigid lower elevation reservoir into the pressure balancing device. For example, in an under-pressure event, a valve may be opened to allow liquid to be transferred from the pressure balancing device into the rigid lower elevation reservoir.

Description Energy can be stored by pumping a lower density liquid into a lower elevation reservoir to displace a higher density liquid in the lower elevation reservoir. In some embodiments, the density of the higher density liquid is similar or approximately the same as the density of seawater or water or other liquid surrounding or adjacent to the lower elevation reservoir. Advantageously, using a higher density liquid having a similar or approximately the same density as seawater or liquid surrounding or adjacent to the lower elevation reservoir can allow the pressure inside the lower elevation reservoir to be the same or similar to the pressure surrounding or adjacent to the lower elevation reservoir, since the density of the higher density liquid inside the system can be approximately the same as the liquid adjacent or surrounding the tank. By having similar hydrostatic pressures inside and outside the lower elevation reservoir, the lower elevation reservoir may require a minimum pressure or pressure differential resistance that is significantly less than the pressure differential between the lower elevation and higher elevation tanks, which may allow for the use of lower cost and/or larger volume tanks. A potential challenge with some embodiments of the presently described process is that the process may be limited to liquids having a density similar to seawater. If the density of the denser liquid in some embodiments of the presently described process is greater than the density of seawater, the hydrostatic pressure of the denser liquid may exceed the hydrostatic pressure of seawater at the depth of the lower elevation reservoir, which may result in the need to use tanks that can withstand the pressure differential between the hydrostatic pressure of the denser liquid and the hydrostatic pressure difference of seawater in the lower elevation reservoir, which may be significantly more expensive than tanks in pressure equilibrium with the surrounding seawater. For example, it may be desirable to employ a denser liquid that has a density greater than seawater due to the potentially resulting greater system energy density. The energy density per cubic meter of liquid in some embodiments depends on the density difference between the lower density liquid and the higher density liquid. Increasing the density of the higher density liquid can substantially increase the energy density of the system by increasing the density difference between the lower density liquid and the higher density liquid. It may be desirable to develop a system that stores electricity by displacing a higher density liquid with a lower density liquid, where the higher density liquid has a density greater than seawater or greater than the density of water adjacent to a lower elevation reservoir, and the lower elevation reservoir may be in pressure equilibrium or operate at a pressure similar to that of the surrounding or adjacent seawater. It may be desirable to develop a system that benefits from greater system energy density by employing a liquid having a density greater than seawater, while simultaneously allowing the lower elevation reservoir to operate in pressure equilibrium with the adjacent seawater.

In some embodiments, the high side elevation reservoir may be located near land at an elevation above the surface of the body of water or above sea level. In some embodiments, the high side elevation reservoir itself may be located at an elevation above the surface of the body of water or above sea level. For example, the high side elevation reservoir may include a structure or tank located at least in part at an elevation higher than the surface of the body of water or above sea level. For example, the high side elevation reservoir may be located on a mountain, or a hill, or a platform, or a floating structure, or a similarly elevated surface, or a combination thereof. In some embodiments, it may be desirable to locate the high side elevation reservoir of the higher density liquid at a higher elevation than the high side elevation reservoir of the lower density liquid. For example, it may be desirable to have the higher elevation reservoir of the lower density liquid located at an elevation near sea level, while the higher elevation reservoir of the higher density liquid may be located more than 10 meters, or more than 25 meters, or more than 50 meters, or more than 75 meters, or more than 100 meters, or more than 125 meters, or more than 150 meters above sea level.
Some embodiments may employ locating the higher elevation reservoir of dense liquid at an elevation above sea level, or above the elevation of the higher elevation reservoir of lower density liquid, or a combination thereof, to ensure that the hydrostatic pressure within the lower elevation reservoir is the same or similar to the hydrostatic pressure adjacent to the lower elevation reservoir. For example, if the dense liquid has a density less than seawater, it may be desirable to increase the elevation of the higher elevation reservoir of dense liquid to match the hydrostatic pressure of seawater adjacent to the lower elevation reservoir. For example, some embodiments may employ freshwater or freshwater with corrosion and biofouling inhibitors as the dense liquid, and the freshwater dense liquid may have a density less than seawater. For example, the density of seawater may be 1.035 g/mL, while the density of freshwater with corrosion and biofouling inhibited may be 1.01 g/mL. If the lower elevation reservoir is located at a seawater depth of 2,500 meters and the higher elevation reservoir of dense liquid is located at sea level, the hydrostatic pressure difference between the seawater and the dense liquid is equivalent to a head of 62.5 meters if the dense liquid comprises suppressed freshwater with a density of 1.01 g/mL. For example, in this case, it may be desirable to locate the higher elevation reservoir of dense liquid at 62.5 meters above sea level if the dense liquid comprises suppressed freshwater having a density of 1.01 g/mL.
In some embodiments, locating a higher elevation reservoir of dense liquid at an elevation above sea level, or above a higher elevation lower density liquid reservoir, or a combination thereof, may be employed to increase the system energy density per cubic meter of stored energy or electricity. Increasing the elevation of the higher elevation higher density liquid reservoir may increase the system energy density. In some embodiments, increasing the elevation of the higher elevation higher density liquid reservoir above sea level may result in the lower elevation reservoir having an internal hydrostatic pressure that exceeds the hydrostatic pressure adjacent to the lower elevation reservoir, which may require the use of tanks that can withstand this hydrostatic pressure difference, which may be expensive. It may be desirable to develop a system that benefits from the greater system energy density of a higher elevation higher density liquid reservoir at an elevation above the surface of an ocean or body of water, while simultaneously allowing the lower elevation reservoir to operate in pressure equilibrium with the adjacent seawater.

SUMMARY Some embodiments of the present invention may relate to systems and methods for enabling the use of high density liquids having a density greater than seawater while allowing the lower elevation reservoir to remain in pressure equilibrium or near pressure equilibrium with seawater or water adjacent to the lower elevation reservoir.

Some embodiments of the present invention may relate to systems and methods for enabling the use of higher elevation reservoirs located above the interface or near the surface of a body of water, while allowing the lower elevation reservoir to remain in pressure equilibrium or near pressure equilibrium with seawater or water adjacent to the lower elevation reservoir.

Some embodiments of the present invention may relate to systems and methods for minimizing or preventing corrosion. For example, some embodiments of the present invention may relate to employing a system for removing dissolved oxygen from high density liquids, low density liquids, or both, to minimize or virtually eliminate corrosion on system equipment due to, for example, low density liquids, high density liquids, or both, within the system.

FIG. 160: Process for storing energy by displacing a higher density liquid with a lower density liquid. This embodiment may include a higher elevation reservoir configured to store a lower density liquid, or a higher elevation reservoir configured to store a lower density liquid and a higher density liquid, or a higher elevation reservoir configured to store a higher density liquid, or a pump, or a turbine, or a power recovery or pressure recovery system, or a lower elevation reservoir configured to store a higher density liquid, or a lower elevation reservoir configured to store a lower density liquid and a higher density liquid, or piping interconnecting one or more components, or a sensor, or a pressure balancing device, or combinations thereof. This embodiment may employ a pressure or power recovery system to, for example, enable the lower elevation reservoir to operate at or near pressure equilibrium with pressures external to, surrounding, or adjacent to the lower elevation reservoir. The lower elevation reservoir may be surrounded by or adjacent to seawater, water, or air, or gas, or solids, or earth, or a combination thereof.
Charging may involve pumping (e.g., "3") a lower-density liquid from a higher-elevation reservoir (e.g., "1") to a lower-elevation region, and power from the lower-density liquid may be recovered (e.g., "5") to displace at least a portion of the higher-density liquid in the lower-elevation reservoir (e.g., "7") and transfer (e.g., "10") the higher-density liquid to the higher-elevation reservoir (e.g., "1" or "11"). During charging, pressure recovery may involve recovering from the lower-density liquid (e.g., "4") at least a portion of the pressure that exceeds the pressure adjacent the lower-elevation region or the lower-elevation reservoir, or both, and providing or transferring this pressure or power to the higher-density liquid (e.g., "10"). After or during pressure recovery, lower density liquid may be transferred into the lower elevation reservoir at or near the pressure of the lower elevation reservoir, or at or near the pressure adjacent to the lower elevation reservoir, or both (e.g., "6"). Before or during receiving power or pressure recovered from the lower elevation liquid due to a power or pressure exchanger, higher density liquid may be removed from the lower elevation reservoir (e.g., "7") (e.g., "9"). After or during receiving power or pressure recovered from the lower elevation liquid due to a power or pressure exchanger, higher density liquid may be transferred from the lower elevation region to a higher elevation reservoir (e.g., either "1" or "11") (e.g., "10").
Discharging may involve enabling the transfer of a higher density liquid from a higher elevation reservoir (e.g., "1" or "11") to a lower elevation region, and power from the higher density liquid may be recovered (e.g., "5") to displace at least a portion of the lower density liquid in the lower elevation reservoir (e.g., "7") and transfer this lower density liquid to a turbine (e.g., "3") to generate electricity (e.g., "5"). During charging, pressure recovery may involve recovering from the higher density liquid (e.g., "10") at least a portion of the pressure that exceeds the pressure adjacent the lower elevation region or the lower elevation reservoir, or both, and providing or transferring this pressure or power to the lower density liquid (e.g., "4"). After or during pressure recovery, the higher density liquid may be transferred into the lower elevation reservoir at or near the pressure of the lower elevation reservoir, or at or near the pressure adjacent to the lower elevation reservoir, or both (e.g., "9"). Before or during receiving power or pressure recovered from the higher density liquid due to a power or pressure exchanger, the lower density liquid may be removed from the lower elevation reservoir (e.g., "7") (e.g., "6"). After or during receiving power or pressure recovered from the higher density liquid due to a power or pressure exchanger, the lower density liquid may be transferred from the lower elevation region to a turbine (e.g., "4") in the higher elevation region (e.g., either "3"). The turbine may generate power from the lower density liquid before or during transfer of the lower density liquid to the higher elevation reservoir (e.g., "1").

Figure 161: This diagram may be the same as Figure 160, except that this diagram may show an embodiment that generates or "discharges" energy.

Figure 162: This diagram may be the same as Figure 160, except that the lower density liquid upper elevation reservoir may be different from the higher density liquid upper elevation reservoir. In some embodiments, the lower density liquid upper elevation reservoir may be at approximately the same elevation as the higher density liquid upper elevation reservoir. In some embodiments, the lower density liquid upper elevation reservoir may be at a higher elevation than the higher density liquid upper elevation reservoir. In some embodiments, the lower density liquid upper elevation reservoir may be at a lower elevation than the higher density liquid upper elevation reservoir. This diagram may show embodiments that store or "charge" energy.

Figure 163: This diagram may be the same as Figure 162, except that this diagram may show an embodiment that generates or "discharges" energy.

Figure 164: This diagram may be the same as Figure 162, except that this diagram may show an embodiment with a lower elevation reservoir, including separating a separate reservoir of low density liquid from a separate reservoir of high density liquid. This diagram may show an embodiment that stores or "charges" energy.

FIG. 165: This diagram may be the same as FIG. 164, except that this diagram may show an embodiment that generates or "discharges" energy.
Illustrative figure legend

Exemplary Pressures in Exemplary Embodiments Exemplary Pressures in Exemplary Embodiments with Dense Liquids Having Densities Greater Than Seawater (Reference Figures 160 and 161)
In this example, the elevation of the "high elevation" region may be approximately 0 meters above sea level, while the elevation of the low elevation region may be greater than minus 2,500 meters above sea level, creating an elevation difference between the low elevation reservoir and the high elevation reservoir equal to approximately 2,500 meters.
In this example, the density of the dense liquid may be 1.30 g/mL, and the dense liquid may include an aqueous solution of calcium chloride.
In this example, the density of the low-density liquid may be 0.573 g/mL, and the low-density liquid may include normal butane or n-butane.
In this example, the density of seawater may be 1.035 g/mL.
Based on the above, the following are example pressures for Figs. 160 and/or 161 for this example:
The pressure of "1" and "2" can be near atmospheric pressure or near the vapor pressure of normal butane. For example, the pressure inside "1" and "2" can be 5 bar or less, or 4 bar or less, or 3 bar or less, or 2 bar or less, or 1 bar or less, or a combination thereof.
○ The pressure at "4" may vary with water depth. The pressure at "4" may increase with water depth and reach a maximum pressure near "5" or near or within the "lower elevation" region. Near "5", the pressure at "4" may be equal to or greater than the hydrostatic pressure of the dense liquid in "10" when the system is storing or "charging", for example, as shown in FIG. 160. Near "5", the pressure at "4" may be equal to or less than the hydrostatic pressure of the dense liquid in "10" when the system is generating or "discharging", for example, as shown in FIG. 161. The pressure at "4" near "5" may be equal to or less than the pressure of 325 bar, or equal to or greater than this pressure, or both.
○ The pressure at "6" may be approximately equal to the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7". The pressure at "6" may be slightly greater than the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, during energy storage or "charging", as shown in FIG. 160. The pressure at "6" may be slightly less than the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, during energy generation or "discharging", as shown in FIG. 161. The pressure at "6" may be less than or equal to a pressure of 258.75 bar, or greater than this pressure, or a combination thereof.
The pressure at "7" may be approximately the same as the hydrostatic pressure of seawater adjacent to "7". The pressure at "7" may be less than or equal to a pressure of 258.75 bar, or greater than or equal to this pressure, or a combination thereof.
The pressure at "8" may be approximately the same as the hydrostatic pressure of seawater adjacent to "8". The pressure at "8" may be up to or equal to a pressure of 258.75 bar, or may be above this pressure, or a combination thereof.
○ The pressure at "9" may be approximately equal to the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7". The pressure at "9" may be slightly below the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, as shown in FIG. 160, during energy storage or "charging". The pressure at "9" may be slightly above the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, as shown in FIG. 161, during energy generation or "discharging". The pressure at "9" may be below or above the pressure of 258.75 bar, or both.
○ The pressure at "10" may vary with water depth. The pressure at "10" may increase with water depth and reach a maximum pressure near "5" or near or within the "lower elevation" region. Near "5", the pressure at "10" may be equal to or greater than the hydrostatic pressure of the low-density liquid in "4" at the same elevation when the system is storing or "charging", as shown in FIG. 160, for example. Near "5", the pressure at "10" may be equal to or greater than the pressure of the low-density liquid in "4" when the system is generating or "discharging", as shown in FIG. 161, for example. The pressure at "10" near "5" may be equal to or less than the pressure of 325 bar, or equal to or greater than this pressure, or a combination thereof.
The seawater pressure adjacent to the "lower elevation" region may be at a pressure of approximately 258.75 bar.
A power or pressure recovery process ("5") can recover pressure in excess of hydrostatic pressure in one liquid stream (e.g., "4" or "10") adjacent to or outside a region of lower elevation and transfer this power or pressure to another liquid stream (e.g., "10" or "4").
For example, the pressure of the low density liquid in "4" near "5" may exceed 325 bar during charging. "5" may recover pressure or power of 66.25 bar or more from "4" and transfer the recovered pressure or power to "10". After pressure recovery, the low density liquid ("6") may be transferred into the lower elevation reservoir at a pressure near that of the lower elevation reservoir and/or the hydrostatic pressure of seawater adjacent to the lower elevation reservoir, or at a pressure of about 258.75 bar.
In some embodiments, a pressure or power exchanger allows the lower elevation reservoir to operate in equilibrium with the pressure surrounding or adjacent to the lower elevation reservoir, regardless of the densities of the lower and/or higher density liquids.

