Power storage system

Abstract

To provide a small-sized power storage system for storing power using hydrogen.SOLUTION: A power storage system 10a comprises: a hydrogen generation unit 12 for electrolyzing water using power supplied externally to generate hydrogen; a redox unit 13 that is configured to make the hydrogen generated by the hydrogen generation unit 12 react with hydrogen carbonate to generate formate and is configured to make the formate generated by a reduction reactor 133 react to generate hydrogen carbonate and hydrogen; and a power generation unit 14 for making the hydrogen generated by the redox unit 13 react with oxygen to generate power.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power storage system. [Background technology]

[0002] Conventionally, a power storage system using an organic hydride method has been proposed (see Patent Document 1 and Patent Document 2). A power storage system using an organic hydride method uses power received at a power receiving area to react hydrogen gas with organic compounds such as aromatic hydrocarbons such as toluene and heterocyclic compounds such as pyridine to generate a hydride (methylcyclohexane when toluene is used as a starting material) in a liquid state at room temperature and normal pressure, transports the generated hydride to a power demand area (consumption area) or its vicinity, separates the hydride into hydrogen and the starting organic compound by a dehydrogenation reaction of the hydride at the demand area or its vicinity, and generates power using the hydrogen obtained by the dehydrogenation reaction. With this configuration, the power supplied at the power receiving area can be stored as a hydride.

[0003] However, in the organic hydride method, a high temperature of 250 to 350°C is required to proceed with the reaction of incorporating hydrogen into a compound or the reaction of separating hydrogen from a compound. Therefore, a system using the organic hydride method requires a heating device that generates high temperatures. In addition, when the reaction of separating hydrogen from an organic compound is proceeded in the organic hydride method, steam generated by volatilization of the organic compound at high temperatures is mixed into the generated hydrogen. Therefore, a power storage system using the organic hydride method requires a device for purifying hydrogen. Thus, in the power storage system using the organic hydride method, it is difficult to reduce the equipment cost and to reduce the size of the system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Registration publication KR2022015798A [Patent Document 2] International Publication KR2022009803A Summary of the Invention

[0005] (Problem to be solved by the invention) In view of the above circumstances, one object of the present invention is to reduce the size of a power storage system that stores power using hydrogen.

[0006] (Means for solving the problem) In order to achieve the above object, the power storage system according to the present invention comprises: a hydrogen generating unit that generates hydrogen by electrolyzing water using power supplied from an external source; a reduction reaction unit configured to generate formate by a reduction reaction between hydrogen generated in the hydrogen generation unit and bicarbonate; an oxidation reaction section configured to generate hydrogen carbonate and hydrogen by an oxidation reaction of the formate generated in the reduction reaction section; and a power generation unit configured to generate power using hydrogen produced in the oxidation reaction unit.

[0007] The temperature of the reduction reaction in which hydrogen carbonate takes in hydrogen and the oxidation reaction in which formate releases hydrogen are lower than the temperature of the reaction in which an organic compound takes in hydrogen and the reaction in which an organic compound releases hydrogen in the organic hydride method. Furthermore, the amount of impurity components mixed into hydrogen gas in the oxidation reaction in which formate releases hydrogen is less than that in the reaction in which an organic compound releases hydrogen in the organic hydride method. Therefore, in the power storage system according to the present invention, a device for adjusting the temperature of the salt solution is not required, or the device for adjusting the temperature can be simplified compared to the organic hydride method. Furthermore, in the power storage system according to the present invention, a device for purifying the released hydrogen gas (i.e., the extracted hydrogen gas) is not required, or the device can be simplified compared to the organic hydride method. Therefore, the power storage system according to the present invention can be made smaller in size than a configuration using the organic hydride method. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a power storage system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a power storage system according to the second embodiment. [Diagram 3] FIG. 3 is a diagram showing a schematic configuration of a power storage system according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The power storage systems 10a, 10b, and 10c according to the respective embodiments of the present invention generate hydrogen using power supplied from an external power supply source 90 (hereinafter sometimes referred to as an external power source 90) and store the generated hydrogen in salt through a reduction reaction of the salt. That is, the power storage systems 10a, 10b, and 10c according to the respective embodiments are configured to use salt as a hydrogen carrier and store power as hydrogen contained in the salt. Furthermore, the power storage systems 10a, 10b, and 10c according to the respective embodiments are configured to extract hydrogen from the salt through an oxidation reaction of the salt and generate power using the extracted hydrogen.

[0010] The external power source 90 is not particularly limited, and various known power plants and power generation devices can be used. More specifically, the external power source 90 can be various known power plants and power generation devices, such as power plants that use fossil fuels as fuel, power generation devices that use fossil fuels as fuel, hydroelectric power plants and hydroelectric power generation devices, nuclear power plants, geothermal power plants, solar power plants and solar power generation devices, wind power plants and wind power generation devices, and power plants and power generation devices that use biomass as fuel.

