JP4752618B2 - Heat storage system - Google Patents

Description

  The present invention relates to a heat storage system capable of realizing a high heat storage density.

  Conventional heat storage technologies include sensible heat storage, latent heat storage, and chemical heat storage. Sensible heat storage is a heat storage technology that uses the heat capacity of a substance (heat storage material), and latent heat storage is a heat storage technology that uses the heat of fusion or vaporization of the heat storage material. The heat storage performance in sensible heat storage and latent heat storage depends on specific heat and phase change heat, which are physical properties of the heat storage material. The amount of heat that can be stored in the latent heat storage material is the sum of sensible heat and phase change heat. Generally, the phase change heat of a heat storage material in a low temperature range is smaller than that in a high temperature range, and the heat storage density is relatively low. In latent heat storage, the phase change temperature is determined according to the temperature of the heat source to be used. As the latent heat storage material, for example, in the case of heat storage for hot water supply, hydrates, paraffins, saccharides, and the like can be used to store generated heat of 100 ° C. or lower. Of these, sodium acetate trihydrate has been well studied. However, the problem of such sensible heat and latent heat storage is that, since the thermal conductivity of the heat storage material is low, the amount of heat that cannot be taken out during heat exchange is practically generated, and the actual heat storage density is reduced.

  On the other hand, chemical heat storage is a heat storage technique that uses reaction heat from a reversible chemical reaction. Chemical heat storage includes an adsorption system, a hydrogen storage alloy system, an organic reaction system, and an inorganic reaction system, depending on the chemical reaction used. Conventional chemical heat storage uses gas-liquid reaction or gas-solid reaction regardless of any of the above chemical reactions. If stored in the form of a gas, the stored gas has a very large volume, so the heat storage density Becomes lower. For this reason, the volume is reduced by using an equiphase change that condenses the gas generated during heat storage, but the generated heat (condensation heat) generated thereby is released to the outside air. For this reason, at the time of heat dissipation, in order to generate gas again, it is necessary to input new heat energy from the outside. Therefore, in the conventional chemical heat storage system, the heat energy that can be stored is, in principle, a value obtained by subtracting the heat energy (heat loss) required for the reaction during heat release from the stored heat energy.

  For example, in Patent Document 1, for such a problem, as shown in FIG. 6, chemical heat storage using a reaction in which a solid inorganic anhydride and water vapor react to generate a solid hydrate is performed. Further, it is disclosed that heat generated by condensation of gaseous water vapor (condensation heat) is recovered by a heat pump that is a heat source for heat storage.

FIG. 6 is a configuration diagram of a conventional chemical heat storage system in Patent Document 1. Of these, the heat pump is exactly the same as the conventional one. The chemical heat storage device includes a first container 13 that stores a reaction material 15 and a second container 14 that stores a material to be reacted 16, and is connected by a steam moving pipe 17 having a valve 18. Further, a heat exchanger 9 is provided in the reaction material 15, and a circulation path is formed by the heat exchanger 11 provided in the discharge side pipe 12-a portion of the compressor 6 and the pipes 23 and 23 ′ having the pump 10. They are connected to form. Further, a heat exchanger 19 is provided in the reaction material 16, and a circulation path is provided by a heat exchanger 22 provided in the suction side pipe 12-b portion of the compressor 6 and pipes 21 and 21 ′ having a pump 20. It is connected so as to constitute. As the reaction material 15, zeolite, calcium chloride dihydrate CaCl ₂ .2H ₂ O, sodium sulfide Na ₂ S, and as the reaction material 16, water, methanol, or the like is used. Heat is taken out while reacting the reaction material 15 and the material 16 to be reacted, and when storing heat, both are decomposed and regenerated for use.
Japanese Patent Publication No. 7-6708

  However, in the above conventional chemical heat storage system, the heat storage material is heated using a heat pump circuit. Therefore, as the temperature of the heat medium on the heating side decreases from the inlet side to the outlet side, this temperature change occurs. Correspondingly, a temperature distribution is formed inside the heat storage material. For this reason, the water vapor desorbed from the high temperature side heat storage material is condensed by the low temperature side heat storage material and changes the hydrate concentration of the heat storage material. There was a problem that it could not be secured.

  An object of the present invention is to provide a heat storage system that solves the above-described conventional problems.

