JP7622477B2 - Thermal storage system - Google Patents

Description

The present invention relates to a heat storage system.

Conventionally, there has been known a heat storage system that temporarily stores heat supplied by a heat supply device and uses the stored heat to operate a heat utilization device. For example, Patent Document 1 discloses a technology that includes multiple heat storage units that contain a heat medium heated by a heat supply device, and supplies heat from the multiple heat storage units to the heat utilization device depending on the state of heat utilization in the heat utilization device.

JP 2006-275394 A

However, even with the above-mentioned prior art, there is still room for improvement in the technology that can improve the start-up performance of the heat utilization device while extending the operating time in the heat storage system. For example, the technology described in Patent Document 1 has two heat storage sections with different heat capacities. Therefore, if a heat storage section with a relatively small heat capacity is selected, the heat medium runs out in a short time, and the operating time of the heat utilization device is shortened. If a heat storage section with a relatively large heat capacity is selected, it takes a long time for the heat medium at a temperature that can operate the heat utilization device to be stored in the heat storage section, so the time until the heat utilization device starts is longer and the start-up performance is reduced.

The present invention has been made to solve the above-mentioned problems, and aims to provide a technology that can improve the start-up performance of a heat utilization device in a thermal storage system while extending its operating time.

The present invention has been made to solve at least some of the above problems, and can be realized in the following form.

(1) According to one aspect of the present invention, a heat storage system is provided. The heat storage system includes a heat storage device that stores a heat medium, a heat supply device that heats the heat medium flowing through a first circulation flow path connected to the heat storage device and supplies the heated heat medium to the heat storage device, a heat utilization device that operates with the heat of the heat medium supplied from the heat storage device through a second circulation flow path connected to the heat storage device, a pump that circulates the heat medium between the first circulation flow path, the second circulation flow path, and the heat storage device, and a heat capacity change device that changes the amount of heat medium stored in the heat storage device to change the heat capacity of the heat storage device.

According to this configuration, the heat capacity change device changes the heat capacity of the heat storage device by changing the amount of heat medium contained in the heat storage device. For example, when the heat capacity of the heat storage device is reduced, the temperature of the heat storage device is easily increased, and therefore it is easy to store a high-temperature heat medium in the heat storage device in a short time. As a result, a high-temperature heat medium can be supplied to the heat utilization device in a short time, and the heat utilization device that operates by the supply of heat from the heat storage device can be operated in a short time. In addition, when the heat capacity of the heat storage device is increased, a relatively large amount of heat medium at a temperature that the heat utilization device can use is stored in the heat storage device, and therefore the heat medium at a temperature at which the heat utilization device can operate can be supplied for a relatively long time. In this way, by changing the heat capacity of the heat storage device, when the operation of the heat utilization device is started, the heat medium at a temperature at which the heat utilization device can operate can be supplied for a relatively long time while the heat medium at a temperature at which the heat utilization device can operate can be supplied in a short time, and therefore the operation time can be extended while improving the startability of the heat utilization device. Furthermore, in the heat utilization device, the time until startup is shortened and the operating time is extended, so the time during which the heat supply device utilizes the heat supplied to the heat storage device is extended. This increases the amount of heat utilized to operate the heat utilization device.

(2) In the heat storage system of the above embodiment, the heat capacity change device may reduce the heat capacity of the heat storage device by discharging at least a portion of the heat medium contained in the heat storage device from the heat storage device, and increase the heat capacity of the heat storage device by supplying the heat medium from the outside of the heat storage system to the heat storage device. According to this configuration, the heat capacity change device reduces the amount of heat medium contained in the heat storage device by discharging at least a portion of the heat medium contained in the heat storage device from the heat storage device, thereby reducing the heat capacity of the heat storage device. In addition, the heat capacity change device increases the amount of heat medium contained in the heat storage device by supplying the heat medium to the heat storage device from the outside of the heat storage system, thereby increasing the heat capacity of the heat storage device. As a result, the heat capacity of the heat storage device can be easily changed by introducing and discharging the heat medium in the heat storage device, and therefore it is easy to achieve both improved startability and longer operation times for the heat utilization device.

(3) The heat storage system of the above embodiment may further include a heat capacity detection unit that detects a value related to the heat capacity of the heat storage device, and a control unit that changes the heat capacity of the heat storage device in accordance with the relationship between the value related to the heat capacity of the heat storage device detected by the heat capacity detection unit and a target value. According to this configuration, the control unit changes the heat capacity of the heat device in accordance with the relationship between the value related to the heat capacity of the heat storage device detected by the heat capacity detection unit and the target value. This makes it possible to match the heat capacity of the heat storage device to the target value, thereby reliably achieving both improved startability and longer operating times for the heat utilization device.

(4) In the heat storage system of the above embodiment, the control unit may relatively reduce the heat capacity of the heat storage device when the heat supply device is stopped compared to when the heat supply device is operating. According to this configuration, the control unit relatively reduces the heat capacity of the heat storage device when the heat supply device is stopped compared to when the heat supply device is operating. The control unit relatively reduces the heat capacity of the heat storage device by discharging at least a portion of the heat medium contained in the heat storage device from the heat storage device. This makes it easier for the temperature of the heat storage device to rise, making it easier to store a high-temperature heat medium in the heat storage device in a short period of time. Therefore, the high-temperature heat medium can be supplied to the heat utilization device in an even shorter period of time, further improving the start-up performance of the heat utilization device.

(5) In the heat storage system of the above embodiment, the control unit may relatively reduce the heat capacity of the heat storage device when the heat utilization device is stopped compared to when the heat utilization device is operating. According to this configuration, the control unit relatively reduces the heat capacity of the heat storage device when the heat utilization device is stopped compared to when the heat utilization device is operating. The control unit relatively reduces the heat capacity of the heat storage device by discharging at least a portion of the heat medium contained in the heat storage device from the heat storage device. As a result, the amount of heat medium contained in the heat storage device is reduced, so that even if the heat medium newly heated by the heat supply device is contained in the heat storage device, the temperature of the heat medium contained in the heat storage device is unlikely to decrease. In other words, the high-temperature heat medium supplied to the heat storage device by the heat supply device is contained in the heat storage device while remaining at a high temperature. As a result, when the heat utilization device is started, a heat medium at an operable temperature can be quickly supplied, thereby further improving the start-up performance of the heat utilization device. In addition, when the heat utilization device is operating, the amount of heat medium contained in the heat storage device is increased by supplying the heat medium to the heat storage device, and the heat capacity of the heat storage device is relatively increased. The heat medium contained in the heat storage device is heated by the heat supply device and then stored again in the heat storage device, so that the heat storage device can store a relatively large amount of heat medium at a temperature at which the heat utilization device can be operated while the heat utilization device is operating. As a result, even if the supply of heat from the heat supply device is stopped and there is a fluctuation in the heat supply from the heat supply device to the heat storage device, the heat utilization device can continue to operate because there is little fluctuation in the heat supply to the heat utilization device. Therefore, the operating time of the heat utilization device can be further extended.

