Heat storage system and heat storage method

Abstract

To provide a heat storage system and a heat storage method which is capable of suppressing reduction of heat storage amount upon heat storage operation and heat release amount upon heat release operation.SOLUTION: A heat storage system concerning this embodiment form includes a heat storage tank group. The heat storage tank group connects an upstream side heat storage tank and a downstream side heat storage tank in series with respect to a flow of fluid upon heat storage operation, presets a first heat storage tank incorporating a solid sensible heat storage material, and arranges a second heat storage tank incorporating a latent heat storage material as the downstream side heat storage tank on the lowermost downstream. Upon the heat storage operation, fluid is caused to flow in the order of the first heat storage tank and the second heat storage tank, all or a part of heat quantity accumulated on solid sensible heat storage material and latent heat storage material is dissipated onto the fluid, and it is characterized that the phase change temperature of the latent heat accumulation material is lower than the heat accumulation temperature of the solid sensible heat accumulation material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE An embodiment of the present invention relates to a heat storage system and a heat storage method. [Background technology]

[0002] In recent years, power generation from natural energy sources such as solar power generation and wind power generation has been increasing, and there are regions where the amount of power generation is greater than the power demand depending on the season and time of day. In addition, there are times when the power demand is high depending on the season and time of day, and the amount of power generation is less than the power demand, resulting in a power shortage. In view of this, there is a conventional technology (see Patent Document 1) that uses heat storage to adjust power, which will be described with reference to Figs. 6 to 8.

[0003] FIG. 6 is a diagram showing a configuration example of a power conditioning system 1 including a thermal storage system 100 according to the conventional technology. A pump 45, a condenser 46, a steam turbine 47, and a boiler 48 are configured in the pipe L1. Pipes L2 and L3 are joined between the joints n1 and n2. Furthermore, a pipe L4 is joined between the joint n1 and the thermal storage tank 38. Furthermore, a pipe L5 is joined between the joint n1 and the thermal storage tank 38. The thermal storage system 100 includes a thermal storage tank 380, an electric heater 39, a first fan 40, a second fan 41, valves 49 to 52, and a boiler 48 to which heat is supplied.

[0004] When there is a surplus of electricity, the pump 45, the steam turbine 47, the generator 47a, and the second blower 410 are stopped. Then, the valves 49 and 50 are opened and the valves 51 and 52 are closed, and the electric heater 390 and the first blower 400 are operated using the surplus electricity. At this time, the first blower 400 circulates the air 5 between the electric heater 390 and the heat storage tank 380. The air 5 is heated by the heat generated by the electric heater 390, and the air 5 transports the heat to the heat storage tank 380 and heats the heat storage material in the heat storage tank 380. The heat storage material is a solid sensible heat storage material 23, such as rock. Heat is stored in this way. The solid arrow indicates the air flow direction 32 during heat storage operation, and the dotted arrow indicates the air flow direction 33 during heat dissipation operation.

[0005] When there is no surplus power, the electric heater 390 and the first blower 400 are stopped, the valves 49 and 50 are closed, the valves 51 and 52 are opened, and the pump 45 and the second blower 410 are operated. The second blower 410 circulates the air 5 between the heat storage tank 380 and the boiler 48. The air 5 is heated by the heat storage material in the heat storage tank 380, and transports the heat to the boiler 48. In the boiler 48, the water 43 brought in by the pump 45 is heated by the heat from the air 5 to produce steam 44, and the air 5 is cooled and discharged. In this way, the heat dissipation operation is performed. The steam 44 flows through the steam turbine 47 at a low temperature and low pressure, thereby rotating the steam turbine 47, which is an impeller, and the generator 47a mechanically connected to the steam turbine 47 generates electricity. The steam discharged from the steam turbine 47 is cooled by cooling water, for example seawater, in the condenser 46, changing into water 43, which is then circulated. As a result, steam 44 is generated using the heat stored in the heat storage material in the heat storage tank 380, and electricity is generated. In this way, power adjustment is performed by using electricity when there is a power surplus, and generating electricity when there is no power surplus.