Exemplary pressures in exemplary embodiments having high density liquid at elevations above sea level, or at elevations above a reservoir of lower density liquid at higher elevations, or combinations thereof (see Figures 162 and 163).
In this embodiment, the elevation of the "High Side Elevation #1" area may be approximately 0 meters above sea level.
In this example, the elevation of the "High Side Elevation #2" area may be approximately 300 meters above sea level.
In this example, the elevation of the lower elevation region may be 2500 meters below sea level.
In this example, the density of the dense liquid may be 1.035 g/mL, and the dense liquid may include an aqueous solution of calcium chloride.
In this example, the density of the low-density liquid may be 0.573 g/mL, and the low-density liquid may include normal butane or n-butane.
In this example, the density of seawater may be 1.035 g/mL.
Based on the above, the following are example pressures for Figs. 162 and/or 163 for this example:
The pressure of "1", "2", or "11", or a combination thereof, can be near atmospheric pressure or near the vapor pressure of normal butane. For example, the pressure inside "1" and "2" can be 5 bar or less, or 4 bar or less, or 3 bar or less, or 2 bar or less, or 1 bar or less, or a combination thereof.
○ The pressure at "4" may vary with water depth. The pressure at "4" may increase with water depth and reach a maximum pressure near "5" or near or within the "lower elevation" region. Near "5", the pressure at "4" may be equal to or greater than the hydrostatic pressure of the dense liquid in "10" when the system is storing or "charging", for example, as shown in FIG. 162. Near "5", the pressure at "4" may be equal to or less than the hydrostatic pressure of the dense liquid in "10" when the system is generating or "discharging", for example, as shown in FIG. 163. The pressure at "4" near "5" may be equal to or less than the pressure of 289.8 bar, or equal to or greater than this pressure, or both.
○ The pressure at "6" may be approximately equal to the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7". The pressure at "6" may be slightly greater than the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, during energy storage or "charging", as shown in FIG. 162. The pressure at "6" may be slightly less than the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, during energy generation or "discharging", as shown in FIG. 163. The pressure at "6" may be less than or equal to a pressure of 258.75 bar, or greater than this pressure, or a combination thereof.
The pressure at "7" may be approximately the same as the hydrostatic pressure of seawater adjacent to "7". The pressure at "7" may be less than or equal to a pressure of 258.75 bar, or greater than or equal to this pressure, or a combination thereof.
The pressure at "8" may be approximately the same as the hydrostatic pressure of seawater adjacent to "8". The pressure at "8" may be up to or equal to a pressure of 258.75 bar, or may be above this pressure, or a combination thereof.
○ The pressure at "9" may be approximately equal to the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7". The pressure at "9" may be slightly below the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, as shown in FIG. 162 during energy storage or "charging". The pressure at "9" may be slightly above the pressure at "7" and/or the hydrostatic pressure of the seawater adjacent to "7", for example, as shown in FIG. 163 during energy generation or "discharging". The pressure at "9" may be below or above the pressure of 258.75 bar, or both.
○ The pressure at "10" may vary with water depth. The pressure at "10" may increase with water depth and reach a maximum pressure near "5" or near or within the "lower elevation" region. Near "5", the pressure at "10" may be equal to or greater than the hydrostatic pressure of the low-density liquid in "4" at the same elevation when the system is storing or "charging", as shown in FIG. 162, for example. Near "5", the pressure at "10" may be equal to or greater than the pressure of the low-density liquid in "4" when the system is generating or "discharging", as shown in FIG. 163, for example. The pressure at "10" near "5" may be equal to or less than the pressure of 289.8 bar, or may be equal to or greater than this pressure, or a combination thereof.
The seawater pressure adjacent to the "lower elevation" area may be at a pressure of approximately 258.75 bar.
A power or pressure recovery process ("5") can recover pressure in excess of hydrostatic pressure in one liquid stream (e.g., "4" or "10") adjacent to or outside a region of lower elevation and transfer this power or pressure to another liquid stream (e.g., "10" or "4").
For example, the pressure of the low density liquid in "4" near "5" may exceed 289.8 bar during charging. "5" may recover 31.05 bar or more of pressure or power from "4" and transfer the recovered pressure or power to "10". After pressure recovery, the low density liquid ("6") may be transferred into the lower elevation reservoir at a pressure near that of the lower elevation reservoir and/or the hydrostatic pressure of seawater adjacent to the lower elevation reservoir, or at a pressure of about 258.75 bar.
In some embodiments, a pressure or power exchanger allows the lower elevation reservoir to operate in equilibrium with the pressure surrounding or adjacent to the lower elevation reservoir, regardless of the hydrostatic pressure of the denser liquid, or the hydrostatic pressure of the less dense liquid, or both.
Illustrative Exemplary Embodiments 1. A system for storing and generating electricity, comprising:
a first storage reservoir configured to store a fluid near the surface of the body of water and having a density less than water;
a second storage reservoir located below the surface of the body of water and configured to store a fluid having a density greater than that of water;
A pump and
a generator;
The pump, the generator, and the first and second reservoirs store electricity by pumping a fluid in the first storage reservoir having a density lower than water into the second storage reservoir to displace a fluid in the second storage reservoir having a density higher than water, and generate or discharge electricity by allowing the fluid in the second storage reservoir having a density lower than water to return to the first storage reservoir;
Fluids that have a density greater than water are in liquid form in the system.
2. The system of embodiment 1, wherein the fluid having a density lower than water is in liquid form.
3. The system of embodiment 1, wherein the elevation of the first reservoir is greater than the elevation of the second reservoir.
4. The system of embodiment 1, further comprising a third reservoir configured to store a liquid having a density higher than water near the surface of the body of water.
5. The system of embodiment 4, wherein the third reservoir is at substantially the same elevation as the fourth reservoir.
6. The system of embodiment 4, wherein a fluid having a density greater than water displaced from the second reservoir during charging is transferred and stored in said third reservoir.
7. The system of embodiment 4, wherein a fluid having a density greater than water displaced from the second reservoir during charging is transferred and stored in said third reservoir.
8. The system of embodiment 1, wherein the fluid having a density greater than water comprises brine, or reverse osmosis effluent brine, or sodium chloride, or sea salt, or calcium chloride, or magnesium chloride, or potassium formate, or magnesium sulfate, or calcium bromide, or sodium bromide, or potassium acetate, or sodium formate, or calcium nitrate, or sodium nitrate, or sodium sulfite, or potassium sulfite, or sodium bisulfite, or potassium bisulfite, or magnesium bisulfite, or calcium bisulfite, or corn syrup, or glycerin, or propylene glycol, or ethylene glycol, or propylene carbonate, or any combination thereof.
9. The system of embodiment 1, wherein the fluid having a density greater than water comprises a halogenated hydrocarbon, or a fluorocarbon, or an organic acid, or an inorganic acid, or carbon dioxide, or sulfur dioxide, or nitrogen oxides, or any combination thereof.
10. The system of embodiment 1, wherein the fluid having a density lower than water comprises a hydrocarbon.
11. The system of embodiment 1, wherein the fluid having a density lower than water comprises air.
12. The system of embodiment 1, wherein the fluid having a density higher than water has a density greater than 1.02 kilograms per liter at 20° C.
13. The system of embodiment 1, wherein the fluid having a density higher than water has a density greater than 1.05 kilograms per liter at 20° C.
14. The system of embodiment 1, wherein the pressure inside the second reservoir and the pressure in the adjacent body of water differ by between about 0 bar and about 10 bar.
15. The system of embodiment 1, further comprising a pressure exchanger.
16. The system of embodiment 15, wherein the pressure exchanger is located near the second reservoir.
17. The system of embodiment 15, wherein during storage, the pressure exchanger extracts pressure from a liquid having a lower density than water and transfers the extracted pressure to a liquid having a higher density than water.
18. The system of embodiment 15, wherein during storage, the pressure exchanger extracts pressure from a liquid having a density higher than water and transfers the extracted pressure to a liquid having a density lower than water.
19. The system of embodiment 17, wherein the pressure extraction occurs (1) while the liquid having a density lower than water is being transferred to the second reservoir, or (2) before the transfer, or (3) both (1) and (2).
20. The system of embodiment 18, wherein the pressure extraction occurs (1) while the liquid having a density greater than water is being transferred to the second reservoir, or (2) before the transfer, or (3) both (1) and (2).
21. The system of embodiment 17, wherein the pressure exchanger extracts a pressure that is less than or equal to the pressure of a liquid having a lower density than water near the second reservoir minus the hydrostatic pressure of the body of water at the elevation of the second reservoir.
22. The system of embodiment 18, wherein the pressure exchanger extracts a pressure equal to or less than the pressure of a liquid having a density higher than water near the second reservoir minus the hydrostatic pressure of the body of water at the elevation of the second reservoir.
23. The system of embodiment 15, wherein the pressure exchanger allows for the use of a liquid having a higher density than the density of the liquid in the body of water while allowing the second reservoir to be in pressure equilibrium with the body of water at the same elevation as the second reservoir.
24. The system of embodiment 15, wherein the pressure exchanger comprises a hydraulic exchanger.
25. The system of embodiment 15, wherein the pressure exchanger regulates pressure extraction to ensure that the pressure of the fluid inside the second reservoir differs from the hydrostatic pressure of the body of water at the same elevation as the second reservoir by less than an allowable tolerance pressure.
26. The second reservoir includes an internal pressure sensor and an external pressure sensor;
an internal pressure sensor for measuring the pressure of the fluid inside the second reservoir;
an external pressure sensor measuring a pressure in a body of water adjacent to the second reservoir;
26. The system of embodiment 25, wherein the internal pressure sensor and the external pressure sensor are configured to communicate with the pressure exchanger.
27. The system of embodiment 25, wherein the allowable pressure difference is less than about 10 atmospheres.
28. The system of embodiment 15, wherein the pressure exchanger is a hydraulic exchanger.
29. The system of embodiment 15, wherein the pressure exchanger is a pump, or a turbine, or a rotary turbine, or any combination thereof.
30. A process for storing and generating electricity, comprising:

Operatively connecting a pump, a generator, a first storage reservoir near the surface of the body of water, and a second storage reservoir located below the surface of the body of water, where the first storage reservoir is configured to store a fluid having a lower density than water and the second storage reservoir is configured to store a fluid having a higher density than water;

Storing electricity by pumping a fluid having a lower density than the water in the first storage reservoir into the second storage reservoir to replace the fluid having a higher density than the water in the second storage reservoir;

Generating or discharging electricity by allowing a fluid having a lower density than water in the second storage reservoir to return to the first storage reservoir;

A process in which a fluid with a density greater than that of water is in liquid form.

Dense liquids have a density greater than 1.035 g/mL.

Subsea power recovery near a low-level reservoir, or near a low-elevation reservoir, to allow the use of fluids with higher densities than seawater while allowing the subsea reservoir to be in pressure equilibrium with seawater.

A pressure balancing device and pressure balancing tank that adds fluid to a reservoir at a lower elevation when the pressure in the reservoir is less than ambient pressure, and removes fluid from a reservoir at a lower elevation when the pressure in the reservoir exceeds ambient pressure.

Refrigeration, cooling, or thermal management of low-density liquids

Low-density liquids and high-density liquids are stored in the same high-level tank.

Low-density liquids and high-density liquids are stored in tanks at different higher elevations.

The reservoir at the higher elevation is pressurized.

Maintaining the high-altitude reservoir below a certain pressure by using thermal management to maintain below a certain temperature.

