JP7848613B2 - Energy storage device - Google Patents

Description

This disclosure relates to an energy storage device.

The amount of electricity generated (hereinafter referred to as "generated electricity") and the amount of electricity demanded (hereinafter referred to as "demanded electricity") do not necessarily match. Therefore, there may be a surplus of electricity (i.e., generated electricity - demanded electricity > 0) or a shortage of electricity (i.e., generated electricity - demanded electricity < 0, for example, a power shortage). In particular, power generation using renewable energy sources such as wind power and solar power often results in large surpluses or shortages of electricity.

Therefore, a device has been developed that incorporates an electric heater and a brick block with a flow channel formed inside (for example, Patent Document 1). The technology described in Patent Document 1 involves operating the electric heater when there is a surplus of electricity to heat and store the heat in the brick block. Then, when electricity is needed (for example, when there is a power shortage), the technology in Patent Document 1 uses water to pass through the flow channel, heating the brick block with the stored heat, and using the heated water (steam) to rotate a turbine and generate electricity.

U.S. Patent Application Publication No. 2008/0219651

For example, in order to stabilize the power grid (realize a smart grid), there is a strong demand for technologies that efficiently store and utilize heat, such as technologies that convert surplus electricity into heat and store it, and then use the stored heat when needed.

In light of these challenges, this disclosure aims to provide an energy storage device that can efficiently store heat and efficiently utilize the stored heat.

To solve the above problems, an energy storage device according to one aspect of the present disclosure includes: a first heat exchanger in which gas is supplied from a gas supply port formed on the bottom or lower surface, and solid particles are supplied from above the gas supply port, and heat is exchanged between the gas and the solid particles; a gas supply unit that supplies gas to the first heat exchanger; a heater that heats either or both of the gas supplied from the gas supply unit to the first heat exchanger and the gas in the first heat exchanger; a solid-gas separator that separates the solid-gas mixture discharged from the first heat exchanger; a high-temperature tank that stores the solid particles separated by the solid-gas separator; and a device in which solid particles are supplied from the high-temperature tank, and the solid particles and The system comprises a second heat exchanger for heat exchange with a fluid, a flow rate adjustment mechanism for adjusting the flow rate of solid particles supplied from a high-temperature tank to the second heat exchanger, a discharge section for discharging solid particles from the second heat exchanger, a low-temperature tank for storing the solid particles discharged by the discharge section, a low-temperature particle supply section for supplying the solid particles stored in the low-temperature tank to the first heat exchanger, and a heat utilization device that utilizes the thermal energy of the fluid whose heat exchange was performed by the second heat exchanger . The discharge section discharges solid particles to the first heat exchanger, and the low-temperature tank is supplied with solid particles that have been discharged by the discharge section, have undergone heat exchange with a gas in the first heat exchanger, and have been separated into solid and gas particles by a solid-gas separator .

Furthermore, the energy storage device may include a preheater that preheats the gas using the heat contained in the high-temperature gas separated by the solid-gas separator, and the gas supply unit may supply the gas preheated by the preheater to the first heat exchanger.

Furthermore, the above-mentioned energy storage device may include a switching unit for switching the supply destination of the solid particles separated by the solid-gas separator to a high-temperature tank or a low-temperature tank.

Furthermore, the heater consumes electricity to heat the gas, and the energy storage device comprises a control unit that controls the gas supply unit, the heater, the flow rate adjustment mechanism, and the low-temperature particle supply unit. The control unit controls the gas supply unit to supply gas to the first heat exchanger, operates the heater to heat the gas, controls the low-temperature particle supply unit to supply solid particles from the low-temperature tank to the first heat exchanger, heats the solid particles with the gas in the first heat exchanger, and then uses a solid-gas separator to... The separated solid particles may be supplied to a high-temperature tank, and in the heat dissipation mode, the flow rate adjustment mechanism may be controlled to supply solid particles from the high-temperature tank to the second heat exchanger. In the second heat exchanger, the fluid may be heated by the solid particles, the heated fluid may be used in heat utilization equipment, the solid particles may be supplied from the second heat exchanger to the first heat exchanger through the discharge section, the heater may be stopped, the gas supply section may be controlled to supply gas to the first heat exchanger, the gas may be heated by the solid particles in the first heat exchanger, and the solid particles separated by the solid-gas separator may be supplied to a low-temperature tank.

Furthermore, the heater consumes electricity to heat the gas, and the energy storage device comprises a control unit that controls the gas supply unit, the heater, the flow rate adjustment mechanism, and the low-temperature particle supply unit. The control unit controls the gas supply unit to supply gas to the first heat exchanger, operates the heater to heat the gas, controls the low-temperature particle supply unit to supply solid particles from the low-temperature tank to the first heat exchanger, heats the solid particles with gas in the first heat exchanger, and separates the solid particles by the solid-gas separator into a high-temperature tank. The system may supply gas to the first heat exchanger, supply the gas separated by the solid-gas separator to the preheater, and in the heat dissipation mode, control the flow rate adjustment mechanism to supply solid particles from the high-temperature tank to the second heat exchanger, heat the fluid with the solid particles in the second heat exchanger, utilize the heated fluid in a heat utilization device, supply solid particles from the second heat exchanger to the first heat exchanger through the discharge section, stop the heater, control the gas supply section to supply gas to the first heat exchanger, heat the gas with the solid particles in the first heat exchanger, and supply the solid particles separated by the solid-gas separator to the low-temperature tank.

Furthermore, the heater may heat the gas using sunlight.

According to this disclosure, it becomes possible to efficiently store heat and efficiently utilize the stored heat.

Figure 1 is a diagram illustrating an energy storage device according to the first embodiment. Figure 2 shows an example of a second heat exchanger and discharge section according to the first embodiment. Figure 3 illustrates the processing of the control unit in the heat storage mode. Figure 4 illustrates the processing of the control unit in heat dissipation mode. Figure 5 is a diagram illustrating an energy storage device according to the first modified example. Figure 6 is a diagram illustrating a heat exchange device according to a second modified example. Figure 7 is a top view of the cross-section of the VI-VI line in Figure 6. Figure 8 is a horizontal cross-sectional view of the wind chamber. Figure 9 illustrates the flow of solid particles in the third operating process. Figure 10 illustrates the flow of solid particles in the fourth operating process. Figure 11 is a diagram illustrating a heat exchange device according to a third modified example. Figure 12 is a diagram illustrating an energy storage device according to a second embodiment.

The embodiments of this disclosure will be described in detail below with reference to the attached drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely illustrative examples for ease of understanding and, unless otherwise specified, do not limit this disclosure. In this specification and the drawings, elements having substantially the same function or configuration are denoted by the same reference numerals to avoid redundant explanations. Elements not directly related to this disclosure are omitted from the illustrations.

[First Embodiment: Energy Storage Device 100]
Figure 1 is a diagram illustrating an energy storage device 100 according to the first embodiment. As shown in Figure 1, the energy storage device 100 includes a gas supply unit 110, a preheater 120, a heating chamber 130, a first heat exchanger 140, a solid-gas separator 150, a switching unit 152, a high-temperature tank 160, a high-temperature particle supply unit 162, a second heat exchanger 170, a fluid supply unit 180, a heat utilization device 182, a discharge unit 190, a low-temperature tank 200, a low-temperature particle supply unit 210, a gas delivery unit 220, a heat utilization device 230, and a control unit 240. In Figure 1, solid arrows indicate the flow of solid particles and solid-gas mixtures. Dashed arrows indicate the flow of gas and fluid.

The gas supply unit 110 supplies gas to the heating chamber 130, which will be described later. The gas supplied by the gas supply unit 110 is, for example, air, carbon dioxide, or combustion exhaust gas. The gas supply unit 110 includes a blower 112 and a gas supply passage 114.

The blower 112 draws in gas and discharges it into the heating chamber 130. The suction side of the blower 112 is connected to the gas supply source. The discharge side of the blower 112 is connected to the gas supply passage 114.

The gas supply passage 114 is a flow path connecting the discharge side of the blower 112 and the heating chamber 130.

The preheater 120 preheats the gas passing through the gas supply passage 114. In this embodiment, the preheater 120 is a heat exchanger that exchanges heat between the high-temperature gas separated by the solid-gas separator 150 (described later) and the gas passing through the gas supply passage 114. In other words, the preheater 120 preheats the gas using the heat contained in the high-temperature gas separated by the solid-gas separator 150.

The heating chamber 130 includes a box 132 and a heater 134. The box 132 is a hollow container. The top surface of the box 132 is made of a breathable dispersion plate. The top surface of the box 132 also functions as the bottom surface of the first heat exchanger 140, which will be described later. Gas is supplied to the box 132 from the gas supply unit 110 (blower 112).

In this embodiment, the heater 134 consumes electricity to heat the gas. The heater 134 is, for example, a resistance heater (a device that utilizes heat generated from a conductor to which electricity is supplied) or an arc heater (a device that utilizes heat generated during arc discharge). The heater 134 is placed inside the enclosure 132. The heater 134 heats the gas supplied into the enclosure 132. Therefore, when the heater 134 is operating, the gas supplied from the gas supply unit 110 into the enclosure 132 is heated by the heater 134 before being supplied to the first heat exchanger 140.

The first heat exchanger 140 receives gas and solid particles from its bottom or lower surface, and exchanges heat between the gas and solid particles. The solid particles are composed of materials with a melting point higher than the required temperature of the heat utilization equipment 182, which will be described later.

