Water electrolysis systems and energy systems

Abstract

To provide a water electrolysis system and an energy system contributing to improving energy efficiency.SOLUTION: A water electrolysis system 10 comprises a water electrolysis device 48 comprising a membrane-electrode assembly formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode and supplying the cathode electrode with water to electrolyze water to generate oxygen gas at the anode electrode, and a water supply device 52 supplying the anode electrode with water resulting from the power generation by a fuel cell stack 16.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water electrolysis system and an energy system. [Background technology]

[0002] In recent years, technological developments related to energy systems that contribute to energy efficiency have been underway in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Patent Document 1 describes an energy system including a water electrolysis system, a booster, and a fuel cell. The water electrolysis system includes a water electrolysis device having a membrane electrode structure formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode. The water electrolysis device supplies water to the cathode electrode and electrolyzes the water to generate oxygen gas at the anode electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-83098 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for better water electrolysis and energy systems.

[0006] The present disclosure aims to solve the above-mentioned problems. [Means for solving the problem]

[0007] A first aspect of the present disclosure is a water electrolysis system including: a water electrolysis device having a membrane electrode assembly formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode, the water electrolysis device supplying water to the cathode electrode and electrolyzing the water to generate oxygen gas at the anode electrode; and a water supply device supplying water generated in conjunction with power generation by a fuel cell stack to the anode electrode.

[0008] A second aspect of the present disclosure is an energy system including the water electrolysis system according to the first aspect and a fuel cell system having the fuel cell stack. [Effects of the Invention]

[0009] According to the present disclosure, a better water electrolysis system and an improved energy system can be provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic configuration diagram of an energy system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of a water electrolysis cell. [Figure 3] FIG. 3 is a block diagram of a control device of the energy system. [Figure 4] FIG. 4 is a flowchart showing an example of a control method for an energy system. DETAILED DESCRIPTION OF THE INVENTION

[0011] In a water electrolysis apparatus, the anode electrode may be corroded by oxygen gas generated at the anode electrode. The present disclosure has been made in view of this problem, and provides a water electrolysis system and an energy system that can suppress corrosion of the anode electrode.

[0012] FIG. 1 is a schematic configuration diagram of an energy system 12 according to one embodiment of the present disclosure. The energy system 12 is a circulatory renewable energy system. That is, the energy system 12 is a system that combines a fuel cell system 14 that generates electricity and water through an electrochemical reaction between oxygen gas and hydrogen gas, and a water electrolysis system 10 that electrolyzes water to generate oxygen gas and hydrogen gas. In the energy system 12, the water electrolysis system 10 uses water generated in the fuel cell system 14 to generate oxygen gas and hydrogen gas required for the power generation of the fuel cell system 14.

[0013] Such an energy system 12 may be installed, for example, on the Earth or the moon, or may be installed on an artificial satellite such as the International Space Station (ISS).

[0014] The fuel cell system 14 includes a fuel cell stack 16. The fuel cell stack 16 has a plurality of power generating cells 18 and a pair of end plates 20. The power generating cells 18 are stacked on top of each other. The pair of end plates 20 sandwich the power generating cells 18 in the stacking direction.

[0015] Detailed illustration of the power generation cell 18 is omitted. The power generation cell 18 includes a membrane electrode assembly and a pair of separators. The membrane electrode assembly is sandwiched between the pair of separators. The membrane electrode assembly has an electrolyte membrane, an anode electrode, and a cathode electrode. The power generation cell 18 generates electricity through an electrochemical reaction between hydrogen gas and oxygen gas. When the power generation cell 18 generates electricity, water is produced at the cathode electrode.

[0016] The fuel cell system 14 further includes a hydrogen gas tank 22, a hydrogen gas supply channel 24, and a hydrogen gas discharge channel 26. The hydrogen gas tank 22 is filled with high-pressure hydrogen gas. The hydrogen gas supply channel 24 supplies the hydrogen gas filled in the hydrogen gas tank 22 to the fuel cell stack 16. An on-off valve 28 is provided in the hydrogen gas supply channel 24. The on-off valve 28 opens and closes the hydrogen gas supply channel 24. Hydrogen exhaust gas discharged from the fuel cell stack 16 flows through the hydrogen gas discharge channel 26. The hydrogen exhaust gas contains unreacted hydrogen gas that did not react in the power generation cell 18.