NOTES • NOTE: The pressure balancing device may be connected to, or attached to, a tank, or a pipe, or a valve, or a fitting, or a connector, or a combination thereof, or both.
Note: A power exchanger, or pressure exchanger, or energy recovery system, or PX pressure exchanger, may include systems similar to those employed in the art for the recovery of hydraulic power or energy in reverse osmosis systems. The terms "power exchanger," or "pressure exchanger," or "energy recovery system," or "PX pressure exchanger" may be used interchangeably.
• Note: Dense liquids may include, but are not limited to, liquids that have a density equal to or greater than the density of water.
Note: Salt solutions may be employed under conditions that minimize or eliminate corrosion. For example, corrosion may be inhibited by a sacrificial anode. For example, some embodiments may include a "closed system" that may allow for the adjustment of composition and/or creation of an environment to minimize corrosion. For example, salt solutions may be deoxygenated with an oxygen scavenger, such as sulfite, nitrite, bisulfite, organic acid, or antioxidant. For example, salt solutions may be deoxygenated with a non-diatomic oxygen gas, such as nitrogen. For example, salt solutions may be deoxygenated by reacting dissolved oxygen with a fuel, such as hydrogen or methane. For example, brine solutions may be deoxygenated by a catalytic deoxygenation process, which involves dissolving hydrogen gas without reacting dissolved oxygen with the dissolved hydrogen in the presence of a catalyst, such as a palladium catalyst, to form water and remove at least a portion of the dissolved diatomic oxygen. Corrosion may be significantly inhibited or virtually eliminated by deoxygenating salt solutions employed in a closed system. Dissolved oxygen levels may be monitored and if the concentration of dissolved oxygen increases or increases above a design threshold or defined concentration, the dissolved oxygen may be removed.
• Note: In some embodiments, the denser liquid may include a halogenated hydrocarbon or fluorocarbon liquid.
Note: Some embodiments of the present invention may include a high-density liquid reservoir having a density greater than seawater and an elevated high-density liquid reservoir having an elevation above sea level.
Note: In some embodiments, both the lower density liquid upper reservoir and the higher density liquid upper reservoir may be at approximately the same or similar elevations and/or both may be at elevations above sea level. In some embodiments, the lower density liquid upper reservoir and the higher density liquid upper reservoir may be at different elevations and/or both may be at elevations above sea level. In some embodiments, the lower density liquid upper reservoir and the higher density liquid upper reservoir may be at different elevations and/or the lower density liquid upper reservoir may be located at a higher elevation than the higher density liquid upper reservoir. In some embodiments, the lower density liquid upper reservoir and the higher density liquid upper reservoir may be at different elevations and/or the lower density liquid upper reservoir may be located at a lower elevation than the higher density liquid upper reservoir.
Note: The concentration of a reagent in a brine can be adjusted. For example, the concentration of a reagent in a solution such as brine can be adjusted if the temperature of the brine changes, or the solubility of the brine changes, or the viscosity of the brine changes, or a combination thereof.
Note: Some dense liquids are more desirable than others, and some dense liquids may be mixed with other liquids. Exemplary dense liquids having a density greater than water, or greater than seawater, or both, may include, but are not limited to, one or more or combinations of the following: water, or brine, or sodium chloride, or sea salt, or reverse osmosis brine, or concentrate, or retentate, or calcium chloride, or magnesium chloride, or potassium formate, or magnesium sulfate, or calcium bromide, or sodium bromide, or potassium acetate, or sodium formate, or calcium nitrate, or sodium nitrate, or magnesium chloride, or magnesium sulfite, or sodium sulfite, or sodium bisulfite, or potassium bisulfite. or calcium bisulfite, or magnesium bisulfite, or sulfur dioxide, or calcium nitrite, or magnesium nitrite, or sodium nitrite, or potassium nitrite, or a carboxylic acid, or a carboxylic acid salt, or acetic acid, or citric acid, or corn syrup, or corn syrup, or glycerin, or an organic reagent having a density greater than water, or a sugar, or sucrose, or dextrose, or a sugar alcohol, or a polyol, or ethylene glycol, or propylene glycol, or propylene carbonate, or an insoluble organic reagent, or a soluble organic reagent, or a fluorocarbon, or a halogenated hydrocarbon, or a perfluorocarbon, or is an inorganic compound, or liquid sulfur dioxide, or liquid carbon dioxide, or dinitrogen tetroxide, or dinitrogen pentoxide, or sulfur trioxide, or dinitrogen monoxide, or organic acid, or inorganic acid, or molten sulfur, or liquid sulfur, or refrigerant, or bromine, or chlorine, or iodine, or halogen, or formic acid, or chlorine dioxide, or hydrogen peroxide, or organic acid, or inorganic acid, or organic base, or inorganic base, or 1,2-dibromoethane, or cis-1,2-dibromoethane, or dibromomethane, or bromal, or bromoform, or 1,1,2,2-tetrabromoethane (Mussmann's solution), or sodium polytungstate, or bromine, or Thoulets' solution, or diiodomethane tungsten, or indium iodide, or barium mercury iodide, or thallium formate + thallium malonate (Clerici solution), or Galinstan (gallium/indium/tin alloy), or mercury, or cesium formate, or lead, or mercury, or gallium, or liquid metal, or nanoparticles, or dispersed nanoparticles, or suspended nanoparticles, or iron, or gold, or nickel, or tungsten, or sulfur dioxide + carbon dioxide, or refrigerant mixture, or sulfurous acid, or nitrous acid, or ionic compound, or organic compound, or chemical containing carbon, or element, or chemical with a density greater than that of a low-density liquid, or chemical with a density greater than that of water, or chemical Note: A pressure or power exchanger may extract power or pressure from a fluid, such as a liquid, or gas, or supercritical fluid, or liquid-solid mixture, or gas-liquid mixture, or combinations thereof. A pressure or power exchanger may extract power or pressure from a fluid and transmit the extracted power or pressure to another fluid. Exemplary pressure or power exchangers may include, but are not limited to, one or more or combinations of the following: rotary pressure exchangers, or hydraulic pressure exchangers, or pneumatic pressure exchangers, or pressure exchangers employed in the art for reverse osmosis systems, or hydraulic turbines, or hydraulic turbochargers, or hydraulic impellers, or mechanical exchangers, or hydraulic exchangers, or electrical exchangers, or displacement exchangers, or turbine nozzles, or diffusers, or booster pumps, or ultra-high pressure PX, or ultra-high pressure hydraulic energy recovery, or energy recovery devices, or high efficiency pressure exchangers, mixed fluid pressure exchangers, pressure exchangers known in the art for desalination systems, or pressure exchangers known in the art for refining and petrochemical systems. Note: Mechanical pressure exchangers can be significantly more energy efficient than, for example, electrical generators. For example, pressure exchangers employed in the art in reverse osmosis have demonstrated energy or pressure exchange efficiencies of up to 98% or 99%.
Note: Some embodiments may include one or more pressure sensors. An internal pressure sensor may include a pressure sensor that measures the pressure of a fluid inside at least a portion of the energy storage process. An external pressure sensor may include a pressure sensor that measures the pressure of a fluid or material outside or external to at least a portion of the energy storage system or process. It may be desirable for the external pressure sensor to measure the pressure of an external fluid or material to determine the pressure of that fluid or material acting on at least one surface of the energy storage system or process.
NOTE: The elevation difference between the first and second reservoirs is less than, greater than, or equal to one or more or combinations of the following: 50 meters, or 100 meters, or 150 meters, or 200 meters, or 250 meters, or 300 meters, or 350 meters, or 400 meters, or 450 meters, or 500 meters, or 550 meters, or 600 meters, or 650 meters, or 700 meters, or 750 meters, or 800 meters, or 850 meters, or 900 meters, or 950 meters, or 1,000 meters, or 1,050 meters, or 1,100 meters, or 1,150 meters, or 1,200 meters, or 1,250 meters, or 1,300 meters, 1,350 meters, or 1,400 meters, or 1,450 meters, or 1,500 meters, or 1,550 meters, or 1,600 meters, or 1,650 meters, or 1,700 meters, or 1,750 meters, or 1,800 meters, or 1,850 meters, or 1,900 meters, or 1,950 meters, or 2,000 meters, or 2,050 meters, or 2,100 meters, or 2,150 meters, or 2,200 meters, or 2,250 meters, or 2,300 meters, or 2,350 meters, or 2,4 00 meters, or 2,450 meters, or 2,500 meters, or 2,550 meters, or 2,600 meters, or 2,650 meters, or 2,700 meters, or 2,750 meters, or 2,800 meters, or 2,850 meters, or 2,900 meters, or 2,950 meters, or 3,000 meters, or 3,100 meters, or 3,200 meters, or 3,300 meters, or 3,400 meters, or 3,500 meters, or 3,600 meters, or 3,700 meters, or 3,800 meters, or 3,900 meters, or 4,000 meters, or 4,100 meters, or 4,200 meters, or 4,30 0 meters, or 4,400 meters, or 4,500 meters, or 4,600 meters, or 4,700 meters, or 4,800 meters, or 4,900 meters, or 5,000 meters, or 5,500 meters, or 6,000 meters, or 6,500 meters, or 7,000 meters, or 7,500 meters, or 8,000 meters, or 8,500 meters, or 9,000 meters, or 9,500 meters, or 10,000 meters, or 10,500 meters, or 11,000 meters, or 11,500 meters, or 12,000 meters, or 12,500 meters, or 13,000 meters, or 13,500 meters NOTE: The elevation difference between the third reservoir and the second reservoir is less than, greater than, or equal to one or more or combinations of the following: 50 meters, or 100 meters, or 150 meters, or 200 meters, or 250 meters, or 300 meters, or 350 meters, or 400 meters, or 450 meters, or 500 meters, or 550 meters, or 600 meters, or 650 meters, or 700 meters, or 750 meters, or 800 meters, or 850 meters, or 900 meters, or 950 meters, or 1,000 meters, or 1,050 meters, or 1,100 meters, or 1,150 meters, or 1,200 meters, or 1,250 meters, or 1,300 meters, 1,350 meters, or 1,400 meters, or 1,450 meters, or 1,500 meters, or 1,550 meters, or 1,600 meters, or 1,650 meters, or 1,700 meters, or 1,750 meters, or 1,800 meters, or 1,850 meters, or 1,900 meters, or 1,950 meters, or 2,000 meters, or 2,050 meters, or 2,100 meters, or 2,150 meters, or 2,200 meters, or 2,250 meters, or 2,300 meters, or 2,350 meters, or 2,4 00 meters, or 2,450 meters, or 2,500 meters, or 2,550 meters, or 2,600 meters, or 2,650 meters, or 2,700 meters, or 2,750 meters, or 2,800 meters, or 2,850 meters, or 2,900 meters, or 2,950 meters, or 3,000 meters, or 3,100 meters, or 3,200 meters, or 3,300 meters, or 3,400 meters, or 3,500 meters, or 3,600 meters, or 3,700 meters, or 3,800 meters, or 3,900 meters, or 4,000 meters, or 4,100 meters, or 4,200 meters, or 4,30 0 meters, or 4,400 meters, or 4,500 meters, or 4,600 meters, or 4,700 meters, or 4,800 meters, or 4,900 meters, or 5,000 meters, or 5,500 meters, or 6,000 meters, or 6,500 meters, or 7,000 meters, or 7,500 meters, or 8,000 meters, or 8,500 meters, or 9,000 meters, or 9,500 meters, or 10,000 meters, or 10,500 meters, or 11,000 meters, or 11,500 meters, or 12,000 meters, or 12,500 meters, or 13,000 meters, or 13,500 meters Note: The elevation difference between the two reservoirs is less than, greater than, or equal to one or more or combinations of the following: 50 meters, or 100 meters, or 150 meters, or 200 meters, or 250 meters, or 300 meters, or 350 meters, or 400 meters, or 450 meters, or 500 meters, or 550 meters, or 600 meters, or 650 meters, or 700 meters, or 750 meters, or 800 meters, or 850 meters, or 900 meters, or 950 meters, or 1,000 meters, or 1,050 meters, or 1,100 meters, or 1,150 meters. torr, or 1,200 meters, or 1,250 meters, or 1,300 meters, 1,350 meters, or 1,400 meters, or 1,450 meters, or 1,500 meters, or 1,550 meters, or 1,600 meters, or 1,650 meters, or 1,700 meters, or 1,750 meters, or 1,800 meters, or 1,850 meters, or 1,900 meters, or 1,950 meters, or 2,000 meters, or 2,050 meters, or 2,100 meters, or 2,150 meters, or 2,200 meters, or 2,250 meters, or 2,300 meters, or 2,350 meters, or 2,400 meters or 2,450 meters, or 2,500 meters, or 2,550 meters, or 2,600 meters, or 2,650 meters, or 2,700 meters, or 2,750 meters, or 2,800 meters, or 2,850 meters, or 2,900 meters, or 2,950 meters, or 3,000 meters, or 3,100 meters, or 3,200 meters, or 3,300 meters, or 3,400 meters, or 3,500 meters, or 3,600 meters, or 3,700 meters, or 3,800 meters, or 3,900 meters, or 4,000 meters, or 4,100 meters, or 4,200 meters, or 4,300 meters or 4,400 meters, or 4,500 meters, or 4,600 meters, or 4,700 meters, or 4,800 meters, or 4,900 meters, or 5,000 meters, or 5,500 meters, or 6,000 meters, or 6,500 meters, or 7,000 meters, or 7,500 meters, or 8,000 meters, or 8,500 meters, or 9,000 meters, or 9,500 meters, or 10,000 meters, or 10,500 meters, or 11,000 meters, or 11,500 meters, or 12,000 meters, or 12,500 meters, or 13,000 meters, or 13,500 meters Note: The viscosity of the liquid may be less than, greater than, or equal to one or more or combinations including, but not limited to, 0.1 cP, or 0.5 cP, or 1 cP, or 1.5 cP, or 2 cP, or 2.5 cP, or 3 cP, or 3.5 cP, or 4 cP, or 4.5 cP, or 5 cP, or 5.5 cP, or 6 cP, or 6.5 cP, or 7 cP, or 7.5 cP, or 8 cP, or 8.5 cP, or 9 cP, or 9.5 cP, or 10 cP, or 11 cP, or 12 cP, or 13 cP, or 14 cP, or 15 cP, or 16 cP, or 17 cP, or 18 cP, or 19 cP, or 20 cP, or 21 cP, or 22 cP, or 23 cP, or 24 cP, or 25 cP, or 26 cP, or 27 cP, or 28 cP, or 29 cP, or 30 cP, or 31 cP, or 32 cP, or 33 cP, or 34 cP, or 35 cP, or 36 cP, or 37 cP P, or 38 cP, or 39 cP, or 40 cP, or 41 cP, or 42 cP, or 43 cP, or 44 cP, or 45 cP, or 46 cP, or 47 cP, or 48 cP, or 49 cP, or 50 cP, or 55 cP, or 60 cP, or 65 cP, or 70 cP, or 75 cP, or 80 cP, or 85 cP, or 90 cP, or 95 cP, or 100 cP, or 105 cP, or 110 cP, or 115 cP, or 120 cP, or 125 cP, or 1 30 cP, or 135 cP, or 140 cP, or 145 cP, or 150 cP, or 155 cP, or 160 cP, or 165 cP, or 170 cP, or 175 cP, or 180 cP, or 185 cP, or 190 cP, or 195 cP, or 200 cP, or 205 cP, or 210 cP, or 215 cP, or 220 cP, or 225 cP, or 230 cP, or 235 cP, or 240 cP, or 245 cP, or 250 cP, or 255 cP, or 2 60 cP, or 265 cP, or 270 cP, or 275 cP, or 280 cP, or 285 cP, or 290 cP, or 295 cP, or 300 cP, or 305 cP, or 310 cP, or 315 cP, or 320 cP, or 325 cP, or 330 cP, or 335 cP, or 340 cP, or 345 cP, or 350 cP, or 355 cP, or 360 cP, or 365 cP, or 370 cP, or 375 cP, or 380 cP, or 385 cP, or 390 cP, or 395 cP, or 400 cP, or 405 cP, or 410 cP, or 415 cP, or 420 cP, or 425 cP, or 430 cP, or 435 cP, or 440 cP, or 445 cP, or 450 cP, or 455 cP, or 460 cP, or 465 cP, or 470 cP, or 475 cP, or 480 cP, or 485 cP, or 490 cP, or 495 cP, or 500 cP, or 550 cP, or 600 cP, or 650 cP, or 700 cP, or 750 cP, or 800 cP, or 850 cP, or 900 cP, or 950 cP, or 1,000 cP, or 1,250 cP, or 1,500 cP, or 1,750 cP, or 2,000 cP, or 2,250 cP, or 2,500 cP, or 2,750 cP, or 3,000 cP, or 3,250 cP, or 3,500 cP, or 3,750 cP, or 4,000 cP, or 4,250 cP, or 4,500 cP, or 4,750 cP, or is 5,000 cP, or 5,250 cP, or 5,500 cP, or 5,750 cP, or 6,000 cP, or 6,250 cP, or 6,500 cP, or 6,750 cP, or 7,000 cP, or 7,250 cP, or 7,500 cP, or 7,750 cP, or 8,000 cP, or 8,250 cP, or 8,500 cP, or 8,750 cP, or 9,000 cP, or 9,250 cP, or 9,500 cP, or 9,750 cP, or 10,000 cP
NOTE: The temperature of the high density liquid, or low density liquid, or heat storage medium, or any combination thereof, may be less than, greater than, or equal to one or more or combinations of the following: -100°C, or -90°C, or -80°C, or -70°C, or -60°C, or -50°C, or -45°C, or -40°C, or -35°C, or -30°C, or -25°C, or -20°C, or -19°C, or -18°C, or -17°C, or -16°C, or -15°C, or -15°C, or -14°C, or -13°C, or -12°C, or -11°C, or -10°C, or -9°C, or -8°C, or -7°C, or -6°C, or -5°C, or -4°C, or -3°C, or -2°C. or -1°C, or 0°C, or 1°C, or 2°C, or 3°C, or 4°C, or 5°C, or 6°C, or 7°C, or 8°C, or 9°C, or 10°C, or 11°C, or 12°C, or 13°C, or 14°C, or 15°C, or 16°C, or 17°C, or 18°C, or 19°C, or 20°C, or 21°C, or 22°C, or 23°C, or 24°C, or 25°C, or 26°C, or 27°C, or 28°C, or 29°C, or 30°C, or 31°C, or 32°C, or 33°C, or 34°C, or 35°C, or 36°C, or 37°C, or 38°C, or 39°C, or 40°C, or 41°C, or 42°C, or 43°C, or 44°C, or 45°C, or 46°C, or 47°C, or 48°C, or 49°C, or 50°C, or 51°C, or 52°C, or 53°C, or 54°C, or 55°C, or 56°C, or 57°C, or 58°C, or 59°C, or 60°C, or 61°C, or 62°C, or 63°C, or 64°C, or 65°C, or 66°C, or 67°C, or 68°C, or 69°C, or 70°C, or 71°C, or 72°C, or 73°C, or 74°C, or 75°C, or 76°C, or 77 °C, or 78°C, or 79°C, or 80°C, or 81°C, or 82°C, or 83°C, or 84°C, or 85°C, or 86°C, or 87°C, or 88, or 89°C, or 90°C, or 91°C, or 92°C, or 93°C, or 94°C, or 95°C, or 96°C, or 97°C, or 98°C, or 99°C, or 100°C, or 110°C, or 120°C, or 130°C, or 140°C, or 150°C, or 160°C, or 170°C, or 180°C, or 190°C, or 200°C, or 210°C, or 220°C, or 230°C, or 240°C, or 250°C, or 260°C, or 270°C, or 280°C, or 290°C, or 300°C, or 310°C, or 320°C, or 330°C, or 340°C, or 350°C, or 360°C, or 370°C, or 380°C, or 390°C, or 400°C, or 410°C, or 420°C, or 430°C, or 440°C, or 450°C, or 460°C, or 470°C, or 480°C, or 490°C, or 500°C, or 550°C, or 600°C, or 700°C, or 800°C, or 900°C, or 1000°C
Note: The weight percent concentration of the higher density liquid in the lower density liquid may be less than, greater than, or equal to one or more or combinations of the following: 0.0001%, or 0.5%, or 1%, or 1.5%, or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%. Or 8.5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5%, or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21. 5%, or 22%, or 22.5%, or 23%, or 23.5%, or 24%, or 24.5%, or 25%, or 25.5%, or 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 30.5%, or 31%, or 31.5%, or 32%, or 32.5%, or 33%, or 33.5%, or 34%, or 34.5% , or 35%, or 35.5%, or 36%, or 36.5%, or 37%, or 37.5%, or 38%, or 38.5%, or 39%, or 39.5%, or 40%, or 40.5%, or 41%, or 41.5%, or 42%, or 42.5%, or 43%, or 43.5%, or 44%, or 44.5%, or 45%, or 45.5%, or 46%, or 46.5%, or 47%, or 47.5%, or is 48%, or 48.5%, or 49%, or 49.5%, or 50%, or 50.5%, or 51%, or 51.5%, or 52%, or 52.5%, or 53%, or 53.5%, or 54%, or 54.5%, or 55%, or 55.5%, or 56%, or 56.5%, or 57%, or 57.5%, or 58%, or 58.5%, or 59%, or 59.5%, or 60%, or 60.5%, or 6 1%, or 61.5%, or 62%, or 62.5%, or 63%, or 63.5%, or 64%, or 64.5%, or 65%, or 65.5%, or 66%, or 66.5%, or 67%, or 67.5%, or 68%, or 68.5%, or 69%, or 69.5%, or 70%, or 70.5%, or 71%, or 71.5%, or 72%, or 72.5%, or 73%, or 73.5%, or 74% , or 74.5%, or 75%, or 75.5%, or 76%, or 76.5%, or 77%, or 77.5%, or 78%, or 78.5%, or 79%, or 79.5%, or 80%, or 80.5%, or 81%, or 81.5%, or 82%, or 82.5%, or 83%, or 83.5%, or 84%, or 84.5%, or 85%, or 85.5%, or 86%, or 86.5%, or 87%, or is 87.5%, or 88%, or 88.5%, or 89%, or 89.5%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.999%
Note: The weight percent concentration of the less dense liquid in the more dense liquid may be less than, greater than, or equal to one or more or combinations of the following: 0.0001%, or 0.5%, or 1%, or 1.5%, or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%. Or 8.5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5%, or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21. 5%, or 22%, or 22.5%, or 23%, or 23.5%, or 24%, or 24.5%, or 25%, or 25.5%, or 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 30.5%, or 31%, or 31.5%, or 32%, or 32.5%, or 33%, or 33.5%, or 34%, or 34.5% , or 35%, or 35.5%, or 36%, or 36.5%, or 37%, or 37.5%, or 38%, or 38.5%, or 39%, or 39.5%, or 40%, or 40.5%, or 41%, or 41.5%, or 42%, or 42.5%, or 43%, or 43.5%, or 44%, or 44.5%, or 45%, or 45.5%, or 46%, or 46.5%, or 47%, or 47.5%, or is 48%, or 48.5%, or 49%, or 49.5%, or 50%, or 50.5%, or 51%, or 51.5%, or 52%, or 52.5%, or 53%, or 53.5%, or 54%, or 54.5%, or 55%, or 55.5%, or 56%, or 56.5%, or 57%, or 57.5%, or 58%, or 58.5%, or 59%, or 59.5%, or 60%, or 60.5%, or 6 1%, or 61.5%, or 62%, or 62.5%, or 63%, or 63.5%, or 64%, or 64.5%, or 65%, or 65.5%, or 66%, or 66.5%, or 67%, or 67.5%, or 68%, or 68.5%, or 69%, or 69.5%, or 70%, or 70.5%, or 71%, or 71.5%, or 72%, or 72.5%, or 73%, or 73.5%, or 74% , or 74.5%, or 75%, or 75.5%, or 76%, or 76.5%, or 77%, or 77.5%, or 78%, or 78.5%, or 79%, or 79.5%, or 80%, or 80.5%, or 81%, or 81.5%, or 82%, or 82.5%, or 83%, or 83.5%, or 84%, or 84.5%, or 85%, or 85.5%, or 86%, or 86.5%, or 87%, or is 87.5%, or 88%, or 88.5%, or 89%, or 89.5%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.999%