The solid particles include, for example, silica, alumina, barite sand (barite, barium sulfate), partially calcined clay, glass spheres, and recovered petroleum catalysts. Preferably, the solid particles are silica and/or alumina. Using silica as the solid particle reduces the cost required for the solid particle. Furthermore, using desert sand or river sand as the solid particle (silica) allows for low-cost and easy acquisition. Additionally, using alumina, which has a relatively high melting point, allows for higher temperatures of the solid particle, resulting in a higher energy storage density.

Solid particles are particles with a diameter of 0.01 mm or more and 10 mm or less. There are no limitations on the shape of the solid particles; they may be spherical or non-spherical.

In this embodiment, the first heat exchanger 140 is a hollow container. Solid particles are supplied to the first heat exchanger 140 from a high-temperature tank 160 and a low-temperature tank 200, which will be described later. As described above, gas is supplied to the first heat exchanger 140 from a gas supply unit 110 through a heating chamber 130. The flow velocity of the gas supplied to the first heat exchanger 140 by the gas supply unit 110 is greater than or equal to the terminal velocity of the solid particles in the first heat exchanger 140. The solid particles are supplied from above through a gas supply port 140a formed in a distribution plate (distributor) located at the bottom surface of the first heat exchanger 140. Therefore, the solid-gas mixture of solid particles and gas passes through the first heat exchanger 140 from bottom to top (bottom surface to top surface). Furthermore, within the first heat exchanger 140, a solid-gas mixture of solid particles and gas is formed, and the solid particles and gas are vigorously agitated, allowing for efficient contact and heat exchange between them.

The solid-gas separator 150 separates the solid-gas mixture discharged from the first heat exchanger 140. The solid-gas separator 150 is, for example, a cyclone or a filter.

The switching unit 152 switches the supply destination of the solid particles separated by the solid-gas separator 150 to either the high-temperature tank 160 or the low-temperature tank 200. The switching unit 152 includes piping 154a and 154b, and valves 156a and 156b. Piping 154a connects the solid particle discharge port of the solid-gas separator 150 to the high-temperature tank 160. Valve 156a is provided on piping 154a. Piping 154b connects the solid particle discharge port of the solid-gas separator 150 to the low-temperature tank 200. Valve 156b is provided on piping 154b. Valves 156a and 156b are exclusively opened and closed by the control unit 240, which will be described later.

The high-temperature tank 160 stores the solid particles separated by the solid-gas separator 150. The high-temperature tank 160 is, for example, a hopper.

The high-temperature particle supply unit 162 supplies solid particles stored in the high-temperature tank 160 to the second heat exchanger 170, which will be described later. The high-temperature particle supply unit 162 includes piping 164 and a flow rate adjustment mechanism 166. Piping 164 connects the lower part of the high-temperature tank 160 to the second heat exchanger 170.

The flow rate adjustment mechanism 166 is installed in the piping 164. The flow rate adjustment mechanism 166 adjusts the flow rate of solid particles supplied from the high-temperature tank 160 to the second heat exchanger 170. The flow rate adjustment mechanism 166 is, for example, a J-valve type loop seal or an L-valve type loop seal.

The second heat exchanger 170 receives solid particles from the high-temperature tank 160 and exchanges heat between the solid particles and a fluid. The fluid can be, for example, water, steam, air, or combustion exhaust gas.

The discharge section 190 discharges solid particles from the second heat exchanger 170 to the first heat exchanger 140.

Figure 2 shows an example of the second heat exchanger 170 and discharge section 190 according to this embodiment. As shown in Figure 2, the second heat exchanger 170 includes a container 172, a dispersion plate 174a, an exhaust pipe 174b, a fluidizing gas supply section 176, and heat transfer tubes 178.

The container 172 is, for example, rectangular in shape. The dispersion plate 174a is provided inside the container 172. The dispersion plate 174a extends horizontally, dividing the inside of the container 172 into a containment chamber 172a and a wind chamber 172b. Multiple holes are formed in the dispersion plate 174a. The size of these holes is such that solid particles cannot pass through, or pass through with difficulty. The containment chamber 172a is formed at the top of the container 172. The wind chamber 172b is formed below the containment chamber 172a within the container 172. The dispersion plate 174a functions as the bottom surface of the containment chamber 172a.

In this embodiment, the piping 164 of the high-temperature particle supply unit 162 penetrates the upper surface of the container 172. The upper end of the piping 164 is connected to the lower part of the high-temperature tank 160. The lower end of the piping 164 is located within the containment chamber 172a. The lower end of the piping 164 is located below the upper end of the discharge pipe 192, which will be described later. In this embodiment, the lower end of the piping 164 is located near the dispersion plate 174a.

The solid particles stored in the high-temperature tank 160 are supplied to the containment chamber 172a through the piping 164. Therefore, the containment chamber 172a is filled with solid particles.

The fluidizing gas supply unit 176 is, for example, a pump, blower, etc. The suction side of the fluidizing gas supply unit 176 is connected to the fluidizing gas supply source. The discharge side of the fluidizing gas supply unit 176 is connected to the wind chamber 172b. The fluidizing gas is, for example, water vapor, air, carbon dioxide, or combustion exhaust gas. The fluidizing gas supply unit 176 supplies the fluidizing gas into the wind chamber 172b via the dispersion plate 174a such that the empty velocity of the fluidizing gas supplied into the containment chamber 172a is greater than or equal to the minimum fluidization velocity Umf and less than the terminal velocity. As a result, solid particles supplied from the high-temperature tank 160 are fluidized by the fluidizing gas, and a fluidized bed (bubble fluidized bed) is formed in the containment chamber 172a. Furthermore, since the empty velocity of the fluidizing gas supplied by the fluidizing gas supply unit 176 is less than the terminal velocity, solid particles do not scatter from the containment chamber 172a.

A portion of the heat transfer tube 178 faces into the containment chamber 172a. A fluid supply unit 180 is connected to the inlet of the heat transfer tube 178. A heat utilization device 182 is connected to the outlet of the heat transfer tube 178.

Furthermore, an exhaust pipe 174b is connected to the top surface of the container 172. The exhaust pipe 174b supplies fluidized gas to the heat utilization equipment 230, which will be described later.

The fluid supply unit 180 supplies fluid to the heat transfer tubes 178. The fluid supply unit 180 is, for example, a pump. The fluid supplied to the heat transfer tubes 178 by the fluid supply unit 180 is then supplied to the heat utilization equipment 182 through the outlet of the heat transfer tubes 178. During its passage through the heat transfer tubes 178, the fluid exchanges heat with the fluidized bed of solid particles formed in the containment chamber 172a, and is heated. Therefore, the heat utilization equipment 182 is supplied with heated fluid.

The heat utilization equipment 182 is equipment that utilizes the thermal energy of the fluid that has been heat-exchanged (heated) by the second heat exchanger 170. Examples of heat utilization equipment 182 include gas turbine generators, steam turbine generators (boilers), steam-supplying boilers, furnaces (kilns), and air conditioning equipment.

In this embodiment, the discharge section 190 includes a discharge pipe 192. The discharge pipe 192 is a pipe connecting the containment chamber 172a and the lower part of the first heat exchanger 140. The upper end of the discharge pipe 192 is connected to the side surface of the container 172, near the upper surface of the fluidized bed in the containment chamber 172a. The lower end of the discharge pipe 192 is connected above the gas supply port 140a in the first heat exchanger 140.

As described above, a fluidized bed of solid particles is formed in the containment chamber 172a. Therefore, when solid particles are supplied from the high-temperature tank 160 through the piping 164, the supplied solid particles are pushed out (overflow) into the discharge pipe 192. These pushed-out solid particles are then supplied to the first heat exchanger 140 through the discharge pipe 192.

Returning to Figure 1, the low-temperature tank 200 stores the solid particles separated by the solid-gas separator 150. Solid particles are supplied to the low-temperature tank 200 at a different timing than the high-temperature tank 160. The low-temperature tank 200 is, for example, a hopper.

The low-temperature particle supply unit 210 supplies solid particles stored in the low-temperature tank 200 to the first heat exchanger 140. The low-temperature particle supply unit 210 includes piping 212 and a flow rate adjustment mechanism 214. Piping 212 connects the lower part of the low-temperature tank 200 to the lower part of the first heat exchanger 140. In this embodiment, the upper end of piping 212 is connected to the lower part of the low-temperature tank 200. The lower end of piping 212 is connected above the gas supply port 140a in the first heat exchanger 140.

The flow rate adjustment mechanism 214 is installed in the piping 212. The flow rate adjustment mechanism 214 adjusts the flow rate of solid particles supplied from the low-temperature tank 200 to the first heat exchanger 140.

The gas delivery unit 220 supplies the gas separated into solid and gas phases by the solid-gas separator 150 to the heat utilization equipment 230 or the preheater 120. The gas delivery unit 220 includes piping 222a and 222b, and valves 224a and 224b. Piping 222a connects the gas exhaust port of the solid-gas separator 150 to the heat utilization equipment 230. Valve 224a is provided on piping 222a. Piping 222b connects the gas exhaust port of the solid-gas separator 150 to the preheater 120. Valve 224b is provided on piping 222b. In this embodiment, valves 224a and 224b are exclusively opened and closed by the control unit 240.