[0017] The fuel cell system 14 further includes an oxygen gas tank 30, an oxygen gas supply channel 32, an oxygen gas discharge channel 34, a gas-liquid separator 36, a circulation channel 38, and an oxygen pump 40. The oxygen gas tank 30 is filled with high-pressure oxygen gas. The pressure of the oxygen gas in the oxygen gas tank 30 is lower than the pressure of the hydrogen gas in the hydrogen gas tank 22. The oxygen gas supply channel 32 supplies the oxygen gas filled in the oxygen gas tank 30 to the fuel cell stack 16. An on-off valve 42 is provided in the oxygen gas supply channel 32. The on-off valve 42 opens and closes the oxygen gas supply channel 32. The oxygen gas discharge channel 34 allows oxygen exhaust gas discharged from the fuel cell stack 16 to flow. The oxygen exhaust gas contains unreacted oxygen gas that did not react in the power generation cell 18. The oxygen exhaust gas also contains water (water vapor) produced at the cathode electrode of the power generation cell 18.

[0018] The gas-liquid separator 36 is connected to the oxygen gas discharge channel 34. The gas-liquid separator 36 separates the oxygen exhaust gas into gas and liquid. That is, the gas-liquid separator 36 removes water vapor from the oxygen exhaust gas. The gas-liquid separator 36 has a reservoir 44 that stores water (liquid water) separated from the oxygen exhaust gas. The circulation channel 38 connects the gas-liquid separator 36 to the oxygen gas supply channel 32. The circulation channel 38 guides the oxygen exhaust gas from which water vapor has been removed by the gas-liquid separator 36 to the oxygen gas supply channel 32. The oxygen pump 40 is provided in the circulation channel 38. The oxygen pump 40 sends the oxygen exhaust gas circulating through the circulation channel 38 to the oxygen gas supply channel 32.

[0019] The fuel cell system 14 may include components other than those described above. That is, the fuel cell system 14 may include, for example, a cooling device for circulating a cooling medium through the fuel cell stack 16.

[0020] The water electrolysis system 10 includes a gas-liquid separator 46, a water electrolysis device 48, a booster device 50, and a water supply device 52. The gas-liquid separator 46 of the water electrolysis system 10 and the gas-liquid separator 36 of the fuel cell system 14 are connected to each other by a connecting path 54. An on-off valve 56 is provided in the connecting path 54. The on-off valve 56 opens and closes the connecting path 54. Water stored in a reservoir 44 of the gas-liquid separator 36 of the fuel cell system 14 is supplied to the gas-liquid separator 46 via the connecting path 54. The gas-liquid separator 46 has a cathode-side reservoir 58 that stores water. The water stored in the cathode-side reservoir 58 is supplied to a cathode electrode 88 of the water electrolysis device 48, which will be described later.

[0021] The water electrolysis device 48 generates oxygen gas and hydrogen gas by electrolyzing water (pure water). The water electrolysis device 48 is, for example, a solid polymer water electrolysis device. The water electrolysis device 48 may also be an alkaline water electrolysis device or a solid oxide water electrolysis device.

[0022] The water electrolysis device 48 includes a water electrolysis stack 60, a water electrolysis power supply 62, a water electrolysis supply channel 64, a water electrolysis discharge channel 66, and an oxygen gas transfer channel 68. The water electrolysis stack 60 includes a plurality of water electrolysis cells 70 and a pair of end plates 72. The plurality of water electrolysis cells 70 are stacked on top of each other. The pair of end plates 72 sandwich the plurality of water electrolysis cells 70 in the stacking direction.

[0023] Fig. 2 is a cross-sectional view of a water electrolysis cell 70. In Fig. 2, the X direction is the stacking direction of the multiple water electrolysis cells 70. As shown in Fig. 2, in the water electrolysis cell 70, water is supplied to the cathode electrode 88. The water electrolysis cell 70 electrolyzes water to generate oxygen gas at the anode electrode 90 and hydrogen gas at the cathode electrode 88.