[0006] FIG. 7 is a diagram showing the state inside the heat storage tank 380 of the heat storage system 100 according to the conventional technology. FIG. 7(a) shows the flow direction of the air 5 in the heat storage tank 380, and FIG. 7(b) shows the temperature distribution in the heat storage tank 380. The horizontal axis shows the position in the heat storage tank 380, and the vertical axis shows the temperature of the solid sensible heat storage material 23, and the temperature of the air 5 in the vicinity is almost the same. During the heat storage operation, a thermocline 26 showing a steep temperature gradient in the flow direction is formed inside the heat storage tank 380, which moves from the upstream side to the downstream side, and the heat storage operation ends when the temperature of the air 5 flowing out of the heat storage tank 380 rises to, for example, the heat resistance temperature of the first blower 400 or the valve 50. FIG. 7(b) shows the temperature distribution of the solid sensible heat storage material 23 in the heat storage tank 380 at the end of the heat storage operation in the first heat storage operation. The lines drawn in FIG. 7(b) represent temperatures. The first heat storage temperature 24 is an example during the heat storage operation. The heat storage temperature rises to the second heat storage temperature 25, and the thermocline 26 reaches the outlet during the heat storage operation. The graph lines of the first heat storage temperature 24 and the second heat storage temperature 25 each include the thermocline 26. When the heat storage tank outlet temperature reaches the heat storage operation end temperature 27, the heat storage operation ends.

[0007] 8A and 8B are diagrams showing the state inside the heat storage tank 380 during heat dissipation operation of the heat storage system 100 according to the conventional technology. Fig. 8(a) shows the flow direction of the air 5 in the heat storage tank 380, and Fig. 8(b) shows the temperature distribution in the heat storage tank 380.

[0008] During the long period between the end of the heat storage operation and the start of the heat dissipation operation, the heat storage tank 380 is left alone, during which the temperature distribution changes from the second heat storage temperature 25, and becomes like the third temperature 55 in FIG. 8(b) at the start of the heat dissipation operation. The graph line of the third temperature 55 includes the horizontal portion of the dashed dotted line. The temperature drops in the relatively high temperature region, and rises in the relatively low temperature region, and the temperature is averaged. The steep thermocline 26 becomes like the sloping line portion of the third temperature 55.

[0009] During the heat dissipation operation, the air 5 is circulated in the opposite direction to that during the heat storage operation. The third temperature 55 shown in FIG. 8(b) is the start of the heat dissipation operation, and the fourth temperature 18 is the end of the heat dissipation operation. The graph line of the fourth temperature 18 includes the thermocline 26a to which the inclined portion of the third temperature 55 has moved, and a steep thermocline portion that occurred at the start of the heat dissipation operation. From the inclination of the thermocline 26, the thermocline including the more averaged thermocline 26a moves from the upstream side to the downstream side in the heat dissipation operation, and the heat dissipation operation ends when the outlet temperature of the heat storage tank during the heat dissipation operation reaches the heat dissipation operation end temperature 31. The heat dissipation operation end temperature 31 is an allowable temperature on the heat demand side, such as the minimum temperature required for the operation of the boiler 48. In the conventional technology, the heat dissipated from the heat storage system 100 is used as a heat source for the steam turbine 47, but it may also be used for purposes such as air conditioning. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent Publication No. 2021-1597 Summary of the Invention [Problem to be solved by the invention]

[0011] In the heat storage operation, since the heat storage is terminated leaving a thermocline inside the heat storage tank 380, the solid sensible heat storage material 23 near the outlet does not reach the heat storage temperature, and the heat storage in the heat storage tank 380 cannot be filled to capacity. For this reason, there is a problem that it is desirable to increase the amount of heat stored in the heat storage tank 380. In addition, since the thermocline averages out during a long period of time left unattended after the end of the heat storage operation, the time at which the heat dissipation operation end temperature is reached during the heat dissipation operation becomes earlier, and the amount of heat dissipation decreases. For this reason, there is a problem that it is desirable to increase the amount of heat dissipation from the heat storage tank 380.