The heat utilization equipment 230 is equipment that utilizes the thermal energy contained in the gas separated by the solid-gas separator 150, or the fluidized gas exhausted from the second heat exchanger 170. Examples of heat utilization equipment 230 include gas turbine generators, steam turbine generators (boilers), steam-supplying boilers, furnaces (kilns), and air conditioning equipment.

The control unit 240 is composed of a semiconductor integrated circuit including a CPU (Central Processing Unit). The control unit 240 reads programs and parameters for operating the CPU from the ROM. The control unit 240 works in cooperation with the RAM (which acts as a work area) and other electronic circuits to manage and control the entire energy storage device 100. In this embodiment, the control unit 240 controls the gas supply unit 110 (blower 112), heater 134, switching unit 152 (valves 156a, 156b), flow rate adjustment mechanism 166, fluidization gas supply unit 176, fluid supply unit 180, flow rate adjustment mechanism 214, and gas delivery unit 220 (valves 224a, 224b).

In this embodiment, the control unit 240 converts surplus power into thermal energy and stores it during periods when there is a power surplus (i.e., generated power - demanded power > predetermined value (e.g., 0)). Hereinafter, the operating mode in which power is converted into thermal energy and stored will be referred to as the heat storage mode. On the other hand, when heat or power is needed, the control unit 240 utilizes the stored thermal energy in the heat utilization equipment 182 and 230. Hereinafter, the operating mode in which the stored thermal energy is utilized in the heat utilization equipment 182 and 230 will be referred to as the heat release mode. In the initial state, the blower 112, heater 134, and fluid supply unit 180 are stopped, and the valves 156a, 156b, 224a, 224b, and flow rate adjustment mechanisms 166 and 214 are closed. Also, in the initial state, solid particles are stored in the low-temperature tank 200. The processing of the control unit 240 in the heat storage mode and heat release mode will be described below.

[Heat storage mode]
Figure 3 illustrates the processing of the control unit 240 in the heat storage mode. For ease of understanding, components not used in the heat storage mode are omitted in Figure 3.

The control unit 240 closes valves 156b and 224a and the flow rate adjustment mechanism 166. The control unit 240 stops the fluidizing gas supply unit 176 and the fluid supply unit 180. Furthermore, as shown in Figure 3, the control unit 240 operates the blower 112 and the heater 134. The control unit 240 also opens valves 156a and 224b. The control unit 240 opens the flow rate adjustment mechanism 214 to adjust the opening degree.

As a result, the excess power is consumed by the heater 134. The gas supplied to the heating chamber 130 by the blower 112 is heated by the heater 134. The heater 134 heats the gas to a first temperature that is below the heat resistance temperature of the solid particles and satisfies the temperature requirement of the heat utilization device 182. For example, the heater 134 heats the gas so that the solid particles heated by the gas reach a second temperature that satisfies the above-mentioned temperature requirement. If the solid particles are silica, the gas is heated to 1600°C or below. Also, the second temperature is lower than the first temperature, but the temperature difference is small. The temperature difference between the second temperature and the first temperature is, for example, about 50°C.

The heated high-temperature gas (gas at the first temperature) is supplied to the first heat exchanger 140. Low-temperature solid particles are also supplied from the low-temperature tank 200 to the first heat exchanger 140. Therefore, in the first heat exchanger 140, the high-temperature gas and low-temperature solid particles are vigorously agitated, and heat exchange occurs between them. As a result, the solid particles are heated by the gas, and the gas is cooled by the solid particles. At the outlet of the first heat exchanger 140, the temperature of the solid particles and the temperature of the gas become approximately equal (the second temperature).

The solid-gas separator 150 then separates the solid-gas mixture discharged from the first heat exchanger 140. The separated high-temperature solid particles (solid particles at the second temperature) are supplied to the high-temperature tank 160 via piping 154a. The high-temperature tank 160 stores the high-temperature solid particles.

Meanwhile, the gas at the second temperature, separated from the solid-gas state, is supplied to the preheater 120 through piping 222b. The preheater 120 exchanges heat between the gas at the second temperature supplied from the solid-gas separator 150 via piping 222b and the gas supplied to the heating chamber 130 by the blower 112. Therefore, the gas supplied to the heating chamber 130 by the blower 112 is heated to a third temperature by the gas at the second temperature. This third temperature is higher than room temperature (e.g., 25°C). In other words, the preheater 120 can preheat the gas before it is supplied to the heating chamber 130 using the heat contained in the gas discharged from the first heat exchanger 140.

Thus, in the heat storage mode, excess electricity is converted into heat and first transferred to the gas. Then, heat exchange takes place between the high-temperature gas and the low-temperature solid particles, and the heat is transferred to the solid particles. In this way, excess electricity is converted into thermal energy and retained (stored) in the solid particles. Since the heat capacity of solid particles is greater than that of gas (air), the heat storage density of solid particles (J/ ^m³ ) is higher than that of gas.

The control unit 240 adjusts the opening of the flow rate adjustment mechanism 214 based on the amount of surplus power (hereinafter referred to as "surplus power"). Specifically, the surplus power is converted into thermal energy by the heater 134, and when solid particles are heated (via gas) with this thermal energy, the amount of solid particles that reach the second temperature is determined. Therefore, the control unit 240 adjusts the opening of the flow rate adjustment mechanism 214 so that the determined amount of solid particles is supplied to the first heat exchanger 140.

This allows the temperature of the solid particles stored in the high-temperature chamber 160 to be steadily maintained at the second temperature, even when the amount of surplus power fluctuates (when the amount of surplus power fluctuates over time). In other words, it can adapt to fluctuations in the amount of surplus power. Therefore, in the heat dissipation mode described later, it becomes possible to supply a fluid at the fourth temperature that meets the required temperature to the heat utilization equipment 182 without using additional energy (for example, without burning auxiliary fuel).

[Heat dissipation mode]
Figure 4 illustrates the processing of the control unit 240 in heat dissipation mode. For ease of understanding, components not used in heat dissipation mode are omitted from Figure 4.

The control unit 240 closes valves 156a and 224b and the flow rate adjustment mechanism 214. The control unit 240 stops the heater 134. Furthermore, as shown in Figure 4, the control unit 240 opens valves 156b and 224a, opens the flow rate adjustment mechanism 166, and adjusts the opening degree. The control unit 240 operates the blower 112, the fluidizing gas supply unit 176, and the fluid supply unit 180.

As a result, high-temperature solid particles (solid particles at the second temperature) are supplied to the second heat exchanger 170 from the high-temperature tank 160. Furthermore, fluidizing gas is supplied to the containment chamber 172a by the fluidizing gas supply unit 176. This creates a fluidized bed of high-temperature solid particles in the second heat exchanger 170. Additionally, fluid is supplied to the heat transfer tubes 178 from the fluid supply unit 180. Therefore, heat exchange occurs between the low-temperature fluid and the high-temperature solid particles in the second heat exchanger 170. This results in the fluid being heated by the solid particles and the solid particles being cooled by the fluid. Thus, the heated fluid in the second heat exchanger 170 is supplied to the heat utilization equipment 182. The temperature of the fluid supplied to the heat utilization equipment 182 and the temperature of the solid particles discharged from the second heat exchanger 170 are approximately equal, representing the fourth temperature. The fourth temperature is a predetermined temperature that satisfies the required temperature of the heat utilization equipment 230 and is lower than the second temperature.

Then, in the second heat exchanger 170, the solid particles, cooled from the second temperature by heat exchange with the fluid, are supplied to the first heat exchanger 140 through the discharge section 190 (discharge pipe 192). Gas is also supplied to the first heat exchanger 140 from the blower 112 through the enclosure 132. Therefore, heat exchange occurs between the low-temperature gas and the high-temperature solid particles in the first heat exchanger 140. As a result, the gas is heated by the solid particles, and the solid particles are cooled by the gas. The temperatures of the solid particles and gas discharged from the first heat exchanger 140 are approximately equal, at the fifth temperature.

The solid-gas separator 150 then separates the solid-gas mixture discharged from the first heat exchanger 140. The separated high-temperature gas (gas at the fifth temperature) is supplied to the heat utilization equipment 230 through piping 222a. The fifth temperature is a predetermined temperature that meets the required temperature of the heat utilization equipment 230 and is lower than the fourth temperature. Furthermore, the fluidized gas heated to the fourth temperature in the second heat exchanger 170 is supplied to the heat utilization equipment 230 through exhaust pipe 174b. This allows the heat energy contained in the gas to be utilized in the heat utilization equipment 230 (for example, for generating electricity). Meanwhile, the solid particles at the fifth temperature, separated from the solid-gas mixture, are supplied to the low-temperature tank 200 through piping 154b. The low-temperature tank 200 stores the solid particles at the fifth temperature.

In this way, in the heat dissipation mode, heat exchange occurs between high-temperature solid particles and low-temperature fluid, and heat is transferred to the fluid. Then, when needed (for example, during periods of power shortage), the high-temperature fluid (fluid at the fourth temperature) is utilized by the heat utilization device 182 (for example, for generating electricity).

The control unit 240 adjusts the opening of the flow rate adjustment mechanism 166 based on the required temperature and flow rate of the heat utilization equipment 182. Specifically, when the fluid supply unit 180 supplies fluid to the heat transfer tubes 178 of the second heat exchanger 170 at the required flow rate of the heat utilization equipment 182, and the fluid is heated by solid particles at a second temperature stored in the high-temperature tank 160, the amount of solid particles needed to heat the fluid to a fourth temperature is determined. Therefore, the control unit 240 adjusts the opening of the flow rate adjustment mechanism 166 so that the determined amount of solid particles is supplied to the second heat exchanger 170.