[0024] The water electrolysis cell 70 is a differential pressure water electrolysis cell in which the pressure of oxygen gas in the anode electrode 90 is higher than the pressure of water in the cathode electrode 88. The water electrolysis cell 70 may also be a constant pressure water electrolysis cell in which the pressure of oxygen gas in the anode electrode 90 is approximately equal to the pressure of water in the cathode electrode 88. The water electrolysis device 48 can generate oxygen gas at the anode electrode 90 at 14.8 MPa, for example.

[0025] Each water electrolysis cell 70 is provided with a water supply passage 74, a water discharge passage 76, and an oxygen gas discharge passage 78, which penetrate the water electrolysis cell 70 in the X direction. The water supply passages 74 of the multiple water electrolysis cells 70 are in communication with one another. The water discharge passages 76 of the multiple water electrolysis cells 70 are in communication with one another. The oxygen gas discharge passages 78 of the multiple water electrolysis cells 70 are in communication with one another.

[0026] The water supply passage 74 and the water discharge passage 76 are provided at positions spaced apart from each other on the outer periphery of the water electrolysis cell 70. The oxygen gas discharge passage 78 is provided at the center of the water electrolysis cell 70. The oxygen gas discharge passage 78 is located between the water supply passage 74 and the water discharge passage 76. The water supply passage 74 supplies water to the cathode electrode 88. The water discharge passage 76 discharges water that has flowed through the cathode electrode 88 and hydrogen gas generated at the cathode electrode 88 to the outside. The oxygen gas discharge passage 78 discharges oxygen gas generated at the anode electrode 90 to the outside.

[0027] The water electrolysis cell 70 includes a membrane electrode assembly 80, a pair of separators 82, and a frame member 84. The membrane electrode assembly 80 is sandwiched between the pair of separators 82. The frame member 84 is formed in an annular shape so as to surround the membrane electrode assembly 80. A seal member 87 is provided between the frame member 84 and the separator 82 to prevent fluids (water and hydrogen gas) from leaking to the outside. Hereinafter, in FIG. 2 , the separator 82 of the pair of separators 82 located in the X1 direction of the membrane electrode assembly 80 may be referred to as the "first separator 82a," and the separator 82 of the pair of separators 82 located in the X2 direction of the membrane electrode assembly 80 may be referred to as the "second separator 82b."

[0028] The membrane electrode assembly 80 is formed in a ring shape. The membrane electrode assembly 80 has an electrolyte membrane 86, a cathode electrode 88, and an anode electrode 90. The electrolyte membrane 86 is sandwiched between the cathode electrode 88 and the anode electrode 90. The electrolyte membrane 86 is an ion exchange membrane. Specifically, the electrolyte membrane 86 is, for example, an anion exchange membrane (AEM). The electrolyte membrane 86 may also be a proton exchange membrane (PEM). The electrolyte membrane 86 prevents oxygen gas generated at the anode electrode 90 from passing through to the cathode electrode 88.

[0029] The cathode electrode 88 has a cathode catalyst layer 92, a protective sheet 94, and a cathode current collector 96. The cathode catalyst layer 92 is bonded to one surface 86a (the surface facing the X1 direction) of the electrolyte membrane 86. The cathode current collector 96 also serves as a gas diffusion layer for supplying water to the cathode catalyst layer 92. The cathode current collector 96 has a portion formed of a porous material. The protective sheet 94 is disposed between the cathode catalyst layer 92 and the cathode current collector 96. The protective sheet 94 prevents the electrolyte membrane 86 from being damaged by being pressed against the cathode current collector 96 by high-pressure oxygen gas generated in the anode electrode 90. The protective sheet 94 has a plurality of through-holes 98 formed therein.

[0030] The outer diameter of the anode electrode 90 is smaller than that of the cathode electrode 88. The anode electrode 90 has an anode catalyst layer 100 and an anode power supply 102. The anode catalyst layer 100 is joined to the other surface 86b (the surface facing the X2 direction) of the electrolyte membrane 86. The anode power supply 102 also serves as a gas diffusion layer for guiding oxygen gas generated in the anode catalyst layer 100. The anode power supply 102 has a portion formed of a porous material.