(6) In the heat storage system of the above embodiment, the control unit may change the heat capacity of the heat storage device depending on the operating status of the heat utilization device. According to this configuration, the control unit changes the heat capacity of the heat storage device depending on the operating status of the heat utilization device. For example, immediately after the heat utilization device starts operating, the heat capacity of the heat storage device is increased by supplying a heat medium to the heat storage device, which has a relatively small heat capacity. This makes it possible to supply a heat medium with heat sufficient to operate the heat utilization device for a long period of time even after the supply of heat from the heat supply device is cut off. This makes it possible to further improve the start-up performance of the heat utilization device and to further extend the operating time of the heat utilization device.

(7) The heat storage system of the above embodiment further includes a heat medium supplying device connected to the heat storage device and the first circulation flow path, which supplies at least a portion of the heat medium discharged from the heat storage device to the first circulation flow path, and the heat medium supplied to the first circulation flow path by the heat medium supplying device may be heated by the heat supplying device in the first circulation flow path and then stored in the heat storage device. According to this configuration, at least a portion of the heat medium discharged from the heat storage device to change the heat capacity of the heat storage device is supplied to the first circulation flow path. The heat medium supplied to the first circulation flow path is heated by the heat supplying device in the first circulation flow path and then stored in the heat storage device. When the heat medium discharged from the heat storage device is a heat medium that has been heated at least once in the heat supplying device, its temperature is often relatively high even if it is not at a temperature at which the heat utilization device can operate. As a result, when the heat medium supplied from the heat medium supply device to the first circulation flow path is heated by the heat supply device, the temperature of the heat medium can be raised to a temperature at which the heat utilization device can operate with a relatively small amount of heat. Therefore, the heat of the heat medium discharged from the heat storage device can be reused, and the heat utilization rate in the heat storage system can be improved.

(8) In the above-described heat storage system, the heat storage device may include a single tank for storing the heat medium. According to this configuration, the heat storage device includes a single tank for storing the heat medium. For example, if multiple tanks with different heat capacities are provided, a configuration for switching the tank that supplies the heat medium to the heat supply device or a configuration for switching the tank that supplies the heat medium to the heat utilization device is required, which makes the configuration complex and the system large. In the above-described configuration, the heat capacity of the heat storage device can be changed by changing the amount of heat medium in a single tank, so that a simple configuration can be used to improve the start-up performance of the heat utilization device and extend its operating time.

The present invention can be realized in various forms, such as a heat storage device, a control method for a heat storage device and a heat storage system, a computer program for executing a heat utilization method in these devices and systems, a server device for distributing the computer program, a non-transitory storage medium on which the computer program is stored, etc.

1 is a schematic diagram showing a schematic configuration of a heat storage system according to a first embodiment; 4 is a flowchart of a process for determining heat utilization in a heat storage system. 4 is a flowchart of a process for determining whether or not to change the heat capacity in the heat storage system. FIG. 2 is a model diagram showing the flow of heat in and out of a heat storage system. 4A and 4B are diagrams illustrating the operation of the heat utilization device of the present embodiment when it is started up. 5A and 5B are diagrams illustrating the operation of the heat utilization device of the first comparative example when it is started up. FIG. 11 is a diagram illustrating the operation of the heat utilization device of the second comparative example when it is started up. FIG. 11 is a diagram comparing values related to the operation when the heat utilization device is started up. FIG. 4 is a diagram illustrating an operation when the heat utilization device of the first embodiment is stopped. FIG. 11 is a diagram illustrating the operation when the heat utilization device of the first comparative example is stopped. FIG. 11 is a diagram illustrating the operation when the heat utilization device of the second comparative example is stopped. FIG. 13 is a diagram comparing values related to operation when a heat utilization device is stopped. FIG. 11 is a diagram for comparing the effects of heat storage systems. FIG. 13 is a schematic diagram showing a schematic configuration of a heat storage system according to a second embodiment.

First Embodiment
FIG. 1 is a schematic diagram showing a schematic configuration of a heat storage system 1 of the first embodiment. The heat storage system 1 of the present embodiment is, for example, a cogeneration system applied to a factory having a heat source. The heat storage system 1 includes a heat storage device 10, a heat supply device 20, a heat utilization device 30, a heat capacity change device 40, and a control unit 50. In the heat storage system 1, the heat supplied by the heat supply device 20 is temporarily stored in the heat storage device 10, and when the heat utilization device 30 operates, the heat stored in the heat storage device 10 is supplied to the heat utilization device 30. In the heat storage system 1, water is used as a heat medium for transferring heat between the heat supply device 20, the heat storage device 10, and the heat utilization device 30. The heat medium is not limited to water, and may be another liquid or a particulate solid.

The heat storage device 10 is a device that can temporarily store heat by storing a heat medium (water). The heat storage device 10 includes a tank 11, a supply side flow path 12, and a usage side flow path 13. The tank 11 stores water. In this embodiment, the heat storage device 10 includes only one tank 11 that stores water. In the heat storage system 1 of this embodiment, a water volume sensor 51 that detects the amount of water in the tank 11 and a water temperature sensor 52 that detects the temperature of the water in the tank 11 are attached to the tank 11. The water volume sensor 51 corresponds to the "heat capacity detection unit" described in the claims.

The supply side flow path 12 is a flow path connected to the tank 11, through which the water stored in the tank 11 flows. A pump 12a that pumps the water in the supply side flow path 12 and a valve 12b that allows or blocks the flow of water in the supply side flow path 12 are attached to the supply side flow path 12. The heat exchange section 12c of the supply side flow path 12 is located inside the heat supply device 20. The dotted arrow F12 shown in FIG. 1 indicates the flow of water in the supply side flow path 12. The supply side flow path 12 corresponds to the "first circulation flow path" described in the claims.

The utilization side flow path 13 is a flow path connected to the tank 11 separately from the supply side flow path 12, and the water stored in the tank 11 flows through it. The utilization side flow path 13 is equipped with a pump 13a that pressurizes the water in the utilization side flow path 13 and a valve 13b that allows or blocks the flow of water in the utilization side flow path 13. The heat exchange section 13c of the utilization side flow path 13 is located inside the heat utilization device 30. The dotted arrow F13 shown in FIG. 1 indicates the flow of water in the utilization side flow path 13. The utilization side flow path 13 corresponds to the "second circulation flow path" described in the claims.

The heat supply device 20 is a so-called gas engine generator, and includes a gas engine 21 and a heat exchanger 22. The gas engine 21 generates heat while generating electricity using gas such as LNG supplied from an external gas tank (not shown). A rotation sensor 53 is attached to the gas engine 21 to detect the operating state of the gas engine 21, for example, the rotation speed of the piston 21a. The heat exchanger 22 is formed so that a relatively high-temperature heat medium heated by the heat generated by the gas engine 21 flows through it. A part of the heat exchanger 22 is formed so as to contact the heat exchanger 12c of the supply-side flow path 12 over a relatively wide area. This allows the heat of the heat medium flowing through the heat exchanger 22 to be efficiently transferred to the water flowing through the supply-side flow path 12 (see the white arrow H1 in FIG. 1). The heat supply device 20 is not limited to a gas engine generator, and may be a gas turbine, a fuel cell, a combustor that burns combustibles such as kerosene, waste, and combustible gases such as methane and city gas, or any other device that generates heat.