  In order to solve the above-described conventional problems, the heat storage system of the present invention performs a heat storage method including a heat storage step of vaporizing and desorbing water molecules from the heat storage material, and heat pump circuit that raises the temperature of the heat medium that heats the heat storage material And a heat storage tank in which a plurality of heat storage units having a space above the heat storage material are stacked, a heat medium passage that penetrates the heat storage unit, and a plurality of water vapors that communicate the space of the stacked heat storage units And the opening area of the water vapor path that penetrates the high temperature side heat storage material is smaller than the opening area of the water vapor path that penetrates the low temperature side heat storage material among the water vapor paths arranged in the same space. It is a feature.

  Further, the heat storage system of the present invention is characterized in that the opening area of the water vapor path penetrating the low temperature side heat storage material is larger than the cross-sectional area of the portion penetrating the heat storage material of the water vapor path.

  In addition, the heat storage system of the present invention heats the heat storage material in a solid-liquid coexistence state with an aqueous solution in which the hydrate and the solute are anhydrous hydrates so as to be higher than the phase change temperature of the hydrate, A heat storage method that separates water from the solid-liquid coexistence state with a solid-liquid coexistence state of a solid from which some or all of the water molecules of the hydrate are desorbed and an aqueous solution in which the solute is an anhydride of the hydrate. It is characterized by.

  In addition, the heat storage system of the present invention heats the heat storage material, which is a hydrate, from the solid phase state to a temperature higher than or equal to the phase change temperature, and separates water from the aqueous solution by forming an aqueous solution in which the solute is an anhydrous hydrate It is characterized by performing a heat storage method.

  Furthermore, the heat storage system of the present invention heats the heat storage material in a solid-liquid coexistence state with an aqueous solution in which the hydrate and the solute are anhydrous hydrates so as to be equal to or higher than the phase change temperature of the hydrate, A heat storage method for separating water from the aqueous solution is performed by using an aqueous solution in which the solute is an anhydrous hydrate.

  According to the present invention, heat storage is performed by sensible heat and latent heat, and further, chemical heat storage that does not require input of new heat energy for promoting heat release reaction in the heat release process is possible, and a low temperature range (100 ° C. or lower). High heat storage density can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, detailed descriptions of known means that have been widely employed are omitted.

(Embodiment 1)
FIG. 1 is a configuration diagram of a heat storage system according to the first exemplary embodiment of the present invention. The heat storage system according to Embodiment 1 of the present invention includes a heat pump circuit and a heat storage tank 106. The heat pump circuit includes a compressor 101, a radiator 102, an expansion means 103, a first evaporator 104, a second
The evaporator 105 is configured. The heat storage tank 106 has a configuration in which a plurality of heat storage units 110 are stacked in the vertical direction. Each of the heat storage units 110 has a portion for storing the heat storage material 107 and a space 108 provided in the upper portion thereof. The heat storage tank 106 is provided with water supply paths 109 joined to the respective heat storage units 110 in order to supply water for reacting with the heat storage material 107 during heat radiation. Further, in the heat storage tank 106, a heat transfer pipe 111 through which a heat medium for heating the heat storage material 107 flows during heat storage, a first fin 112 for promoting heat transfer inside the heat storage material 107, and heat storage during heat storage. A first water vapor path 113 through which water vapor desorbed from the material 107 flows and a second fin 114 for promoting heating of the heat storage material 107 by water vapor are installed.

  Next, operation | movement of the thermal storage system concerning Embodiment 1 of this invention is demonstrated. Here, magnesium sulfate heptahydrate is used as the heat storage material. FIG. 2 is a state diagram in which the horizontal axis represents the concentration of magnesium acetate, the temperature is displayed on the vertical axis, and the concentration and temperature are shown.

  First, the heat storage process will be described. As shown in FIG. 2, at the start of the heat storage operation, magnesium sulfate heptahydrate is a solid at room temperature. By heating magnesium sulfate heptahydrate, the phase changes to a solid-liquid coexistence state in which a solid with an increased magnesium sulfate molar fraction and an aqueous solution having a solute of magnesium sulfate coexist at about 50 ° C. At this time, a large endotherm occurs. Subsequently, the temperature of the heat storage material is raised to about 80 ° C. (Step A). Further, by heating, water is desorbed (evaporated) from the solid-liquid coexistence state to become a solid state in which the molar fraction of magnesium sulfate is increased, and the heat storage operation is finished (step B). At this time, as in the phase change, a large endotherm occurs. A large heat storage density can be realized by such two large heat absorptions.