[0031] A support member 104 that supports the membrane electrode assembly 80 is provided between the first separator 82a and the cathode current collector 96. A communication passage 106 is formed in the support member 104. The communication passage 106 guides water introduced from the water supply passage 74 into the cathode current collector 96. The communication passage 106 also guides a mixed fluid of water and hydrogen gas inside the cathode current collector 96 to the water discharge passage 76.

[0032] A load-applying mechanism 108 that biases the anode power supply 102 in the X1 direction is provided between the second separator 82b and the anode power supply 102. The load-applying mechanism 108 has, for example, a leaf spring 110, a leaf spring holder 112, and a conductive sheet 114. An annular member 116 is provided between the second separator 82b and the outer periphery of the electrolyte membrane 86. The annular member 116 is in liquid-tight and airtight contact with the other surface 86b of the electrolyte membrane 86.

[0033] An annular seal member 118 is disposed between the annular member 116 and the load-applying mechanism 108. The seal member 118 is in liquid-tight and airtight contact with each of the second separator 82b and the electrolyte membrane 86. A space (anode chamber 120) that houses the anode electrode 90 is formed inside the seal member 118. The load-applying mechanism 108 is disposed in the anode chamber 120.

[0034] 1, the water electrolysis power supply 62 is a DC power supply. The water electrolysis power supply 62 applies a voltage between the cathode power supply 96 and the anode power supply 102 (see FIGS. 1 and 2).

[0035] The water electrolysis supply channel 64 connects the cathode reservoir 58 and the water electrolysis stack 60. The water electrolysis supply channel 64 communicates with the water supply passage 74 (see FIG. 2 ) of the water electrolysis cell 70. The water electrolysis supply channel 64 guides water stored in the cathode reservoir 58 to the water electrolysis stack 60. A water pump 122 is provided in the water electrolysis supply channel 64. The water pump 122 sends water circulating through the water electrolysis supply channel 64 to the water electrolysis stack 60.

[0036] The water electrolysis discharge channel 66 connects the gas-liquid separator 46 and the water electrolysis stack 60. The water electrolysis discharge channel 66 communicates with the water discharge passage 76 (see FIG. 2 ) of the water electrolysis cell 70. The water electrolysis discharge channel 66 guides a mixed fluid of hydrogen generated at the cathode electrode 88 of the water electrolysis cell 70 and water that was not electrolyzed to the gas-liquid separator 46. The gas-liquid separator 46 separates the mixed fluid guided from the water electrolysis discharge channel 66 into gas and liquid. The water separated from the mixed fluid is stored in the cathode-side reservoir 58.

[0037] The oxygen gas transfer path 68 transfers oxygen gas generated in the water electrolysis stack 60 to the fuel cell system 14. The oxygen gas transfer path 68 is connected to the oxygen gas discharge passage 78 (see FIG. 2 ) of the water electrolysis cell 70. The oxygen gas transfer path 68 includes an oxygen gas outlet path 124, a first branch path 126, and a second branch path 128. The oxygen gas outlet path 124 is connected to the water electrolysis stack 60. The first branch path 126 and the second branch path 128 branch off from the oxygen gas outlet path 124. The first branch path 126 is connected to the oxygen gas tank 30 of the fuel cell system 14. The second branch path 128 is connected to the oxygen gas supply path 32 of the fuel cell system 14.

[0038] The first branch path 126 is provided with a back pressure valve 130. The back pressure valve 130 opens when the pressure of the oxygen gas led from the water electrolysis stack 60 is equal to or higher than a predetermined oxygen gas pressure threshold. The back pressure valve 130 closes when the pressure of the oxygen gas led from the water electrolysis stack 60 is lower than the oxygen gas pressure threshold. The second branch path 128 is provided with an on-off valve 132. The on-off valve 132 Second Fork 128 Opens and closes.

[0039] The water electrolysis device 48 may include components other than those described above.