[0011] First Embodiment Fig. 1 is a diagram showing a schematic configuration of a power storage system 10a according to the first embodiment. As shown in Fig. 1, the power storage system 10a according to the first embodiment includes a power adjustment unit 11, a hydrogen generation unit 12, a reduction-oxidation reaction unit 13, a power generation unit 14, and a control unit 15.

[0012] The power adjustment unit 11 is connected to the external power source 90 so that it can receive power from the external power source 90. The power adjustment unit 11 adjusts the power supplied from the external power source 90 to a power suitable for use in the hydrogen generation unit 12 (it can also be said that the power adjustment unit 11 converts the power into a power suitable for use in the hydrogen generation unit 12). The configuration of the power adjustment unit 11 is appropriately determined according to the power supplied from the external power source 90 and the power used in the hydrogen generation unit 12. For example, if the power supplied from the external power source 90 is DC power and the power used in the hydrogen generation unit 12 is AC power, the power adjustment unit 11 includes a DC-AC inverter that converts the DC power into AC power. If the power supplied from the external power source 90 and the power used in the hydrogen generation unit 12 are DC power, the power adjustment unit 11 includes a DC-DC inverter that converts the voltage and current of the DC power. If the power supplied from the external power source 90 and the power used in the hydrogen generation unit 12 are DC power, the power adjustment unit 11 does not need to include an inverter.

[0013] The hydrogen generating unit 12 generates hydrogen gas using the electric power adjusted by the electric power adjusting unit 11. The pressure of the hydrogen gas generated by the hydrogen generating unit 12 is preferably equal to or higher than atmospheric pressure, and more preferably equal to or higher than 1 MPa. The reason for this is that in the reaction unit described below, the higher the pressure of the hydrogen gas, the higher the efficiency of salt reduction.

[0014] The hydrogen generating unit 12 includes a water electrolysis device 121, a hydrogen gas purification device 122, a first hydrogen gas compression device 123, and a first hydrogen gas storage tank 124. The water electrolysis device 121 is configured to generate hydrogen gas by electrolyzing water using the power adjusted by the power adjustment unit 11. The configuration of the water electrolysis device 121 is not particularly limited. Various known water electrolysis devices such as an alkaline water electrolysis device, a solid polymer water electrolysis device, and a solid oxide water electrolysis device can be applied to the water electrolysis device 121. The hydrogen gas purification device 122 is configured to increase the purity of the hydrogen gas by removing impurity components from the hydrogen gas generated by the water electrolysis device 121. The configuration of the hydrogen gas purification device 122 is not particularly limited, and various known hydrogen gas purification devices can be applied. The hydrogen generating unit 12 does not necessarily have to include the hydrogen gas purification device 122. The first hydrogen gas compression device 123 is configured to pressurize the generated hydrogen gas to a pressure suitable for use in the reduction-oxidation reaction unit 13. The first hydrogen gas storage tank 124 is configured to store hydrogen gas at a pressure suitable for use in the reduction-oxidation reaction section 13. The configurations of the first hydrogen gas compression device 123 and the first hydrogen gas storage tank 124 are not particularly limited, and various known compressors and pressure vessels can be applied.

[0015] The reduction-oxidation reaction unit 13 is configured to generate formate from bicarbonate and hydrogen gas by reducing bicarbonate, store the generated formate, generate bicarbonate and hydrogen gas from formate by oxidizing the stored formate (take out hydrogen gas), and store hydrogen carbonate generated from formate. The reduction-oxidation reaction unit 13 includes a closed-loop aqueous solution path 131 through which an aqueous solution of salts (bicarbonate and formate) flows in a circulating manner, and includes a bicarbonate storage tank 132, a reduction reactor 133, a formate storage tank 134, and an oxidation reactor 135 arranged on the aqueous solution path 131. The bicarbonate storage tank 132, the reduction reactor 133, the formate storage tank 134, and the oxidation reactor 135 are arranged on the aqueous solution path 131 in the above-mentioned order in the direction of flow of the aqueous salt solution. In addition, a liquid delivery pump (not shown) controlled by a control unit 15 (described later) is arranged on the aqueous solution path 131. In addition, the reduction / oxidation reaction section 13 is provided with a second hydrogen gas compression device 136 that compresses the extracted hydrogen gas, and a second hydrogen gas storage tank 137 that stores the compressed hydrogen gas.

[0016] The reduction / oxidation reaction unit 13 in the first embodiment is an apparatus in which the reduction reactor 133 and the oxidation reactor 135 are integrated. That is, the power storage system 10a according to the first embodiment is an integrated system including the reduction reactor 133 and the oxidation reactor 135 integrated together.

[0017] The bicarbonate storage tank 132 is configured to be capable of storing an aqueous solution of bicarbonate. The configuration of the bicarbonate storage tank 132 is not particularly limited, and various known liquid containers can be used.