[0012] An object of the present invention is to provide a heat storage system and a heat storage method capable of suppressing a decrease in the amount of heat stored in a heat storage tank during a heat storage operation and a decrease in the amount of heat released during a heat release operation. [Means for solving the problem]

[0013] The heat storage system according to the present embodiment includes a heat storage tank group. The heat storage tank group is connected in series with respect to the flow of fluid during heat storage operation between an upstream heat storage tank composed of one or more heat storage tanks and a downstream heat storage tank composed of one or more heat storage tanks, with the first heat storage tank containing a solid sensible heat storage material as the upstream heat storage tank, and the second heat storage tank containing a latent heat storage material as the downstream heat storage tank, which is disposed at the most downstream position. During heat storage operation, the fluid is circulated in the order of the first heat storage tank and the second heat storage tank, and all or a part of the heat held in the fluid is absorbed and stored, and during heat dissipation operation, the fluid is circulated in the opposite direction to that during heat storage operation, and all or a part of the heat stored in the solid sensible heat storage material and the latent heat storage material is dissipated to the fluid, and the phase change temperature of the latent heat storage material is lower than the heat storage temperature of the solid sensible heat storage material. Effect of the Invention

[0014] According to this embodiment, it is possible to suppress a decrease in the amount of stored heat during the heat storage operation and a decrease in the amount of released heat during the heat release operation. [Brief description of the drawings]

[0015] [Figure 1]FIG. 2 is a diagram showing an example of the configuration of a first heat storage tank and a second heat storage tank according to the first embodiment. [Diagram 2] 4 is a diagram showing an example of air flow direction and temperature distribution during heat storage operation of the heat storage tank according to the first embodiment. FIG. [Diagram 3] FIG. 11 is a diagram showing an example of the configuration of a first heat storage tank and a second heat storage tank according to a second embodiment. [Figure 4] FIG. 11 is a diagram showing an example of the configuration of a first heat storage tank and a second heat storage tank according to a third embodiment. [Diagram 5] FIG. 13 is a diagram showing an example of the configuration of a first heat storage tank and a second heat storage tank according to a fourth embodiment. [Figure 6] FIG. 1 is a diagram showing an example of the configuration of a power adjustment system including a thermal storage system according to a conventional technique. [Figure 7] FIG. 13 is a diagram showing a state inside a heat storage tank during a heat storage operation of a heat storage system according to a conventional technique. [Figure 8] FIG. 13 is a diagram showing a state inside a heat storage tank during a heat dissipation operation of a heat storage system according to a conventional technique. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments.

[0017] (First embodiment) A first embodiment corresponding to claims 1, 4, and 5 will be described with reference to Fig. 1. Note that the same numbers are used to denote parts that are the same as those in the prior art, and the description thereof may be omitted.

[0018] The heat storage system 100 according to this embodiment includes an electric heater 39, a first fan 40, a second fan 41, valves 49 to 52, and a boiler 48 to which heat is supplied, and replaces the heat storage tank 380 in FIG. 6 with a heat storage tank group 2. The heat storage tank group 2 according to this embodiment is composed of a first heat storage tank 29 and a second heat storage tank 30. The fluid that is the heat medium is air 5. FIG. 1 is a diagram showing a configuration example of the first heat storage tank 29 and the second heat storage tank 30 according to the first embodiment. As shown in FIG. 1, the first heat storage tank 29 and the second heat storage tank 30 according to the first embodiment divide the solid sensible heat storage tank 380 in the conventional technology in series in the air flow direction. The heat storage tank group 2 according to this embodiment may be divided any number of times, but in the example of FIG. 1, it is divided into two parts, the first heat storage tank 29 on the upstream side and the second heat storage tank 30 on the downstream side, with respect to the air flow during heat storage operation. The first heat storage tank 29, which is the heat storage tank other than the most downstream one, is a sensible heat storage tank containing a solid sensible heat storage material 23. The second heat storage tank 30, which is the most downstream heat storage tank, is a latent heat storage tank containing a latent heat storage material.

[0019] In this manner, the first heat storage tank 29, which is a sensible heat storage tank, and the second heat storage tank 30, which is a latent heat storage tank, are connected in the order of air flow during heat storage operation. Note that, in Fig. 1, an example in which the heat storage tank 380 is divided into the first heat storage tank 29 and the second heat storage tank 30 is described, but this is not limiting. For example, the sensible heat storage tank portion may be divided into two or more parts, or the latent heat storage tank portion may be divided into two or more parts.

[0020] The latent heat storage material absorbs heat when it changes phase from solid to liquid or from liquid to gas. The temperature is constant at the melting point when solid and liquid are mixed, and at the boiling point when liquid and gas are mixed. In the second heat storage tank 30 according to the first embodiment, for example, a latent heat storage material that changes phase from solid to liquid is used. The latent heat storage material in the liquid state is the first latent heat storage material (liquid) 38, and the latent heat storage material in the solid state is the first latent heat storage material (solid) 39.