[0040] The booster device 50 has a booster stack 134, a booster power supply 136, a booster supply channel 138, a booster discharge channel 140, and a hydrogen gas transfer channel 142. The booster stack 134 boosts the hydrogen gas generated in the water electrolysis device 48. The booster stack 134 includes a plurality of booster cells 144 and a pair of end plates 146. The plurality of booster cells 144 are stacked on top of each other. The pair of end plates 146 sandwich the plurality of booster cells 144 in the stacking direction of the plurality of booster cells 144.

[0041] Detailed illustration of the booster cell 144 is omitted. In the booster cell 144, while humidified hydrogen gas is supplied to the anode electrode, the booster power supply 136 applies a voltage between the anode power supply of the anode electrode and the cathode power supply of the cathode electrode. This generates hydrogen ions at the anode electrode, and the hydrogen ions pass through the electrolyte membrane (ion exchange membrane) of the booster cell 144 and are guided to the cathode electrode. At the cathode electrode, the hydrogen ions combine to generate hydrogen gas. The electrolyte membrane of the booster cell 144 prevents the hydrogen gas generated at the cathode electrode from passing to the anode electrode. The booster device 50 can generate high-pressure hydrogen gas at the cathode electrode. The booster device 50 can boost the hydrogen gas to, for example, 70 MPa. In other words, the hydrogen gas boosted by the booster device 50 has a higher pressure than the oxygen gas generated by the water electrolysis device 48.

[0042] The booster supply channel 138 connects the gas-liquid separator 46 and the booster stack 134. The booster supply channel 138 guides the hydrogen gas from which moisture has been removed by the gas-liquid separator 46 to the booster stack 134. A hydrogen pump 147 is provided in the booster supply channel 138. The hydrogen pump 147 sends the hydrogen gas circulating through the booster supply channel 138 to the booster stack 134. The hydrogen gas supplied from the booster supply channel 138 to the booster stack 134 contains an appropriate amount of water vapor. As a result, the electrolyte membrane of the booster cell 144 is humidified by the water vapor.

[0043] The pressurized discharge passage 140 connects the gas-liquid separator 46 and the pressurized stack 134. The pressurized discharge passage 140 guides unreacted hydrogen gas from the pressurized stack 134 to the gas-liquid separator 46 together with water vapor.

[0044] The hydrogen gas transport path 142 transports hydrogen gas generated at the cathode electrode of the booster cell 144 to the fuel cell system 14. The hydrogen gas transport path 142 includes a hydrogen gas outlet path 148, a first branch path 150, and a second branch path 152. The hydrogen gas outlet path 148 is connected to the booster stack 134. The first branch path 150 and the second branch path 152 branch off from the hydrogen gas outlet path 148. The first branch path 150 is connected to the hydrogen gas tank 22 of the fuel cell system 14. The second branch path 152 is connected to the hydrogen gas supply path 24 of the fuel cell system 14.

[0045] The first branch line 150 is provided with a backpressure valve 154. The backpressure valve 154 opens the first branch line 150 when the pressure of the hydrogen gas led from the booster stack 134 is equal to or higher than a predetermined hydrogen gas pressure threshold. The backpressure valve 154 closes the first branch line 150 when the pressure of the hydrogen gas led from the booster stack 134 is lower than the hydrogen gas pressure threshold. The second branch line 152 is provided with an on-off valve 156. The on-off valve 156 opens and closes the second branch line 152.

[0046] The booster device 50 may include components other than those described above.

[0047] The water supply device 52 supplies water produced in conjunction with power generation by the fuel cell stack 16 to the anode electrode 90 of the water electrolysis device 48. The pressure inside the anode electrode 90, to which the produced water is supplied, is higher than the pressure inside the cathode electrode 88. The water supply device 52 includes a pressing device 158, a water inlet channel 160, a water supply channel 162, a hydrogen gas inlet channel 164, and a discharge channel 166. The pressing device 158 includes a cylindrical portion 168 and a piston 170. The piston 170 is disposed within the cylindrical portion 168 so as to be slidable on the inner circumferential surface of the cylindrical portion 168. The piston 170 divides the internal space of the cylindrical portion 168 into a first chamber 172a and a second chamber 172b. The first chamber 172a is an anode-side reservoir 174 capable of storing water to be supplied to the anode electrode 90 of the water electrolysis cell 70. The second chamber 172b is a pressurizing chamber 176 into which hydrogen gas pressurized by the pressure increasing device 50 can be introduced.