[0018] The reduction reactor 133 is configured to introduce hydrogen gas delivered from the hydrogen generating unit 12 into the aqueous solution of bicarbonate supplied from the bicarbonate storage tank 132, and generate formic acid from the bicarbonate and hydrogen gas by promoting a reduction reaction in which the bicarbonate takes in hydrogen using a catalyst. For this reason, the reduction reactor 133 is connected to the hydrogen generating unit 12 by a path (e.g., a pipe) through which gas can flow so that the hydrogen gas generated in the hydrogen generating unit 12 can be introduced into the aqueous solution of bicarbonate. Furthermore, the reduction reactor 133 includes a temperature control device (specifically, a heating device) that maintains the aqueous solution of bicarbonate at a temperature suitable for the generation of a reduction reaction (room temperature to 100°C in this embodiment). The configuration of the reduction reactor 133 is not particularly limited, and a conventionally known configuration can be applied.

[0019] The hydrogen carbonate that can be used in the present embodiment is not particularly limited, and examples thereof include ammonium hydrogen carbonate, trimethylammonium hydrogen carbonate, triethylammonium hydrogen carbonate, tetraethylammonium hydrogen carbonate, diisopropylimidazolium hydrogen carbonate, 1,3-di-t-butylimidazolium hydrogen carbonate, aminoguanidine hydrogen carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, cesium hydrogen carbonate, tetraamminepalladium hydrogen carbonate, and tetraammineplatinum hydrogen carbonate. From an economical viewpoint, it is preferable to use a hydrogen carbonate containing an alkali metal as the hydrogen carbonate.

[0020] In addition, a metal supported on a polymer or carbon, or a metal complex containing an organic ligand can be used as a catalyst for the progress of the reduction reaction in the reduction reactor 133. In this case, the metal is preferably an element of Group 9 or Group 10.

[0021] The formate storage tank 134 is configured so as to be able to store the formate produced in the reduction reactor 133 as an aqueous solution of the formate. The configuration of the formate storage tank 134 is not particularly limited, and various known liquid containers can be used.

[0022] The oxidation reactor 135 is configured to generate hydrogen carbonate and hydrogen by an oxidation reaction from the formate generated in the reduction reactor 133 (the formate aqueous solution delivered from the formate reservoir 134). In other words, the oxidation reactor 135 is configured to extract hydrogen from the formate. Specifically, the oxidation reactor 135 includes a temperature regulator (not shown) so as to maintain the formate aqueous solution at a temperature at which the oxidation reaction proceeds. The oxidation reactor 135 generates hydrogen carbonate and hydrogen gas from the formate by proceeding with an oxidation reaction of the formate (the formate contained in the formate aqueous solution delivered from the formate reservoir 134) under normal pressure by the action of a catalyst.

[0023] The catalyst used for the oxidation reaction of the formate in the oxidation reactor 135 may be a metal supported on a polymer or carbon, or a metal complex containing an organic ligand. More specifically, the metal is preferably an element of group 9 or group 10. The temperature at which the oxidation reaction proceeds is 20 to 70° C. From the viewpoint of reducing energy consumption, the temperature of the aqueous solution of the formate when the oxidation reaction proceeds in the oxidation reactor 135 is preferably 20 to 50° C., and more preferably room temperature.

[0024] The formate oxidized in the oxidation reactor 135 is the formate generated from the hydrogen carbonate in the reduction reactor 133 as described above. Therefore, the formate applied in this embodiment is determined according to the hydrogen carbonate. For example, if the hydrogen carbonate is as described above, the formate is ammonium formate, trimethylammonium formate, triethylammonium formate, tetraethylammonium formate, diisopropylimidazolium formate, 1,3-di-t-butylimidazolium formate, aminoguazine formate, lithium formate, sodium formate, potassium formate, cesium formate, tetraamminepalladium formate, or tetraammineplatinum formate. From an economical point of view, it is preferable to select a formate containing an alkali metal.

[0025] The aqueous solution of bicarbonate produced in the oxidation reactor 135 is sent to and stored in the bicarbonate storage tank 132. The aqueous solution of bicarbonate stored in the bicarbonate storage tank 132 is then sent to the reduction reactor 133 and used to produce formate in the reduction reactor 133. In this way, the reduction-oxidation reaction unit 13 is configured to store and extract hydrogen by using a reduction / oxidation cycle of bicarbonate and formate.

[0026] The second hydrogen gas compression device 136 compresses the hydrogen gas generated in the oxidation reactor 135. The second hydrogen gas storage tank 137 stores the hydrogen gas compressed by the second hydrogen gas compression device 136. The configurations of the second hydrogen gas compression device 136 and the second hydrogen gas storage tank 137 are not particularly limited and can be incorporated as necessary. Various known compressors can be applied to the second hydrogen gas compression device 136, and various known pressure vessels can be applied to the second hydrogen gas storage tank 137. In addition, the reduction / oxidation reaction unit 13 may be equipped with a condenser that removes water vapor contained in the generated hydrogen gas.