This allows the temperature of the fluid supplied to the heat utilization device 182 to be brought to the required temperature of the heat utilization device 182. Therefore, it becomes possible to stably supply the heat utilization device 182 with fluid at a fourth temperature that meets the required temperature, without using additional energy (for example, without burning auxiliary fuel). Even if the required temperature of the heat utilization device 182 (for example, the required amount of power generation) fluctuates over time, this can be addressed by adjusting the supply amount of solid particles.

Furthermore, in the first heat exchanger 140, heat exchange takes place between the solid particles discharged from the second heat exchanger 170 and the gas. The gas, from which the heat of the solid particles has been recovered, is supplied to the heat utilization device 230 through the solid-gas separator 150 and piping 222a. The heat utilization device 230 utilizes the heat contained in the gas. The configuration, comprising the gas supply unit 110 and the first heat exchanger 140, allows for the effective utilization of the heat of the solid particles after the fluid has been heated to the fourth temperature.

As described above, the energy storage device 100 according to this embodiment converts surplus electricity into thermal energy and stores it in solid particles. This makes it possible to store energy at a lower cost compared to conventional technologies that store surplus electricity in secondary batteries or convert surplus electricity into hydrogen. Furthermore, compared to conventional technologies that convert surplus electricity into hydrogen and store it, the stored energy can be rapidly converted into thermal or electrical energy when needed (for example, when there is a power shortage).

Furthermore, compared to conventional heat storage technologies using brick blocks, this technology allows for the storage of solid particles at a specified second temperature even when surplus power fluctuates, by adjusting the amount of solid particles stored in the heat storage mode.

Furthermore, in the heat dissipation mode, by setting the flow rate of the fluid supplied by the fluid supply unit 180 to the flow rate required by the heat utilization equipment 182, and adjusting the amount of solid particles supplied to the second heat exchanger 170, the temperature of the fluid supplied to the heat utilization equipment 182 can be set to the temperature required by the heat utilization equipment 182. Therefore, it is possible to respond to temporal load fluctuations of the heat utilization equipment 182 without requiring auxiliary fuel.

Furthermore, as described above, the second heat exchanger 170 exchanges heat between the solid particles at the second temperature stored in the high-temperature tank 160 and the fluid used by the heat utilization device 182. Therefore, the second heat exchanger 170 can directly transfer the heat from the solid particles to the fluid. In other words, the second heat exchanger 170 can transfer the heat from the solid particles to the fluid without the need for other heat transfer media. As a result, the second heat exchanger 170 can efficiently heat the fluid. This allows the heat utilization device 182 to efficiently utilize the heat stored by the solid particles.

Furthermore, as described above, the energy storage device 100 includes a preheater 120. In the heat storage mode, the preheater 120 preheats the gas separated by the solid-gas separator 150 before supplying it to the heater 134. This allows the heat generated by the heater 134 to be efficiently stored in the solid particles during the heat storage mode.

[First modified example: Energy storage device 300]
In the first embodiment described above, an example was given in which the energy storage device 100 is equipped with a heat utilization device 230. However, the energy storage device 300 does not necessarily have to be equipped with a heat utilization device 230.

Figure 5 illustrates an energy storage device 300 according to the first modified example. As shown in Figure 5, the energy storage device 300 includes a gas supply unit 110, a preheater 120, a heating chamber 130, a first heat exchanger 140, a solid-gas separator 150, a switching unit 152, a high-temperature tank 160, a high-temperature particle supply unit 162, a second heat exchanger 170, a fluid supply unit 180, a heat utilization device 182, a discharge unit 190, a low-temperature tank 200, a low-temperature particle supply unit 210, a gas delivery unit 320, and a control unit 240. In Figure 5, solid arrows indicate the flow of solid particles and solid-gas mixtures. Dashed arrows indicate the flow of gas and fluid. Components substantially equivalent to those of the energy storage device 100 are denoted by the same reference numerals and their descriptions are omitted.

In the first modified example, the gas delivery unit 320 supplies the gas separated into solid and gas phases by the solid-gas separator 150 to the blower 112 or preheater 120. The gas delivery unit 320 includes piping 322a, 322b, and flow rate adjustment mechanisms 324a, 324b. Piping 322a connects the gas exhaust port of the solid-gas separator 150 to the preheater 120. Flow rate adjustment mechanism 324a is provided on piping 322a. Piping 322b connects the gas exhaust port of the solid-gas separator 150 to the suction side of the blower 112. Flow rate adjustment mechanism 324b is provided on piping 322b.

In the first modified configuration, the control unit 240 opens the flow rate adjustment mechanism 324a and closes the flow rate adjustment mechanism 324b in the heat storage mode. This allows the temperature of the solid particles stored in the low-temperature tank 200 to be increased by supplying high-temperature gas to the preheater 120 in the heat storage mode. In the heat storage mode, the blower 112 draws in atmospheric air. Furthermore, in the heat dissipation mode, the control unit 240 opens the flow rate adjustment mechanism 324b and closes the flow rate adjustment mechanism 324a. This allows the high-temperature gas to be recirculated via the blower 112 in the heat dissipation mode.

In the first modified example, the gas delivery unit 320 can supply high-temperature gas to the blower 112 in the heat dissipation mode, thereby increasing the temperature of the solid particles stored in the low-temperature chamber 200. Therefore, in the next heat storage mode, even with less power supplied to the heater 134, it becomes possible to increase the amount of solid particles at the second temperature stored in the high-temperature chamber 160.

[Second variation]
In the first modified example described above, a configuration in which the preheater 120 and the second heat exchanger 170 are separate components was given as an example. However, the preheater 120 and the second heat exchanger 170 may be integrally formed.

Figure 6 illustrates a heat exchanger 400 according to a second modified example. Figure 7 is a top view of the cross-section along line VI-VI in Figure 6. Figure 8 is a horizontal cross-sectional view of the wind chamber WR. Note that, for ease of understanding, the heat transfer tubes 178, 480, cyclone 490, and solid particles are omitted in Figure 7.

As shown in Figure 6, the heat exchanger 400 includes a container 410, a dispersion plate 420, a partition plate 430, a first compartment plate 432, a second compartment plate 434, a first dividing plate 440, a second dividing plate 442, a third dividing plate 444, a fluidizing gas supply device 450, a heat transfer tube 178, a heat transfer tube 480, and a cyclone 490. In Figure 6, solid arrows indicate fluid flow. Components substantially equivalent to those of the energy storage device 100 are given the same reference numerals and their descriptions are omitted.

The container 410 is, for example, rectangular in shape. In the second modification, an exhaust port 412 is formed on the upper surface TS of the container 410.

The dispersion plate 420 is installed inside the container 410. The dispersion plate 420 extends horizontally, dividing the container 410 into a containment chamber AR and a wind chamber WR. Multiple holes are formed in the dispersion plate 420. The size of these holes is such that solid particles, described later, cannot or have difficulty passing through them.

The containment chamber AR is formed at the top of the container 410. Solid particles are contained within the containment chamber AR. The dispersion plate 420 functions as the bottom surface of the containment chamber AR.

The wind chamber WR is formed below the containment chamber AR within the container 410.

The partition plate 430 is installed within the containment chamber AR. The partition plate 430 is a plate extending vertically. The upper end of the partition plate 430 is separated from the upper surface of the containment chamber AR (the upper surface TS of the container 410). The lower end of the partition plate 430 is separated from the distribution plate 420 (the bottom surface of the containment chamber AR).

As shown in Figure 7, both ends of the partition plate 430 in the horizontal direction (front-to-back and left-to-right directions) are connected to the side surface SS of the container 410. The partition plate 430 divides the storage chamber AR into a first chamber FR and a second chamber SR.

Although not shown in the diagram, in the second modified example, the piping 164 of the high-temperature particle supply unit 162 penetrates the upper surface TS of the container 410. The lower end of the piping 164 is located within the first chamber FR. The lower end of the piping 164 is located below the upper end of the discharge pipe 192. In the second modified example, the lower end of the piping 164 is located near the dispersion plate 174a in the first chamber FR. The upper end of the discharge pipe 192 is connected to the side surface of the container 410, near the upper surface of the fluidized bed in the first chamber FR.

Returning to Figure 6, the first partition plate 432 is a plate erected upward from the bottom surface of the first chamber FR in the containment chamber AR (the portion of the distribution plate 420 located in the first chamber FR). The upper end (tip) of the first partition plate 432 is located above the lower end of the partition plate 430.

The second partition plate 434 is a plate erected above the bottom surface of the second chamber SR in the containment chamber AR (the portion of the distribution plate 420 located in the second chamber SR). The upper end (tip) of the second partition plate 434 is located above the lower end of the partition plate 430.

As shown in Figure 7, both horizontal ends of the first compartment plate 432 are connected to the side surface SS of the container 410. Similarly, both horizontal ends of the second compartment plate 434 are connected to the side surface SS of the container 410.

Returning to Figure 6, the first dividing plate 440, the second dividing plate 442, and the third dividing plate 444 are installed within the wind chamber WR. The first dividing plate 440, the second dividing plate 442, and the third dividing plate 444 divide the space within the wind chamber WR into four sections.