[0048] The outer peripheral surface of piston 170 is in liquid-tight and air-tight contact with the inner peripheral surface of tubular portion 168. An annular groove 178 is formed on the outer peripheral surface of piston 170. An inert gas such as nitrogen gas is sealed in annular groove 178. This prevents the water in anode-side reservoir 174 and the hydrogen gas in pressurizing chamber 176 from mixing with each other.

[0049] The water inlet channel 160 connects the reservoir 44 of the fuel cell system 14 to the tubular portion 168. The water inlet channel 160 introduces water stored in the reservoir 44 of the fuel cell system 14 into the anode-side reservoir 174. The water may be introduced into the anode-side reservoir 174 by pressure transfer using a pump (not shown). Alternatively, gas may be exhausted from the pressurizing chamber 176 via the exhaust valve 188 to reduce the pressure in the pressurizing chamber 176, thereby moving the piston 170 toward the pressurizing chamber 176 and expanding the space in the anode-side reservoir 174. The water inlet channel 160 is provided with an ion exchanger 180 and an on-off valve 182. The ion exchanger 180 removes impurities from the water introduced from the reservoir 44 of the fuel cell system 14. The on-off valve 182 opens and closes the water inlet channel 160.

[0050] The water supply channel 162 connects the cylindrical portion 168 and the water electrolysis stack 60. The water supply channel 162 communicates with the anode chambers 120 (see FIG. 2) of each water electrolysis cell 70. That is, the water supply channel 162 can guide water (pure water) stored in the anode-side reservoir 174 to the anode electrodes 90 (see FIG. 2) of each water electrolysis cell 70. The water supply channel 162 is provided with an on-off valve 184. The on-off valve 184 opens and closes the water supply channel 162.

[0051] The hydrogen gas inlet path 164 connects the hydrogen gas transfer path 142 (hydrogen gas outlet path 148) and the cylindrical portion 168. The hydrogen gas inlet path 164 guides hydrogen gas flowing through the hydrogen gas transfer path 142 to the pressurizing chamber 176 of the cylindrical portion 168. An on-off valve 186 is provided in the hydrogen gas inlet path 164. The on-off valve 186 opens and closes the hydrogen gas inlet path 164.

[0052] The exhaust path 166 exhausts the hydrogen gas in the pressurized chamber 176 to the outside. The exhaust path 166 is provided with an exhaust valve 188. The exhaust valve 188 opens and closes the exhaust path 166. The exhaust valve 188 opens when the pressure in the pressurized chamber 176 is equal to or greater than a predetermined pressure threshold. The exhaust valve 188 closes when the pressure in the pressurized chamber 176 is less than the pressure threshold.

[0053] The water supply device 52 may include components other than those described above.

[0054] In the water electrolysis system 10, the water supply device 52 and the water electrolysis stack 60 are arranged so that the potential energy of the anode-side reservoir 174 is higher than the potential energy of the anode electrode 90 of the water electrolysis cell 70. Specifically, the height of the anode-side reservoir 174 in the direction of gravity is greater than the height of the water electrolysis cell 70 in the direction of gravity. This allows the water stored in the anode-side reservoir 174 to be introduced into the anode electrode 90 of the water electrolysis cell 70 by utilizing the potential energy.

[0055] In the following description, the above-mentioned on-off valves 28, 42, 56, 132, 156, 182, 184, and 186 may be simply referred to as "on-off valve 190."

[0056] Fig. 3 is a block diagram of the control device 194 of the energy system 12. As shown in Fig. 3, the energy system 12 further includes a sensor 192 and a control device 194. The sensor 192 detects various types of information about the energy system 12. Detection signals from the sensor 192 are sequentially transmitted to the control device 194. The sensor 192 includes, for example, a water level sensor for measuring the amount of water in the anode-side reservoir 174. The sensor 192 also includes a voltage sensor for measuring the voltage between the cathode power supply 96 and the anode power supply 102 of the water electrolysis cell 70.