The heat utilization device 30 is a so-called adsorption heat pump (AHP) and includes an adsorption air conditioning unit 31 and a heat exchange unit 32. The adsorption air conditioning unit 31 has an adsorbent (not shown) and generates cold heat by utilizing heat above a predetermined temperature. The adsorption air conditioning unit 31 is equipped with an output sensor 54 that detects the output of the adsorption air conditioning unit 31. The heat exchange unit 32 is formed so that a heat medium flows through it to provide heat in a predetermined temperature range to the adsorbent (not shown) provided in the adsorption air conditioning unit 31. A part of the heat exchange unit 32 is formed so as to contact the heat exchange unit 12c of the utilization side flow path 13 over a relatively wide area. This allows the heat of the water flowing through the utilization side flow path 13 to be efficiently transferred to the heat medium flowing through the heat exchange unit 32 (see the white arrow H2 in FIG. 1). The heat utilization device 30 is not limited to an adsorption heat pump, and may be another heat source, a heating device, or a hot water supply device, as long as it is a device that operates by utilizing heat.

The adsorption type air conditioning unit 31 can operate when the temperature of the water flowing through the heat exchange unit 13c of the utilization side flow path 13 is within a predetermined temperature range. Therefore, the lower limit of the temperature range of the water flowing through the heat exchange unit 13c at which the adsorption type air conditioning unit 31 can operate is set as the "lower limit of the usable temperature", and the upper limit of this temperature range is set as the "upper limit of the usable temperature". In this embodiment, the lower limit of the usable temperature of the adsorption type air conditioning unit 31 is, for example, 70 (°C), and the upper limit of the usable temperature is, for example, 80 (°C). That is, when the temperature of the water flowing through the heat exchange unit 13c of the utilization side flow path 13 falls below 70 (°C), the heat utilization device 30 does not operate. Also, when the temperature of the water flowing through the heat exchange unit 13c of the utilization side flow path 13 exceeds 80 (°C), the heat capacity change device 40 causes room temperature water to flow into the tank 11, and the same amount of water is discharged to the outside of the tank 11, so that part of the heat of the heat storage device 10 is discarded and the temperature of the water drops.

In the heat storage system 1 of this embodiment, a water circulation flow path is formed by the inside of the tank 11, the supply side flow path 12, and the utilization side flow path 13. As a result, heat supplied from the heat supply device 20 in the supply side flow path 12 is supplied to the heat utilization device 30 via the heat storage device 10.

The heat capacity change device 40 includes a heat medium discharge flow path 41 and a heat medium intake flow path 42. The heat medium discharge flow path 41 and the heat medium intake flow path 42 are each connected to the tank 11. The heat medium discharge flow path 41 is equipped with a check valve (not shown) that allows water to flow from the tank 11 to the outside of the heat storage system 1 (solid line arrow F41 in FIG. 1) and blocks water flow from the outside of the heat storage system 1 to the tank 11. The heat medium intake flow path 42 is equipped with a check valve (not shown) that allows water to flow from the outside of the heat storage system 1 to the tank 11 (solid line arrow F42 in FIG. 1) and blocks water flow from the tank 11 to the outside of the heat storage system 1. The heat medium discharge flow path 41 and the heat medium intake flow path 42 are each equipped with valves 41a and 42a that allow or block the flow of water in the respective flow paths. The heat capacity change device 40 changes the amount of water contained in the heat storage device 10 by controlling the opening and closing of the valves 41a and 42a. This makes it possible to change the heat capacity of the entire heat storage device 10, which is mainly the sum of the heat capacity of the tank 11 and the heat capacity of the water contained in the tank 11. In the heat storage device 10 of this embodiment, a "heat capacity lower limit value" is set at which the amount of water in the tank 11 is the smallest and therefore the heat capacity is the smallest, and a "heat capacity upper limit value" is set at which the amount of water in the tank 11 is the largest and therefore the heat capacity is the largest.

The control unit 50 has a CPU 50a, a storage unit 50b, and a ROM/RAM (not shown). The control unit 50 is electrically connected to the water volume sensor 51 and water temperature sensor 52 of the heat storage device 10, the rotation sensor 53 of the heat supply device 20, and the output sensor 54 of the heat utilization device 30. The control unit 50 is also electrically connected to the heat supply device 20, the heat utilization device 30, the pumps 12a, 13a, and the valves 12b, 13b, 41a, and 42a. The CPU 50a determines the operating state of the heat supply device 20 from the value output by the rotation sensor 53, and determines the operating state of the heat utilization device 30 from the value output by the output sensor 54. The CPU 50a controls the operation of the entire heat storage system by expanding and executing a computer program stored in the ROM into the RAM based on the signals output from these sensors. The CPU 50a includes a calculation unit (not shown) and performs calculations for various determination processes in the heat storage system 1. The memory unit 50b records the values calculated in these determination processes.

In the heat storage system 1 of this embodiment, when the heat supply device 20 is started by a command from the control unit 50, heat is generated by the combustion of gas. The heat supply device 20 uses the generated heat to heat the water flowing through the supply side flow path 12 to a temperature equal to or higher than the lower limit of the usable temperature of the heat utilization device 30. In this embodiment, the lower limit of the usable temperature of the heat utilization device 30 is set to 70°C. The water heated by the heat supply device 20 is stored in the tank 11. Thereafter, when the heat utilization device 30 is started by a command from the control unit 50, the control unit 50 drives the pump 13a to supply the water stored in the tank 11 to the heat utilization device 30. The water supplied to the heat utilization device 30 exchanges heat with the adsorbent of the heat utilization device 30 in the heat exchange unit 32. As a result, the adsorption type air conditioning unit 31 generates cold heat.

In the heat storage system 1 of this embodiment, the control unit 50 performs calculations using various parameters related to the heat storage system 1 and performs multiple determination processes. Depending on the results of these determination processes, the control unit 50 adjusts the heat capacity of the heat storage device 10, improving the start-up ability of the heat utilization device 30 while extending the operating time.

Next, the details of the multiple determination processes executed by the control unit 50 will be described. These determination processes start when the heat storage system 1 is started, and are performed continuously while the heat storage system 1 is operating.

First, the heat supply determination process will be described. In this determination process, the heat capacity of the heat storage device 10 is adjusted according to the operating state of the heat supply device 20. Specifically, when the heat supply device 20 is stopped, i.e., when the heat input to the heat storage device 10 is zero, the water in the tank 11 is discharged so that the heat capacity of the heat storage device 10 is smaller than when the heat supply device 20 is operating. This makes it easier for the temperature of the heat storage device 10 to rise the next time the heat supply device 20 starts up and supplies heat to the heat storage device 10.

Figure 2 is a flowchart of the heat utilization determination process in the heat storage system 1. Figure 3 is a flowchart of the heat capacity change determination process in the heat storage system 1. Next, the heat utilization determination process and the heat capacity change determination process will be described. In the heat storage system 1 of this embodiment, the control unit 50 performs the heat utilization determination process and the heat capacity change determination process consecutively. In this embodiment, prior to the determination process shown in Figures 2 and 3, the temperature of the water contained in the heat storage device 10 is measured by the water temperature sensor 52. The measured water temperature is recorded in the memory unit of the control unit 50.

First, as a heat utilization determination process, the amount of heat dissipation from the heat storage system 1 is calculated (step S11). The control unit 50 calculates the amount of heat dissipation from the heat storage system 1 using the heat transfer coefficient of air and the surface area of the heat storage system 1, particularly the surface areas of the heat storage device 10 and the heat utilization device 30.