The first dividing plate 440 is positioned within the wind chamber WR at a location corresponding to the first compartment plate 432. The first dividing plate 440 is a plate extending vertically. The upper end of the first dividing plate 440 is connected to the upper surface (dispersion plate 420) of the wind chamber WR. The lower end of the first dividing plate 440 is connected to the bottom surface of the wind chamber WR (bottom surface of the container 410).

The second dividing plate 442 is provided in a position corresponding to the second compartment plate 434 within the wind chamber WR. The second dividing plate 442 is a plate extending vertically. The upper end of the second dividing plate 442 is connected to the upper surface of the wind chamber WR. The lower end of the second dividing plate 442 is connected to the bottom surface of the wind chamber WR.

The third dividing plate 444 is provided between the first dividing plate 440 and the second dividing plate 442 within the wind chamber WR. In the second modified example, the third dividing plate 444 is provided at a position corresponding to the partition plate 430 within the wind chamber WR. The third dividing plate 444 is a plate extending vertically. The upper end of the third dividing plate 444 is connected to the upper surface of the wind chamber WR. The lower end of the third dividing plate 444 is connected to the bottom surface of the wind chamber WR.

As shown in Figure 8, both horizontal ends of the first dividing plate 440 are connected to the side surface SS of the container 410. Similarly, both horizontal ends of the second dividing plate 442 are connected to the side surface SS of the container 410. Furthermore, both horizontal ends of the third dividing plate 444 are connected to the side surface SS of the container 410.

Therefore, the first divided space P (first space) is formed by the dispersion plate 420, the side surface SS and bottom surface of the container 410, and the first divided plate 440. Furthermore, the second divided space S (second space) is formed by the dispersion plate 420, the side surface SS and bottom surface of the container 410, and the second divided plate 442. The third divided space Q (fifth space) is formed by the dispersion plate 420, the bottom surface of the container 410, the first divided plate 440, and the third divided plate 444. Finally, the fourth divided space R (fourth space) is formed by the dispersion plate 420, the bottom surface of the container 410, the second divided plate 442, and the third divided plate 444.

Returning to Figure 6, the fluidizing gas supply device 450 supplies fluidizing gas to the wind chamber WR. In the second modified example, the fluidizing gas is a high-temperature gas separated into solid and gas phases by the solid-gas separator 150. The fluidizing gas supply device 450 includes piping 322a, a first branch pipe 460, a first flow control valve V1, a second branch pipe 462, a second flow control valve V2, a third branch pipe 464, a third flow control valve V3, a fourth branch pipe 466, and a fourth flow control valve V4.

The first branch pipe 460 connects the piping 322a and the first divided space P. The first flow control valve V1 is installed in the first branch pipe 460. The first flow control valve V1 changes the flow path cross-sectional area formed in the first branch pipe 460.

The second branch pipe 462 connects the piping 322a and the second divided space S. The second flow control valve V2 is installed in the second branch pipe 462. The second flow control valve V2 changes the flow path cross-sectional area formed in the second branch pipe 462.

The third branch pipe 464 connects the piping 322a and the third divided space Q. The third flow control valve V3 is installed in the third branch pipe 464. The third flow control valve V3 changes the flow path cross-sectional area formed in the third branch pipe 464.

The fourth branch pipe 466 connects piping 322a to the fourth divided space R. The fourth flow control valve V4 is installed in the fourth branch pipe 466. The fourth flow control valve V4 changes the flow path cross-sectional area formed in the fourth branch pipe 466.

A portion of the heat transfer tube 178 faces into the first chamber FR.

A portion of the heat transfer tube 480 faces into the second chamber SR. The discharge side of the blower 112 is connected to the inlet of the heat transfer tube 480. The gas supply passage 114 is connected to the outlet of the heat transfer tube 480.

Cyclone 490 separates the solid-gas mixture exhausted from the exhaust port 412 of container 410. The solid-gas mixture contains solid particles and fluidizing gas. The fluidizing gas separated by cyclone 490 is exhausted to the outside. The solid particles separated by cyclone 490 are returned to the containment chamber AR.

In the second modified configuration, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, the third flow control valve V3, and the fourth flow control valve V4. In the second modified configuration, the control unit 240 performs a preheating operation in the heat storage mode. The preheating operation will be described below.

[Preheating process]
The preheating operation process involves exchanging heat between the gas passing through the heat transfer tube 480 and the solid particles, and stopping the heat exchange between the fluid passing through the heat transfer tube 178 and the solid particles.

In the preheating operation process, the control unit 240 adjusts the opening degree of the second flow control valve V2. In the second modified example, the control unit 240 adjusts the opening degree of the second flow control valve V2 so that the empty column velocity Vb of the fluidizing gas supplied into the second chamber SR through the second divided space S and the dispersion plate 420 is greater than a predetermined velocity VB that is greater than the minimum fluidizing velocity Umf. The velocity VB is expressed by the following formula (1).
VB = Umf × (Horizontal cross-sectional area of the second divided space S + Horizontal cross-sectional area of the fourth divided space R) / (Horizontal cross-sectional area of the second divided space S) Equation (1)

Furthermore, during the preheating operation, the control unit 240 closes the first flow control valve V1, the third flow control valve V3, and the fourth flow control valve V4.

When the preheating process is executed, the solid particles in the second chamber (SR) become fluid. Furthermore, the heat from the fluidizing gas heats the solid particles in the second chamber (SR). This results in heat exchange between the fluidized solid particles and the gas passing through the heat transfer tubes (480). Additionally, since the supply of fluidizing gas to the first chamber (FR) is stopped, the solid particles in the first chamber (FR) do not become fluid. In other words, the solid particles in the first chamber (FR) hardly move. Also, the solid particles in the first chamber (FR) are not heated by the fluidizing gas.

In other words, during the preheating process, the second chamber SR and the heat transfer tube 480 function as preheaters that preheat the gas passing through the gas supply passage 114.

Furthermore, the control unit 240 in the second modified example performs the first operation process, the second operation process, or the third operation process in the heat dissipation mode. Each operation process will be described below.

[First Operation Process]
The first operating process involves exchanging heat between the fluid passing through the heat transfer tube 178 and the solid particles, and stopping the heat exchange between the gas passing through the heat transfer tube 480 and the solid particles.

In the first operation process, the control unit 240 adjusts the opening degree of the first flow control valve V1. In the second modified example, the control unit 240 adjusts the opening degree of the first flow control valve V1 so that the empty tower velocity Va of the fluidizing gas supplied into the first chamber FR through the first divided space P and the dispersion plate 420 is greater than a predetermined velocity VA that is greater than the minimum fluidization velocity Umf. The velocity VA is expressed by the following equation (2).
VA = Umf × (Horizontal cross-sectional area of the first divided space P + Horizontal cross-sectional area of the third divided space Q) / (Horizontal cross-sectional area of the first divided space P) Equation (2)

Furthermore, during the first operation process, the control unit 240 closes the second flow control valve V2, the third flow control valve V3, and the fourth flow control valve V4.

When the first operation process is executed, the solid particles in the first chamber FR become fluid. Furthermore, the heat from the fluidizing gas heats the solid particles in the first chamber FR. This results in heat exchange between the fluidized solid particles and the fluid passing through the heat transfer tube 178. However, since the supply of fluidizing gas to the second chamber SR is stopped, the solid particles in the second chamber SR do not become fluid. In other words, the solid particles in the second chamber SR hardly move. Also, the solid particles in the second chamber SR are not heated by the fluidizing gas. Therefore, no heat exchange occurs with the gas passing through the heat transfer tube 480.

In other words, during the first operating process, the first chamber FR and the heat transfer tube 178 function as a second heat exchanger, receiving solid particles from the high-temperature bath 160 and exchanging heat between the solid particles and the fluid.

[Second Operation Process]
The second operating process involves exchanging heat between the fluid passing through the heat transfer tube 178 and the solid particles, and exchanging heat between the gas passing through the heat transfer tube 480 and the solid particles, thereby making the temperatures of the fluid and the gas substantially equal.

In the second operation process, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, the third flow control valve V3, and the fourth flow control valve V4. In the second modified example, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, the third flow control valve V3, and the fourth flow control valve V4 so that the empty column velocity of the fluidizing gas supplied to the first chamber FR through the first divided space P, the third divided space Q, and the dispersion plate 420, and the empty column velocity of the fluidizing gas supplied to the second chamber SR through the second divided space S, the fourth divided space R, and the dispersion plate 420, are at a predetermined velocity greater than the minimum fluidization velocity Umf.

When the second operating process is executed, the solid particles in the first chamber FR and the solid particles in the second chamber SR become fluid. Furthermore, the heat from the fluidizing gas heats the solid particles in the first chamber FR and the solid particles in the second chamber SR. As a result, heat exchange occurs between the fluidized solid particles and the fluid passing through the heat transfer tube 178 in the first chamber FR, and between the fluidized solid particles and the gas passing through the heat transfer tube 480 in the second chamber SR.

Furthermore, the control unit 240 makes the empty velocity of the fluidizing gas supplied to the first chamber FR substantially equal to the empty velocity of the fluidizing gas supplied to the second chamber SR. This allows the solid particles in the first chamber FR and the solid particles in the second chamber SR to be heated substantially equally. It also allows the solid particles in the first chamber FR and the solid particles in the second chamber SR to be fluidized substantially equally. Therefore, by executing the second operation process, the temperatures of the fluid and gas can be made substantially equal.