Note: The weight percent concentration of water in the dense liquid may be less than, greater than, or equal to one or more or combinations of the following: 0.0001%, or 0.5%, or 1%, or 1.5%, or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%, or 8.5%. %, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5%, or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21.5%, or is 22%, or 22.5%, or 23%, or 23.5%, or 24%, or 24.5%, or 25%, or 25.5%, or 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 30.5%, or 31%, or 31.5%, or 32%, or 32.5%, or 33%, or 33.5%, or 34%, or 34.5%, or 35%, or 35.5%, or 36%, or 36.5%, or 37%, or 37.5%, or 38%, or 38.5%, or 39%, or 39.5%, or 40%, or 40.5%, or 41%, or 41.5%, or 42%, or 42.5%, or 43%, or 43.5%, or 44%, or 44.5%, or 45%, or 45.5%, or 46%, or 46.5%, or 47%, or 47.5%, or 48 %, or 48.5%, or 49%, or 49.5%, or 50%, or 50.5%, or 51%, or 51.5%, or 52%, or 52.5%, or 53%, or 53.5%, or 54%, or 54.5%, or 55%, or 55.5%, or 56%, or 56.5%, or 57%, or 57.5%, or 58%, or 58.5%, or 59%, or 59.5%, or 60%, or 60.5%, or 61% , or 61.5%, or 62%, or 62.5%, or 63%, or 63.5%, or 64%, or 64.5%, or 65%, or 65.5%, or 66%, or 66.5%, or 67%, or 67.5%, or 68%, or 68.5%, or 69%, or 69.5%, or 70%, or 70.5%, or 71%, or 71.5%, or 72%, or 72.5%, or 73%, or 73.5%, or 74%, or 74.5%, or 75%, or 75.5%, or 76%, or 76.5%, or 77%, or 77.5%, or 78%, or 78.5%, or 79%, or 79.5%, or 80%, or 80.5%, or 81%, or 81.5%, or 82%, or 82.5%, or 83%, or 83.5%, or 84%, or 84.5%, or 85%, or 85.5%, or 86%, or 86.5%, or 87%, or is 87.5%, or 88%, or 88.5%, or 89%, or 89.5%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.999%
Note: The weight percent concentration of water in the low density liquid may be less than, greater than, or equal to one or more or combinations of the following: 0.0001%, or 0.5%, or 1%, or 1.5%, or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%, or 8%. .5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 13.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5%, or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21.5%, or 22%, or 22.5%, or 23%, or 23.5%, or 24%, or 24.5%, or 25%, or 25.5%, or 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 30.5%, or 31%, or 31.5%, or 32%, or 32.5%, or 33%, or 33.5%, or 34%, or 34.5%, or is 35%, or 35.5%, or 36%, or 36.5%, or 37%, or 37.5%, or 38%, or 38.5%, or 39%, or 39.5%, or 40%, or 40.5%, or 41%, or 41.5%, or 42%, or 42.5%, or 43%, or 43.5%, or 44%, or 44.5%, or 45%, or 45.5%, or 46%, or 46.5%, or 47%, or 47.5%, or 4 8%, or 48.5%, or 49%, or 49.5%, or 50%, or 50.5%, or 51%, or 51.5%, or 52%, or 52.5%, or 53%, or 53.5%, or 54%, or 54.5%, or 55%, or 55.5%, or 56%, or 56.5%, or 57%, or 57.5%, or 58%, or 58.5%, or 59%, or 59.5%, or 60%, or 60.5%, or 61 %, or 61.5%, or 62%, or 62.5%, or 63%, or 63.5%, or 64%, or 64.5%, or 65%, or 65.5%, or 66%, or 66.5%, or 67%, or 67.5%, or 68%, or 68.5%, or 69%, or 69.5%, or 70%, or 70.5%, or 71%, or 71.5%, or 72%, or 72.5%, or 73%, or 73.5%, or 74%, or 74.5%, or 75%, or 75.5%, or 76%, or 76.5%, or 77%, or 77.5%, or 78%, or 78.5%, or 79%, or 79.5%, or 80%, or 80.5%, or 81%, or 81.5%, or 82%, or 82.5%, or 83%, or 83.5%, or 84%, or 84.5%, or 85%, or 85.5%, or 86%, or 86.5%, or 87%, or is 87.5%, or 88%, or 88.5%, or 89%, or 89.5%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.999%
●Note: In some embodiments, to ensure maximum energy density and minimize the required liquid volume, the elevation difference between the first and second reservoirs is one or more or a combination of the following, or greater: 50 meters, or 100 meters, or 150 meters, or 200 meters, or 250 meters, or 500 meters, or 750 meters, or 1,000 meters, or 1,250 meters, or 1,500 meters ●Note: The energy storage round trip energy efficiency can be one or more or a combination of the following, or greater. 0.0001%, or 0.5%, or 1%, or 1.5%, or 2%, or 2.5%, or 3%, or 3.5%, or 4%, or 4.5%, or 5%, or 5.5%, or 6%, or 6.5%, or 7%, or 7.5%, or 8%, or 8.5%, or 9%, or 9.5%, or 10%, or 10.5%, or 11%, or 11.5%, or 12%, or 12.5%, or 13%, or 1 3.5%, or 14%, or 14.5%, or 15%, or 15.5%, or 16%, or 16.5%, or 17%, or 17.5%, or 18%, or 18.5%, or 19%, or 19.5%, or 20%, or 20.5%, or 21%, or 21.5%, or 22%, or 22.5%, or 23%, or 23.5%, or 24%, or 24.5%, or 25%, or 25.5%, or is 26%, or 26.5%, or 27%, or 27.5%, or 28%, or 28.5%, or 29%, or 29.5%, or 30%, or 30.5%, or 31%, or 31.5%, or 32%, or 32.5%, or 33%, or 33.5%, or 34%, or 34.5%, or 35%, or 35.5%, or 36%, or 36.5%, or 37%, or 37.5%, or 38%, or is 38.5%, or 39%, or 39.5%, or 40%, or 40.5%, or 41%, or 41.5%, or 42%, or 42.5%, or 43%, or 43.5%, or 44%, or 44.5%, or 45%, or 45.5%, or 46%, or 46.5%, or 47%, or 47.5%, or 48%, or 48.5%, or 49%, or 49.5%, or 50%, or 50.5% , or 51%, or 51.5%, or 52%, or 52.5%, or 53%, or 53.5%, or 54%, or 54.5%, or 55%, or 55.5%, or 56%, or 56.5%, or 57%, or 57.5%, or 58%, or 58.5%, or 59%, or 59.5%, or 60%, or 60.5%, or 61%, or 61.5%, or 62%, or 62.5%, or 63% , or 63.5%, or 64%, or 64.5%, or 65%, or 65.5%, or 66%, or 66.5%, or 67%, or 67.5%, or 68%, or 68.5%, or 69%, or 69.5%, or 70%, or 70.5%, or 71%, or 71.5%, or 72%, or 72.5%, or 73%, or 73.5%, or 74%, or 74.5%, or 75%, or 75. 5%, or 76%, or 76.5%, or 77%, or 77.5%, or 78%, or 78.5%, or 79%, or 79.5%, or 80%, or 80.5%, or 81%, or 81.5%, or 82%, or 82.5%, or 83%, or 83.5%, or 84%, or 84.5%, or 85%, or 85.5%, or 86%, or 86.5%, or 87%, or 87.5%, or 8 8%, or 88.5%, or 89%, or 89.5%, or 90%, or 90.5%, or 91%, or 91.5%, or 92%, or 92.5%, or 93%, or 93.5%, or 94%, or 94.5%, or 95%, or 95.5%, or 96%, or 96.5%, or 97%, or 97.5%, or 98%, or 98.5%, or 99%, or 99.5%, or 99.999%
Note: The density of the liquid can be one or more or a combination of, less than, or greater than the following: 0.5 g/mL, or 0.51 g/mL, or 0.52 g/mL, or 0.53 g/mL, or 0.54 g/mL, or 0.55 g/mL, or 0.56 g/mL, or 0.57 g/mL, or 0.58 g/mL, or 0.59 g/mL, or 0.6 g/mL, or 0.61 g/mL, or 0.62 g/mL, or 0.63 g/mL, 0.64 g/mL, or 0.65 g/mL, or 0.66 g/mL, or 0.67 g/mL, or 0.68 g/mL, or 0.69 g/mL, or 0.70 g/mL, or 0.71 g/mL, or 0.72 g/mL, or 0.73 g/mL, or 0.74 g/mL, or 0.75 g/mL, or 0.76 g/mL, or 0.77 g/mL, or 0.78 g/mL, or 0.79 g/mL, or 0.8 g/mL, or 0.805 g/mL, or 0.81 g/mL, or 0.815 g/mL, or 0.82 g/mL, or 0.825 g/mL, or 0.83 g/mL, or 0.835 g/mL, or 0.84 g/mL, or 0 . 845 g/mL, or 0.85 g/mL, or 0.855 g/mL, or 0.86 g/mL, or 0.865 g/mL, or 0.87 g/mL, or 0.875 g/mL, or 0.88 g/mL, or 0.885 g/mL, or 0.89 g/mL, or 0.895 g/mL, or 0.9 g/mL, or 0.905 g/mL, or 0.91 g/mL, or . 915 g/mL, or 0.92 g/mL, or 0.925 g/mL, or 0.93 g/mL, or 0.935 g/mL, or 0.94 g/mL, or 0.945 g/mL, or 0.95 g/mL, or 0.955 g/mL, or 0.96 g/mL, or 0.965 g/mL, or 0.97 g/mL, or 0.975 g/mL, or 0.98 g/mL, or 0.985 g/mL, or 0.99 g/mL, or 0.995 g/mL, or 1 g/mL, or 1.005 g/mL, or 1. 01 g/mL, or 1.015 g/mL, or 1.02 g/mL, or 1.025 g/mL, or 1.03 g/mL, or 1.035 g/mL, or 1.04 g/mL, or 1.045 g/mL, or 1.05 g/mL, or 1.055 g/mL, or 1.06 g/mL, or 1.065 g/mL, or 1.07 g/mL, or 1.075 g/mL, or 1.08 g/mL, or 1.085 g/mL, or 1.09 g/mL, or 1.095 g/mL, or 1.1 g/mL, or 1 11 g/mL, or 1.12 g/mL, or 1.13 g/mL, or 1.14 g/mL, or 1.15 g/mL, or 1.16 g/mL, or 1.17 g/mL, or 1.18 g/mL, or 1.19 g/mL, or 1.2 g/mL, or 1.21 g/mL, or 1.22 g/mL, or 1.23 g/mL, or 1.24 g/mL, or 1.25 g/mL, or 1.26 g/mL, or 1.27 g/mL, or 1.28 g/mL, or 1.29 g/mL, or 1.3 g/mL, or is 1.31 g/mL, or 1.32 g/mL, or 1.33 g/mL, or 1.34 g/mL, or 1.35 g/mL, or 1.36 g/mL, or 1.37 g/mL, or 1.38 g/mL, or 1.39 g/mL, or 1.4 g/mL, or 1.41 g/mL, or 1.42 g/mL, or 1.43 g/mL, or 1.44 g/mL, or 1.45 g/mL, or 1.46 g/mL, or 1.47 g/mL, or 1.48 g/mL, or 1.49 g/mL, or 1.5 g/mL
Note: The density of the fluid can be one or more or a combination of, less than, or greater than the following: 0.5 g/mL, or 0.51 g/mL, or 0.52 g/mL, or 0.53 g/mL, or 0.54 g/mL, or 0.55 g/mL, or 0.56 g/mL, or 0.57 g/mL, or 0.58 g/mL, or 0.59 g/mL, or 0.6 g/mL, or 0.61 g/mL, or 0.62 g/mL, or 0.63 g/mL, 0.64 g/mL, or 0.65 g/mL, or 0.66 g/mL, or 0.67 g/mL, or 0.68 g/mL, or 0.69 g/mL, or 0.70 g/mL, or 0.71 g/mL, or 0.72 g/mL, or 0.73 g/mL, or 0.74 g/mL, or 0.75 g/mL, or 0.76 g/mL, or 0.77 g/mL, or 0.78 g/mL, or 0.79 g/mL, or 0.8 g/mL, or 0.805 g/mL, or 0.81 g/mL, or 0.815 g/mL, or 0.82 g/mL, or 0.825 g/mL, or 0.83 g/mL, or 0.835 g/mL, or 0.84 g/mL, or 0 . 845 g/mL, or 0.85 g/mL, or 0.855 g/mL, or 0.86 g/mL, or 0.865 g/mL, or 0.87 g/mL, or 0.875 g/mL, or 0.88 g/mL, or 0.885 g/mL, or 0.89 g/mL, or 0.895 g/mL, or 0.9 g/mL, or 0.905 g/mL, or 0.91 g/mL, or . 915 g/mL, or 0.92 g/mL, or 0.925 g/mL, or 0.93 g/mL, or 0.935 g/mL, or 0.94 g/mL, or 0.945 g/mL, or 0.95 g/mL, or 0.955 g/mL, or 0.96 g/mL, or 0.965 g/mL, or 0.97 g/mL, or 0.975 g/mL, or 0.98 g/mL, or 0.985 g/mL, or 0.99 g/mL, or 0.995 g/mL, or 1 g/mL, or 1.005 g/mL, or 1. 01 g/mL, or 1.015 g/mL, or 1.02 g/mL, or 1.025 g/mL, or 1.03 g/mL, or 1.035 g/mL, or 1.04 g/mL, or 1.045 g/mL, or 1.05 g/mL, or 1.055 g/mL, or 1.06 g/mL, or 1.065 g/mL, or 1.07 g/mL, or 1.075 g/mL, or 1.08 g/mL, or 1.085 g/mL, or 1.09 g/mL, or 1.095 g/mL, or 1.1 g/mL, or 1 11 g/mL, or 1.12 g/mL, or 1.13 g/mL, or 1.14 g/mL, or 1.15 g/mL, or 1.16 g/mL, or 1.17 g/mL, or 1.18 g/mL, or 1.19 g/mL, or 1.2 g/mL, or 1.21 g/mL, or 1.22 g/mL, or 1.23 g/mL, or 1.24 g/mL, or 1.25 g/mL, or 1.26 g/mL, or 1.27 g/mL, or 1.28 g/mL, or 1.29 g/mL, or 1.3 g/mL, or is 1.31 g/mL, or 1.32 g/mL, or 1.33 g/mL, or 1.34 g/mL, or 1.35 g/mL, or 1.36 g/mL, or 1.37 g/mL, or 1.38 g/mL, or 1.39 g/mL, or 1.4 g/mL, or 1.41 g/mL, or 1.42 g/mL, or 1.43 g/mL, or 1.44 g/mL, or 1.45 g/mL, or 1.46 g/mL, or 1.47 g/mL, or 1.48 g/mL, or 1.49 g/mL, or 1.5 g/mL
Note: The density of the low density fluid may be one or more or a combination of, less than, or greater than the following: 0.01 g/mL, or 0.05 g/mL, or 0.1 g/mL, or 0.15 g/mL, or 0.20 g/mL, or 0.25 g/mL, or 0.3 g/mL, or 0.35 g/mL, or 0.4 g/mL, or 0.45 g/mL, 0.5 g/mL, or 0.51 g/mL, or 0.52 g/mL. mL, or 0.53 g/mL, or 0.54 g/mL, or 0.55 g/mL, or 0.56 g/mL, or 0.57 g/mL, or 0.58 g/mL, or 0.59 g/mL, or 0.6 g/mL, or 0.61 g/mL, or 0.62 g/mL, or 0.63 g/ml, 0.64 g/mL, or 0.65 g/mL, or 0.66 g/mL, or 0.67 g/mL, or 0.68 g/mL, or 0.69 g/mL, or 0.70 g/mL, or 0.71 g/mL, or 0.72 g/mL, or 0.73 g/mL, or 0.74 g/mL, or 0.75 g/mL, or 0.76 g/mL, or 0.77 g/mL, or 0.78 g/mL, or 0.79 g/mL, or 0.8 g/mL, or 0.805 g/mL, or 0.81 g/mL, or 0.815 g/mL, or 0.82 g/mL, or 0.825 g/mL, or 0.83 g/mL L, or 0.835 g/mL, or 0.84 g/mL, or 0.845 g/mL, or 0.85 g/mL, or 0.855 g/mL, or 0.86 g/mL, or 0.865 g/mL, or 0.87 g/mL, or 0.875 g/mL, or 0.88 g/mL, or 0.885 g/mL, or 0.89 g/mL, or 0.895 g/mL, or 0.9 g/mL, or 0.905 g/mL, or 0.91 g/mL, or. 915 g/mL, or 0.92 g/mL, or 0.925 g/mL, or 0.93 g/mL, or 0.935 g/mL, or 0.94 g/mL, or 0.945 g/mL, or 0.95 g/mL, or 0.955 g/mL, or 0.96 g/mL, or 0.965 g/mL, or 0.97 g/mL, or 0.975 g/mL, or 0.98 g/mL, or 0.985 g/mL, or 0.99 g/mL, or 0.995 g/mL, or 1 g/mL, or 1.005 g/mL, or 1. 01 g/mL, or 1.015 g/mL, or 1.02 g/mL, or 1.025 g/mL, or 1.03 g/mL, or 1.035 g/mL, or 1.04 g/mL, or 1.045 g/mL, or 1.05 g/mL, or 1.055 g/mL, or 1.06 g/mL, or 1.065 g/mL, or 1.07 g/mL, or 1.075 g/mL, or 1.08 g/mL, or 1.085 g/mL, or 1.09 g/mL, or 1.095 g/mL, or 1.1 g/mL, or 1 11 g/mL, or 1.12 g/mL, or 1.13 g/mL, or 1.14 g/mL, or 1.15 g/mL, or 1.16 g/mL, or 1.17 g/mL, or 1.18 g/mL, or 1.19 g/mL, or 1.2 g/mL, or 1.21 g/mL, or 1.22 g/mL, or 1.23 g/mL, or 1.24 g/mL, or 1.25 g/mL, or 1.26 g/mL, or 1.27 g/mL, or 1.28 g/mL, or 1.29 g/mL, or 1.3 g/mL, or is 1.31 g/mL, or 1.32 g/mL, or 1.33 g/mL, or 1.34 g/mL, or 1.35 g/mL, or 1.36 g/mL, or 1.37 g/mL, or 1.38 g/mL, or 1.39 g/mL, or 1.4 g/mL, or 1.41 g/mL, or 1.42 g/mL, or 1.43 g/mL, or 1.44 g/mL, or 1.45 g/mL, or 1.46 g/mL, or 1.47 g/mL, or 1.48 g/mL, or 1.49 g/mL, or 1.5 g/mL
Note: The density of the dense liquid may be one or more or a combination of, less than, or greater than the following: 0.01 g/mL, or 0.05 g/mL, or 0.1 g/mL, or 0.15 g/mL, or 0.20 g/mL, or 0.25 g/mL, or 0.3 g/mL, or 0.35 g/mL, or 0.4 g/mL, or 0.45 g/mL, 0.5 g/mL, or 0.51 g/mL, or 0.52 g/mL. mL, or 0.53 g/mL, or 0.54 g/mL, or 0.55 g/mL, or 0.56 g/mL, or 0.57 g/mL, or 0.58 g/mL, or 0.59 g/mL, or 0.6 g/mL, or 0.61 g/mL, or 0.62 g/mL, or 0.63 g/ml, 0.64 g/mL, or 0.65 g/mL, or 0.66 g/mL, or 0.67 g/mL, or 0.68 g/mL, or 0.69 g/mL, or 0.70 g/mL, or 0.71 g/mL, or 0.72 g/mL, or 0.73 g/mL, or 0.74 g/mL, or 0.75 g/mL, or 0.76 g/mL, or 0.77 g/mL, or 0.78 g/mL, or 0.79 g/mL, or 0.8 g/mL, or 0.805 g/mL, or 0.81 g/mL, or 0.815 g/mL, or 0.82 g/mL, or 0.825 g/mL, or 0.83 g/mL L, or 0.835 g/mL, or 0.84 g/mL, or 0.845 g/mL, or 0.85 g/mL, or 0.855 g/mL, or 0.86 g/mL, or 0.865 g/mL, or 0.87 g/mL, or 0.875 g/mL, or 0.88 g/mL, or 0.885 g/mL, or 0.89 g/mL, or 0.895 g/mL, or 0.9 g/mL, or 0.905 g/mL, or 0.91 g/mL, or. 915 g/mL, or 0.92 g/mL, or 0.925 g/mL, or 0.93 g/mL, or 0.935 g/mL, or 0.94 g/mL, or 0.945 g/mL, or 0.95 g/mL, or 0.955 g/mL, or 0.96 g/mL, or 0.965 g/mL, or 0.97 g/mL, or 0.975 g/mL, or 0.98 g/mL, or 0.985 g/mL, or 0.99 g/mL, or 0. 995 g/mL, or 1 g/mL, or 1.005 g/mL, or 1.01 g/mL, or 1.015 g/mL, or 1.02 g/mL, or 1.025 g/mL, or 1.03 g/mL, or 1.035 g/mL, or 1.04 g/mL, or 1.045 g/mL, or 1.05 g/mL, or 1.055 g/mL, or 1.06 g/mL, or 1.065 g/mL, or 1.07 g/mL, or 1.075 g/mL, or 1.08 g/mL, or 1.085 g/mL, or 1.09 g/mL, or 1.095 g/mL, or 1.1 g/mL, or 1.11 g/mL, or 1.12 g/mL, or 1.13 g/mL, or 1.14 g/mL, or 1.15 g/mL, or 1.16 g/mL, or 1.17 g/mL, or 1.18 g/mL, or 1.19 g/mL, or 1.2 g/mL, or 1.21 g/mL, or 1 .22 g/mL, or 1.23 g/mL, or 1.24 g/mL, or 1.25 g/mL, or 1.26 g/mL, or 1.27 g/mL, or 1.28 g/mL, or 1.29 g/mL, or 1.3 g/mL, or 1.31 g/mL, or 1.32 g/mL, or 1.33 g/mL, or 1.34 g/mL, or 1.35 g/mL, or 1.36 g/mL, or 1.37 g/mL, or 1.38 g/mL, or is 1.39 g/mL, or 1.4 g/mL, or 1.41 g/mL, or 1.42 g/mL, or 1.43 g/mL, or 1.44 g/mL, or 1.45 g/mL, or 1.46 g/mL, or 1.47 g/mL, or 1.48 g/mL, or 1.49 g/mL, or 1.5 g/mL, or 1.55 g/mL, or 1.6 g/mL, or 1.65 g/mL, or 1.7 g/mL, or 1.75 g/mL, or 1.8 g/mL, or 1.85 g/mL, or 1.9 g/mL, or 1.95 g/mL, or 2.00 g/mL, or 2.05 g/mL, or 2.1 g/mL, or 2.2 g/mL, or 2.3 g/mL, or 2.4 g/mL, or 2.5 g/mL, or 2.6 g/mL, or 2.7 g/mL, or 2.8 g/mL, or 2.9 g/mL, or 3.0 g/mL, or 3.1 g/mL, or 3.2 g/mL, or 3.3 g/mL, or 3.4 g/mL, or 3.5 g/mL, or 3.6 g/mL, or 3.7 g/mL, or 3.8 g/mL, or 3.9 g/mL, or 4.0 g/mL, or 4.1 g/mL, or 4.2 g/mL, or 4.3 g/mL, or 4.4 g/mL, or 4.5 g/mL, or 4.6 g/mL, or 4.7 g/mL, or 4.8 g/mL, or 4.9 g/mL, or 5.0 g/mL, 6.0 g/mL L, or 7.0 g/mL, or 8.0 g/mL, or 9.0 g/mL, or 10.0 g/mL, or 11.0 g/mL, or 12.0 g/mL, or 13.0 g/mL, or 14.0 g/mL, or 15.0 g/mL, or 16.0 g/mL, or 17.0 g/mL, or 18.0 g/mL, or 19.0 g/mL, or 20.0 g/mL, or 21.0 g/mL, or 22.0 g/mL, or 23.0 g/mL
Note: The allowable pressure difference for the lower elevation reservoir or "secondary reservoir" may include the maximum design pressure difference between the pressure of the fluid within the lower elevation reservoir or "secondary reservoir" and the pressure of any fluid or material or solid outside or adjacent to the fluid within the lower elevation reservoir or "secondary reservoir" at the same elevation as the fluid within the lower elevation reservoir or "secondary reservoir".
NOTE: The allowable pressure difference for the lower elevation reservoir or "secondary reservoir" may be less than, greater than, or equal to one or more or combinations of the following: 0 bar, or 0.01 bar, or 0.25 bar, or 0.5 bar, or 0.75 bar, or 1 bar, or 1.5 bar, or 2 bar, or 2.5 bar, or 3 bar, or 3.5 bar, or 4 bar, or 4.5 bar, or 5 bar, or 5.5 bar, or 6 bar, or 6.5 bar, or 7 bar, or 7.5 bar, or 8 bar, or 8.5 bar, or 9 bar, or 9.5 bar, or 10 bar, or 11 bar, or 12 bar, or 13 bar, or 14 bar, or 15 bar, or 16 bar, or 17 bar, or 18 bar, or 19 bar, or 20 bar, or 21 bar, or 22 bar, or 23 bar, or 24 bar, or 25 bar, or 26 bar, or 27 bar, or 2 8 bar, or 29 bar, or 30 bar, or 31 bar, or 32 bar, or 33 bar, or 34 bar, or 35 bar, or 36 bar, or 37 bar, or 38 bar, or 39 bar, or 40 bar, or 41 bar, or 42 bar, or 43 bar, or 44 bar, or 45 bar, or 46 bar, or 47 bar, or 48 bar, or 49 bar, or 50 bar, or 55 bar, or 60 bar, or 65 bar, or 70 bar, or 75 bar, or 80 bar, or 85 bar, or 90 bar, or 95 bar, or 100 bar, or 105 bar, or 110 bar, or 115 bar, or 120 bar, or 125 bar, or 130 bar, or 135 bar, or 140 bar, or 145 bar, or 150 bar, or 160 bar, or 170 bar, or 180 bar, or 190 bar, or 200 bar, or 225 bar, or 250 bar, or 275 bar, or 300 bar Note: The hydrostatic pressure of a fluid may be calculated using the density of the fluid, the gravitational constant, and the difference in elevation or the difference in elevation traversed by the fluid in succession.The hydrostatic pressure of a fluid may be calculated using the density of the fluid, the gravitational constant, and the difference in elevation or the difference in elevation traversed by the fluid in succession. The practical hydrostatic pressure of a liquid may also include friction losses and other potential pressure losses that may occur in a practical system, which may be calculated using fluid dynamics equations and/or simulation tools known in the art.
Note: In some embodiments, the low density fluid may comprise a gas or a supercritical fluid. For example, the low density fluid may comprise air, which may comprise a gas and/or a supercritical fluid. At pressures above about 55 bar, air may comprise a supercritical fluid.
NOTE: The pressure difference between a liquid or fluid stored in a reservoir at a higher elevation and a fluid, material, or solid outside or adjacent to the reservoir at the higher elevation at the same elevation may be less than, equal to, or greater than one or more of the following or a combination thereof: 0 bar, or 0.01 bar, or 0.25 bar, or 0.5 bar, or 0.75 bar, or 1 bar, or 1.5 bar, 2 bar, or 2.5 bar, or is 3 bar, or 3.5 bar, or 4 bar, or 4.5 bar, or 5 bar, or 5.5 bar, or 6 bar, or 6.5 bar, or 7 bar, or 7.5 bar, or 8 bar, or 8.5 bar, or 9 bar, or 9.5 bar, or 10 bar, or 11 bar, or 12 bar, or 13 bar, or 14 bar, or 15 bar, or 16 bar, or 17 bar, or 18 bar, or 19 bar, or 20 bar, or 21 bar, or 22 bar, or 23 bar, or 24 bar 1, or 25 bar, or 26 bar, or 27 bar, or 28 bar, or 29 bar, or 30 bar, or 31 bar, or 32 bar, or 33 bar, or 34 bar, or 35 bar, or 36 bar, or 37 bar, or 38 bar, or 39 bar, or 40 bar, or 41 bar, or 42 bar, or 43 bar, or 44 bar, or 45 bar, or 46 bar, or 47 bar, or 48 bar, or 49 bar, or 50 bar, or 55 bar, or 60 bar, or 6 5 bar, or 70 bar, or 75 bar, or 80 bar, or 85 bar, or 90 bar, or 95 bar, or 100 bar, or 105 bar, or 110 bar, or 115 bar, or 120 bar, or 125 bar, or 130 bar, or 135 bar, or 140 bar, or 145 bar, or 150 bar, or 160 bar, or 170 bar, or 180 bar, or 190 bar, or 200 bar, or 225 bar, or 250 bar, or 275 bar, or 300 bar. Note: In some embodiments, the lower elevation reservoir may comprise two or more different reservoirs. For example, in some embodiments, the lower elevation reservoir may include at least one reservoir for a low-density liquid and at least one reservoir for a high-density liquid. For example, in some embodiments, the lower elevation reservoir may include a separate reservoir for a low-density liquid and a separate reservoir for a high-density liquid. For example, in some embodiments, the lower elevation reservoir may include two separate tanks, one tank for storing a low-density liquid and one tank for storing a high-density liquid. For example, in some embodiments, the lower elevation reservoir may include two separate tanks, one tank for storing a low-density liquid and one tank for storing a high-density liquid, each tank comprising a bladder tank. For example, in some embodiments, the lower elevation reservoir may include two separate tanks, one tank for storing a low-density liquid and one tank for storing a high-density liquid, each tank comprising a rigid tank. For example, in some embodiments, the lower elevation reservoir may include two separate tanks, one tank for storing a lower density liquid and one tank for storing a higher density liquid, each tank including a rigid tank, or a bladder tank, or a combination thereof. Some examples of the embodiments described herein may include, but are not limited to, Figures 77 and 78.