Next, it is determined whether the temperature of the water in the tank 11 is less than the lower limit of the usable temperature of the heat utilization device 30 (step S12). The control unit 50 determines whether the temperature of the water in the tank 11 measured before starting this determination process is less than the lower limit of the usable temperature of the adsorption-type air conditioning unit 31. If the temperature of the water in the tank 11 is less than the lower limit of the usable temperature (step S12: YES), the control unit 50 sets the amount of heat used by the heat utilization device 30 (hereinafter referred to as the "used heat amount") to 0 (step S13). This means that the heat utilization device 30 cannot operate in the current state of the heat storage device 10. If the temperature of the water in the tank 11 is equal to or greater than the lower limit of the usable temperature (step S12: NO), the control unit 50 sets the used heat set value as the used heat amount (step S14). This "used heat set value" is the amount of heat required for the heat utilization device 30 to operate.

After steps S13 and S14, the temperature of the water stored in the heat storage device 10 is updated based on the amount of heat supplied, the amount of heat used, the amount of heat released, and the heat capacity (step S15). The "amount of heat supplied" in step S15 refers to the amount of heat supplied by the heat supply device 20 to the heat storage device 10, and is the rated amount of heat output by the heat supply device 20. The "amount of heat used" is the amount of heat used by the heat utilization device 30 set in step S13 or step S14 (0, or the heat utilization setting value). The "amount of heat released" is the amount of heat released by the heat storage system 1 calculated in step S11. The "heat capacity" refers to the heat capacity of the entire heat storage system 1, and in particular, the heat capacity of the heat storage device 10 and the heat utilization device 30. The heat capacity of the heat storage device 10 varies depending on the amount of water stored in the heat storage device 10, so it is calculated using the value measured by the water volume sensor 51. The control unit 50 uses these values to calculate the flow of heat in and out of the heat storage system 1, and calculates the temperature of the water stored in the heat storage device 10.

Next, as a heat capacity change judgment process, it is judged whether the temperature of the water in the tank 11 is less than the lower limit of the usable temperature of the heat utilization device 30 (step S16). The control unit 50 judges whether the temperature of the water in the tank 11 calculated in step S15 is a temperature less than the lower limit of the usable temperature of the adsorption-type air conditioning unit 31. If the temperature of the water in the tank 11 is less than the lower limit of the usable temperature (step S16: YES), the control unit 50 changes the heat capacity of the heat storage device 10 to the default heat capacity lower limit (step S17). Furthermore, when changing the heat capacity of the heat storage device 10 to the heat capacity lower limit, the water in the tank 11 is discharged using the heat medium discharge flow path 41 of the heat capacity change device 40. The control unit 50 calculates the heat to be discarded together with the discharged water (hereinafter referred to as "discarded heat") (step S18) and proceeds to the judgment process to step S24. If the temperature of the water in the tank 11 is equal to or higher than the lower limit of the usable temperature (step S16: NO), the control unit 50 advances the determination process to step S19. The lower limit of the usable temperature of the heat utilization device 30 corresponds to the "target value" in the claims.

In step S19, it is determined whether the temperature of the water in the tank 11 is less than the upper limit of the usable temperature of the heat utilization device 30 (step S19). The control unit 50 determines whether the temperature of the water in the tank 11 calculated in step S15 is less than the upper limit of the usable temperature of the adsorption-type air conditioning unit 31. If the temperature of the water in the tank 11 is less than the upper limit of the usable temperature (step S19: YES), the control unit 50 advances the determination process to step S24. If the temperature of the water in the tank 11 is less than the upper limit of the usable temperature (step S19: NO), the control unit 50 advances the determination process to step S20. The upper limit of the usable temperature of the heat utilization device 30 corresponds to the "target value" described in the claims.

In step S20, the heat capacity is changed so that the temperature of the water in the tank 11 becomes the upper usable temperature limit (step S20). The control unit 50 increases the heat capacity of the heat storage device 10 by using the heat medium intake passage 42 of the heat capacity change device 40 to flow room temperature water into the tank 11. This reduces the temperature of the water in the tank 11, making it possible to make it approximately the same temperature as the upper usable temperature limit of the heat utilization device 30.

Next, it is determined whether the heat capacity of the heat storage device 10 is equal to or less than the heat capacity upper limit (step S21). The control unit 50 determines whether the heat capacity of the heat storage device 10 is equal to or less than the heat capacity upper limit by changing the heat capacity of the heat storage device 10 in step S20. If the heat capacity of the heat storage device 10 is equal to or less than the heat capacity upper limit (step S21: YES), the control unit 50 advances the determination process to step S24. If the heat capacity of the heat storage device 10 is not equal to or less than the heat capacity upper limit (step S21: NO), that is, if the heat capacity of the heat storage device 10 is greater than the heat capacity upper limit because too much water has flowed into the tank 11, the control unit 50 advances the determination process to step S22. The heat capacity upper limit corresponds to the "target value" described in the claims.

In step S22, the heat capacity of the heat storage device 10 is changed to the heat capacity upper limit value (step S22). When changing the heat capacity in step S20, there is a risk that more room temperature water than the capacity of the tank 11 has been put in in order to lower the water temperature in the tank 11. Therefore, by discharging water from the heat storage device 10, the heat capacity of the heat storage device 10 is changed to the default heat capacity upper limit value (step S22). Furthermore, in order to discharge the water from the tank 11, the control unit 50 calculates the waste heat at this time (step S23) and proceeds to the determination process at step S24.

Finally, the changed heat capacity of the heat storage device 10 is recorded (step S24), and the current determination process ends. After the current determination process ends, the water temperature sensor 52 measures the temperature of the water contained in the heat storage device 10, and then the same determination process is executed. The control unit 50 executes the above-mentioned heat utilization determination process (steps S11 to S15) and heat capacity change determination process (steps S16 to S24) at regular time intervals.

Next, the operation of the heat storage system 1 of this embodiment will be described. Here, the operation of the heat storage system 1 will be described, particularly the operation when the heat utilization device 30 starts and the operation when the heat utilization device 30 stops.

Fig. 4 is a model diagram showing the flow of heat in and out of the heat storage system. Fig. 4 shows a schematic diagram of a zero-dimensional model of the heat storage system 1 of this embodiment, and in particular, for the heat storage device 10 and the heat utilization device 30, the relationship between the respective heat capacities and the amount of heat entering and leaving is shown typically. Each of the letters in Fig. 4 refers to the following parameters.
Heat capacity C _hsd : Heat capacity of the heat storage device 10 (= C _tan + C _tmm )
C _tan : heat capacity of the tank 11 of the heat storage device 10 C _tmm : heat capacity of the water in the tank 11 of the heat storage device 10 (lower limit: C _min , upper limit: C _max )
C _ahp : Heat capacity of the heat utilization device 30 C _sum : Sum of the heat capacity of the heat storage device 10 and the heat capacity of the heat utilization device 30 (C _hsd + C _aph )
Amount of heat Q _in : Amount of heat supplied by the heat supply device 20 (amount of supplied heat)
Q _out : Amount of heat used by the heat utilization device 30 (amount of heat used)
Q _dum : Amount of heat discarded from the heat storage device 10 (amount of discarded heat)
Q _roo : Heat release amount/temperature of the heat storage system 1 T _tmm : Temperature of water in the tank 11 of the heat storage device 10

As shown in Fig. 4, in the heat storage system 1 of this embodiment, the heat capacity of the heat storage device 10 can be changed by changing the amount of water in the tank 11 using the heat capacity change device 40. Specifically, the heat capacity of the water in the tank 11 can be changed from a lower limit value _Cmin to an upper limit value _Cmax . This allows the heat capacity of the heat storage device 10 to be changed from a lower limit value ( _Ctan + _Cmin ) to an upper limit value ( _Ctan + _Cmax ).