[0021] The phase change temperature of the first latent heat storage material 38, 39 is the melting point, and the material of the first latent heat storage material 38, 39 is selected so that the melting point is lower than the heat storage temperature of the solid sensible heat storage material 23. The material is, for example, paraffin. In the second heat storage tank 30 according to the first embodiment, at the melting point, during heat storage operation, a solid in an amount corresponding to the amount of heat is melted and undergoes a phase change to liquid, and during heat dissipation operation, a liquid in an amount corresponding to the amount of cooling is condensed and undergoes a phase change to solid. At this time, the change in density between the liquid and solid is small, and since there is a small amount of air in the second heat storage tank 30, the second heat storage tank 30 is not deformed by the expansion and contraction of the contents.

[0022] Fig. 2 is a diagram showing an example of the flow direction of air 5 and temperature distribution during heat storage operation of heat storage tank 380 according to the first embodiment. Fig. 2(a) is a diagram showing the flow direction of air 5 during heat storage operation of heat storage tank 380. Fig. 2(b) is a diagram showing an example of temperature distribution in heat storage tank 380 after heat dissipation operation.

[0023] As shown in Fig. 2(a), during heat storage operation, air 5 flows through first heat storage tank 29 and then second heat storage tank 30. During heat storage operation, air 5 flows through first heat storage tank 29, heats solid sensible heat storage material 23, and is stored in solid sensible heat storage material 23. At this time, the heat storage temperature of solid sensible heat storage material 23 and the temperature of air 5 are approximately the same. Air 5 flowing out of first heat storage tank 29 flows into second heat storage tank 30. As the heat storage operation progresses and the thermocline reaches the position of the thermocline 26 of the second heat storage temperature 25 in the conventional technology (the position also depicted by the dotted thermocline 26 in FIG. 2(b)), the air 5 flowing out of the first heat storage tank 29 has reached the heat storage temperature end temperature 27, but in the second heat storage tank 30, the air temperature drops as the fourth air temperature 28 while heating the first latent heat storage material 39 (38), becoming lower than the heat storage temperature end temperature 27 and flowing out of the second heat storage tank 30, so the heat storage operation continues. The outlet temperature of the second heat storage tank 30 is the phase change temperature 22 of the first latent heat storage materials 38, 39.

[0024] As the heat storage operation continues, the air 5 near the outlet of the first heat storage tank 29 has a first air temperature 36, which is almost the same temperature as the fixed sensible heat storage material 23, and in the second heat storage tank 30 has a second air temperature 37. As the heat storage operation continues, the air 5 inside the second heat storage tank 30 has a third air temperature 21, and the outlet temperature of the second heat storage tank 30 reaches the heat storage operation end temperature 27, and the heat storage operation ends. At this time, the heat storage temperature of the solid sensible heat storage material 23 is the fifth heat storage temperature 19. The heat storage temperature of the latent heat storage materials 38, 39 is the sixth heat storage temperature 20, which is the phase change temperature 22 of the first latent heat storage material 38, 39.

[0025] 2(b), there is no thermocline at the fifth heat storage tank 19, and the heat storage temperature is reached in all areas up to the solid sensible heat material 23 near the outlet, so the heat storage is full. Therefore, the amount of heat stored in the first heat storage tank 29, which is a solid sensible heat storage tank, is increased while the outlet temperature of the second heat storage tank 30 is kept low.

[0026] As described above, in contrast to the conventional technology shown in FIG. 8, when the heat storage operation is completed, there is no thermocline in the first heat storage tank 29 according to this embodiment, so the thermocline does not average out during the long period of time left after the heat storage operation is completed, and the entire region is maintained at a high heat storage temperature. Therefore, when the thermocline 26 occurs in the first heat storage tank 29 during the heat dissipation operation, it becomes steep, and the thermocline 26 moves from the upstream side to the downstream side in the heat dissipation operation, and when the heat storage tank outlet temperature during the heat dissipation operation reaches the heat dissipation operation end temperature 31, the thermocline 26 that rises steeply is maintained. Therefore, the heat dissipation time is longer. Since there is no gentle part in the thermocline in this embodiment, at the time corresponding to the fourth temperature 18 (see FIG. 8) according to the conventional technology, there is no gentle thermocline 26a, and all are steep, so the heat storage tank outlet temperature during the heat dissipation operation is the same temperature as the second heat storage temperature 25, and does not reach the heat dissipation operation end temperature 31. In this way, at the end of the heat storage operation, since there is no thermocline in the first heat storage tank 29 in this embodiment, more heat is stored, and during the heat dissipation operation, the heat dissipation time is longer, allowing more heat to be dissipated.