In some embodiments, the low-density liquid and/or the high-density liquid may comprise a stored fuel. For example, the stored fuel may include one or more or any combination of the following, including, but not limited to, butane, propane, LPG, ethane, LNG, diesel, kerosene, gasoline, petroleum ether, ammonia, hydrogen, a hydrogen derivative, ethanol, or methanol. In some embodiments, the stored fuel may include a carrier fuel. For example, the stored fuel may include a hydrogen carrier, including, but not limited to, one or more or any combination of the following: methylcyclohexane, toluene, methanol, ammonia, or hydrazine. If desired, the stored fuel may be employed in other applications in addition to liquid displacement energy storage.

For example, the stored fuel can be employed as a fuel source for a combustion power plant. The combustion power plant can include a floating power plant, an onshore power plant, an offshore power plant, or any combination thereof. The combustion power plant can include a gas turbine, an internal combustion engine, a combined cycle, a Rankine cycle, a cogeneration system, a peaker power plant, an open-cycle engine, a closed-cycle engine, a heat engine, or any combination thereof. The combustion power plant can be operated as desired. For example, the combustion power plant can be operated when electrical demand exceeds the power capacity of the pumps and/or generators. For example, the combustion power plant can be operated when the gravity energy storage system is fully discharged or nearly fully discharged. For example, the combustion power plant can be operated in the event of an emergency. For example, the combustion power plant can substantially extend the potential duration of the energy storage system. For example, in some cases, liquid displacement energy storage can provide 90% of the annual energy storage needs, and the combustion power plant can provide 10% of the annual energy storage needs. For example, in some cases, liquid displacement energy storage may provide 95% of the annual energy storage needs, while the combustion power plant may provide 5% of the annual energy storage needs. For example, in some cases, liquid displacement energy storage may provide 80% of the annual energy storage needs, while the combustion power plant may provide 20% of the annual energy storage needs. Due to the significant potential fuel storage in the liquid displacement energy storage system, the integration of liquid displacement energy storage with a combustion power plant may result in high round-trip energy storage efficiency of the energy storage system and multiple months of usable energy storage duration. The integration of liquid displacement energy storage with a backup combustion power plant may result in an end-to-end energy storage solution for the creation of a power grid powered by nearly 100% or 100% renewable energy, especially when the stored fuel includes renewable fuel or fuel derived from renewable energy. The integration of liquid displacement energy storage with backup combustion power plants can result in an end-to-end energy storage solution for the creation of a power grid powered by near or 100% _CO2 emission-free energy, especially if the stored fuel includes carbon-free, or low-carbon, or renewable, or carbon-neutral fuels.

In some embodiments, fuel or supplemental fuel may be provided from an external source and/or may be provided via a vessel, or a pipeline, or any combination thereof. In some embodiments, fuel or supplemental fuel may be provided from an internal or on-site source and/or may be synthesized or otherwise generated internally or on-site. For example, in some embodiments, low-density liquids including hydrogen, or liquid hydrogen, or ammonia, or methanol, or ethanol, or butane, or kerosene, or methane, or LPG, or any combination thereof, may be generated on-site. For example, in some embodiments, low-density fluids including hydrogen, or liquid hydrogen, or ammonia, or methanol, or ethanol, or butane, or kerosene, or methane, or LPG, or any combination thereof, may be generated on-site. For example, in some embodiments, hydrogen, or liquid hydrogen, or ammonia, or methanol, or ethanol, or butane, or kerosene, or methane, or LPG, or any combination thereof, may be generated on-site. For example, in some embodiments, hydrogen, or ammonia, or methanol, or ethanol, or butane, or kerosene, or methane, or LPG, or any combination thereof, may be produced on-site using, for example, electricity, or renewable electricity, or water, or air, or nitrogen, or carbon dioxide, or any combination thereof.

In some cases, water may be employed as the low-density liquid. For example, in some embodiments, the low-density liquid may include water and the high-density liquid may include saltwater brine. For example, in some embodiments, the low-density liquid may include water and the high-density liquid may include a fluorocarbon.

In some cases, the high-density liquid, or the high-density fluid, or the low-density liquid, or the low-density fluid, or any combination thereof, may comprise a solid-liquid mixture, or an emulsion, or a suspension, or both. For example, an exemplary solid-liquid mixture may include milk. For example, the solid-liquid mixture may include, but is not limited to, one or more or any combination of the following: water, or an aqueous solution, or coal, or fly ash, or limestone, or zinc tailings, or phosphate rock, or Gilsonite, or copper concentrate, or iron ore, or talc, or kaolin, or cement, or concrete, or aggregate, or a high-density solid, or a high-density solid, or a solid having a density higher than the low-density fluid, or a solid having a density higher than water, a fluorocarbon, a halogenated reagent, or a halogen. For example, the solid-liquid mixture may include, but is not limited to, one or more or any combination of the following: water, or an aqueous solution, or a low-density solid, or a plastic, or a hydrocarbon. It may be desirable for a high density liquid, a high density fluid, a low density liquid, a low density fluid, or any combination thereof to be an essentially incompressible fluid. In some descriptions herein, a fluid may be described as a "liquid." "Liquid" may include any fluid that contains at least a portion of a liquid, and may include, but is not limited to, a liquid and/or a solid-liquid mixture.

Some exemplary embodiments related to gas pockets and recessed structures: Exemplary embodiments may include a "wall" connected to the bottom or side of the liquid structure. The liquid structure may include, but is not limited to, one or more or any combination of the following: a floating structure, a dock, a buoy, a platform, a float, a boat, a pontoon, a skiff, or a surface structure. A liquid structure may also include a structure moored to or at least partially supported by land while simultaneously being in, near, in contact with, submerged in, or in contact with water or another liquid.

In an exemplary embodiment, the structure may be a dock (note: a dock is provided as an exemplary floating structural object, and elements of the embodiments described herein may be applicable to other floating or non-floating structures described herein). A "wall" may be connected to the side or bottom of the dock, or near the perimeter of the bottom of the dock, and may be connected to or present as a component of the dock or a feature of the shape of the bottom of the dock. Alternatively, the shape of the bottom of the dock may be adapted to have the "wall," for example, such that the "wall" may be part of the shape of the dock rather than a separate connected material. The "wall" may protrude beyond the vertical water depth of most or all of the floating dock that comes into contact with the water. The connection of the "wall" to the structure may ideally be airtight or watertight. The "wall" may simply comprise a concave structure or a protruding portion of a concave structure.

The wall may, for example, result in the formation of a recessed region or cavity located near the bottom of the floating structure, or may include a majority of the bottom of the floating structure. In this embodiment, a gas or low-density liquid or other fluid may occupy at least a portion of the recessed region. The fluid may include, but is not limited to, one or more of the following, or any combination thereof: air, nitrogen, water vapor, methane, hydrogen, flue gas, carbon dioxide, oxygen, inert gases, argon, helium, practically water-insoluble gases, hydrocarbons, butane, propane, ethane, ozone, or combinations thereof. For illustrative purposes, the fluid may be referred to as a "gas," although gas may merely be an exemplary state of fluid; other fluid states may be adopted, including, but not limited to, liquid, or supercritical, or any combination thereof. The gas may be "trapped" within the recessed region at least temporarily, semi-permanently, or practically permanently. The "trapped" gas in the recessed region may be referred to as a "gas pocket" or "air pocket." The gas remains in the recessed region due to, for example, 1) the greater density of water than the gas, and/or 2) the practical inability of the gas to pass through the water/gas interface, and/or 3) the relative airtightness or air-tight seal of the recessed region.

The principle of operation of an air pocket can be illustrated by using a simple empty drinking cup and a container filled with water. When the empty drinking cup is turned upside down and submerged below the surface of the water in the upside-down position, air within the drinking cup can become trapped inside the drinking cup because the air cannot flow upward through the drinking cup and therefore the water may not be able to displace the air. The trapped air can be an example of an air pocket, and the area within the cup where air is trapped can be an example of a recessed area or cavity. An exemplary application in which the air pocket effect has been employed in the prior art can include a "diving bell."

The gas or air pocket may result in the formation of a separation or discontinuous separation between the water and at least a portion of the surface of the recessed region. Water may be isolated from contact with at least a portion of the solid surface of the recessed region due to the physical separation or barrier of the gas pocket between the water and the solid surface. A significant portion of the surface area of the solid surface of the recessed region may be in contact with the gas pocket. A significant portion of the surface area of water transported by the air pocket may be in contact with the air pocket at the air-water interface. The surface area in contact with the recessed region or gas pocket may include, for example, a significant portion of, or substantially all of the surface area of the underside of a surface structure. The surface area in contact with the recessed region or gas pocket may include a significant portion or substantially all of the surface area that may be exposed to, vulnerable to, or otherwise in contact with water or other liquids. The substantial portion may include more than 5%, or more than 10%, or more than 20%, or more than 30%, or more than 40%, or more than 50%, or more than 60%, or more than 70%, or more than 80%, or more than 90%, or more than 95% of the underside of the surface of the structure that contacts the liquid or body of water.

Fouling, scaling, or growth formation can be inhibited by the separation or discontinuous separation between the liquid and, for example, at least a portion of the surface of the recessed region resulting from the gas pocket. Fouling, scaling, or growth formation generally occurs in aqueous environments when water is in direct contact with a solid surface. The air pocket allows a substantial surface area of water that would otherwise be in contact with the solid surface to contact the water-gas or water-air interface rather than the solid surface. The gas separation or air barrier prevents liquid- or water-based fouling, scaling, or growth from adhering to the solid surface. The recessed region can include at least a portion of the surface area of the floating structure or lower portion of the structure that contacts the liquid. The recessed region can include a substantial portion, a majority, or nearly all of the surface area of the floating structure or lower portion of the structure that contacts the liquid, which can allow for a substantial reduction in fouling, scaling, or growth formation on the same structure without the gas or air pocket.

Fouling deposits, scalants, or growths generally adhere to surfaces from water through direct contact with the solid surface. Water-based fouling deposits, scalants, or growths generally cannot pass through air or other gases to reach solid surfaces. It is important to note that if water-based fouling deposits, scalants, or growths can somehow pass through air or other gases to reach solid surfaces, the mass transport through the gas may be orders of magnitude less than if water were in direct contact with the solid surface. As a result, water-based fouling deposits, scalants, or growths may not have sufficient mass transport to achieve substantially any or relatively equivalent fouling deposition, scaling, or growth in a gas or air environment relative to an environment of direct water-to-solid surface contact.
Gas pockets or recessed areas, or both, may increase or decrease stability. Stability may be increased, for example, due to a "suction" effect or force created by a structure having a gas-solid interface on one side and a solid-water interface on the other. Stability may be increased by reducing the center of gravity of the dock, for example, by adding weight to the "walls" of the recessed areas. By adding weight to the walls of the recessed areas or near the bottom of the structure, the structure may be less likely to heel enough to lose the gas in the gas pocket, for example, in the event of a weight imbalance on the structure or large waves. Gas pockets or recessed areas may decrease stability by potentially increasing the center of gravity. If the structure is in an environment with the potential for significant waves or rough water, it may be desirable to incorporate, for example, gyroscopic stabilizers, or stabilizing anchors, or stabilizing weights, or stabilizing earthing structures to increase stability or minimize heeling.
Gas pockets or recessed areas, or surface modifications that enable gas pockets, may be employed to prevent corrosion or degradation. For example, corrosion-sensitive materials or devices may be placed in a gas pocket when stored underwater. For example, a boat propeller may be surrounded by a gas pocket when the propeller or boat is not in use, which may be made possible by encasing or surrounding the propeller with a recessed area. For example, underwater hydraulic equipment or underwater trim tabs may be surrounded by a gas pocket when not in use.
A tube may be placed in a gas pocket or recessed region, and gas (including, but not limited to, gases described herein, such as air or nitrogen) may be pumped into the recessed region using the tube and/or a gas pump (which may be connected to the tube). One of the openings of the tube may be located within or below the recessed region. The initial pumping of gas into the recessed region may allow a gas pocket to form within the recessed region. After the gas pocket is formed, additional gas may be pumped into the region, for example, including, but not limited to, one or more or a combination of the following: to expand the gas pocket to replace gas that may have escaped from the gas pocket, or to allow excess gas to overflow or spill from the gas pocket and recessed region.

The recessed area or gas pocket may become infiltrated with water, for example, during large waves or when the structure tilts at a significant angle. For example, to minimize potential scaling, fouling, or corrosion resulting from water contact, it may be advantageous for the water contact to be temporary or of as short a duration as possible. One means of potentially minimizing the frequency of water contact may include pumping air or other gas into the recessed area or cavity, for example, using tubing or a pressurized air tank. The air or other gas may be pumped into the recessed area continuously, or may be pumped into the recessed area only on specific occasions. For example, the specific occasion may include when a gas or air pocket is at risk of losing air or when there is a risk of water infiltration into the recessed area. For example, the specific occasion may include when the structure tilts beyond a specified angle, which may be triggered or measured, for example, using a device for measuring angular change or movement known in the art. For example, the particular occasion may include when a portion of the solid surface of the recessed region is wet, or at least partially wet, or in contact with water, which may be triggered or measured, for example, using a water or wetness sensor or similar device known in the art.