In other words, during the second operating process, the first chamber FR and heat transfer tube 178 function as a second heat exchanger, receiving solid particles supplied from the high-temperature bath 160 and exchanging heat between the solid particles and the fluid. Furthermore, during the second operating process, the second chamber SR and heat transfer tube 480 function as a preheater, preheating the gas passing through the gas supply passage 114.

[Third Operation Process]
The third operating process involves exchanging heat between the fluid passing through the heat transfer tube 178 and the solid particles, and exchanging heat between the gas passing through the heat transfer tube 480 and the solid particles, thereby raising the temperature of the gas above the temperature of the fluid.

In the third operation process, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, the third flow control valve V3, and the fourth flow control valve V4. In the second modified example, the control unit 240 adjusts the opening degrees of the first flow control valve V1 and the third flow control valve V3 so that the empty column velocity of the fluidizing gas supplied to the first chamber FR through the first divided space P, the third divided space Q, and the dispersion plate 420 becomes the minimum fluidization velocity Umf. Furthermore, the control unit 240 adjusts the opening degrees of the second flow control valve V2 and the fourth flow control valve V4 so that the empty column velocity of the fluidizing gas supplied to the second chamber SR through the second divided space S, the fourth divided space R, and the dispersion plate 420 becomes a predetermined velocity greater than the minimum fluidization velocity Umf.

Figure 9 illustrates the flow of solid particles during the third operating process. In Figure 9, the white arrows indicate the flow of the fluidizing gas, while the black arrows indicate the flow of solid particles.

When the third operating process is executed, the solid particles in the first chamber FR and the solid particles in the second chamber SR become fluid. Furthermore, the heat from the fluidizing gas heats the solid particles in the first chamber FR and the solid particles in the second chamber SR. As a result, heat exchange occurs between the fluidized solid particles and the fluid passing through the heat transfer tube 178 in the first chamber FR, and between the fluidized solid particles and the gas passing through the heat transfer tube 480 in the second chamber SR.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied to the second chamber SR is greater than the empty velocity of the fluidizing gas supplied to the first chamber FR. Therefore, as shown in Figure 9, the solid particles in the second chamber SR rise within the second chamber SR, pass over the partition plate 430, and move to the first chamber FR. Also, as described above, the empty velocity of the fluidizing gas supplied to the first chamber FR is the minimum fluidization velocity Umf. Therefore, the amount of solid particles supplied from the second chamber SR to the first chamber FR is equal to the amount of solid particles that move from the first chamber FR to the second chamber SR through the space between the partition plate 430 and the dispersion plate 420. In this way, the solid particles circulate between the second chamber SR and the first chamber FR.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied from the fourth divided space R into the second chamber SR is greater than the minimum fluidization velocity Umf. Therefore, the movement of solid particles from the first chamber FR to the second chamber SR can be promoted.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied from the third divided space Q into the first chamber FR is smaller than the empty velocity of the fluidizing gas supplied from the fourth divided space R into the second chamber SR. Therefore, backflow of solid particles from the second chamber SR to the first chamber FR can be prevented.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied to the second chamber (SR) is greater than the empty velocity of the fluidizing gas supplied to the first chamber (FR). Therefore, the solid particles in the second chamber (SR) are heated more by the fluidizing gas than the solid particles in the first chamber (FR).

Therefore, by executing the third operational process, the temperature of the gas can be made higher than that of the fluid.

In other words, in the third operating process, the first chamber FR and heat transfer tube 178 function as a second heat exchanger, receiving solid particles supplied from the high-temperature bath 160 and exchanging heat between the solid particles and the fluid. Furthermore, in the third operating process, the second chamber SR and heat transfer tube 480 function as a preheater, preheating the gas passing through the gas supply passage 114.

[Fourth Operation Process]
The fourth operating process involves exchanging heat between the fluid passing through the heat transfer tube 178 and the solid particles, and exchanging heat between the gas passing through the heat transfer tube 480 and the solid particles, thereby raising the temperature of the fluid above the temperature of the gas.

In the fourth operation process, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, the third flow control valve V3, and the fourth flow control valve V4. In the second modified example, the control unit 240 adjusts the opening degrees of the first flow control valve V1 and the third flow control valve V3 so that the empty column velocity of the fluidizing gas supplied to the first chamber FR through the first divided space P, the third divided space Q, and the dispersion plate 420 becomes a predetermined velocity greater than the minimum fluidization velocity Umf. Furthermore, the control unit 240 adjusts the opening degrees of the second flow control valve V2 and the fourth flow control valve V4 so that the empty column velocity of the fluidizing gas supplied to the second chamber SR through the second divided space S, the fourth divided space R, and the dispersion plate 420 becomes the minimum fluidization velocity Umf.

Figure 10 illustrates the flow of solid particles during the fourth operating process. In Figure 10, the white arrows indicate the flow of the fluidizing gas, while the black arrows indicate the flow of solid particles.

When the fourth operating process is executed, the solid particles in the first chamber FR and the solid particles in the second chamber SR become fluid. Furthermore, the heat from the fluidizing gas heats the solid particles in the first chamber FR and the solid particles in the second chamber SR. As a result, heat exchange occurs between the fluidized solid particles and the fluid passing through the heat transfer tube 178 in the first chamber FR, and between the fluidized solid particles and the gas passing through the heat transfer tube 480 in the second chamber SR.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied to the first chamber FR is greater than the empty velocity of the fluidizing gas supplied to the second chamber SR. Therefore, as shown in Figure 10, the solid particles in the first chamber FR rise within the chamber FR, pass over the partition plate 430, and move to the second chamber SR. Also, as described above, the empty velocity of the fluidizing gas supplied to the second chamber SR is the minimum fluidization velocity Umf. Therefore, the amount of solid particles supplied from the first chamber FR to the second chamber SR is equivalent to the amount of solid particles that move from the second chamber SR to the first chamber FR through the space between the partition plate 430 and the dispersion plate 420. In this way, the solid particles circulate between the first chamber FR and the second chamber SR.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied from the third divided space Q into the first chamber FR is greater than the minimum fluidization velocity Umf. Therefore, the movement of solid particles from the second chamber SR to the first chamber FR can be promoted.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied from the fourth divided space R into the second chamber SR is smaller than the empty velocity of the fluidizing gas supplied from the third divided space Q into the first chamber FR. Therefore, backflow of solid particles from the first chamber FR to the second chamber SR can be prevented.

Furthermore, as described above, the empty velocity of the fluidizing gas supplied to the first chamber (FR) is greater than the empty velocity of the fluidizing gas supplied to the second chamber (SR). Therefore, the solid particles in the first chamber (FR) are heated more by the fluidizing gas than the solid particles in the second chamber (SR).

Therefore, by executing the fourth operating process, the fluid temperature can be made higher than that of the gas.

In other words, in the fourth operating process, the first chamber FR and heat transfer tube 178 function as a second heat exchanger, receiving solid particles supplied from the high-temperature bath 160 and exchanging heat between the solid particles and the fluid. Furthermore, in the fourth operating process, the second chamber SR and heat transfer tube 480 function as a preheater, preheating the gas passing through the gas supply passage 114.

As described above, the heat exchanger 400 according to the second modification comprises heat transfer tubes 178 and 480 within a single containment chamber AR, allowing for different flow states of solid particles in the first chamber FR where the heat transfer tube 178 is located and the second chamber SR where the heat transfer tube 480 is located. This makes it possible to miniaturize the heat exchanger 400 while exchanging heat between a fluid and a gas at different temperatures.

[Third variation]
In the second modification described above, the case in which the heat exchanger 400 is equipped with a third dividing plate 444 was given as an example. However, the heat exchanger 400 may be provided without a third dividing plate 444.

Figure 11 illustrates a heat exchanger 500 according to a third modified example. As shown in Figure 11, the heat exchanger 500 includes a container 410, a dispersion plate 420, a partition plate 430, a first compartment plate 432, a second compartment plate 434, a first dividing plate 440, a second dividing plate 442, a fluidizing gas supply device 550, a heat transfer tube 178, a heat transfer tube 480, and a cyclone 490. In Figure 11, solid arrows indicate fluid flow. Components substantially equivalent to those of the heat exchanger 400 are denoted by the same reference numerals, and their descriptions are omitted.

Unlike the heat exchanger 400, the heat exchanger 500 does not have a third dividing plate 444. Therefore, in the heat exchanger 500, a first divided space P (first space) is formed by the dispersion plate 420, the side surface SS and bottom surface of the container 410, and the first dividing plate 440. Furthermore, a second divided space S (second space) is formed by the dispersion plate 420, the side surface SS and bottom surface of the container 410, and the second dividing plate 442. A divided space T (third space) is formed by the dispersion plate 420, the bottom surface of the container 410, the first dividing plate 440, and the second dividing plate 442.

The fluidized gas supply device 550 includes piping 322a, a first branch pipe 460, a first flow control valve V1, a second branch pipe 462, a second flow control valve V2, a third branch pipe 464, and a third flow control valve V3.

The third branch pipe 464 connects the piping 322a and the divided space T. The third flow control valve V3 is installed in the third branch pipe 464. The third flow control valve V3 changes the flow path cross-sectional area formed in the third branch pipe 464.

In the third modified example, the control unit 240 adjusts the opening of the second flow control valve V2 to perform a preheating operation. During the preheating operation, the control unit 240 adjusts the opening of the second flow control valve V2 so that the empty velocity Vb of the fluidizing gas supplied to the second chamber SR through the second divided space S and the dispersion plate 420 is greater than the velocity VB. Furthermore, during the preheating operation, the control unit 240 closes the first flow control valve V1 and the third flow control valve V3.