[0027] In the second heat storage tank 30, which is a latent heat storage tank, the first latent heat storage material 38, 39 stores latent heat, and also stores sensible heat from the outside temperature (for example, atmospheric temperature) to the phase change temperature. During the heat dissipation operation, since the second heat storage tank 30 is located upstream of the first heat storage tank 29, the lower temperature heat stored in the second heat storage tank 30 is also taken out and effectively used. As a result, the second heat storage tank 30, which is a latent heat storage tank, can store an amount of heat that could not be stored by sensible heat storage alone, which also has the effect of increasing the amount of stored heat and the amount of released heat. In this way, the effect of increasing the amount of stored heat and the amount of released heat of the solid sensible heat storage tank, and increasing the amount of stored heat and the amount of released heat of the entire heat storage tank can be obtained. In this embodiment, the heat medium is air 5, but it may be a gas other than air or a liquid. The heat dissipated from the heat storage system 100 may be used as a heat source for the steam turbine 47, or may be used for air conditioning or other purposes.

[0028] As described above, according to this embodiment, the first heat storage tank 29, which is a sensible heat storage tank, and the second heat storage tank 30, which is a latent heat storage tank, are connected in series in the order of the flow of air 5 during heat storage operation, and air 5, which is a high-temperature heat medium, is circulated from the first heat storage tank 29 side to the second heat storage tank 30 during heat storage operation. In addition, the substances of the first latent heat storage materials 38 and 39 are selected so that the phase change temperature 22 is lower than the heat storage temperature of the solid sensible heat storage material 23. This makes it possible to maintain the temperature of the air 5 discharged from the second heat storage tank 30 at or below the heat storage operation end temperature 27 until the heat storage in the first heat storage tank 29 becomes full, and thus makes it possible to suppress a decrease in the amount of heat storage during heat storage operation. Furthermore, in this way, when the heat storage is completed, the first heat storage tank 29 according to this embodiment is full of heat storage, and there is no thermocline, so the thermocline does not average out, and the high heat storage temperature can be maintained in the entire region even when left for a long time after the heat storage operation. Therefore, in the heat dissipation operation, when the heat storage tank outlet temperature during the heat dissipation operation reaches the heat dissipation operation completion temperature 31, the thermocline 26 has a steep temperature gradient and is not gradual, so the heat dissipation time is longer and more heat can be dissipated.

[0029] Second embodiment The heat storage system 100 according to the second embodiment differs from the heat storage system 100 according to the first embodiment in that a first valve 16 is provided in a flow path between the first heat storage tank 29 and the second heat storage tank 30. The differences from the heat storage system 100 according to the first embodiment will be described below.

[0030] A second embodiment corresponding to claims 1, 2, 4, and 5 will be described with reference to Fig. 3. Fig. 3 is a diagram showing an example of the configuration of a first heat storage tank 29 and a second heat storage tank 30 according to the second embodiment. As shown in Fig. 3, a heat storage system 100 according to the second embodiment has a first heat storage tank 29, a second heat storage tank 30, and a first valve 16.

[0031] When the system is left unused for a long time after the end of the heat storage operation, the first valve 16 is closed. This prevents the temperature of the outlet side of the first heat storage tank 29 from dropping due to heat transfer from the outlet side of the first heat storage tank 29 during the heat storage operation to the second heat storage tank 30, which has a lower temperature. The retention of heat stored in the second heat storage tank 30 is further strengthened, and it becomes possible to prevent temperature distribution from occurring in the second heat storage tank 30. In this embodiment, the fluid that is the heat medium is air 5, but it may be a gas other than air or a liquid. The heat dissipated from the heat storage system 100 may be used as a heat source for the steam turbine 47, or may be used for purposes such as air conditioning.

[0032] Third embodiment The heat storage system 100 according to the third embodiment differs from the heat storage system 100 according to the second embodiment in that a second valve 17 is provided in the outlet side pipe L5 during the heat storage operation of the second heat storage tank 30. The differences from the heat storage system 100 according to the second embodiment will be described below.