  Next, the heat dissipation process will be described. The heat dissipation process (process C, D) is started from the state where the heat storage process (process A, B) is completed. By supplying water to the solid state in which the molar fraction of magnesium sulfate in Step B is increased, a solid-liquid coexistence state consisting of a solid in which the molar fraction of magnesium sulfate is increased and an aqueous solution in which the solute is magnesium sulfate is obtained. At this time, a large exotherm occurs (step C). Furthermore, by cooling, at about 50 ° C., the phase changes to a solid and a large exotherm occurs (step D).

  Next, the concentration and temperature changes in FIG. 2 will be described in light of the operation on the heat storage system.

  First, the space 108 in the heat storage tank 106, the first water vapor path 113, the second water vapor path 115, and the inside of the tank 116 that stores water desorbed from magnesium sulfate heptahydrate as the heat storage material 107. After the pressure is reduced by operating the vacuum pump 117, the heat storage operation is started.

  At the time of heat storage, water as a heat medium heated by heat exchange with the high-temperature and high-pressure refrigerant in the radiator 102 of the heat pump circuit is supplied to the upper part of the heat storage tank 106 via the heat medium flow path 120. . The water (heat medium) supplied to the heat storage tank 106 flows through the heat transfer pipe 111, is taken out from the lower part of the heat storage tank 106, and is circulated again to the radiator 102 of the heat pump circuit.

  Here, the water (heat medium) flowing through the heat transfer tube 111 heats the heat storage material 107 via the wall of the heat transfer tube 111 and the first fin 112, so that the heat storage material 107 has water (heat medium). The temperature is raised in order from the top to be supplied. At about 50 ° C., a large endotherm occurs, and the phase changes to a solid-liquid coexistence state consisting of an aqueous solution in which the molar fraction of magnesium sulfate is increased and an aqueous solution in which the solute is magnesium sulfate. The

  Further, by heating, water is desorbed from the heat storage material 107 in the solid-liquid coexistence state, and a solid state in which the molar fraction of magnesium sulfate is increased is obtained. At this time, the temperature of the heat storage material 107 on the lower side is lower than the temperature of the heat storage material 107 on the upper side of the heat storage unit 110 stacked in a plurality of stages in the vertical direction, and is further lower than the temperature of the heat storage material 107 on the lower side. Since the temperature of the heat storage material (0 to 20 ° C.) at the time of flowing into the evaporator 105 is lower, the water vapor desorbed from the heat storage material 107 is condensed and circulated through the first water vapor path 113. After that, it becomes water in the second evaporator 105. Thereby, even if the operation of the vacuum pump 117 is stopped, the reduced pressure state is maintained.

  The water vapor desorbed from the heat storage material 107 partially passes through the first water vapor path 113 and passes through the wall of the first water vapor path 113 and the second fin 114 to the lower heat storage material 107. On the other hand, it is condensed by dissipating heat. That is, the process B is performed by the upper-stage heat storage material 107, and the process A is performed by using the heat of condensation of water vapor desorbed from the heat-storage material 107 to heat the lower-stage heat storage material 107. It means that. In this way, the amount of heat obtained from water can be stored in the system with high efficiency. Further, the water vapor that could not be condensed in the first water vapor path 113 is condensed by heat radiation to the atmosphere in the process of passing through the second water vapor path 115 and heat exchange with the refrigerant in the second evaporator 105. And stored in the tank 116.

  Further, at the time of heat dissipation, water as a heat medium is supplied from the water supply path 109 to the lower part of the heat storage tank 106 in order to cause the heat storage material 107 of the heat storage unit 110 to react with the heat storage material 107 in order from the lower stage. The water supplied to the heat storage tank 106 circulates through the heat transfer pipe 111, is taken out from the upper part of the heat storage tank 106, and is used for applications such as hot water supply.