[0057] The control device 194 includes a calculation unit 196 and a storage unit 198. The calculation unit 196 is configured by a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the calculation unit 196 is configured by processing circuitry.

[0058] Calculation unit 196 has control unit 200, information acquisition unit 202, and determination unit 204. Control unit 200, information acquisition unit 202, and determination unit 204 can be realized by calculation unit 196 executing a program stored in storage unit 198.

[0059] At least a part of the control unit 200, the information acquisition unit 202, and the determination unit 204 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), etc. Also, at least a part of the control unit 200, the information acquisition unit 202, and the determination unit 204 may be configured by an electronic circuit including a discrete device.

[0060] The storage unit 198 is composed of a volatile memory (not shown) and a non-volatile memory (not shown). An example of the volatile memory is a random access memory (RAM). The volatile memory is used as a working memory for the processor, and temporarily stores data necessary for processing or calculation. An example of the non-volatile memory is a read-only memory (ROM) or a flash memory. The non-volatile memory is used as a storage memory, and stores programs, tables, maps, etc. At least a part of the storage unit 198 may be provided in the processor, integrated circuit, etc. described above.

[0061] The control unit 200 is responsible for overall control of the energy system 12. The control unit 200 controls the on-off valve 190, the oxygen pump 40, the water pump 122, the hydrogen pump 147, the water electrolysis power supply 62, and the boost power supply 136. The information acquisition unit 202 acquires information measured by the sensor 192.

[0062] Next, a description will be given of the operation of the energy system 12. Fig. 4 is a flowchart showing an example of a method for controlling the energy system 12.

[0063] 4, in step S1, the control unit 200 starts up the energy system 12. Specifically, the control unit 200 starts up the fuel cell system 14. That is, the control unit 200 controls the on-off valve 42 to open the oxygen gas supply path 32 and controls the on-off valve 28 to open the hydrogen gas supply path 24. When the on-off valve 42 opens, oxygen gas filled in the oxygen gas tank 30 is introduced into the fuel cell stack 16 via the oxygen gas supply path 32. When the on-off valve 28 opens, hydrogen gas filled in the hydrogen gas tank 22 is introduced into the fuel cell stack 16 via the hydrogen gas supply path 24.

[0064] In the fuel cell stack 16, each power generation cell 18 generates electricity through an electrochemical reaction between oxygen gas and hydrogen gas. Unreacted hydrogen gas that was not used in power generation is discharged to a hydrogen gas discharge channel 26 as hydrogen exhaust gas. Unreacted oxygen gas that was not used in power generation is discharged to an oxygen gas discharge channel 34 as oxygen exhaust gas together with water produced during power generation. The oxygen exhaust gas discharged to the oxygen gas discharge channel 34 is separated into gas and liquid in a gas-liquid separator 36. The water (liquid water) separated from the oxygen exhaust gas is stored in a storage unit 44. The control unit 200 drives the oxygen pump 40 to guide the oxygen exhaust gas, from which moisture has been removed, from the gas-liquid separator 36 to the oxygen gas supply channel 32.

[0065] The control unit 200 also starts the water electrolysis system 10. That is, the control unit 200 drives the water pump 122 and controls the water electrolysis power supply 62 to apply a voltage between the cathode power supply 96 and the anode power supply 102 of the water electrolysis cell 70. When the water pump 122 is driven, water stored in the cathode reservoir 58 is supplied to the water supply passage 74 of the water electrolysis stack 60 via the water electrolysis supply channel 64. The water supplied to the water supply passage 74 is guided to the cathode catalyst layer 92 via the communication passage 106 of the support member 104, the inside of the cathode power supply 96, and the through-hole 98 of the protective sheet 94.

[0066] When the electrolyte membrane 86 is an anion exchange membrane, water is electrolyzed in the cathode catalyst layer 92 to produce hydrogen gas and hydroxide ions. The hydroxide ions pass through the anion exchange membrane and are guided to the anode catalyst layer 100. In the anode catalyst layer 100, the hydroxide ions combine to produce oxygen gas and water.