It may be desirable for the "wall" to be durable, capable of handling the weight of a dock or docks, and resistant to damage from other objects or elements. For example, the wall may include a "skirt," e.g., a material that may be structurally flexible but may contain air pockets. The "skirt" may be similar to the "skirt" employed in hovercraft, but unlike hovercraft, the skirt may remain partially or entirely below the water's surface.

An exemplary durable wall may include a tube connected to the bottom of the dock and attached, for example, near the perimeter of the bottom of the dock, surrounding the perimeter of the dock. To prevent damage to the "wall," the tube may be collapsible when the dock is moving. The tube may be expanded or made more rigid using, for example, but not limited to, pneumatic or hydraulic means, such as by filling it with air or hydraulic fluid. The tube may be connected to the dock in a manner that prevents air or water from passing through the connection between the dock and the "wall" of the tube.

The present invention and/or elements of the present invention, which may include, but are not limited to, "walls," gas pockets, recessed areas, tubes, gas or air pumps, and/or other elements of the embodiments described herein, may be retrofitted onto an existing structure or may be elements of a new structure.

The present invention may also be applicable to preventing or minimizing fouling deposits or scabs or growths in non-aqueous liquid environments.

A portion of the floating structure may be in contact with the water or liquid, including, for example, solid surfaces outside of recessed areas or gas pockets. Such solid surfaces in contact with the water or liquid may be susceptible to growth, fouling, or scaling. It is important to note that a large portion of the solid surface area below the surface of the water or liquid may be in contact with the gas pocket and, as a result, may be less susceptible or less susceptible to growth, fouling, or scaling. This may have the effect of significantly reducing or eliminating growth, fouling, or scaling on a large portion of the surface area below the surface of the solid structure. Surfaces in contact with water or liquid may have growth formation, fouling, or scaling, but it may be important to note that 1) sidewalls are generally easier to clean/scrub than the underside/underbody/underbelly of the floating structure, 2) the total amount of growth formation, fouling, or scaling may be significantly less than if the present invention were not employed, and 3) by pumping excess air into the recessed area and encouraging the formation of small air bubbles that can rise up the sides of the structure, an air curtain may be created that minimizes growth formation on areas not protected by air pockets.

Water may refer to a body of liquid, including, but not limited to, a body of liquid that contains at least a portion of water that contains saltwater. Such a body of liquid may include, but is not limited to, a marine environment, an aquatic environment, a river, a lake, a brine pool, a frac water, a wastewater, an oil storage tank, a chemical storage tank, or other liquid environment.

A gas pocket may be trapped or stationary under conditions of low, minimal, or no turbulence. No turbulence conditions may include environments where the water is calm and motionless to the naked eye, and the submerged structures are also motionless to the naked eye. Low or minimal turbulence conditions may include environments where the water is calm and motionless to the naked eye, and/or the submerged structures are calm and motionless to the naked eye. In a low turbulence environment, there is discernible movement, but the movement of the water or structure is insufficient to cause more than 10%, more than 20%, more than 25%, more than 30%, more than 40%, or more than 50% of the gas in the gas pocket to flow out from beneath the structure in a 30-second period. It is important to note that gas flow may not include intentional removal of gas from the gas pocket or flow of gas through tubing interconnected to the gas pocket.
Some embodiments may be employed to enhance growth formation, such as specific forms of growth. For example, embodiments described herein, such as gas pockets, may be formed in specific areas to kill invasive algae species or invasive fish eggs, or other potentially harmful aquatic lifeforms. For example, gas pockets may enable localized oxygenation. For example, gas pockets may enable localized deoxygenation. For example, gas pockets may enable localized cooling, which may include evaporative cooling, which may increase the longevity or improve the health of, for example, corals. For example, gas pockets may enable localized pH adjustment, such as _CO2 removal or pH increase due to _CO2 gas removal.

Illustrative exemplary embodiments:
A system for preventing fouling and scaling on water structures, including:
a structure including a recessed region; the recessed region including a gas pocket; the gas pocket providing a discontinuous separation between water and at least a portion of the surface of the recessed region;

A system for preventing fouling and scaling on water structures, including:
Illustrative Example Subembodiments: ● a structure including a cavity ● the cavity includes a gas pocket ● the gas pocket provides a discontinuous separation between a liquid and at least a portion of the cavity ● the discontinuous separation inhibits the formation of scalrants, fouling deposits, and growths on solid surfaces in contact with the area occupied by the gas pocket ● a tube having an opening located below or within the recessed area is interconnected to a pressurized gas source ● the pressurized gas source may include an air pump, a gas pump, a pressurized gas line, or a combination thereof ● the tube is connected to a valve that allows gas to be controlled through the tube into and out of the gas pocket ● at least a portion of the solid surface area in contact with the gas pocket is separated from or does not directly contact water for more than 30%, or more than 40%, or more than 50%, or more than 60%, or more than 70%, or more than 80%, or more than 90%, or more than 95% of the time the structure is in the water ● the water includes a liquid area ● the gas pocket displaces liquid ● The gas pocket is trapped or stationary under conditions of low or minimal turbulence or no turbulence ● Gas can be pumped into the gas pocket continuously, semi-continuously, or on occasions when gas needs to be replenished ● Gas is pumped into the gas pocket beyond the volumetric capacity of the cavity or recessed area, resulting in an overflow foam ● The overflow foam reduces fouling on solid surface areas not in direct contact with the gas pocket ● The overflow foam is systematically distributed along the solid surface areas not in direct contact with the gas pocket using geometric modifications to sections of the structure ● The geometric modifications can include perforations, dimples, microscopic modifications, surface morphology, or microscopic modifications ● The height of the structure above the water surface can be adjusted by increasing or decreasing the volume of gas in the recessed area or cavity ● The recessed area or cavity is retrofitted to an existing structure ● The recessed area or cavity is an aspect of the shape of an existing structure ● The recessed area or cavity is an aspect of the shape of a new structure ● The shape or size or strength or stiffness of the recessed area or cavity may be adjustable ● The adjustability may include controlled formation or collapse of the recessed area or the "walls" of the recessed area ● The adjustability may include controlled formation or collapse of the recessed area or the "walls" of the recessed area using pneumatic or hydraulic means ● The adjustability may include controlled volume or depth or surface area of the recessed area ● The volume, shape, surface area or depth of the gas pocket is adjustable ● The adjustability of the gas pocket includes one or more or a combination of the following: the ability to add or remove gas from the gas pocket, the ability to change the shape or contour of the gas pocket or recessed area, the ability to adjust the shape or size of the "walls" of the recessed area ● The gas pocket contains a non-aqueous liquid in addition to or instead of gas ● The surface of the gas pocket is hydrophobic or includes a hydrophobic coating ● The gas pocket or recessed area or cavity may function as a diving bell or temporary shelter or storage area The tube is connected to a check valve that allows gas (such as air) to enter the tube and/or the recessed area, but does not allow air to escape from the area.
"1" or "(1)": Upper section of floating platform or dock; "2" or "(2)": Lower section of float or pontoon, floating platform or dock; "3" or "(3)": Gas or air pocket that may be in a concave area below or underneath "2";"4" or "(4)": Body of liquid such as water or oil; "5" or "(5)": Extended wall that may extend beyond the vertical depth of the air pocket; "6" or "(6)": Air or gas bubble curtain on the side wall of "2" that contacts the water. "6" may result from gas being pumped into the concave area and the gas pocket exceeding the volume of the gas capacity of the concave area. The bubble curtain may be facilitated by perforations or depressions in the side wall. The bubble curtain may reduce growth formation on surfaces not in contact with the gas pocket.
- "7" or "(7)": an air or gas pump (line with arrow) connected to a tube that may interconnect the gas or air pumped by the pump with the recessed area.

Figure 1: An exemplary dock having a recessed area "gas pocket" ("3") on the underside of each float or pontoon. The gas pocket may allow the surface area on the underside of the dock, or the majority of the dock's surface area in contact with the air pocket, to have minimal or no levels of fouling deposits, scale, or growth.

Figure 2: An exemplary dock having a recessed area "gas pocket" ("3") beneath each float or pontoon. Tubes may be placed beneath the dock or connected to the bottom of the dock. Air or other gas is pumped into the tubes, directing the gas into the gas pocket. If the volume of gas exceeds the volume of the recessed area or cavity, bubbles may migrate up the sides of the dock, forming a bubble curtain ("6") along the side of the dock, if desired. Such a bubble curtain may be facilitated, for example, by placing dimples or perforations in the "walls" of the recessed area. The dimples or perforations may be located near the bottom of the vertical depth of the "walls" of the recessed area. Such a bubble curtain may be desirable to minimize fouling, scaling, and growth outside the gas pocket. If a continuous bubble curtain is desired, a continuous flow of pumped air may be required.

Figure 3: An exemplary embodiment having an extended "wall" that may be employed to prevent air or gas loss, for example, in the event of waves, turbulent water, or a significant change in the angle of the dock. The extended wall may extend to a depth beyond the depth of the air pocket. If desired, the extended wall may be weighted to reduce the center of gravity. It may be desirable to prevent the air pocket from extending to the full depth of the extended wall (e.g., to ensure the dock remains stable), in which case it may be desirable to include small perforations in certain portions of the extended wall. Air or other gas may need to be pumped into the air pocket less frequently or on fewer occasions in embodiments having extended walls.

Figure 4: An exemplary embodiment in which varying the volume of gas in gas pockets adjusts the height and/or angle above the water surface of a floating structure, such as a dock. Figure 4 may show that by pumping air into two recessed areas, increasing the volume of the air pockets and displacing water from the recessed areas, the height of the dock above the water surface increases. This embodiment may be advantageous for increasing or decreasing the height of the dock or reducing the draft of the dock. Advantageously, relatively little energy may be required to increase the height of the dock due to, for example, potentially lower air pressure in the recessed areas resulting from a relatively smaller head height. Advantageously, no moving parts are required to come into contact with the liquid.

Figure 5: An exemplary embodiment in which varying the volume of gas in a gas pocket adjusts the height and/or angle above the water surface of a floating structure, such as a dock. Figure 5 may show that by releasing air from a recessed area, increasing the volume of the air pocket, and displacing water from the recessed area, the height of the dock above the water surface decreases. This embodiment may be advantageous for increasing or decreasing the height of a dock or reducing the dock's draft.

Tidal Power System, or Power Storage System, or Any Combination Thereof Description: The present embodiments may relate to systems and methods for generating energy from changes in water level due to tides. Some embodiments may be applicable, for example, to tidal power energy generation systems that generate energy from changes in water level due to tides. Some embodiments may involve generating energy, such as electricity, using displacement of air or other fluid from a storage area due to a rise in water level due to tides. Some embodiments may involve generating electricity using movement of air or other fluid into a storage area due to a decrease in water level due to tides. The movement or displacement of air may be transported to the surface, for example, through one or more tubes, and/or converted to electricity, for example, using an air generator. If desired, the generation of electricity, air pumps, air generators, and/or other components may be located on a surface outside of the water or storage area. If desired, another gas or fluid other than, in addition to, or in combination with air may be employed. The storage area may include a water-, air-, or fluid-impermeable material or structure having a recessed area containing a space that can be occupied by a fluid. The recessed area may be occupied by a porous material, such as sand, rock, cinderblock, plastic bottle, or packing material, which may contain a space that can be occupied by a fluid such as water or air. The storage area may include a watertight or airtight liner or tarp that forms a recessed area over a portion of the sand, rock, cinderblock, plastic bottle, packing material, or solid material, which has a space that can be occupied by a fluid such as water or air. The storage area may include a rigid structure, such as an old ship, or a plastic container. The storage area may include a bag, bladder, or flexible structure that expands when filled with gas or a low-density liquid, for example, at low tide, and may be collapsible when the gas or low-density liquid is released through a generator, for example, at high tide. The recessed area may include an open space that can be occupied by a fluid such as water or air. The recessed region may be positioned so that it faces toward the Earth's surface (e.g., the direction of gravity) so that less dense fluid can be trapped in the recessed region, if desired. The recessed region may include a tube having an opening therein. The tube may be interconnected to a surface where it may be connected to an air pump or generator or a hydraulic pump or generator. The tube may be disposed, for example, below and around the recessed region rather than through the material of the storage region, as this may reduce the likelihood of leakage through the storage region.

The recessed or storage area may include infrastructure employed for other purposes, which may include, but is not limited to, one or more or a combination of the following: a sewer system, a wastewater system, an outflow system, a drainage system, a wastewater pipe, an intake pipe, an outflow pipe, or a water storage area.

The recessed or storage area may be filled with a porous material filler, which may include one or more or a combination of the following, but is not limited to: sand, gravel, rocks, packing material, cinder blocks, plastic bottles, plastic containers, plastic buckets, interconnected cinder blocks, interconnected plastic containers, or interconnected packing material.

The recessed or storage area may be incorporated into or be a component of an existing or new offshore structure. For example, the recessed or storage area (which may be integrated with air tubes and pneumatic generators/pumps) may be fabricated as a component embankment, barrier, building foundation, landfill or land extension, or artificial island. Advantageously, the interior surface of waterfront land that is rarely seen or utilized after construction may be converted into a means for generating renewable electricity from the tidal or water level changes of a body of water.

For example, a recessed area or storage area may be constructed as part of a dike, landfill, or artificial island in three general steps: 1) Air tubes may be placed in the area where the marine structure will be constructed. The air tubes may have ends located at a vertical elevation near the vertical elevation of the ultimately constructed recessed area or storage area. Advantageously, water pipes may be placed in the area where the marine structure will be constructed to promote water flow in the ultimately constructed recessed area or storage area. Alternatively, for example, if water pipes are not employed, flooding or seepage may be the only source of water flow. 2) Porous material filler may be added, such as rock, sand, or cinder block, or other filler material, or other porous fill materials described herein, or combinations thereof. The filler material may include the interior of the recessed area or storage area. The filler material may surround the air tubes. It may be desirable for the filler material to surround, but not substantially or completely block, kink, or clog, the air tubes. The fill material may be carefully placed to match the design or contour of the storage area or recessed area liner. 3) A liner may be placed over the fill material and pipe. It may be desirable for the liner to match the contours of the fill material, or it may be desirable for the liner to surround the fill material for the full vertical depth of the fill material or storage area. The liner may include one or more or a combination of the following, but is not limited to: HDPE liner, LDPE liner, aluminum liner, steel liner, metal-coated liner, metal liner, cement liner, cement layer, clay liner, landfill liner, pond liner, lake liner, storage tank liner, nylon liner, geosynthetic liner, PVC liner, bag, fabric, fabric, mesh, high-strength polymer liner, woven liner, braided liner, liner including multiple layers of material for strength and fluid tightness, or tarpaulin.

After the liner is in place, additional materials may be added, including the remainder of the offshore structure, to construct the offshore structure, for example. Advantageously, cushioning material may be added to the top or bottom of the liner to minimize potential wear and tear or prevent the formation of perforations in the liner. Such cushioning material may include, but is not limited to, one or more or combinations of the following: sand, or burlap, or twine, or woven fabric, or Kevlar, or gravel, or clay, or mud, or foam, or cement, or concrete, or mesh, or fabric, or textile, or rubber. Advantageously, the tidal power system may be constructed without any moving parts below the water surface, underground, or within a storage area or cavity.

For example, the recessed or storage area may be constructed from a container or structure that can be submerged, such as in the form of an artificial reef, or otherwise. For example, the recessed or storage area may be constructed from an upside-down container, ship, boat, tank, or barge. Advantageously, the hull of the ship may already be fluid-tight, although additional patching or re-strengthening may be employed if desired. An exemplary implementation may include one or more of the following steps: 1) Placing tubes and/or water pipes inside the container. Air tube openings may be located or attached near the bottom of the container (which may be near the eventual top of the storage or recessed area, if the container becomes a storage or recessed area). Water tubes may be employed to promote water flow into and out of the storage or recessed area. 2) Placing porous filler material within at least a portion of the container. The porous filler material may be employed to prevent the container from floating when the container's free space is occupied by air. Alternatively or additionally, anchors and lines may be used, which may be evenly distributed throughout the container, to prevent the container from floating. If necessary, a portion of the remaining air space inside the container may be filled with water to aid in sinking. 3) The container is inverted upside down and placed at or near the bottom of the body of water. It may be desirable for the filler material to be at least partially contained within the container to prevent significant and uncontrolled leakage of the filler material. The filler material may be contained due to an at least partially covered compartment of the container's interior. Alternatively or additionally, the filler material may be contained using fabric, mesh, thread, or netting. For example, it may be advantageous to perform this step when the container is near the bottom of the body of water to minimize uncontrolled leakage of the filler material. The air pipe may be connected to an air pump or air generator located near, on, or above the surface. The water pipe may be open to the surrounding body of water. Advantageously, if the storage or recessed area is located near the bottom of the body of water, the storage or recessed area may experience near or close to the full head of the body of water throughout the energy generation step, which may depend on the vertical height of the recessed area relative to the depth of the body of water and the water level difference between low and high tides.

Some embodiments may generate electricity from differences in water pressure in a storage area of a body of water due to changes in water level that may result from tides. Embodiments may include a storage area below the surface of a body of water. During relatively low water levels or tides, air may be pumped into the storage area, for example, using one or more tubes, to displace water within the storage area. During relatively high water levels or tides, water may be allowed to displace air from the storage area, and the air may pass through, for example, one or more tubes into an air generator to generate useful work or electricity. It is important to note that at higher water levels or tides, the water pressure within the storage area may be significantly greater than the water pressure within the storage area during lower water levels or tides. Net energy or electricity may be generated, for example, due to a significantly greater amount of energy or electricity generated from air being transferred to a generator at high water levels or higher tides than the energy or power required to pump air into the storage area during lower water levels or lower tides. The net energy or electricity generated may include the difference between the energy generated during higher water levels or higher tides compared to the energy consumed during lower water levels or lower tides.

Embodiments may generate electricity during one or more of the tidal cycles. For example, some embodiments may generate electricity during four tidal cycles in a period of about one day (e.g., two high tides, two low tides), an example of which may be an embodiment employing an underground cavity with a depth within the range of seawater levels at the high and/or low tides. For example, some embodiments may generate electricity during two tidal cycles in a period of about one day (e.g., two high tides), an example of which may be an embodiment employing an underwater storage area at a depth below, near, or approximately the same as the low tide depth within the area. For example, some embodiments may generate electricity during fewer cycles than their available capacity allows, an example of which may be an embodiment employing an underground cavity with a depth within the range of seawater levels at the high and/or low tides, where this process generates electricity only during the high tides. An embodiment that generates power only during high tides may be advantageous because some cavities may not be structurally suitable for the partial vacuum that may be required to generate power during all four tidal movements during the day.

The process may employ hydroelectric or hydro generators, if advantageous. It is important to keep in mind that costs must be minimized and service life maximized, and it may be advantageous to employ pneumatic generators powered by air displacement.

Cavity, storage area, or recessed area may be similar or synonymous terms.