Next, based on the model shown in Fig. 4, calculations were performed using a simulation to evaluate changes in various values during the operation of the thermal storage system 1. The parameters used in this simulation are shown below together with the set values.
Room temperature: T _roo =25 (℃)
Heat transfer coefficient of air: h = 0.1 [kJ/(s·K·m ² )]
Contact area between the heat storage system and the air: A = 1 ( ^m2 )
Heat supply setting value of heat supply device: Q _in0 = 60 (kJ/min)
Heat capacity of the tank of the heat storage device: C _tan = 5 (kJ/K)
Temperature of water in the tank of the heat storage device: T _tmm = 25 (°C)
Lower limit of heat capacity of water in the tank: C _min = 10 (kJ/K)
Upper limit of heat capacity of water in the tank: C _max = 60 (kJ/K)
Heat utilization setting value of the heat utilization device: Q _out0 =60 (kJ/min)
Lower limit of usable temperature of heat utilization device: T _min = 70 (°C)
Upper limit of usable temperature of the heat utilization device: T _max = 80 (°C)
Heat capacity of the heat utilization device: C _ahp =5 (kJ/K)
End time in the simulation: t _end = 100 (min)
In this simulation, the fact that the heat capacity of the heat storage device is variable is shown by the fact that the "lower limit value of the heat capacity of the water in the tank" and the "upper limit value of the heat capacity of the water in the tank" are different.

In explaining the operation of the heat storage system 1, similar simulations were performed and evaluated for the operation of two types of heat storage systems with a fixed heat capacity of the heat storage device as comparative examples of the heat storage system 1 of this embodiment. The first comparative example is a heat storage system in which the heat capacity of the water in the tank is relatively small, and the "lower limit value of the heat capacity of the water in the tank" and the "upper limit value of the heat capacity of the water in the tank" in the above-mentioned parameter list are the same value, 10 (kJ/K). The second comparative example is a heat storage system in which the heat capacity of the water in the tank is relatively large, and the "lower limit value of the heat capacity of the water in the tank" and the "upper limit value of the heat capacity of the water in the tank" in the above-mentioned parameter list are the same value, 60 (kJ/K).

5 is a diagram for explaining the operation of the heat utilization device 30 of this embodiment when it is started. First, the operation of the heat utilization device 30 when it is started will be explained. FIG 5 shows the time changes of the following six parameters among the parameters shown in FIG 3:
T _tmm : Temperature of water in the tank of the heat storage device C _tmm : Heat capacity of water in the tank of the heat storage device Q _in : Amount of heat supplied by the heat supply device (amount of heat supplied)
Q _out : Amount of heat used by the heat utilization device (amount of heat used)
Q _dum : Amount of heat discarded from the heat storage device (amount of discarded heat)
Q _roo : Amount of heat released by the heat storage system The values on the vertical axis in Fig. 5 indicate the amount of heat per unit time, and correspond to the amount of heat supplied Q _in , the amount of heat used Q _out , the amount of heat wasted Q _dum , and the amount of heat released Q _roo . The temperature T _tmm of the water in the tank and the heat capacity C _tmm of the water in the tank are separately indicated by using dotted lines indicating the corresponding values.

5, in the heat storage system 1 of this embodiment, when the water temperature T _tmm is lower than the lower limit T _min of the usable temperature and the supply heat amount Q _in becomes greater than 0 (time: 0 minutes), the water in the tank receives the supply heat amount Q _in and the temperature rises. In the heat storage system 1, when the heat utilization device 30 is stopped, the heat capacity of the water contained in the heat storage device 10 is set to 10 (kJ/K), which is relatively larger than when the heat utilization device 30 is operating. As a result, the rate of increase in the temperature of the water contained in the heat storage device 10 is relatively high. When the water temperature T _tmm reaches the lower limit T _min of the usable temperature (time t11), heat utilization by the heat utilization device 30 is started (Q _out <0). As a result, in the heat storage system 1 of this embodiment, the time until the heat utilization device 30 starts is the time t11 from the time 0 when the supply heat amount Q _in becomes greater than 0 to the time when the utilized heat amount Q _out becomes smaller than 0. After time t11, the amount of heat used to increase the water temperature decreases, so the rate at which the water temperature increases becomes slower (between time t11 and time t12). When the water temperature T _tmm reaches the upper limit T _max of the usable temperature (time t12), water heated by the heat supply device 20 is supplied to the heat storage device 10 so that the water temperature T _tmm is maintained at the upper limit T _max . As a result, the heat capacity C _tmm of the water in the tank increases, and the excess heat is stored in the heat storage device 10. Thereafter, when the heat capacity C _tmm of the water reaches the upper limit C _max of the heat capacity of water, which is 60 (kJ/K), the excess heat is discarded (time t13).

In the heat storage system 1 of this embodiment, the control unit 50 increases the heat capacity of the heat storage device 10 by supplying water to the heat storage device 10 immediately after the heat utilization device 30 starts operating (see time t12 in FIG. 5). As a result, while the heat utilization device 30 is operating, the heat capacity of the heat storage device 10 is set to 60 (kJ/K) (see time t13 in FIG. 5).

FIG. 6 is a diagram for explaining the operation when the heat utilization device of the first comparative example starts. In the heat storage system of the first comparative example, as described above, the heat capacity of the water in the tank is a constant 10 (kJ/K). As shown in FIG. 6, at 0 minutes, the water in the tank starts to receive the supplied heat amount Q _{in ,} so the temperature rises. Since the heat capacity of the water at this time is 10 (kJ/K), which is the same as the lower limit value C _min of the heat capacity of the water in the tank 11 in the heat storage system 1 of this embodiment, the temperature rise rate is relatively high. Therefore, heat utilization starts as quickly as in the heat storage system 1 of this embodiment (time t21 when Q _out <0). As a result, in the heat storage system of the first comparative example, the time until the heat utilization device starts is as short as in this embodiment. However, since the heat capacity of the water in the tank is small, the time until the temperature of the water reaches the upper limit value T _max of the usable temperature is also relatively short, and surplus heat starts to be discarded immediately after the start of heat utilization (time t22). Since this time t22 is shorter than the time t13 in this embodiment, a large amount of surplus heat is wasted, and the utilization efficiency of the heat supplied by the heat supply device is low in the first comparative example.