[0033] A third embodiment corresponding to claims 1, 2, 3, 4, and 5 will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of the configuration of a first heat storage tank 29 and a second heat storage tank 30 according to the third embodiment. As shown in Fig. 4, a second valve 17 is further provided in the outlet side pipe L5 during the heat storage operation of the second heat storage tank 30.

[0034] During the heat storage operation, the downstream pipe L5 is at approximately the same temperature as the vicinity of the outlet of the second heat storage tank 30. However, if the system is left for a long time after the end of the heat storage operation, heat leaks to the outside world (e.g., the atmosphere) which has a lower temperature, and the temperature of the pipe L5 drops, so that heat may leak from the first latent heat storage materials 38, 39 near the outlet of the second heat storage tank 30 to the pipe L5. For this reason, the second valve 17 is closed when the system is left for a long time after the end of the heat storage operation. This suppresses heat leakage from the outlet side of the second heat storage tank 30 to the pipe L5, and the retention of heat stored in the second heat storage tank 30 is further strengthened.

[0035] (Fourth embodiment) The heat storage system 100 according to the fourth embodiment differs from the heat storage systems 100 according to the first to third embodiments in that the latent heat storage material in the second heat storage tank 30 is a substance that absorbs heat when it changes phase from liquid to gas. The differences from the heat storage systems 100 according to the first to third embodiments will be described below.

[0036] A fourth embodiment corresponding to claims 1, 2, 3, and 5 will be described with reference to FIG. 5. FIG. 5 is a diagram showing an example of the configuration of a first heat storage tank 29 and a second heat storage tank 30 according to the fourth embodiment. As shown in FIG. 5, the latent heat storage material of the second heat storage tank 30 is a substance that absorbs heat when it changes phase from liquid to gas. The gas state is the second latent heat storage material (gas) 34, and the liquid state is the second latent heat storage material (liquid) 35. In addition, a gas 40 is built into the second heat storage tank 30. The valves 16 and 17 may not be provided, as in the first and second embodiments.

[0037] The phase change temperature of the second latent heat storage materials 34, 35 is the boiling point, and the material of the second latent heat storage materials 34, 35 is selected so that the boiling point is lower than the heat storage temperature of the solid sensible heat storage material 23. This material is, for example, water. The boiling point is 100°C at atmospheric pressure, and the higher the pressure, the higher the boiling point becomes, but in practice, the boiling point does not become drastically high. At the boiling point, during heat storage operation, an amount of liquid water corresponding to the amount of heating boils and changes phase to gaseous vapor, and during heat dissipation operation, an amount of gaseous vapor corresponding to the amount of cooling condenses and changes phase to liquid water.

[0038] Now, the first latent heat storage materials 38, 39 in Example 1 have a small change in density between liquid and solid, so the second heat storage tank 30 does not deform due to expansion and contraction of the contents. However, since the second latent heat storage material (gas) 34 is a gas, when the second heat storage tank 30 is heated under a condition where the internal volume of the second heat storage tank 30 is constant, the pressure becomes sufficiently large as the temperature rises. Therefore, the second heat storage tank 30 contains a sufficient amount of gas 40 together with the second latent heat storage materials 34, 35. The gas 40 is, for example, air, and may be any substance that is in a gaseous state at the temperature experienced by the second latent heat storage materials 34, 35.

[0039] If, in the pre-heating state, the second latent heat storage material (liquid) 35 is the majority, the number of moles of the second latent heat storage material (gas) 34 is small, and the number of moles of the gas 40 is 100 times the number of moles of the second latent heat storage material (gas) 34, then even if the number of moles of the second latent heat storage material (gas) 34 increases 100 times, the number of moles of the mixed gas of the second latent heat storage material (gas) 34 and the gas 40 only becomes slightly less than twice as large. In addition, since the end-of-heat-storage-operation temperature 27 is a height determined to protect the valves and the blower, the absolute temperature of the mixed gas of the second latent heat storage material (gas) 34 and the gas 40 at the end of the heat storage operation is less than twice that at the start of the heat storage operation. Since the pressure at a constant volume is mostly dependent on the total number of moles and the temperature, the gas 40 buffers the increase in pressure of the second latent heat storage material (gas) 34. Therefore, the pressure of the contents in the second heat-storage tank 30 does not increase drastically, and the second heat-storage tank 30 is prevented from being deformed due to expansion and contraction of the contents, so that the second heat-storage tank 30 is practically usable.