Some embodiments may relate to a tank applicable to storing low-density fluids underwater. For example, some embodiments may relate to a rigid structure or a flexible structure. For example, some embodiments may relate to a tank or storage area containing a porous solid medium, where a low-density fluid may be stored in the pores of the porous medium. For example, some embodiments may relate to a tank or storage area containing a porous solid medium, where a low-density fluid is stored in the porous medium by pumping or otherwise directing the low-density fluid into the porous medium to displace a higher-density fluid stored in the porous medium. For example, some embodiments may employ a storage reservoir including a porous medium, where the density or weight of the porous medium may reduce the buoyancy of the storage reservoir. For example, some embodiments may employ a storage reservoir including a porous medium, the presence of which prevents the reservoir from substantially collapsing, for example, when the pressure inside the reservoir is less than the pressure outside, adjacent to, surrounding, or at the same elevation as the reservoir. For example, some embodiments may employ a storage reservoir including a porous medium, the presence of which prevents the reservoir from substantially collapsing, for example, when fluid is pumped out of or removed from the storage reservoir at a volumetric rate greater than the volumetric rate at which fluid is added to or pumped into the storage reservoir. For example, some embodiments may employ a storage reservoir including a porous medium, the presence of which prevents the reservoir from substantially collapsing, for example, when fluid is pumped out of or removed from the storage reservoir without the simultaneous addition of another fluid to the reservoir. Substantial collapse can include the storage reservoir decreasing in total volume by one or more, or a combination or more, of the following: 1 percent, or 5 percent, or 10 percent, or 15 percent, or 20 percent, or 25 percent, or 30 percent, or 35 percent, or 40 percent, or 45 percent, or 50 percent, or 55 percent, or 60 percent, or 65 percent, or 70 percent, or 75 percent, or 80 percent, or 85 percent, or 90 percent, or 95 percent. Exemplary advantages:
Cost:
o Low material costs, which may simply include the liner, pipe, fill material (if not already available in the surrounding environment), air generator or pump. o Labor costs may vary depending on whether the installation is part of another undertaking, such as building an offshore structure, and whether the installation requires digging below ground surface or dredging.
●Resilience and durability:
o Some embodiments may be located underground or below the surface of a body of water to reduce potential hazards from waves and debris.
o Some embodiments have no moving parts below the surface of the body of water, which may reduce or eliminate potential hazards from corrosion, fouling, or debris.
No moving parts may contact or directly contact water or a body of water, reducing costs and increasing expected lifespan if desired.
Efficiency: Pneumatic generators powered using relatively low pressure compressed air can generate electricity with efficiencies of greater than 50%, or greater than 60%, or greater than 70%, or greater than 80%, or greater than 90%.

An exemplary step-by-step description of underground air and water cavities:
Overview: Figures 14-19 may illustrate embodiments employing underground storage areas or cavities that may be employed to generate energy from tides and/or store energy in gravitational potential energy displacing higher density fluids with lower density fluids. Some figures may illustrate exemplary steps in a process for generating electricity from changes in water levels due to, for example, but not limited to, tides. In Figures 14-19, the storage area or cavity may primarily comprise empty space for a fluid to occupy, such as air, or a lower density liquid, or water, or a higher density liquid, or any combination thereof.

Figure 14: Step 1 (Rising Tide, Filling, Power Generation): Figure 14 may show an embodiment during power generation. Air may be released through an opening in a valve in the air tube or air pump, allowing the air to exit the storage area, pass through a pipe, and enter the air generator, which may generate electricity. Due to a relatively high water level in the surrounding or nearby body of water compared to the water level in the storage area, the air pressure in the storage area may exceed atmospheric air pressure. Water from the surrounding or nearby body of water may pass through the pump or move into the storage area via seepage, displacing the air within the storage area. The flow rate of air exiting the storage area and the flow rate of water entering the storage area may be controlled by controlling the flow rate of air entering the air generator.

Figure 15: Step 2 (High Tide, Cavity Full): Figure 15 may show an embodiment in which the storage area is nearly full with water. A storage area may be considered nearly full with water when it achieves either of the following: 1) the water level in the storage area is near or at the maximum water level of the recent tidal range of a nearby body of water, or 2) the volume of water has reached the maximum practical volumetric capacity of the storage area.

Figure 16: Step 3 (Ebb Tide, Empty, Generate Power): Figure 16 may show an embodiment in which power is being generated when the water level of the surrounding body of water is relatively low compared to the water level inside the storage area. Energy may be generated due to the inflow of air into the storage area as water leaves the storage area, with the air flow powering, for example, an air generator. Water exiting the storage area may be through a water pipe or by flooding. It is important to note the depth of the storage area, or whether a water pipe is connected to the storage area; the depth of the water pipe may desirably be less than the depth of the water in the body of water to prevent uncontrolled water or air from entering the storage area. The exit of air flow and water may be controlled through the opening of a valve connected to the air tube or air generator.

Figure 17: Step 4 (Low Tide, Empty): Figure 17 may show an embodiment in which the storage area is nearly filled with water. The storage area may be considered nearly empty once it achieves either: 1) the water level in the storage area is near or at the minimum level of the recent tide range of a nearby body of water, or 2) there is no water in the storage area.

Figure 18: Step 4 Alternative (Depending on low tide, emptiness, time of year, and location): Figure 18 may show an embodiment in which the storage area is completely emptied of water. It is important to note that energy generation from water exiting the storage area may require the water pipes or storage area to be at least partially below the water surface to prevent unintended air or water flow. It is important to note that a storage area that is almost completely occupied by air may maximize potential energy generation capacity.

19: Step 5 (Undertide, Pump Residual Water Out): FIG. 19 may illustrate an embodiment in which air or another low-density fluid is pumped into the storage area to replace the water. For example, it may be desirable to pump air or another low-density fluid into the storage area during periods when the water level or tides of the surrounding body of water are relatively low, or when electricity or power is in excess or relatively cheap, or any combination thereof. In some embodiments, the energy required to pump air into the storage area (and displace the residual water) during undertide may be significantly less than the energy generated from the increase in displaceable volume occupied by the air in the storage area. In some embodiments, the energy required to pump air or other low-density fluid to displace the water may be equal to or greater than the amount of energy generated by the water displacing the air or other low-density fluid. This embodiment may include an energy storage process. This embodiment may include an energy storage system, and the presence of tidal or tidal power may improve round-trip energy efficiency and/or allow for the generation of more electricity than is needed during charging or storage. Additionally, air or other low-density fluid can be pumped into the storage area to remove water that may be trapped in the air pipes.

Exemplary embodiments in which the water/air cavity or storage area contains a porous material:
Overview: Figures 20-23 may illustrate embodiments employing an underground storage area or cavity. Each figure may illustrate exemplary steps in a process for generating electricity from changes in water levels, for example, due to, but not limited to, tides. In Figures 14-19, the storage area or cavity may contain primarily porous fill material that may include space for a fluid, such as air or water, to occupy. The steps for generating electricity may be similar to those shown in Figures 14-19.

Figure 20: Step 1 (Upwelling, Filling, Power Generation): Figure 20 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material.

Figure 21: Step 2 (High Tide, Cavity Full): Figure 21 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material.

Figure 22: Step 3 (Unload, Empty, Generate Power): Figure 22 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material.

Figure 23: Step 4 (Downstream, Empty): Figure 23 shows an exemplary embodiment in which the water/air cavity or storage area contains a porous material.

Below the water vessel (which may be close to full head height throughout the power generation and may also include the energy storage system and tidal power system):
FIG. 24: Step 1 (Upwelling, Filling, Power Generation): FIG. 24 shows an exemplary embodiment where the water/air cavity or storage area is located on or within a body of water.

Figure 25: Step 2 (High Tide, High Water): Figure 25 shows an exemplary embodiment in which the water/air cavity or storage area is located on or within the body of water.

Figure 26: Step 3 (Undertow, Empty): Figure 26 shows an exemplary embodiment in which the water/air cavity or storage area is located above or within the body of water.

Figure 27: Alternative Step 3 (low tide, empty, depending on tide and location): Figure 28 shows an exemplary embodiment in which the water/air cavity or storage area is located on or within the body of water.

Figure 28: Step 4 (Undertide, Empty): Figure 28 shows an exemplary embodiment in which the water/air cavity or storage area is located above or within the body of water.

Figure 29: Figure 29 shows an exemplary embodiment with a floating pump or floating generator station.

While many of the above figures show a vessel or other storage structure at or near the bottom of a body of water, it will be understood that the body of water may be located in any convenient location below the surface. In some embodiments, it may be retained below and/or above the body of water.

Air may be substituted with other fluids described herein. If the fluid includes a liquid, a hydraulic or hydroelectric generator may be employed instead of an air-powered generator.

A relatively high tide is when the water level in a body of water is higher than the water level during a relatively low tide. The change in water level can be primarily due to changes in water level caused by gravity tides.
Illustrative exemplary embodiments:
Tidal power system comprising:
o An area including a cavity, recessed area, or storage area surrounded by at least a portion of a water impermeable material o Water displaces air from the area at relatively high tides o Air displaces water at relatively low tides o Generating electricity from the movement of air into or out of the area Exemplary illustrative sub-embodiments:
● Energy is produced or electricity is generated using air turbines or generators ● The area is located below ground level, inside a dike, on a landfill, an artificial island, a barrier, a building foundation, a structure foundation, or a combination thereof ● The storage area contains a porous fill material ● The porous material fill includes one or more or a combination of the following: sand, gravel, rock, packing material, cinder blocks, plastic bottles, plastic containers, plastic buckets, interconnected cinder blocks, interconnected plastic containers, or interconnected packing material ● The water impermeable material may include a liner ● Air enters and leaves the area using pipes ● The pipes have openings within the storage area, or have openings above the water level, or both ● Water enters and leaves the area via infiltration ● Water enters and leaves the area via pipes ● Water enters and leaves the area through openings in the area or through impermeable material ● It is structurally rigid ● The area is structurally flexible or inflatable or collapsible and may include a float, bag, or similar device ● The air is located inside the structurally flexible area, which expands during an ebb tide and collapses during a flood tide ● The collapse generates electricity via the transfer of air from the structurally flexible area into an air generator ● The area includes infrastructure employed for other purposes, such as one or more or a combination of the following: a sewer system, a wastewater system, an outflow system, a drainage system, a drain pipe, an intake pipe, an intake system, an outflow pipe, an outflow system, or a storage area.
The liner may comprise one or more or a combination of the following: HDPE liner, or LDPE liner, or aluminum liner, or steel liner, or metal coated liner, or metal liner, or cement liner, or cement layer, or clay liner, or landfill liner, or pond liner, or lake liner, storage tank liner, or nylon liner, or geosynthetic liner, or PVC liner, or bag, or fabric, or fabric, or mesh, or high strength polymer liner, or woven liner, or braided liner, or a liner comprising multiple layers of material for strength and fluid tightness, or waterproof sheeting.
● The area consists of a vessel or structure that may be submerged, in the form of an artificial reef, or otherwise, or a combination thereof ● Air is pumped into the area during an ebb tide and released from the area into a generator during an up tide ● The energy generated during the up tide exceeds the energy consumed during the down tide ● Air is pumped into the area to store electricity ● Air is released from the area to generate electricity ● The invention can function as a tidal power energy generation device, an energy storage device, or both

Chilled Water Power Generation The less dense fluid and/or the more dense fluid may be at a temperature lower than, higher than, or different from the ambient air temperature, the air temperature at the water surface, or the water temperature at one or more depths, or any combination thereof. For example, the less dense fluid and/or the more dense fluid may be at a temperature lower than, for example, the surface water temperature, the surface air temperature, or both, within a thermocline body of water when being transferred from a lower elevation reservoir to a higher elevation reservoir. For example, in some embodiments where the system is located in a thermocline body of water, the energy storage system may be designed such that at least a portion of heat is removed from the less dense fluid and/or the more dense fluid when being transferred to, stored in, or transferred from the lower elevation reservoir, or any combination thereof. For example, in some embodiments where the system is located in a thermocline body of water, the energy storage system may be designed such that at least a portion of the heat is removed from the low-density fluid and/or the high-density fluid by heat exchange with seawater or the body of water as it is transferred to, stored in, or transferred from a lower-elevation reservoir, or any combination thereof.

In some embodiments where the system is located within a thermocline body of water, low-density fluids and/or high-density fluids, which may be at temperatures different from the surface water or air temperatures, may be employed in the heat engine to generate electricity.

For example, in some embodiments where the system is located in thermocline waters, the low-density fluid and/or high-density fluid may be at a temperature lower than the surface air or water temperature when the low-density fluid and/or high-density fluid is transferred from a lower-elevation reservoir to a higher-elevation reservoir. The lower-temperature low-density fluid and/or high-density fluid may be employed in the cold side or heat sink of a heat engine. For example, the cold low-density fluid and/or high-density fluid may be in heat exchange with a working fluid in a heat engine such that heat is transferred from the working fluid in the heat engine to the lower-temperature low-density fluid and/or high-density fluid. The hot side of the heat engine may include a heat source, which may include, but is not limited to, air, surface air, water, surface water, an application requiring cooling, waste heat, condenser water, or any combination thereof.

The heat engine may include one or more or a combination of heat engines, which may include, but are not limited to, a Rankine cycle, an organic Rankine cycle, a Kalina cycle, an open cycle, a closed cycle, an air turbine, an agitator motor, a heat engine for generating electricity from small temperature differences, an osmotic heat engine, or any combination thereof.

A thermocline body of water may include a body of water in which the temperature of the water varies with depth. For example, a thermocline body of water may include an ocean-connected body of water, or an ocean, or a lake, or a body of water in which the temperature of the water near the surface of the body of water exceeds the temperature of the water near the bottom of the body of water.

In some embodiments, it may be desirable to employ a low-density fluid and/or a high-density fluid with an increased specific heat capacity. For example, some embodiments may employ a fluid with a specific heat capacity greater than that of water. For example, some embodiments may employ a fluid with a specific heat capacity greater than that of glycol antifreeze. For example, some embodiments may employ a fluid-fluid phase change fluid with an enthalpy of fluid-fluid phase change, which may result in an effective specific heat capacity greater than the specific heat capacities of the individual chemicals comprising the fluid-fluid phase change fluid within a desired temperature range. The increased specific heat capacity may enable greater power generation and/or total heat transfer and/or heat storage per cubic meter of low-density fluid and/or high-density fluid. The increased specific heat capacity may enable greater power generation and/or total heat transfer and/or heat storage per cubic meter of low-density fluid and/or high-density fluid, for example, in embodiments employing low-density fluid and/or high-density fluid as a heat source, heat sink, or enthalpy source.

Some embodiments of the present invention may include a closed system. For example, in some embodiments, the low-density fluid and/or the high-density fluid may not directly contact the air or water of the external environment during normal operation of the system. In some embodiments, a low-density fluid and/or a high-density fluid in a closed system may be advantageous because it may prevent or minimize potential biofouling, scaling, or corrosion, or any combination thereof. In some embodiments, a low-density fluid and/or a high-density fluid in a closed system may be advantageous because it may prevent or minimize potential biofouling, scaling, or corrosion, or any combination thereof, thereby increasing the service life and/or long-term efficiency and/or reducing the capital cost of an ocean thermal energy conversion system, or a system for generating energy from temperature differentials, or any combination thereof, employing the low-density fluid and/or the high-density fluid.

In some embodiments, a subsea heat exchanger, heat exchange process, or any combination thereof, for facilitating heat exchange with deep water or heat removal from the low-density fluid and/or high-density fluid. In some embodiments, the heat exchange may include pipes, risers, or storage vessels, or any combination thereof, employed in the system or lower elevation reservoir. In some embodiments, the heat exchange may include a subsea heat exchanger, heat exchange coils, or any combination thereof, for facilitating heat transfer between the low-density fluid and/or high-density fluid and deep water, or for facilitating heat removal from the low-density fluid and/or high-density fluid, or any combination thereof.

In some embodiments, for example, when electrical power is required, it may be desirable to generate electricity from the temperature difference between the low-density fluid and/or the high-density fluid and another medium. For example, electricity may be generated from a heat engine instead of, or in addition to, generating electricity from displacing the low-density fluid with the high-density fluid. For example, electricity may be generated from a heat engine instead of, or in addition to, generating electricity from discharging an energy storage system.

For example, the table below shows the estimated kWh of power generated from one cubic meter of low-density and/or high-density fluid with a cold side of 45°F and a hot side of 85°F, at 50% Carnot efficiency, along with the specific heat capacities and densities below. As shown below, depending on the density and specific heat capacity, the amount of power generated per cubic meter of low-density and/or high-density fluid can be significant compared to the energy stored or generated from displacing water with the low-density fluid. In some cases, the amount of power generated from the temperature difference between the low-density and/or high-density fluid and the heat source can exceed the amount of energy stored from fluid displacement energy storage. In some embodiments, the energy storage system can include a simultaneous heat engine and, on its own, can generate more power than is stored.

Specific Embodiments of the "System and Method for Preventing Fouling on Marine Structures" Embodiment 1. A system for reducing fouling on an aquatic structure, comprising:
an aquatic structure comprising at least one surface exposed to water;
1. A system comprising: a recessed region on at least one portion of a surface exposed to water, the recessed region configured to maintain a substantially discontinuous physical separation between the water and the region, at least a portion of the recessed region being occupied by a gas.
2. The system of embodiment 1, wherein the substantially non-continuous physical separation is maintained by controlling the amount of gas within the recessed region.
3. The system of embodiment 1, further comprising a controller and a gas source operably connected to the recessed area, the controller and gas source controlling the amount of gas.
4. The system of embodiment 3, wherein the controller and gas source are employed to displace water with gas in at least a portion of the recessed region.
5. The system of embodiment 1, wherein the gas pocket is controllably fixed for a controlled period of time.
6. The system of embodiment 5, wherein the period of time is at least about 5 seconds.
7. The system of embodiment 1, wherein the substantially non-continuous physical separation exists for more than 30% of the time the structure is in use.
8. A system for reducing fouling on an aquatic structure, comprising:
an aquatic structure comprising at least one surface exposed to water when the structure is in use;
a recessed region on at least a portion of a surface exposed to water, the recessed region configured to maintain a substantially discontinuous physical separation between the water and the region.
9. The system of embodiment 8, wherein the volume below the recessed region is adjustable.
10. The system of embodiment 8, wherein the surface area of the recessed region is adjustable.
11. The system of embodiment 8, wherein the height of the recessed area relative to the water is adjustable.
12. The system of embodiment 8, wherein at least one of the volume below the recessed region, the surface area of the recessed region, or the height of the recessed region above the water is adjusted by varying the surface morphology of or on the recessed region.
13. The system of embodiment 8, wherein at least a portion of the surface exposed to water is substantially hydrophobic.
14. An improved aquatic structure comprising:
1. A structure comprising at least one surface that is exposed to water when the structure is in use, the improvement comprising:
An improved aquatic structure, comprising configuring at least a portion of the surface exposed to water such that the portion has a discontinuous separation from the water when the structure is in use, the portion having a discontinuous separation from the water providing a gas pocket between the portion and the water when the structure is in use.
15. The improved aquatic structure of embodiment 14, wherein the amount of substantially discontinuous physical separation of the water-exposed surface from the water is controlled by adjusting the amount of gas within the pocket.
16. The improved aquatic structure of embodiment 14, wherein the discontinuous separation exists for more than 30% of the time the structure is in use.
17. The improved aquatic structure of embodiment 14, wherein the portions configured to be discontinuous reduce visible fouling by at least 50% compared to a similar structure lacking the discontinuous portions.
18. The improved aquatic structure of embodiment 14, wherein the amount of gas in the pocket is adjustable.
19. The improved aquatic structure of embodiment 14, wherein the volume of the gas pocket is adjustable.
20. The improved aquatic structure of embodiment 14, wherein the surface area or volume of the discontinuous separated portions is adjustable.
21. The system of embodiment 14, wherein the height of the discontinuous separated portion relative to the water is adjustable.