  As described above, by supplying water to a solid state in which the molar fraction of magnesium sulfate is increased, a solid-liquid coexistence state consisting of a solid in which the molar fraction of magnesium sulfate is increased and an aqueous solution in which the solute is magnesium sulfate A large exotherm occurs when and when the phase changes to a solid at about 50 ° C. The generated heat is radiated to water, which is a heat medium flowing through the heat transfer tube 111, through the wall of the heat transfer tube 111 and the first fins 112. Thereby, the temperature of the water flowing through the heat transfer tube 111 is raised in the process of flowing from the lower side to the upper side of the heat storage tank 106.

  Next, the characteristics of the shape of the first water vapor path 113 of the heat storage device according to the first embodiment of the present invention and the operation thereof will be described.

  At the time of heat storage, the temperature of the water as the heat medium decreases as it flows through the heat transfer tube 111 from the inlet side to the outlet side of the heat storage tank 106. Corresponding to this temperature change, a temperature difference occurs in the heat storage material 107 between the plurality of heat storage units 110. For this reason, when the water vapor desorbed (evaporated) from the high temperature side heat storage material 107 is condensed by the low temperature side heat storage material 107, the hydrate concentration of the heat storage material 107 changes, and a predetermined heat storage density cannot be secured. Problems can occur. Further, the above problem may become a particularly serious problem as the heat storage / heat dissipation cycle is repeated.

  In order to solve the above problem, in the heat storage device according to the first embodiment, the first water vapor path 113 has a specific shape.

FIG. 3 is a configuration diagram of the first water vapor path 113 in which a part of the heat storage units 110 in the heat storage tank 106 is enlarged. At the time of heat storage, the upper heat storage unit 110 has a high temperature, and the lower heat storage unit 110 has a low temperature. The first opening 118 in the lower space 108a of the first water vapor path 113a that penetrates the upper (high temperature side) heat storage material 107 has a throttle structure, and the lower (low temperature side) heat storage material 107 The space 108 above the first water vapor path 113b that penetrates.
The second opening 119 in a has an open structure.

  Thus, by reducing the area of the first opening 118, the flow rate of water vapor flowing out of the first opening 118 can be improved. In addition, by improving the flow rate of water vapor, the effect of drawing the surrounding fluid into this flow due to the viscosity of the water vapor is obtained.

  Further, in the first embodiment, the second opening 119 having a large opening area is arranged around the first opening 118. This configuration acts as a resistance to the inflow of water vapor from the space 108a to the first water vapor path 113b.

  Therefore, when the fast-flowing water vapor flows out from the first opening 118, the amount of water vapor around the first opening 118 existing in the space 108a is reduced, and the space around the first opening 118 is reduced. A region having a lower pressure than 108a is formed. By such a mechanism, water vapor flows from the space 108a toward the first water vapor path 113b, so that the water vapor desorbed from the high temperature side heat storage material 107 is condensed by the low temperature side heat storage material 107, and the heat storage material 107 It can suppress that a hydrate concentration changes. For this reason, a predetermined heat storage density can be ensured even if the heat storage / heat radiation cycle is repeated.

  Moreover, although it is a side effect, when the 2nd opening part 119 is made into an open structure like FIG. 3, when water vapor | steam detach | desorbs from the thermal storage material 107, scattering of the solution by boiling arises. Moreover, it can prevent flowing in into the 1st water vapor flow path 113b.

  In the first embodiment, the first opening 118 and the second opening 119 are configured as shown in FIG. 3, but the present invention is not limited to this, and the first opening shown in FIGS. Even if the opening 118 and the second opening 119 are used in any combination, the same effect as described above can be obtained.

  Further, although magnesium sulfate heptahydrate is used as the heat storage material 107, it is not limited to this. The hydrate used as the heat storage material 107 was selected from the group consisting of chloride, bromide, iodide, hydroxide, nitrate, sulfate, thiosulfate, phosphate, borate, and acetate. It may be at least one compound. In the case of the above-mentioned compound, magnesium sulfate is contained in the range of 36 wt% to 53 wt%, the rest is a composition comprising water, sodium thiosulfate is contained in the range of 52 wt% to 75 wt%, and the rest is water. A composition comprising: calcium chloride in a range of 47% to 64% by weight, the balance comprising water, calcium bromide in a range of 58% to 74% by weight, and the remainder comprising water A composition, such as a composition containing zinc nitrate in the range of 51 wt% to 84 wt%, with the remainder being water, is preferred.