[0027] The power generation unit 14 is configured to generate power using hydrogen gas generated (extracted) in the reduction-oxidation reaction unit 13. The power generation unit 14 is connected to the reduction-oxidation reaction unit 13 by a pipeline capable of supplying gas so that the power generation unit 14 can receive the supply of hydrogen gas generated in the reduction-oxidation reaction unit 13. The power generation unit 14 includes a fuel cell that generates power by reacting hydrogen with oxygen. The type and configuration of the fuel cell are not particularly limited, and various known hydrogen fuel cells can be applied. For example, the fuel cell that can be applied to the power storage system 10a according to this embodiment can be any of a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid polymer electrolyte fuel cell, and a solid oxide fuel cell.

[0028] Thus, the power storage system 10a according to the first embodiment includes a hydrogen generation unit 12 that generates hydrogen, a power generation unit 14 that generates power using hydrogen, and a reduction-oxidation reaction unit 13 that is provided between the hydrogen generation unit 12 and the power generation unit 14 and stores and releases hydrogen by an oxidation-reduction reaction mediated by a metal catalyst.

[0029] The control unit 15 controls each part of the power storage system 10a. The control unit 15 is a device including a computer equipped with a CPU, a ROM, a RAM, and an I / F. The ROM of the computer stores a computer program for controlling each part of the power storage system 10a in advance. The CPU of the computer reads the computing stored in the ROM and executes it using the RAM as a work area. In this way, each part of the power storage system 10a is controlled.

[0030] Next, the operation of the power storage system 10a will be described. The power storage system 10a according to the first embodiment operates while power is being supplied from the external power source 90. The control unit 15 controls the operation of the power adjustment unit 11 so as to convert the power supplied from the external power source 90 into power suitable for use in the hydrogen generation unit 12. The control unit 15 also controls the operation of the hydrogen generation unit 12 so as to electrolyze water using the power adjusted in the power adjustment unit 11 to generate hydrogen gas. The control unit 15 controls the operation of the reduction / oxidation reaction unit 13 so as to generate formate in the reduction reactor 133 while hydrogen is being supplied from the hydrogen generation unit 12 to the reduction reactor 133 of the reduction / oxidation reaction unit 13 (specifically, while the hydrogen generation unit 12 is operating or while hydrogen gas at a pressure equal to or higher than a predetermined pressure is stored in the first hydrogen gas storage tank 124 of the hydrogen generation unit 12). Specifically, the temperature of the aqueous solution of bicarbonate stored in the reduction reactor 133 is maintained at a temperature at which the reduction reaction proceeds, and hydrogen gas is continuously introduced into the aqueous solution of bicarbonate stored in the reduction reactor 133. In this manner, the control unit 15 synchronously controls the hydrogen generation unit 12 and the reduction reactor 133 of the reduction-oxidation reaction unit 13 (controls the hydrogen generation unit 12 and the reduction reactor 133 of the reduction-oxidation reaction unit 13 so as to operate synchronously).

[0031] The control unit 15 maintains the aqueous solution of hydrogencarbonate in the reduction reactor 133 at 20 to 100° C. to advance the reduction reaction and generate formate. From the viewpoint of reducing energy consumption, the temperature of the aqueous solution of hydrogencarbonate in the reduction reactor 133 is preferably 20 to 70° C., and more preferably 20 to 50° C.

[0032] The control unit 15 operates a pump (not shown) arranged on the aqueous solution path 131 to supply the aqueous solution of formate produced in the reduction reactor 133 to the formate storage tank 134. This causes the aqueous solution of formate to be stored in the formate storage tank 134. In other words, the power supplied from the external power supply 90 is stored as hydrogen contained in the formate.

[0033] The control unit 15 operates a pump (not shown) arranged on the aqueous solution path 131 to feed the aqueous solution of formate stored in the formate storage tank 134 to the oxidation reactor 135. Then, the control unit 15 controls the temperature of the aqueous solution of formate stored in the oxidation reactor 135 so that the oxidation reaction of the aqueous solution of formic acid proceeds in the oxidation reactor 135. Furthermore, while the oxidation reaction of the formate proceeds in the oxidation reactor 135 (i.e., while hydrogen gas is being extracted from the formate), the control unit 15 operates the second hydrogen gas compression device 136 to compress the generated hydrogen gas and store the compressed hydrogen gas in the second hydrogen gas storage tank 137. Then, the control unit 15 feeds the hydrogen gas stored in the second hydrogen gas storage tank 137 to the power generation unit 14, and controls the power generation unit 14 so that power is generated by the hydrogen gas in the power generation unit 14.

[0034] In this way, the control unit 15 controls the oxidation reactor 135 and the power generation unit 14 in synchronization with each other so that the power generation unit 14 operates (generates electricity) while hydrogen gas is being supplied from the oxidation reactor 135 to the power generation unit 14 (while the oxidation reactor 135 is operating, or while hydrogen gas at a predetermined pressure or more is stored in the second hydrogen gas storage tank 137). The control unit 15 also operates a pump (not shown) arranged on the aqueous solution path 131 to supply the aqueous solution of bicarbonate generated in the oxidation reactor 135 to the bicarbonate storage tank 132.