"Low Density Fluid Displacement to Generate Electricity" Embodiment 1. A system for generating electricity, comprising:
a first storage reservoir configured to store a low-density fluid near the surface of a body of water and that is substantially immiscible with water;
a second storage reservoir located below the surface of the body of water and configured to store water; and a pump.
a generator;
A system in which the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping a low-density fluid in the first storage reservoir into the second storage reservoir to displace water in the second storage reservoir, and to generate electricity (or discharge electricity) by allowing the low-density fluid in the second storage reservoir to return to the first storage reservoir.
2. The system of embodiment 1, wherein the pump and the generator can be the same unit.
3. The system of embodiment 1, wherein the second storage reservoir comprises an expandable or contractible structure.
4. The system of embodiment 1, wherein the second storage reservoir comprises a swim bladder, a bladder, or a balloon.
5. The system of embodiment 1, wherein the second storage reservoir includes a recessed region having an opening near a bottom of the recessed region that is open to the body of water.
6. The system of embodiment 1, wherein the second storage reservoir is anchored beneath the body of water.
7. The system of embodiment 1, wherein the low density fluid comprises a hydrocarbon liquid or natural gas.
8. The system of embodiment 1, wherein the low density fluid comprises compressed natural gas or liquid natural gas.
9. The system of embodiment 1, operably connected to a unit requiring electricity.
10. A process for producing energy, comprising:
storing energy by replacing at least a portion of a first fluid having a first density with a second fluid having a second density lower than the first fluid, the first and second fluids being substantially immiscible with each other;
and displacing at least a portion of the second, less dense fluid with the first, more dense fluid, thereby enabling the discharge;
A process wherein the generating step, the enabling step, or both, is facilitated by pressure and gravity.
11. The process of embodiment 10, wherein the generating, enabling, or both, occurs below the surface of the water employed to promote pressure.
12.17. The process of embodiment 10, wherein the first fluid is water.
13. The process of embodiment 10, wherein the second fluid comprises compressed natural gas, liquid natural gas, liquid hydrocarbon, petroleum ether, or crude oil.
14. The process of embodiment 10, wherein the second fluid having the second density is stored near the surface of the body of water.
15. The process of embodiment 10, further comprising converting the discharge into electricity.
16. The process of embodiment 10, further comprising storing the discharge.
17. The process of embodiment 10, further comprising converting the discharge into electricity.
18. The process of embodiment 10, wherein the first or second fluid comprises a waste fluid.
19. The process of embodiment 10, wherein the first or second fluid comprises a fluid produced from solid waste.
20. The process of embodiment 10, wherein the first or second fluid comprises cooking oil.

Underwater Energy Storage and Electricity Embodiment 1. A process for generating electricity from tides, comprising:
providing a cavity operatively connected to tidal water, the cavity configured such that air is replaced with water at the uptide and water is replaced with air at the downtide;
replacing at least a portion of the air in the cavity with water at an uptide;
and replacing at least a portion of the water in the cavity with air at an ebb tide;
The displacement of water, air, or both generates electricity, a process.
2. The process of embodiment 1, wherein the cavity is open at the bottom.
3. The process of embodiment 1, further comprising transferring at least a portion of the displaced air to an air generator.
4. The process of embodiment 1, further comprising controlling the air flow rate during the air replacement.
5. The process of embodiment 1, further comprising controlling the flow rate of water during the displacement of air.
6. The process of embodiment 1, wherein the cavity is above ground level.
7. The process of embodiment 1, wherein the cavity is below ground level.
8. The process of embodiment 1, wherein the cavity is at least partially submerged in tidal waters.
9. The process of embodiment 1, further comprising transporting at least a portion of the displaced air through one or more pipes to an air generator.
10. The process of embodiment 1, wherein the cavity comprises a flexible liner.
11. The process of embodiment 1, wherein the cavity is rigid.
12. The process of embodiment 1, wherein the cavity is expandable or collapsible.
13. The process of embodiment 1, wherein the power generated during the uptide exceeds any power consumed during the downtide.
14. A process for generating electricity from tides, comprising:
providing a cavity at least partially filled with porous material and air, the cavity being operably connected to tidal water and configured such that air is replaced with water at high tides and water is replaced with air at low tides;
replacing at least a portion of the air in the cavity with water at an uptide;
and replacing at least a portion of the water in the cavity with air at an ebb tide;
The displacement of water, air, or both generates electricity, a process.
15. The process of embodiment 14, wherein the porous material comprises sand, gravel, rock, packing material, or cinder blocks, or plastic bottles, or plastic containers, or plastic buckets, or interconnected cinder blocks, or interconnected plastic containers, interconnected packing material, or a mixture thereof.
16. The process of embodiment 14, wherein the cavity comprises a flexible liner.
17. The process of embodiment 14, wherein the cavity is rigid.
18. The process of embodiment 14, wherein the cavity is expandable or collapsible.
19. The process of embodiment 14, further comprising transferring at least a portion of the displaced air to an air generator.
20. The process of embodiment 14, further comprising controlling the flow rate of water during the displacement of air.

Additional Embodiments 1. A system for storing and generating electricity, comprising:
a first storage reservoir near the surface of the body of water and configured to store a first fluid;
a second storage reservoir located below the surface of the body of water and configured to store a second fluid having a density greater than that of the first fluid;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected such that electricity is stored by pumping a first fluid in the first storage reservoir into the second storage reservoir to displace a second fluid having a higher density than the first fluid in the second storage reservoir, and electricity is generated or discharged by allowing the first fluid in the second storage reservoir to return to the first storage reservoir;
The system wherein the first fluid is a liquid.
2. The system of embodiment 1, further comprising a third reservoir configured to store a second fluid.
3. The system of embodiment 1, wherein the elevation of the first reservoir is greater than the elevation of the second reservoir.
4. The system of embodiment 2, wherein the second reservoir is at substantially the same elevation as the first reservoir.
5. The system of embodiment 2, wherein the third reservoir is at substantially the same elevation as the second reservoir.
6. The system of embodiment 2, wherein the third reservoir is at an elevation greater than the elevation of the first reservoir. 7. The system of embodiment 2, wherein the second fluid displaced from the second reservoir during charging is transferred and stored in the third reservoir.
8. The system of embodiment 1, wherein the second fluid comprises brine, or reverse osmosis effluent brine, or sodium chloride, or sea salt, or calcium chloride, or magnesium chloride, or potassium formate, or magnesium sulfate, or calcium bromide, or sodium bromide, or potassium acetate, or sodium formate, or calcium nitrate, or sodium nitrate, or sodium sulfite, or potassium sulfite, or sodium bisulfite, or potassium bisulfite, or magnesium bisulfite, or calcium bisulfite, or corn syrup, or glycerin, or propylene glycol, or ethylene glycol, or propylene carbonate, or any combination thereof.
9. The system of embodiment 1, wherein the second fluid comprises a halogenated hydrocarbon, or a fluorocarbon, or an organic acid, or an inorganic acid, or carbon dioxide, or sulfur dioxide, or nitrogen oxides, or any combination thereof.
10. The system of embodiment 1, wherein the first fluid comprises a hydrocarbon.
11. The system of embodiment 1, wherein the first fluid comprises air.
12. The system of embodiment 1, wherein the second fluid has a density greater than 1.02 kilograms per liter at 20° C.
13. The system of embodiment 1, wherein the first fluid comprises water.
14. The system of embodiment 1, wherein the pressure within the second reservoir and the pressure in the adjacent body of water differ by between about 0 bar and about 10 bar.
15. The system of embodiment 1, further comprising a pressure exchanger.
16. The system of embodiment 15, wherein the pressure exchanger is located near the second reservoir.
17. The system of claim 15, wherein during storage, the pressure exchanger extracts pressure from the first fluid and transfers the extracted pressure to the second fluid.
18. The system of embodiment 15, wherein during power generation, the pressure exchanger extracts pressure from the second fluid and transfers the extracted pressure to the first fluid.
19. The system of embodiment 17, wherein the pressure extraction occurs (1) while the first fluid is being transferred to the second reservoir, or (2) before the transfer, or (3) both (1) and (2).
20. The system of embodiment 18, wherein the pressure extraction occurs (1) while the second fluid is being transferred to the second reservoir, or (2) before the transfer, or (3) both (1) and (2).
21. The system of embodiment 17, wherein the pressure exchanger extracts a pressure that is less than or equal to the pressure of the first fluid near the second reservoir minus the hydrostatic pressure of the body of water at the elevation of the second reservoir.
22. The system of embodiment 18, wherein the pressure exchanger extracts a pressure that is less than or equal to the pressure of the second fluid near the second reservoir minus the hydrostatic pressure of the body of water at the elevation of the second reservoir.
23. The system of embodiment 15, wherein the pressure exchanger allows for the use of the second fluid while allowing the second reservoir to be in pressure equilibrium with a body of water at the same elevation as the second reservoir.
24. The system of embodiment 15, wherein the pressure exchanger comprises a hydraulic exchanger.
25. The system of embodiment 15, wherein the pressure exchanger regulates pressure extraction to ensure that the pressure of the fluid inside the second reservoir differs from the hydrostatic pressure of the body of water at the same elevation as the second reservoir by less than an allowable tolerance pressure.
26. The second reservoir includes an internal pressure sensor and an external pressure sensor;
an internal pressure sensor for measuring the pressure of the fluid inside the second reservoir;
an external pressure sensor measuring a pressure in a body of water adjacent to the second reservoir;
26. The system of embodiment 25, wherein the internal pressure sensor and the external pressure sensor are configured to communicate with the pressure exchanger.
27. The system of embodiment 25, wherein the allowable pressure differential is less than about 10 atmospheres. 28. The system of embodiment 25, wherein the allowable pressure differential is less than about 200 atmospheres. 29. The system of embodiment 15, wherein the pressure exchanger is a pump, or a turbine, or a rotary turbine, or any combination thereof.
30. A process for storing and generating electricity, comprising:
operatively connecting a pump, a generator, a first storage reservoir near a surface of the body of water, and a second storage reservoir located below the surface of the body of water, the first storage reservoir configured to store a first fluid and the second storage reservoir configured to store a second fluid having a higher density than the first fluid;
storing electricity by pumping a first fluid in a first storage reservoir to a second storage reservoir to displace a second fluid in a second storage reservoir;
generating or discharging electricity by allowing the first fluid in the second storage reservoir to return to the first storage reservoir;
The process wherein the second fluid is a liquid.
It should also be noted that the present specification discloses the following aspects.
[Aspect 1]
1. A system for storing and generating electricity, comprising:
a first storage reservoir near the surface of the body of water and configured to store a first fluid;
a second storage reservoir located below the surface of the body of water and configured to store a second fluid having a density greater than that of the first fluid;
A pump and
a generator;
the pump, the generator, and the first and second reservoirs are operatively connected to store electricity by pumping the first fluid in the first storage reservoir into the second storage reservoir to displace the second fluid having a higher density than the first fluid in the second storage reservoir, and to generate or discharge electricity by allowing the first fluid in the second storage reservoir to return to the first storage reservoir;
The system wherein the first fluid is a liquid.
[Aspect 2]
2. The system of claim 1, wherein the elevation of the first reservoir is greater than the elevation of the second reservoir.
[Aspect 3]
Aspect 10. The system of aspect 1, further comprising a third reservoir configured to store the second fluid.
[Aspect 4]
Aspect 4. The system of aspect 3, wherein the third reservoir is at substantially the same elevation as the first reservoir.
[Aspect 5]
Aspect 4. The system of aspect 3, wherein the elevation of the third reservoir is greater than the elevation of the first reservoir.
[Aspect 6]
A system as described in aspect 3, wherein the second fluid displaced from the second reservoir during charging is transferred to and stored in the third reservoir.
[Aspect 7]
2. The system of aspect 1, wherein the second fluid comprises brine, or reverse osmosis effluent brine, or sodium chloride, or sea salt, or calcium chloride, or magnesium chloride, or potassium formate, or magnesium sulfate, or calcium bromide, or sodium bromide, or potassium acetate, or sodium formate, or calcium nitrate, or sodium nitrate, or sodium sulfite, or potassium sulfite, or sodium bisulfite, or potassium bisulfite, or magnesium bisulfite, or calcium bisulfite, or corn syrup, or glycerin, or propylene glycol, or ethylene glycol, or propylene carbonate, or a halogenated hydrocarbon, or a halogen, or a fluorocarbon, or an organic acid, or an inorganic acid, or carbon dioxide, or sulfur dioxide, or nitric oxide, or any combination thereof.
[Aspect 8]
2. The system of claim 1, wherein the first fluid is selected from a hydrocarbon, water, or ammonia.
[Aspect 9]
10. The system of claim 1, further comprising a pressure exchanger.
[Aspect 10]
10. The system of claim 9, wherein the pressure exchanger is located near the second reservoir.
[Aspect 11]
10. The system of claim 9, wherein during storage, the pressure exchanger extracts pressure from the first fluid and transfers the extracted pressure to the second fluid.
[Aspect 12]
10. The system of aspect 9, wherein the pressure exchanger extracts pressure from the second fluid and transfers the extracted pressure to the first fluid during power generation.
[Aspect 13]
10. The system of claim 9, wherein the pressure exchanger adjusts pressure extraction to ensure that the pressure of the fluid inside the second reservoir differs from the hydrostatic pressure of the body of water at the same elevation as the second reservoir by less than an allowable tolerance pressure.
[Aspect 14]
the second reservoir includes an internal pressure sensor and an external pressure sensor;
the internal pressure sensor measures the pressure of the fluid inside the second reservoir;
the external pressure sensor measures the pressure in the body of water adjacent to the second reservoir;
Aspect 14. The system of aspect 13, wherein the internal pressure sensor and the external pressure sensor are configured to communicate with the pressure exchanger.
[Aspect 15]
1. A process for storing and generating electricity, comprising:
operatively connecting a pump, a generator, a first storage reservoir near a surface of a body of water, and a second storage reservoir located below the surface of the body of water, the first storage reservoir configured to store a first fluid and the second storage reservoir configured to store a second fluid having a higher density than the first fluid;
storing electricity by pumping the first fluid in the first storage reservoir into the second storage reservoir to replace the second fluid in the second storage reservoir;
generating or discharging electricity by allowing the first fluid in the second storage reservoir to return to the first storage reservoir;
The process wherein the first fluid is a liquid.

Claims (13)

1. A system for storing and generating electricity, comprising:
a first storage reservoir near the surface of the body of water and configured to store a first fluid;
a second storage reservoir located below the surface of the body of water and configured to store a second fluid having a density greater than that of the first fluid;
A pump and
a generator;
the pump, the generator, and the first and second storage reservoirs are operatively connected to store electricity by pumping the first fluid in the first storage reservoir into the second storage reservoir to displace the second fluid having a higher density than the first fluid in the second storage reservoir, and to generate or discharge electricity by allowing the first fluid in the second storage reservoir to return to the first storage reservoir;
the first fluid is a liquid;
The system further comprises a pressure exchanger ;
the pressure exchanger adjusts pressure extraction to ensure that the pressure of the fluid within the second storage reservoir differs from the hydrostatic pressure of the body of water at the same elevation as the second storage reservoir by less than an allowable tolerance pressure of the second storage reservoir;
system. The system of claim 1, wherein the elevation of the first storage reservoir is higher than the elevation of the second storage reservoir. The system of claim 1, further comprising a third storage reservoir configured to store the second fluid. The system of claim 3, wherein the third storage reservoir is at substantially the same elevation as the first storage reservoir. The system of claim 3, wherein the elevation of the third storage reservoir is higher than the elevation of the first storage reservoir. The system of claim 3, wherein the second fluid displaced from the second storage reservoir during charging is transferred to and stored in the third storage reservoir. The system of claim 1, wherein the second fluid comprises brine, reverse osmosis effluent brine, sodium chloride, sea salt, calcium chloride, magnesium chloride, potassium formate, magnesium sulfate, calcium bromide, sodium bromide, potassium acetate, sodium formate, calcium nitrate, sodium nitrate, sodium sulfite, potassium sulfite, sodium bisulfite, potassium bisulfite, magnesium bisulfite, calcium bisulfite, corn syrup, glycerin, propylene glycol, ethylene glycol, propylene carbonate, halogenated hydrocarbon, halogen, fluorocarbon, organic acid, inorganic acid, carbon dioxide, sulfur dioxide, nitric oxide, or any combination thereof. The system of claim 1, wherein the first fluid is selected from the group consisting of a hydrocarbon, water, and ammonia. The system of claim 1, wherein the pressure exchanger is located near the second storage reservoir. The system of claim 1, wherein during storage, the pressure exchanger extracts pressure from the first fluid and transfers the extracted pressure to the second fluid. The system of claim 1, wherein during power generation, the pressure exchanger extracts pressure from the second fluid and transfers the extracted pressure to the first fluid. the second storage reservoir includes an internal pressure sensor and an external pressure sensor;
the internal pressure sensor measures the pressure of fluid within the second storage reservoir;
the external pressure sensor measures the pressure in the body of water adjacent the second storage reservoir;
The system of claim 1 , wherein the internal pressure sensor and the external pressure sensor are configured to communicate with the pressure exchanger. 1. A method for storing and generating electricity, comprising:
operatively connecting a pump, a generator, a first storage reservoir near a surface of a body of water, and a second storage reservoir located below the surface of the body of water, the first storage reservoir configured to store a first fluid and the second storage reservoir configured to store a second fluid having a higher density than the first fluid;
storing electricity by displacing the second fluid in the second storage reservoir by pumping the first fluid in the first storage reservoir into the second storage reservoir;
generating or discharging electricity by allowing the first fluid in the second storage reservoir to return to the first storage reservoir;
the first fluid is a liquid, and the method further includes regulating pressure extraction using a pressure exchanger to ensure that the pressure of the fluid within the second storage reservoir differs from the hydrostatic pressure of the body of water at the same elevation as the second storage reservoir by less than an allowable tolerance pressure of the second storage reservoir .
method .