FIG. 7 is a diagram for explaining the operation when the heat utilization device of the second comparative example starts. In the heat storage system of the second comparative example, as described above, the heat capacity of the water in the tank is a constant 60 (kJ/K). As shown in FIG. 7, at 0 minutes, the water in the tank receives the supplied heat amount Q _in and the temperature rises. However, since the heat capacity of the water is 60 (kJ/K), which is the same as the heat capacity upper limit value C _max of the water in the tank 11 in the heat storage system 1 of this embodiment, the temperature rise rate is smaller than that of this embodiment and the first comparative example. Therefore, in the heat storage system of the second comparative example, the time when heat utilization starts is slower than that of the heat storage system 1 of this embodiment (time t31). On the other hand, since the heat capacity of the water in the tank is large, the time until the temperature of the water reaches the upper limit value T _max of the usable temperature is relatively long. The time when the surplus heat starts to be discarded in the second comparative example (time t32) is longer than that of the first comparative example, but shorter than that of this embodiment.

FIG. 8 is a diagram comparing values related to the operation when the heat utilization device starts in each of the heat storage systems shown in FIG. 5 to FIG. 7. FIG. 8(a) is a diagram comparing the time taken from when the supply heat amount Q _in becomes larger than 0 until the heat utilization device starts (hereinafter referred to as "start-up time"). FIG. 8(b) is a diagram comparing the amount of heat used by the heat utilization device to generate cold heat. As shown in FIG. 8(a), the start-up time of the heat utilization device was almost the same in this embodiment and the first comparative example (small heat capacity), but it was revealed that the second comparative example (large heat capacity) required more than three times as long as this embodiment. In addition, as shown in FIG. 8(b), it was revealed that the heat used by the heat utilization device to generate cold heat in the second comparative example was less because the start-up time was long.

FIG. 9 is a diagram for explaining the operation when the heat utilization device 30 of this embodiment is stopped. Next, the operation when the heat utilization device is stopped will be explained. In FIG. 9, the time when the supply heat amount _Qin becomes 0 is set to 0 minutes, and the time changes of the temperature _Ttmm of the water in the tank 11, the heat capacity _Ctmm of the water in the tank 11, the supply heat amount _Qin , the utilized heat amount _Qout , the waste heat amount _Qdum , and the dissipated heat amount _Qroo are shown. In the heat storage system 1 of this embodiment, as described above, the heat capacity of the heat storage device 10 is increased when the heat utilization device 30 is operating, and as shown in FIG. 9, the heat capacity of the heat storage device 10 is at a maximum of 60 (kJ/K). That is, the heat storage device 10 contains a relatively large amount of heat medium at a temperature that can be used by the heat utilization device 30. As a result, in the heat storage system 1, the heat utilization device 30 can be operated for a relatively long time by the heat of the water contained in the heat storage device 10. Therefore, it is clear that at time t41 after the supply heat quantity _Qin becomes 0, the absolute value of the utilized heat quantity _Qout begins to decrease, and at time t42, the heat utilization device 30 stops. Under the conditions of this simulation, the time t41 is about 10 minutes.

FIG. 10 is a diagram for explaining the operation when the heat utilization device of the first comparative example is stopped. In the heat storage system of the first comparative example, the heat capacity of the water in the tank is constant at 10 (kJ/K), so as shown in FIG. 10, the time t51 at which the absolute value of the utilized heat amount _Qout starts to decrease after the supplied heat amount _Qin becomes 0 is shorter than that of this embodiment. This is because the heat capacity of the water in the tank is smaller than the heat capacity of the water in the tank 11 when the heat utilization device 30 is stopped in this embodiment, so the heat of 60 (kJ) that allows the heat utilization device to operate cannot be supplied for a long time. Under the conditions of this simulation, the time t51 is about 3 minutes, which is about 1/3 of the time of this embodiment.

Fig. 11 is a diagram for explaining the operation when the heat utilization device of the second comparative example is stopped. In the heat storage system of the second comparative example, the heat capacity of the water in the tank is constant at 60 (kJ/K), so as shown in Fig. 11, the time t61 from when the supply heat amount _Qin becomes 0 to when the absolute value of the utilized heat amount _Qout starts to decrease is about the same length as in this embodiment. This is because the heat capacity of the water in the tank is the same as the heat capacity of the water in the tank 11 when the heat utilization device 30 in this embodiment is stopped. Under the conditions of this simulation, the time t61 is about 10 minutes.

FIG. 12 is a diagram comparing values related to the operation when the heat utilization device stops in each of the heat storage systems shown in FIG. 9 to FIG. 11. FIG. 12(a) is a diagram showing the time from when the supply heat amount Q _in becomes 0 until the heat utilization device stops (hereinafter referred to as "duration time"). FIG. 12(b) is a diagram comparing the amount of heat used to generate cold energy until the heat utilization device stops. As shown in FIG. 12(a), the duration was almost the same in this embodiment and the second comparative example (large heat capacity), but it was revealed that the duration was about 1/3 of that in the first comparative example (small heat capacity). In addition, as shown in FIG. 12(b), in a comparison of the heat that the heat utilization device could use to generate cold energy, it was revealed that the duration was short in the first comparative example, and therefore the heat that could be used to generate cold energy was also reduced.

Figure 13 is a diagram comparing the effects of heat storage systems. Figure 13 is a table summarizing the results of comparing the start-up time of the heat utilization device, the heat utilization at start-up, the duration of the heat utilization device, and the heat utilization at stop, as described in Figures 8 and 12. When the first comparative example, in which the heat capacity of the water in the tank is relatively small, is compared to the heat storage system 1, the characteristics at start-up ("start-up time" and "heat utilized at start-up") are comparable, but the characteristics at stop ("duration" and "heat utilized at stop") are inferior. Also, when the second comparative example, in which the heat capacity of the water in the tank is relatively large, is compared to the heat storage system 1, the characteristics at stop are comparable, but the characteristics at start-up are inferior. In this way, it has become clear that the heat storage system 1 of this embodiment has excellent characteristics of each of the first and second comparative examples.

According to the heat storage system 1 of the present embodiment described above, the heat capacity change device 40 changes the heat capacity of the heat storage device 10 by changing the amount of water stored in the heat storage device 10. For example, when the heat capacity of the heat storage device 10 is reduced, the temperature of the heat storage device 10 is easily increased, so that high-temperature water can be easily stored in the heat storage device 10 in a short time. As a result, high-temperature water can be supplied to the heat utilization device 30 in a short time, so that the heat utilization device 30, which operates by the supply of heat from the heat storage device 10, can be operated in a short time. In addition, when the heat capacity of the heat storage device 10 is increased, a relatively large amount of water at a temperature that the heat utilization device 30 can use is stored, so that even if the supply of heat from the heat supply device 20 becomes zero, water at a temperature at which the heat utilization device 30 can operate can be supplied for a relatively long time. In this way, by changing the heat capacity of the heat storage device 10, when the operation of the heat utilization device 30 is started, water at a temperature at which the heat utilization device 30 can operate can be supplied for a relatively long time while supplying water at a temperature at which the heat utilization device 30 can operate. This improves the startability of the heat utilization device 30 while extending its operating time.

In addition, according to the heat storage system 1 of this embodiment, the start-up time of the heat utilization device 30 is shortened and the operating time is extended, so that the time for utilizing the heat of the water stored in the heat storage device 10 is extended. This makes it possible to increase the amount of heat utilized to operate the heat utilization device 30 (total utilized heat amount), and to improve the ratio of utilized heat amount to the amount of heat supplied by the heat supply device 20.