[0040] With regard to the heat storage operation and the heat dissipation operation, the same actions and effects as those of the first to third embodiments are obtained. As described above, when the number of boiling moles is small, the latent heat storage material may be a material that absorbs heat during a phase change from liquid to gas. The selection of the latent heat storage material takes into consideration the heat resistance temperature and cost of the blower, and has the effect of widening the range of choices. For example, when priority is given to low cost and easy mass availability of the latent heat storage material, a material that stores the latent heat of a phase change from liquid to gas is selected. In addition, the heat storage system 100 using a heat storage material that stores the latent heat of a phase change from solid to liquid as the latent heat storage material has the effect of easily preventing deformation of the heat storage tank due to expansion and contraction of the contents, and the effect of suppressing the size of the heat storage tank. [Explanation of symbols]

[0041] 1: power adjustment system, 2: group of heat storage tanks, 5: air, 16: first valve, 17: second valve, 22: phase change temperature, 23: solid sensible heat storage material, 24: first heat storage temperature, 28: fourth air temperature, 29: first heat storage tank, 30: second heat storage tank, 31: end temperature of heat dissipation operation, 32: air flow direction during heat storage operation, 33: air flow direction during heat dissipation operation, 34: second latent heat storage material (gas), 35: second latent heat Heat storage material (liquid), 37: second air temperature, 38: first latent heat storage material (liquid), 39: first latent heat storage material (solid), 40: gas, 43: water, 44: steam, 45: pump, 46: condenser, 47: steam turbine, 47a: generator, 48: boiler, 55: third temperature, 100: heat storage system, 380: heat storage tank, 390: electric heater, 400: first blower, 410: second blower.

Claims

1. a heat storage tank group in which an upstream heat storage tank composed of one or more heat storage tanks and a downstream heat storage tank composed of one or more heat storage tanks are connected in series with respect to a flow of fluid during a heat storage operation, a first heat storage tank containing a solid sensible heat storage material being the upstream heat storage tank, and a second heat storage tank containing a latent heat storage material being the downstream heat storage tank and being disposed at the most downstream position; During the heat storage operation, the fluid is circulated through the first heat storage tank and then the second heat storage tank, and all or a part of the heat retained in the fluid is absorbed and stored; During the heat dissipation operation, the fluid is circulated in a direction opposite to that during the heat storage operation, and all or a part of the heat stored in the solid sensible heat storage material and the latent heat storage material is dissipated to the fluid; A heat storage system, wherein the phase change temperature of the latent heat storage material is lower than the heat storage temperature of the solid sensible heat storage material.

2. The heat storage system according to claim 1 , further comprising: a first valve provided in a flow path between the first heat storage tank and the second heat storage tank; and the first valve is closed from the end of the heat storage operation to the start of the heat dissipation operation.

3. The heat storage system according to claim 1 or 2, wherein a second valve is provided in a flow path on an outlet side of the second heat storage tank during the heat storage operation, and the second valve is closed from the end of the heat storage operation to the start of the heat dissipation operation.

4. 4. The heat storage system according to claim 1, 2 or 3, wherein the latent heat storage material is a heat storage material that stores latent heat of a phase change from a solid to a liquid, and the phase change temperature is a melting point of the latent heat storage material.

5. A heat storage method for a heat storage system including a heat storage tank group, in which an upstream heat storage tank composed of one or more heat storage tanks and a downstream heat storage tank composed of one or more heat storage tanks are connected in series with respect to a flow of fluid during a heat storage operation, a first heat storage tank containing a solid sensible heat storage material is the upstream heat storage tank, and a second heat storage tank containing a latent heat storage material is the downstream heat storage tank and is disposed at the most downstream position, During the heat storage operation, the fluid is circulated through the first heat storage tank and then the second heat storage tank, and all or a part of the heat retained in the fluid is absorbed and stored; During the heat dissipation operation, the fluid is circulated in a direction opposite to that during the heat storage operation, and all or a part of the heat stored in the solid sensible heat storage material and the latent heat storage material is dissipated to the fluid; A heat storage method for a heat storage system, wherein the phase change temperature of the latent heat storage material is lower than the heat storage temperature of the solid sensible heat storage material.

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