[0035] According to the power storage system 10a of the first embodiment, compared to a configuration in which power is stored (hydrogen is generated) using an organic hydride method, it is possible to reduce equipment costs and save space (size) of the system. That is, in a configuration in which hydrogen is taken up into an organic compound by the organic hydride method, the organic compound must be heated to a high temperature of 250 to 350°C. Therefore, a heating device is required to heat the organic compound to a high temperature. Furthermore, in the organic hydride method, the generated hydrogen gas is mixed with steam of hydrides and dehydrogenates (toluene, which is the starting material, in the case of dehydrogenating methylcyclohexane). Therefore, in order to obtain high-purity hydrogen gas, a refining device is required to remove substances other than hydrogen. Therefore, it is difficult to reduce the size of the power storage system 10a.

[0036] In contrast, in the power storage system 10a according to the first embodiment, the temperature at which the reduction and oxidation reactions proceed is in the range of room temperature to about 100°C, so that a temperature adjustment device (heating device) is not required, or a heating device with a smaller amount of heat than in a configuration using an organic hydride method is sufficient. Also, in the power storage system 10a according to the first embodiment, the purity of the hydrogen gas generated in the reduction-oxidation reaction section 13 is high (there is no volatilization of organic substances), so that a hydrogen gas purification device is not required, or a simple device is sufficient. This makes it possible to reduce the size of the power storage system 10a.

[0037] Furthermore, according to the power storage system 10a of the first embodiment, as described above, a temperature adjustment device for the salt water solution and a hydrogen gas purification device are not required or only simple devices are required, so that it is possible to reduce the equipment costs of the system and to reduce the operating costs (energy required for operation) of the power storage system 10a.

[0038] Furthermore, according to the power storage system 10a of the first embodiment, the hydrogen conversion efficiency (the ratio of the amount of hydrogen generated in the oxidation reactor 135 to the amount of hydrogen generated in the hydrogen generation unit 12) can be increased compared to a configuration using an organic hydride method. This makes it possible to increase the energy efficiency (the ratio of the power output by the power generation unit 14 to the power consumption of the power storage system 10a). In particular, while the hydrogen conversion efficiency is approximately 70% in the organic hydride method, the hydrogen conversion efficiency of the power storage system 10a of the first embodiment is approximately 90%, so that the energy efficiency can be increased.

[0039] In addition, the power storage system 10a according to the first embodiment can easily use a power source derived from natural energy such as solar power or wind power as the external power source 90. That is, since the amount of power generated from natural energy is unstable depending on time and climate change, in a configuration in which the power storage system requires a large amount of power for operation, the amount of heat obtained from the power becomes unstable and the reaction may not proceed. In particular, in a configuration using an organic hydride method that requires a high temperature of 250 to 350°C, there is a risk that hydrogen cannot be stored and extracted stably. In contrast, according to the power storage system 10a according to the first embodiment, the reaction temperature in the reduction reactor 133 and the reaction temperature in the oxidation reactor 135 are in the range of room temperature to 100°C, so the energy required for the reaction to proceed can be reduced. Therefore, even if the power is derived from natural energy, hydrogen can be stored and extracted stably.

[0040] Second Embodiment Next, a power storage system 10b according to a second embodiment of the present invention will be described. The power storage system 10b according to the second embodiment is a separate system in which the reduction reactor 133 and the oxidation reactor 135 can be installed independently. For this reason, the power storage system 10b according to the second embodiment is suitable for a case in which the location where the external power source 90 is installed and the location where the power generated by the power storage system 10b is consumed are geographically or geographically separated. However, the reduction reactor 133 and the oxidation reactor 135 may be installed in an integrated manner.

[0041] FIG. 2 is a diagram showing a schematic configuration of a power storage system 10b according to the second embodiment. Note that components common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and descriptions thereof may be omitted. As shown in FIG. 2, the power storage system 10b according to the second embodiment includes a reduction reaction section 16b and an oxidation reaction section 17b instead of the reduction-oxidation reaction section 13 of the first embodiment. The reduction reaction section 16b includes a bicarbonate storage tank 132 and a reduction reactor 133. The oxidation reaction section 17b includes a formate storage tank 134 and an oxidation reactor 135.

[0042] The reduction-oxidation reaction unit 13 in the first embodiment includes a hydrogencarbonate storage tank 132, a reduction reactor 133, a formate storage tank 134, and an oxidation reactor 135, and is an integrated device. In contrast, in the second embodiment, the reduction reaction unit 16b and the oxidation reaction unit 17b are not integrated and are located at positions geographically or physically separated from each other. For example, the reduction reaction unit 16b is installed together with the power adjustment unit 11 and the hydrogen generation unit 12 near the external power source 90, and the oxidation reaction unit 17b is installed together with the power generation unit 14 in or near the power demand area. In the second embodiment, it can be said that the power adjustment unit 11, the hydrogen generation unit 12, and the reduction reaction unit 16b form a single subsystem, and the oxidation reaction unit 17b and the power generation unit 14 form a single subsystem. However, the manner in which the bicarbonate reservoir 132, the reduction reactor 133, the formate reservoir 134, and the oxidation reactor 135 are connected is the same as in the first embodiment.