In the third modified example, the control unit 240 adjusts the opening degree of the first flow control valve V1 to execute the first operation process. During the first operation process, the control unit 240 adjusts the opening degree of the first flow control valve V1 so that the empty column velocity Va of the fluidizing gas supplied to the first chamber FR through the first divided space P and the dispersion plate 420 is greater than the velocity VA. Also during the first operation process, the control unit 240 closes the second flow control valve V2 and the third flow control valve V3.

In the third modified example, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, and the third flow control valve V3 to perform the second operation process. In the second operation process, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, and the third flow control valve V3 so that the empty velocity of the fluidizing gas supplied to the first chamber FR through the first divided space P, the divided space T, and the dispersion plate 420, and the empty velocity of the fluidizing gas supplied to the second chamber SR through the second divided space S, the divided space T, and the dispersion plate 420, are at predetermined velocities greater than the minimum fluidization velocity Umf.

In the third modified example, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, and the third flow control valve V3 to execute the third operation process. In the third operation process, the control unit 240 adjusts the opening degrees of the first flow control valve V1 and the third flow control valve V3 so that the empty column velocity of the fluidizing gas supplied to the first chamber FR through the first divided space P, the divided space T, and the dispersion plate 420 becomes the minimum fluidization velocity Umf. Furthermore, the control unit 240 adjusts the opening degree of the second flow control valve V2 so that the empty column velocity of the fluidizing gas supplied to the second chamber SR through the second divided space S and the dispersion plate 420 becomes a predetermined velocity greater than the minimum fluidization velocity Umf.

In the third modified example, the control unit 240 adjusts the opening degrees of the first flow control valve V1, the second flow control valve V2, and the third flow control valve V3 to execute the fourth operation process. In the fourth operation process, the control unit 240 adjusts the opening degrees of the second flow control valve V2 and the third flow control valve V3 so that the empty column velocity of the fluidizing gas supplied to the second chamber SR through the second divided space S, the divided space T, and the dispersion plate 420 becomes the minimum fluidization velocity Umf. Furthermore, the control unit 240 adjusts the opening degree of the first flow control valve V1 so that the empty column velocity of the fluidizing gas supplied to the first chamber FR through the first divided space P and the dispersion plate 420 becomes a predetermined velocity greater than the minimum fluidization velocity Umf.

In the third modified heat exchange device 500, a heat transfer tube 178 and a heat transfer tube 480 are provided within a single containment chamber AR. The flow state of solid particles can be made different in the first chamber FR where the heat transfer tube 178 is located and the second chamber SR where the heat transfer tube 480 is located. This allows the heat exchange device 500 to be miniaturized while exchanging heat between a fluid and a gas at different temperatures.

[Second Embodiment: Energy Storage Device 600]
Figure 12 is a diagram illustrating an energy storage device 600 according to a second embodiment. As shown in Figure 12, the energy storage device 600 includes a gas supply unit 110, a preheater 120, a heating chamber 610, a first heat exchanger 140, a solid-gas separator 150, a solid particle supply pipe 620, a high-temperature tank 160, a high-temperature particle supply unit 162, a second heat exchanger 170, a fluid supply unit 180, a heat utilization device 182, a discharge unit 630, a low-temperature tank 200, a low-temperature particle supply unit 210, a gas delivery unit 640, and a control unit 650. In Figure 12, solid arrows indicate the flow of solid particles and solid-gas mixtures. Dashed arrows indicate the flow of fluids and gases. Dotted arrows indicate focused sunlight. Components that are substantially the same as those in the energy storage devices 100 and 300 are given the same reference numerals and their descriptions are omitted.

In the second embodiment, the heating chamber 610 includes a box 132 and a heater 612. In this embodiment, the heater 612 heats the gas by concentrating sunlight. The heater 612 is, for example, a light concentrator. The heater 612 concentrates sunlight onto the gas supplied into the box 132. As a result, the air inside the box 132 is heated.

The solid particle supply pipe 620 supplies the solid particles separated into solid and gaseous states by the solid-gas separator 150 to the high-temperature tank 160. The upper end of the solid particle supply pipe 620 is connected to the solid-gas separator 150. The lower end of the solid particle supply pipe 620 is connected to the high-temperature tank 160.

The discharge section 630 discharges solid particles from the second heat exchanger 170 to the low-temperature tank 200. In this embodiment, the discharge section 630 includes a discharge pipe 632. The discharge pipe 632 is a pipe connecting the containment chamber 172a and the low-temperature tank 200. The upper end of the discharge pipe 632 is connected to the side surface of the container 172, near the upper surface of the fluidized bed in the containment chamber 172a. The lower end of the discharge pipe 632 is connected to the upper surface of the low-temperature tank 200.

The gas delivery unit 640 includes piping 322a and a flow rate adjustment mechanism 324a.

The control unit 650 is composed of a semiconductor integrated circuit including a CPU (Central Processing Unit). The control unit 650 reads programs and parameters for operating the CPU from the ROM. The control unit 650 works in cooperation with the RAM (which acts as a work area) and other electronic circuits to manage and control the entire energy storage device 600. In this embodiment, the control unit 650 controls the gas supply unit 110 (blower 112), heater 612, flow rate adjustment mechanism 166, fluidization gas supply unit 176, fluid supply unit 180, flow rate adjustment mechanism 214, and gas delivery unit 640 (flow rate adjustment mechanism 324a).

[Heat storage mode]
The control unit 650 closes the flow rate adjustment mechanism 166. The control unit 650 stops the fluidizing gas supply unit 176 and the fluid supply unit 180. The control unit 650 also operates the blower 112 and the heater 612. The control unit 650 also opens the flow rate adjustment mechanism 324a and adjusts the opening degree. The control unit 650 opens the flow rate adjustment mechanism 214 and adjusts the opening degree.

As a result, sunlight is concentrated by the heater 612, and the gas supplied from the gas supply unit 110 to the box 132 is heated. The heater 612 heats the gas to the first temperature.

The heated high-temperature gas (gas at the first temperature) is supplied to the first heat exchanger 140. Low-temperature solid particles are also supplied from the low-temperature tank 200 to the first heat exchanger 140. Therefore, in the first heat exchanger 140, the high-temperature gas and low-temperature solid particles are vigorously agitated, and heat exchange occurs between them. As a result, the solid particles are heated by the gas, and the gas is cooled by the solid particles. At the outlet of the first heat exchanger 140, the temperature of the solid particles and the temperature of the gas become approximately equal (the second temperature).

The solid-gas separator 150 then separates the solid-gas mixture discharged from the first heat exchanger 140. The separated high-temperature solid particles (solid particles at the second temperature) are supplied to the high-temperature tank 160 through the solid particle supply pipe 620. The high-temperature tank 160 stores the high-temperature solid particles.

Meanwhile, the gas at the second temperature, separated from the solid-gas state, is supplied to the preheater 120 through piping 322a. The preheater 120 exchanges heat between the gas at the second temperature supplied from the solid-gas separator 150 via piping 322a and the gas supplied to the heating chamber 610 by the blower 112. Therefore, the gas supplied to the heating chamber 610 by the blower 112 is heated to the third temperature by the gas at the second temperature.

In this way, in the heat storage mode, sunlight is converted into heat and first transferred to the gas. Then, heat exchange takes place between the high-temperature gas and the low-temperature solid particles, and the heat is transferred to the solid particles. In this way, sunlight is converted into thermal energy and retained (stored) in the solid particles. Since the heat capacity of solid particles is greater than that of gas (air), the heat storage density of solid particles is higher than that of gas.

The control unit 650 adjusts the opening of the flow rate adjustment mechanism 214 based on the energy of the concentrated sunlight. Specifically, the energy of the sunlight concentrated by the heater 612 is converted into thermal energy, and when solid particles are heated (via gas) with this thermal energy, the amount of solid particles that reach the second temperature is determined. Therefore, the control unit 650 adjusts the opening of the flow rate adjustment mechanism 214 so that the determined amount of solid particles is supplied to the first heat exchanger 140.

This allows the temperature of the solid particles stored in the high-temperature chamber 160 to be steadily maintained at the second temperature, even when the amount of sunlight fluctuates (when the amount of sunlight fluctuates over time). In other words, it can adapt to fluctuations in the amount of sunlight. Therefore, in the heat dissipation mode described later, it becomes possible to supply a fluid at the fourth temperature, which satisfies the required temperature, to the heat utilization equipment 182 without using additional energy (for example, without burning auxiliary fuel).

[Heat dissipation mode]
The control unit 650 closes the flow rate adjustment mechanism 324a and the flow rate adjustment mechanism 214. The control unit 650 stops the blower 112 and the heater 612. The control unit 650 also opens the flow rate adjustment mechanism 166 and adjusts the opening degree. The control unit 650 operates the fluid supply unit 180.

As a result, high-temperature solid particles (solid particles at the second temperature) are supplied to the second heat exchanger 170 from the high-temperature tank 160. Fluid is also supplied to the heat transfer tubes 178 from the fluid supply unit 180. Therefore, heat exchange occurs between the low-temperature fluid and the high-temperature solid particles in the second heat exchanger 170. This heats the fluid, and the fluid cools the solid particles. In this way, the heated fluid in the second heat exchanger 170 is supplied to the heat utilization equipment 182. The temperature of the fluid supplied to the heat utilization equipment 182 and the temperature of the solid particles discharged from the second heat exchanger 170 are approximately equal, at the fourth temperature.