In addition, according to the heat storage system 1 of this embodiment, by increasing the heat capacity of the heat storage device 10, water at a temperature at which the heat utilization device 30 can operate can be supplied to the heat utilization device 30 for a relatively long time. This reduces the effect of heat supply fluctuations accompanying fluctuations in the operating state of the heat supply device 20 on the operation of the heat utilization device 30. Therefore, the heat utilization device 30 can be operated stably. Furthermore, even if the heat supply device 20 stops, the heat utilization device 30 can be operated using the relatively large amount of hot water stored in the heat storage device 10, so the duration can be extended.

Furthermore, according to the heat storage system 1 of this embodiment, the heat capacity change device 40 reduces the amount of water contained in the heat storage device 10 by discharging at least a portion of the water contained in the heat storage device 10 from the heat storage device 10, thereby reducing the heat capacity of the heat storage device 10. Furthermore, the heat capacity change device 40 increases the amount of heat medium contained in the heat storage device by supplying a heat medium to the heat storage device from outside the heat storage system 1, thereby increasing the heat capacity of the heat storage device. As a result, the heat capacity of the heat storage device can be easily changed by supplying and discharging the heat medium to and from the heat storage device, so that it is easy to improve the start-up performance of the heat utilization device while also extending the operating time.

In addition, according to the heat storage system 1 of this embodiment, the control unit 50 changes the heat capacity of the heat device according to the relationship between the amount of water in the heat storage device 10 detected by the water amount sensor 51 and the available temperature of the heat utilization device 30. This makes it possible to change the heat capacity so that the temperature of the water stored in the heat storage device 10 matches the available temperature of the heat utilization device 30, thereby ensuring both improved start-up performance and longer operating times for the heat utilization device 30.

In addition, according to the heat storage system 1 of this embodiment, when the heat supply device 20 is stopped, the control unit 50 makes the heat capacity of the heat storage device 10 relatively smaller than when the heat supply device 20 is operating. This makes it easier for the temperature of the heat storage device 10 to rise, making it easier to store high-temperature water in the heat storage device 10 in a short period of time. Therefore, high-temperature water can be supplied to the heat utilization device 30 in an even shorter period of time, further improving the start-up performance of the heat utilization device 30.

In addition, according to the heat storage system 1 of this embodiment, when the heat utilization device 30 is stopped, the control unit 50 discharges at least a portion of the water stored in the heat storage device 10 from the heat storage device 10, thereby making the heat capacity of the heat storage device 10 relatively smaller than when the heat utilization device 30 is operating. As a result, the amount of water stored in the heat storage device 10 is reduced, so that even if newly heated water by the heat supply device 20 is stored in the heat storage device 10, the temperature of the water stored in the heat storage device 10 is unlikely to drop. In other words, the high-temperature water supplied to the heat storage device 10 by the heat supply device 20 is stored in the heat storage device 10 while remaining at a high temperature. As a result, when the heat utilization device 30 is started, water at an operable temperature can be quickly supplied, thereby further improving the start-up performance of the heat utilization device 30.

In addition, according to the heat storage system 1 of this embodiment, when the heat utilization device 30 is operating, the control unit 50 increases the amount of water stored in the heat storage device 10 by supplying water to the heat storage device 10, and makes the heat capacity of the heat storage device 10 relatively larger than when the heat utilization device 30 is stopped. The water stored in the heat storage device 10 is heated by the heat supply device 20 and is stored again in the heat storage device 10, so that the heat storage device 10 can store a relatively large amount of water at a temperature at which the heat utilization device 30 can be operated while the heat utilization device 30 is operating. As a result, for example, even if the supply of heat from the heat supply device 20 is stopped and there is a fluctuation in the heat supply from the heat supply device 20 to the heat storage device 10, the heat supply to the heat utilization device 30 is unlikely to fluctuate, so the heat utilization device 30 can be operated continuously. Therefore, the operating time of the heat utilization device 30 can be further extended.

In addition, according to the heat storage system 1 of this embodiment, the control unit 50 changes the heat capacity of the heat storage device 10 depending on the operating status of the heat utilization device 30. For example, as shown in FIG. 5, immediately after the heat utilization device 30 starts operating, the heat capacity of the heat storage device 10, which has a relatively small heat capacity, is increased by supplying water to the heat storage device 10. As a result, as shown in FIG. 9, even after the supply of heat from the heat supply device 20 is cut off, water with enough heat to operate the heat utilization device 30 can be supplied for a long period of time. Therefore, the start-up ability of the heat utilization device 30 can be further improved, and the operation time of the heat utilization device 30 can be further extended.

In addition, according to the heat storage system 1 of this embodiment, the heat storage device 10 includes a single tank 11 for storing water. For example, if multiple tanks with different heat capacities are included, a configuration is required in which the supply device switches between tanks that supply heat medium, and a configuration is required in which the supply device switches between tanks that supply heat medium to the heat utilization device, which makes the configuration more complex and the system larger. In the heat storage system 1, the heat capacity of the heat storage device 10 can be changed by changing the amount of water in the single tank 11, so that it is possible to improve the start-up ability of the heat utilization device 30 and extend its operating time with a simple configuration.

Second Embodiment
Fig. 14 is a schematic diagram showing a schematic configuration of a heat storage system according to a second embodiment. A heat storage system 2 according to the second embodiment is different from the heat storage system 1 according to the first embodiment (Fig. 1) in that the heat storage system 2 according to the second embodiment includes a configuration for circulating the heat medium discharged from the heat storage device.

The heat storage system 2 of the second embodiment includes a heat storage device 10, a heat supply device 20, a heat utilization device 30, a heat capacity change device 40, a control unit 50, and a heat medium supply device 60.

The heat medium supply device 60 is connected to the heat storage device 10 and the supply side flow path 12. The heat medium supply device 60 includes a storage section 61 and a connection flow path 62.

The storage unit 61 is connected to the heat transfer medium discharge flow path 41 of the heat capacity change device 40. The storage unit 61 is a tank capable of storing water, and temporarily stores the water discharged from the heat storage device 10 via the heat transfer medium discharge flow path 41.

The connection flow path 62 is connected to the storage section 61 and the supply side flow path 12. The connection flow path 62 is provided with a pump 62a that pumps a portion of the water stored in the storage section 61 toward the supply side flow path 12, and a valve 62b that allows or blocks the flow of water in the connection flow path 62. The connection flow path 62 supplies a portion of the water stored in the storage section 61 to the supply side flow path 12. The pump 62a and the valve 62b are electrically connected to the control section 50.

In the heat storage system 2, when the heat capacity of the heat storage device 10 is changed, the water discharged from the heat storage device 10 is stored in the storage section 61. A part of the water stored in the storage section 61 is returned to the supply side flow path 12 via the connection flow path 62 in response to a command from the control section 50. The water returned to the supply side flow path 12 is heated by the heat supply device 20 and stored in the heat storage device 10, and is used as a heat source when the heat utilization device 30 is operating.