  In addition, the heat storage material 107 that is a hydrate is heated from the solid phase to a phase change temperature or higher, and the solid and solute from which some or all of the water molecules of the hydrate are desorbed are hydrate anhydrides. A heat storage method is used in which a solid-liquid coexisting state with an aqueous solution is used, and water is separated from the solid-liquid coexisting state. However, as long as it includes a step of storing water by desorbing water molecules from the heat storage material 107, the method is limited thereto. Is not to be done.

  Furthermore, although the structure which performs heat exchange with the thermal storage material 107 and water is made into the fin and tube heat exchanger, if the same effect as the above is acquired, it will not be limited to this.

According to the present invention, heat storage is performed by sensible heat and latent heat, and further, chemical heat storage that does not require input of new heat energy for promoting heat release reaction in the heat release process is possible, and a low temperature range (100 ° C. or lower). In this case, a high heat storage density can be realized, and a heat storage tank such as a CO ₂ heat pump can be downsized.

The block diagram of the thermal storage system concerning Embodiment 1 of this invention. The figure showing the density | concentration of a thermal storage material in the thermal storage method concerning Embodiment 1 of this invention, and a temperature change The block diagram of the 1st water vapor path | route which expanded the one part thermal storage unit in the thermal storage tank concerning Embodiment 1 of this invention. (A) Configuration diagram of one form of first opening and second opening according to Embodiment 1 of the present invention (b) Bird's-eye view of (a) above (A) Configuration diagram of one form of first opening and second opening according to Embodiment 1 of the present invention (b) Bird's-eye view of (a) above Configuration diagram of conventional heat storage system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Condenser 2 Evaporator 3, 4 Fan 5 Pressure reduction mechanism 6 Compressor 9, 11, 19, 22 Heat exchanger 10, 20 Pump 12, 21, 23 Pipe 13 First container 14 Second container 15 Reactant 16 Reacted material Material 17 Evaporation moving pipe 18 Valve 101 Compressor 102 Radiator 103 Expansion means 104 First evaporator 105 Second evaporator 106 Heat storage tank 107 Heat storage material 108 Space 109 Water supply path 110 Heat storage unit 111 Heat transfer pipe 112 First Fin 113 First water vapor path 114 Second fin 115 Second water vapor path 116 Tank 117 Vacuum pump 118 First opening 119 Second opening 120 Heat medium flow path

Claims (5)

A heat storage method including a heat storage step of vaporizing and desorbing water molecules from the heat storage material, a heat pump circuit that raises the temperature of a heat medium that heats the heat storage material, and housing the heat storage material, on the upper portion of the heat storage material A heat storage tank in which a plurality of heat storage units having a space are stacked, a heat medium flow path that penetrates the heat storage unit, and a plurality of water vapor paths that communicate the spaces of the adjacent heat storage units, and in the same space Among the arranged water vapor paths, a heat storage system in which an opening area of the water vapor path that penetrates the heat storage material on the high temperature side is smaller than an opening area of the water vapor path that penetrates the heat storage material on the low temperature side. The opening area of the water vapor path that penetrates the heat storage material on the low temperature side is larger than the cross-sectional area of the portion that penetrates the heat storage material of the water vapor path,
The heat storage system according to claim 1. Heat a heat storage material that is in a solid-liquid coexistence state with an aqueous solution in which the hydrate and solute are anhydrous hydrates so that the temperature of the hydrate exceeds the phase change temperature of the hydrate. A solid-liquid coexistence state of an all-solid-dissociated solid and an aqueous solution in which the solute is a hydrate anhydride, and a heat storage method is performed to separate water from the solid-liquid coexistence state.
The heat storage system according to claim 1 or 2. A heat storage material that is a hydrate is heated to a temperature higher than a phase change temperature from a solid phase, and an aqueous solution in which a solute is an anhydride of a hydrate is performed, and a heat storage method is performed to separate water from the aqueous solution.
The heat storage system according to claim 1 or 2. Heat the heat storage material that is in a solid-liquid coexistence state with an aqueous solution in which the hydrate and solute are anhydrous hydrates so that the temperature is higher than the phase change temperature of the hydrate, and the solute is the anhydrous hydrate. A heat storage method for separating the water from the aqueous solution,
The heat storage system according to claim 1 or 2.

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