Then, in the second heat exchanger 170, the solid particles cooled from the second temperature through heat exchange with the fluid are supplied to the low-temperature tank 200 through the discharge section 630 (discharge pipe 632). The low-temperature tank 200 stores the solid particles at the fourth temperature.

In this way, in the heat dissipation mode, heat exchange occurs between high-temperature solid particles and low-temperature fluid, and heat is transferred to the fluid. Then, when needed (for example, during periods of power shortage), the high-temperature fluid (fluid at the fourth temperature) is utilized by the heat utilization device 182 (for example, for generating electricity).

The control unit 650 adjusts the opening of the flow rate adjustment mechanism 166 based on the required temperature and flow rate of the heat utilization equipment 182. Specifically, when the fluid supply unit 180 supplies fluid to the heat transfer tubes 178 of the second heat exchanger 170 at the required flow rate of the heat utilization equipment 182, and the fluid is heated by solid particles at a second temperature stored in the high-temperature tank 160, the amount of solid particles needed to heat the fluid to a fourth temperature is determined. Therefore, the control unit 650 adjusts the opening of the flow rate adjustment mechanism 166 so that the determined amount of solid particles is supplied to the second heat exchanger 170.

This allows the temperature of the fluid supplied to the heat utilization device 182 to be brought to the required temperature of the heat utilization device 182. Therefore, it becomes possible to stably supply the heat utilization device 182 with fluid at a fourth temperature that meets the required temperature, without using additional energy (for example, without burning auxiliary fuel). Even if the required temperature of the heat utilization device 182 (for example, the required amount of power generation) fluctuates over time, this can be addressed by adjusting the supply amount of solid particles.

While embodiments have been described above with reference to the attached drawings, it goes without saying that this disclosure is not limited to the embodiments described above. It will be obvious to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally fall within the technical scope of this disclosure.

For example, in the embodiments and modifications described above, the gas supply unit 110 was described using a configuration that includes a blower 112 as an example. However, the gas supply unit 110 is not limited in its configuration as long as it can supply gas to the first heat exchanger 140. For example, the gas supply unit 110 may be equipped with a compressed gas source (e.g., a compressed air source) or a pump instead of the blower 112.

Furthermore, in the above embodiments and modifications, a configuration in which gas is supplied from the bottom of the first heat exchanger 140 was described as an example. However, the gas may be supplied from below the solid particle supply point in the first heat exchanger 140. For example, the gas may be supplied from the lower part of the first heat exchanger 140. Also, the gas supply unit 110 may supply gas at atmospheric pressure or pressurized gas.

Furthermore, in the above embodiments and modifications, a configuration in which the second heat exchanger 170 forms a fluidized bed of solid particles was described as an example. This allows for efficient preheating of the fluid using the heat of the solid particles in the heat dissipation mode. However, the configuration of the second heat exchanger 170 is not limited as long as it can exchange heat between solid particles and the fluid. For example, the second heat exchanger 170 may be composed of solid particles.

Furthermore, in the first embodiment described above, the period during which there is a surplus of electricity (generated electricity - demanded electricity > predetermined value (e.g., 0)) was designated as the heat storage mode. However, the heat storage mode may also be used when it is necessary to convert electricity into other energy (for example, when it is necessary to consume electricity to stabilize the power grid). Also, the heat release mode was used when necessary. However, the heat release mode may also be used when it is necessary to utilize the heat (for example, when it is necessary to utilize the heat in a cement factory).

Furthermore, in the second and third modified examples described above, the control unit 240 was given as an example in which it performs the preheating operation, the first operation, the second operation, the third operation, and the fourth operation. However, the control unit 240 only needs to perform the preheating operation and one of the first to fourth operation processes.

Furthermore, in the first modified example described above, a configuration in which the gas delivery unit 320 is equipped with a flow rate adjustment mechanism 324a was given as an example. However, the gas delivery unit 320 does not necessarily need to be equipped with a flow rate adjustment mechanism 324a.

Furthermore, in the second embodiment described above, an example was given in which the energy storage device 600 is equipped with a gas delivery unit 640. However, the energy storage device 600 may be equipped with a gas delivery unit 320 instead of the gas delivery unit 640. In other words, the energy storage device 600 may be equipped with a gas delivery unit 320 that includes piping 322a, 322b and flow rate adjustment mechanisms 324a, 324b.

Furthermore, a heater or another heat exchanger may be installed inside the first heat exchanger 140.

This disclosure can, for example, contribute to Sustainable Development Goal (SDG) 7, "Ensure access to affordable, reliable, sustainable and modern energy."

100 Energy storage device 110 Gas supply unit 120 Preheater 134 Heater 140 First heat exchanger 140a Gas supply port 150 Solid-gas separator 152 Switching unit 160 High-temperature tank 166 Flow rate adjustment mechanism 170 Second heat exchanger 182 Heat utilization equipment 190 Discharge unit 200 Low-temperature tank 210 Low-temperature particle supply unit 240 Control unit 300 Energy storage device 600 Energy storage device 612 Heater 630 Discharge unit

Claims (6)

A first heat exchanger is provided, in which gas is supplied from a gas supply port formed on the bottom or lower surface, and solid particles are supplied from above the gas supply port, and heat is exchanged between the gas and the solid particles.
A gas supply unit that supplies gas to the first heat exchanger,
A heater that heats either or both of the gas supplied from the gas supply unit to the first heat exchanger, and the gas in the first heat exchanger.
A solid-gas separator for separating the solid-gas mixture discharged from the first heat exchanger,
A high-temperature tank for storing the solid particles separated by the solid-gas separator,
The solid particles are supplied from the high-temperature bath, and a second heat exchanger is used to exchange heat between the solid particles and the fluid.
A flow rate adjustment mechanism for adjusting the flow rate of the solid particles supplied from the high-temperature bath to the second heat exchanger,
A discharge section for discharging the solid particles from the second heat exchanger,
A low-temperature tank for storing the solid particles discharged by the discharge unit,
A low-temperature particle supply unit that supplies the solid particles stored in the low-temperature tank to the first heat exchanger,
A heat utilization device that utilizes the thermal energy of the fluid whose heat has been exchanged by the second heat exchanger,
Equipped with ,
The discharge unit discharges the solid particles to the first heat exchanger.
The low-temperature tank is supplied with the solid particles that have been discharged by the discharge section, have undergone heat exchange with the gas in the first heat exchanger, and have been separated into solid and gaseous forms by the solid-gas separator . The system includes a preheater that preheats the gas using the heat contained in the high-temperature gas separated by the solid-gas separator,
The energy storage device according to claim 1 , wherein the gas supply unit supplies the gas preheated by the preheater to the first heat exchanger. The energy storage device according to claim 1 or 2, further comprising a switching unit for switching the supply destination of the solid particles separated by the solid-gas separator to the high-temperature tank or the low-temperature tank. The heater consumes electricity to heat the gas,
The system comprises the gas supply unit, the heater, the flow rate adjustment mechanism, and the control unit for controlling the low-temperature particle supply unit.
The control unit,
Among several modes, including heat storage mode and heat dissipation mode,
In the heat storage mode, the gas supply unit is controlled to supply gas to the first heat exchanger, the heater is operated to heat the gas, the low-temperature particle supply unit is controlled to supply the solid particles from the low-temperature tank to the first heat exchanger, the solid particles are heated by the gas in the first heat exchanger, and the solid particles separated by the solid-gas separator are supplied to the high-temperature tank.
The energy storage device according to claim 1, wherein in the heat dissipation mode, the flow rate adjustment mechanism is controlled to supply the solid particles from the high-temperature tank to the second heat exchanger, the fluid is heated by the solid particles in the second heat exchanger, the heated fluid is used in the heat utilization equipment, the solid particles are supplied from the second heat exchanger to the first heat exchanger through the discharge section, the heater is stopped, the gas supply section is controlled to supply gas to the first heat exchanger, the gas is heated by the solid particles in the first heat exchanger, and the solid particles separated by the solid-gas separator are supplied to the low -temperature tank. The heater consumes electricity to heat the gas,
The system comprises the gas supply unit, the heater, the flow rate adjustment mechanism, and the control unit for controlling the low-temperature particle supply unit.
The control unit,
Among several modes, including heat storage mode and heat dissipation mode,
In the heat storage mode, the gas supply unit is controlled to supply gas to the first heat exchanger, the heater is operated to heat the gas, the low-temperature particle supply unit is controlled to supply the solid particles from the low-temperature tank to the first heat exchanger, the solid particles are heated with the gas in the first heat exchanger, the solid particles separated by the solid-gas separator are supplied to the high-temperature tank, and the gas separated by the solid-gas separator is supplied to the preheater.
The energy storage device according to claim 2, wherein in the heat dissipation mode, the flow rate adjustment mechanism is controlled to supply the solid particles from the high-temperature tank to the second heat exchanger, the fluid is heated by the solid particles in the second heat exchanger, the heated fluid is used in the heat utilization equipment, the solid particles are supplied from the second heat exchanger to the first heat exchanger through the discharge section, the heater is stopped, the gas supply section is controlled to supply gas to the first heat exchanger, the gas is heated by the solid particles in the first heat exchanger, and the solid particles separated by the solid-gas separator are supplied to the low-temperature tank . The energy storage device according to claim 1, wherein the heater heats the gas using sunlight.