According to the heat storage system 2 of this embodiment described above, at least a part of the water discharged from the heat storage device 10 to change the heat capacity of the heat storage device 10 is supplied to the supply side flow path 12. The water supplied to the supply side flow path 12 is heated by the heat supply device 20 in the supply side flow path 12 and then stored in the heat storage device 10. If the water discharged from the heat storage device 10 has been heated at least once in the heat supply device 20, the temperature is often relatively high even if the temperature is not at which the heat utilization device 30 can operate. As a result, when the water supplied from the heat medium supply device 60 to the supply side flow path 12 is heated by the heat supply device 20, it is possible to make the temperature at which the heat utilization device 30 can operate with a relatively small amount of heat. Therefore, since the heat of the water discharged from the heat storage device 10 can be reused, the heat utilization rate in the heat storage system 2 can be improved.

<Modifications of this embodiment>
The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit and scope of the invention. For example, the following modifications are also possible.

[Modification 1]
In the above embodiment, when changing the heat capacity of the heat storage device 10, the water in the tank 11 is discharged to the outside of the tank 11, or external water is supplied to the tank 11. However, the method of changing the amount of water in the tank 11 is not limited to this. It is sufficient if the amount of water flowing through the flow path formed by the supply side flow path 12, the utilization side flow path 13, and the inside of the tank 11 can be changed, and in the above embodiment, for example, in order to reduce the heat capacity, the heat medium removed from the heat storage device may be accommodated in a position where it is not circulated by the two pumps 12a and 13a.

[Modification 2]
In the above embodiment, the heat capacity of the heat storage device 10 is changed based on the detection value of the water volume sensor 51 of the tank 11 using the calculation process shown in Fig. 2 and Fig. 3. However, the calculation process for changing the heat capacity of the heat storage device 10 is not limited to this. For example, the heat capacity of the heat storage device 10 may be changed based on the amount of water flowing into the tank 11 and the amount of water discharged from the tank 11.

[Modification 3]
In the above embodiment, the control unit 50 relatively reduces the heat capacity of the heat storage device 10 when the heat supply device 20 is stopped or when the heat utilization device 30 is stopped. However, the timing for relatively reducing the heat capacity of the heat storage device 10 is not limited to this. It is desirable for the heat capacity of the heat storage device 10 to be relatively small immediately before the heat utilization device 30 starts operating. This is because, even if the heat supply device 20 starts in conjunction with the start of the heat utilization device 30 and high-temperature water is supplied to the heat storage device 10, the water is stored in the heat storage device 10 while still at a high temperature, and water at an operable temperature can be quickly supplied.

[Modification 4]
In the above embodiment, the control unit 50 reduces the heat capacity of the heat storage device 10 when the heat supply device 20 is stopped compared to when the heat supply device 20 is operating. In this case, the condition for reducing the heat capacity of the heat storage device 10 may be set to reduce the heat capacity of the heat storage device 10 when the heat supply device 20 is stopped and is scheduled to continue to be stopped in the future.

[Modification 5]
In the above-described embodiment, the control unit relatively increases the heat capacity of the heat storage device 10 when the heat utilization device 30 is operating, as shown in Fig. 5 and Fig. 9. However, the timing for relatively increasing the heat capacity of the heat storage device 10 is not limited to this. It is desirable for the heat capacity of the heat storage device 10 to be relatively large immediately before the heat supply device 20 is stopped. This is because a relatively large amount of water at a temperature at which the heat utilization device 30 can be operated can be stored.

[Modification 6]
In the above embodiment, the heat medium is water. However, the type of heat medium is not limited to this. The heat medium may be, for example, an aggregate of solid particles or a combination of water and a solid object. In the case of a combination of water and a solid object, heat exchange with a heat supply device or a heat utilization device is performed by flowing water, and heat may be temporarily stored in the heat storage device by heat exchange between the solid object contained in the heat storage device and the water. In this case, the heat capacity of the heat storage device can be changed by removing a part of the solid object contained in the heat storage device from the heat storage device or by putting a new solid object into the heat storage device.

[Modification 7]
In the second embodiment, the storage section 61 of the heat medium supplying device 60 is connected to the heat medium discharge flow path 41 of the heat capacity change device 40. The storage section 61 may also be connected to the heat medium intake flow path 42. This makes it possible to return the water stored in the storage section 61 to the heat storage device 10 when the heat capacity of the heat storage device 10 is increased. Since the water stored in the storage section 61 is often at a temperature higher than room temperature, the heat capacity of the heat storage device 10 can be increased without significantly lowering the temperature of the heat storage device 10.

Although this aspect has been described above based on the embodiment and modified examples, the embodiment of the above-mentioned aspect is intended to facilitate understanding of this aspect and does not limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and this aspect includes equivalents. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

Reference Signs List 1, 2...Heat storage system 10...Heat storage device 11...Tank 12...Supply side flow path 12a, 13a...Pump 13...Use side flow path 20...Heat supply device 30...Heat utilization device 40...Heat capacity change device 41...Heat medium discharge flow path 42...Heat medium intake flow path 50...Control unit 51...Water volume sensor 52...Water temperature sensor 60...Heat medium supply device C _hsd ...Heat capacity of heat storage device

Claims (5)

1. A thermal storage system comprising:
A heat storage device that accommodates a heat medium;
a heat supply device that heats a heat medium circulating through a first circulation flow path connected to the heat storage device and supplies the heated heat medium to the heat storage device, the heat supply device having a first heat medium that exchanges heat with the heat medium circulating through the first circulation flow path;
a heat utilization device that operates using heat of a heat medium supplied from the heat storage device through a second circulation flow path connected to the heat storage device, the heat utilization device having a second heat medium that exchanges heat with the heat medium supplied from the heat storage device;
a pump that circulates a heat medium between the first circulation flow path, the second circulation flow path, and the heat storage device;
a heat capacity change device that changes the amount of heat medium contained in the heat storage device to change the heat capacity of the heat storage device;
a heat capacity detection unit for detecting a value related to a heat capacity of the heat storage device;
a control unit that changes the heat capacity of the heat storage device according to a relationship between a value related to the heat capacity of the heat storage device detected by the heat capacity detection unit and a value that is preset as a target value ;
The heat capacity change device is
Reducing the heat capacity of the heat storage device by discharging at least a portion of the heat medium contained in the heat storage device from the heat storage device;
A heat medium is supplied to the heat storage device from outside the heat storage system to increase the heat capacity of the heat storage device;
When the heat supply device is stopped, the control unit relatively reduces the heat capacity of the heat storage device compared to when the heat supply device is operating, regardless of a relationship between the value related to the heat capacity of the heat storage device detected by the heat capacity detection unit and the target value.
Heat storage system. The thermal storage system according to claim 1 ,
The control unit, when the heat utilization device is stopped, makes the heat capacity of the heat storage device relatively smaller than that when the heat utilization device is operating.
Heat storage system. The thermal storage system according to claim 1 ,
The control unit changes the heat capacity of the heat storage device according to an operating condition of the heat utilization device.
Heat storage system. The heat storage system according to any one of claims 1 to 3 further comprises:
a heat medium supplying device connected to the heat storage device and the first circulation flow path and configured to supply at least a portion of the heat medium discharged from the heat storage device to the first circulation flow path;
The heat medium supplied to the first circulation flow path by the heat medium supply device is heated by the heat supply device in the first circulation flow path and then stored in the heat storage device.
Heat storage system. A heat storage system according to any one of claims 1 to 4 ,
The heat storage device includes a single tank for storing the heat medium.
Heat storage system.

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