[0043] The configuration of the reduction reaction unit 16b and the oxidation reaction unit 17b is not limited to the above configuration. For example, the reduction reaction unit 16b may include a reduction reactor 133 and a formate storage tank 134, and the oxidation reaction unit 17b may include an oxidation reactor 135 and a bicarbonate storage tank 132. Furthermore, the reduction reaction unit 16b and the oxidation reaction unit 17b may include both the bicarbonate storage tank 132 and the formate storage tank 134. In a configuration in which the reduction reaction unit 16b and the oxidation reaction unit 17b include both the bicarbonate storage tank 132 and the formate storage tank 134, the bicarbonate storage tanks 132 of the reduction reaction unit 16b and the oxidation reaction unit 17b are connected to each other so as to be able to feed an aqueous solution of bicarbonate, and the formate storage tanks 134 of the reduction reaction unit 16b and the oxidation reaction unit 17b are connected to each other so as to be able to feed an aqueous solution of formate.

[0044] According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment. Moreover, according to the second embodiment, even if the external power source 90 and the power demand area (power usage area) are geographically or physically separated, it is possible to store power and generate power (supply power) in the power demand area.

[0045] Third embodiment Next, a power storage system 10c according to a third embodiment of the present invention will be described. Similar to the second embodiment, the third embodiment is a preferred embodiment when an external power source 90 and a power demand area are geographically or physically separated from each other.

[0046] FIG. 3 is a diagram showing a schematic configuration of a power storage system 10c according to the third embodiment. Note that components common to the first or second embodiment are given the same reference numerals as those in the first or second embodiment, and explanations may be omitted. The power storage system 10c according to the third embodiment is different from the power storage system 10a according to the first embodiment in that it includes a first solidification device 18 and a second solidification device 19, and does not include an aqueous solution path 131 through which an aqueous solution of salt circulates. That is, in the power storage system 10c according to the third embodiment, the bicarbonate storage tank 132 and the reduction reactor 133 are connected, and the formate storage tank 134 and the oxidation reactor 135 are connected. On the other hand, in the power storage system 10c according to the third embodiment, the bicarbonate storage tank 132 and the reduction reactor 133 are separated from the formate storage tank 134 and the oxidation reactor 135, and are not connected by the aqueous solution path 131 through which an aqueous solution of salt can flow.

[0047] The first solidification device 18 is configured to precipitate solid crystals of formate from the aqueous solution of formate generated in the reduction reactor 133. The first solidification device 18 includes, for example, a container capable of storing an aqueous solution of formate, and a heating device (electric heater, gas heater, oil heater, etc.) capable of heating the aqueous solution of formate stored in the container. The first solidification device 18 heats the aqueous solution of formate to evaporate water and precipitate crystals (solid) of formate. The second solidification device 19 is configured to precipitate crystals of bicarbonate from the aqueous solution of bicarbonate generated in the oxidation reactor 135. The second solidification device 19 includes, for example, a container capable of storing an aqueous solution of bicarbonate, and a heating device capable of heating the aqueous solution of bicarbonate stored in the container. The first solidification device 18 heats the aqueous solution of bicarbonate to evaporate water and precipitate crystals (solid) of bicarbonate.

[0048] The crystals of the formate precipitated in the first solidification device 18 are transported to the oxidation reaction section 17c, and an aqueous solution of the formate (an aqueous solution containing the formate precipitated in the first solidification device 18 as a solute) is generated in the formate storage tank 134 of the oxidation reaction section 17c, and is used for the oxidation reaction of the formate in the oxidation reactor 135. The crystals of the bicarbonate precipitated in the second solidification device 19 are transported to the reduction reaction section 16c, and an aqueous solution of the bicarbonate (an aqueous solution containing the bicarbonate precipitated in the second solidification device 19 as a solute) is generated in the bicarbonate storage tank 132 of the reduction reaction section 16c, and is used for the reduction reaction of the bicarbonate in the reduction reactor 133. The method of transporting the formate and the bicarbonate is not particularly limited. For example, when the reduction reaction section 16c and the oxidation reaction section 17c are installed geographically separated from each other, various types of transportation (e.g., transportation by automobile) can be applied to transport the formate from the reduction reaction section 16c to the oxidation reaction section 17c, and to transport the bicarbonate from the oxidation reaction section 17c to the reduction reaction section 16c.

[0049] According to this configuration, it is possible to obtain the same effects as those of the first and second embodiments. In addition, since the salt is transported in a solidified form, the volume can be made smaller than in a configuration in which the salt is transported in a solution state, and therefore it is possible to reduce the transportation cost.

[0050] In the third embodiment, the configuration in which the formate crystals and the hydrogencarbonate crystals are transported is shown, but the present invention is not limited to such a configuration. For example, the formate solution may be transported from the reduction reaction section 16c to the oxidation reaction section 17c, and the hydrogencarbonate solution may be transported from the oxidation reaction section 17c to the reduction reaction section 16c. With such a configuration, the first solidification device 18 and the second solidification device 19 are not necessary, so that the equipment cost and the system size are not increased.

[0051] (Summary of the embodiment) The power storage systems 10a, 10b, and 10c according to the respective embodiments include: A hydrogen generating unit 12 that generates hydrogen by electrolyzing water using power supplied from an external source; a reduction reaction unit (reduction-oxidation reaction unit 13, reduction reaction units 16b, 16c) configured to generate formate by a reduction reaction between hydrogen generated in the hydrogen generation unit 12 and hydrogen carbonate; an oxidation reaction section (reduction / oxidation reaction section 13, oxidation reaction sections 17b, 17c) configured to generate hydrogencarbonate and hydrogen by an oxidation reaction of the formate generated in the reduction reaction section (reduction / oxidation reaction section 13, reduction reaction sections 16b, 16c); and a power generation unit 14 configured to generate power using hydrogen produced in the oxidation reaction unit (reduction-oxidation reaction unit 13, reduction reaction units 16b, 16c).

[0052] In addition, in the power storage systems 10a, 10b, and 10c according to the respective embodiments, The hydrogen generation unit 12 and the reduction reaction unit (reduction-oxidation reaction unit 13, reduction reaction units 16b, 16c) are connected to each other so that hydrogen generated in the hydrogen generation unit 12 can be supplied to the reduction reaction unit (reduction-oxidation reaction unit 13, reduction reaction units 16b, 16c), and are configured to operate in synchronization with each other. The oxidation reaction section (reduction / oxidation reaction section 13, oxidation reaction sections 17b, 17c) and the power generation section 14 are connected so that hydrogen generated in the oxidation reaction section (reduction / oxidation reaction section 13, oxidation reaction sections 17b, 17c) can be supplied to the power generation section 14, and are configured to operate in synchronization with each other.

[0053] According to the power storage systems 10a, 10b, and 10c of the respective embodiments, hydrogen is taken up into salt by a reduction reaction of the salt, and hydrogen is taken out from the salt by an oxidation reaction of the salt. That is, the power storage systems 10a, 10b, and 10c of the respective embodiments are configured to use salt as a hydrogen carrier, and to store and take out hydrogen (i.e., electricity) in and from the salt by a cycle of reduction and oxidation reactions of the salt. According to such a configuration, it is possible to reduce the size of the power storage systems 10a, 10b, and 10c, reduce equipment costs, and reduce operating costs, as compared to a configuration in which hydrogen is taken up into an organic compound (a configuration using an organic hydride method).

[0054] The power storage systems 10a, 10b, and 10c according to the respective embodiments are suitable for small-scale and medium-scale power storage systems. A small-scale power storage system is a system with a power capacity in the range of 0.05 to 0.5 megawatts, and is intended for small buildings and general households. A medium-scale power storage system is a system with a power capacity in the range of 0.5 to 2 megawatts, and is intended for medium-scale factories and buildings. A large-scale power storage system is a system with a power capacity of more than 2 megawatts, and is intended for large factories, department stores, and office buildings.

[0055] The power storage systems 10a and 10b include: The reduction reaction section (reduction / oxidation reaction section 13, reduction reaction section 16b) includes a reduction reactor 133 configured to generate the aqueous solution of the formate by reducing the aqueous solution of the hydrogencarbonate with hydrogen, and a formate storage tank 134 capable of storing the aqueous solution of the formate generated in the reduction reactor 133; The oxidation reaction section (reduction-oxidation reaction section 13, oxidation reaction section 17b) includes an oxidation reactor 135 configured to generate the aqueous solution of hydrogencarbonate and hydrogen by oxidizing the aqueous solution of formate, and a bicarbonate storage tank 132 capable of storing the aqueous solution of hydrogencarbonate generated in the oxidation reactor 135; The formate reservoir 134 and the oxidation reactor 135 are connected to each other so that the aqueous solution of the formate stored in the formate reservoir 134 can be supplied to the oxidation reactor 135. The bicarbonate reservoir 132 and the reduction reactor 133 are connected so that the aqueous solution of bicarbonate stored in the bicarbonate reservoir 132 can be supplied to the oxidation reactor 135 .

[0056] According to this configuration, an aqueous solution of salts (hydrogen carbonate and formate) circulates through the reduction reactor 133 and the oxidation reactor 135. When the aqueous solution of salt circulates through the reduction reactor 133 and the oxidation reactor 135, hydrogen gas intake and hydrogen gas release (hydrogen gas extraction) are alternately repeated due to a cycle of salt reduction and oxidation reactions. By storing an aqueous solution of formate in the formate storage tank 134, electricity supplied from the external power source 90 can be stored as hydrogen contained in the formate. According to this configuration, the reduction reactor 133 and the oxidation reactor 135 can be integrated. Furthermore, by arranging the reduction reactor 133 and the oxidation reactor 135 at locations geographically or physically separated from each other, electricity can be stored and electricity can be generated at the electricity demand area even when the external power source 90 and the electricity demand area (electricity consumption area) are separated from each other.

[0057] In the power storage system 10c, The reduction reaction section 16c includes a reduction reactor 133 configured to generate the formate aqueous solution by reducing the hydrogencarbonate aqueous solution with hydrogen, and a first solidification device 18 that precipitates solid crystals of the formate from the formate aqueous solution generated in the reduction reactor 133, The oxidation reaction section 17c includes an oxidation reactor 135 configured to generate the aqueous hydrogencarbonate solution and hydrogen by oxidizing the aqueous solution of the formate, and a second solidification device 19 that precipitates solid crystals of the hydrogencarbonate from the aqueous hydrogencarbonate solution generated in the oxidation reactor 135; The reduction reaction section 16c generates an aqueous solution of the formate from an aqueous solution containing the hydrogencarbonate crystals precipitated in the second solidification device 19 as a solute, The oxidation reaction section 17c produces the aqueous solution of hydrogencarbonate and hydrogen from an aqueous solution containing the formate crystals precipitated in the first solidification device 18 as a solute.

[0058] According to such a configuration, by disposing the reduction reaction section 16c including the reduction reactor 133 and the oxidation reaction section 17c including the oxidation reactor 135 at locations that are geographically or physically separated, even if the external power source 90 and the area where electricity is demanded (the area where electricity is consumed) are separated, electricity can be stored and electricity can be generated in the area where electricity is demanded.

[0059] In the power storage systems 10a, 10b, and 10c according to the respective embodiments, The hydrogen generating unit 12 includes a water electrolysis device 121 having a solid oxide electrolysis cell, The power generating section 14 includes a power generating device including a solid oxide fuel cell. [Industrial Applicability]

[0060] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Various modifications of the present invention are possible without departing from the spirit of the invention, and such modifications are also included in the technical scope of the present invention. [Explanation of symbols]

[0061] 10a, 10b, 10c...power storage system, 12...hydrogen generation section, 13...reduction / oxidation reaction section, 14...power generation section, 15...control section, 16b, 16c...reduction reaction section, 17b, 17c...oxidation reaction section, 18...first solidification device, 19...second solidification device, 90...external power source

Claims

1. a hydrogen generating unit that generates hydrogen by electrolyzing water using power supplied from an external source; a reduction reaction unit configured to generate formate by a reduction reaction between hydrogen generated in the hydrogen generation unit and bicarbonate; an oxidation reaction section configured to generate hydrogen carbonate and hydrogen by an oxidation reaction of the formate generated in the reduction reaction section; a power generation unit configured to generate electricity using hydrogen generated in the oxidation reaction unit; A power storage system comprising:

2. The power storage system according to claim 1, the hydrogen generation unit and the reduction reaction unit are connected to each other so that hydrogen generated in the hydrogen generation unit can be supplied to the reduction reaction unit, and are configured to operate in synchronization with each other; The oxidation reaction unit and the power generation unit are connected to each other so as to be able to supply hydrogen generated in the oxidation reaction unit to the power generation unit, and are configured to operate in synchronization with each other.

3. The power storage system according to claim 1 or 2, the reduction reaction unit includes a reduction reactor configured to generate the formate aqueous solution by reducing the hydrogencarbonate aqueous solution with hydrogen, and a formate storage tank capable of storing the formate aqueous solution generated in the reduction reactor; the oxidation reaction unit includes an oxidation reactor configured to generate the aqueous hydrogencarbonate solution and hydrogen by oxidizing the aqueous solution of the formate, and a bicarbonate storage tank capable of storing the aqueous hydrogencarbonate solution generated in the oxidation reactor; The formate reservoir and the oxidation reactor are connected so that the aqueous solution of the formate stored in the formate reservoir can be supplied to the oxidation reactor; The bicarbonate reservoir and the reduction reactor are connected so that the aqueous solution of bicarbonate stored in the bicarbonate reservoir can be supplied to the oxidation reactor.

4. The power storage system according to claim 1 or 2, the reduction reaction unit includes a reduction reactor configured to generate the formate aqueous solution by reducing the hydrogencarbonate aqueous solution with hydrogen, and a first solidification device that precipitates solid crystals of the formate from the formate aqueous solution generated in the reduction reactor, the oxidation reaction section includes an oxidation reactor configured to generate the aqueous hydrogencarbonate solution and hydrogen by oxidizing the aqueous solution of the formate, and a second solidification device that precipitates solid crystals of the hydrogencarbonate from the aqueous hydrogencarbonate solution generated in the oxidation reactor; the reduction reaction section generates an aqueous solution of the formate from an aqueous solution having the hydrogencarbonate crystals precipitated in the second solidification device as a solute; The oxidation reaction unit produces the aqueous solution of bicarbonate and hydrogen from an aqueous solution having the formate crystals precipitated in the first solidification device as a solute.

5. The power storage system according to claim 1, the hydrogen generating unit includes a water electrolysis device including a solid oxide electrolysis cell; The power generation unit includes a power generation device including a solid oxide fuel cell.

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