[0067] When the electrolyte membrane 86 is a proton exchange membrane, the water introduced to the cathode catalyst layer 92 passes through the proton exchange membrane and is introduced to the anode catalyst layer 100. In the anode catalyst layer 100, the water is electrolyzed to produce oxygen gas and hydrogen ions. The hydrogen ions pass through the proton exchange membrane and are introduced to the cathode catalyst layer 92. In the cathode catalyst layer 92, the hydrogen ions combine to produce hydrogen gas.

[0068] The oxygen gas generated in the anode catalyst layer 100 is guided to the oxygen gas transfer channel 68 via the oxygen gas discharge passage 78. In the oxygen gas transfer channel 68, the first branch channel 126 is closed by the backpressure valve 130, and the second branch channel 128 is closed by the on-off valve 132. This allows oxygen gas to be stored in a closed space, thereby increasing the pressure of the oxygen gas generated in the water electrolysis stack 60. When the pressure of the oxygen gas generated in the water electrolysis stack 60 reaches or exceeds the oxygen gas pressure threshold, the backpressure valve 130 opens, and the oxygen gas is charged into the oxygen gas tank 30. The control unit 200 may supply the oxygen gas generated in the water electrolysis stack 60 to the oxygen gas supply channel 32 by opening the on-off valve 132.

[0069] The mixed fluid of hydrogen gas produced in the cathode catalyst layer 92 and water that was not electrolyzed is returned to the gas-liquid separator 46 via the water discharge communication hole 76 and the water electrolysis discharge channel 66. The gas-liquid separator 46 separates the mixed fluid into gas and liquid. The water separated from the mixed fluid is stored in the cathode-side reservoir 58.

[0070] Furthermore, the control unit 200 drives the hydrogen pump 147 and controls the boost power supply 136 to apply a voltage between the cathode power supply and the anode power supply of the boost cell 144. When the hydrogen pump 147 is driven, hydrogen gas in the gas-liquid separator 46 is supplied to the anode electrode of the boost cell 144 via the boost supply path 138. In the boost cell 144, hydrogen ions generated at the anode electrode pass through the electrolyte membrane and are guided to the cathode electrode, where the hydrogen ions combine to produce hydrogen gas.

[0071] The hydrogen gas generated at the cathode electrode is guided to the hydrogen gas transfer path 142. In the hydrogen gas transfer path 142, the first branch path 150 is closed by the backpressure valve 154, and the second branch path 152 is closed by the on-off valve 156. In addition, the hydrogen gas inlet path 164 is closed by the on-off valve 186. This allows hydrogen gas to be stored in a closed space, thereby increasing the pressure of the hydrogen gas generated in the booster stack 134. When the pressure of the hydrogen gas generated in the booster cell 144 reaches or exceeds the hydrogen gas pressure threshold, the backpressure valve 154 opens, and the hydrogen gas is filled into the hydrogen gas tank 22. The control unit 200 may supply the hydrogen gas pressurized in the booster stack 134 to the hydrogen gas supply path 24 by opening the on-off valve 156.

[0072] In this energy system 12, water is present in the anode electrode 90 during operation of the water electrolysis device 48. However, depending on the operating conditions of the water electrolysis cell 70, the anode electrode 90 may become dehydrated due to a lack of water. In particular, in a differential pressure water electrolysis cell 70, the water in the anode electrode 90 is pushed by high-pressure oxygen gas and flows to the cathode electrode 88 through the electrolyte membrane 86, making the anode electrode 90 prone to drying. If the anode electrode 90 dries, the oxygen gas may corrode the anode electrode 90 (anode power supply 102). Furthermore, components (e.g., the load-applying mechanism 108) provided in the anode chamber 120 may also corrode. In this embodiment, such corrosion of the anode electrode 90 and the like is suppressed.

[0073] After the start-up of the energy system 12 is completed, the process proceeds to step S2.

[0074] In step S2, the determination unit 204 determines whether the water volume in the anode-side reservoir 174 is less than a predetermined first water volume threshold. The water volume in the anode-side reservoir 174 is acquired by the information acquisition unit 202 based on the detection signal from the sensor 192. The first water volume threshold is set appropriately based on the total capacity obtained by adding up the capacities of the anode chambers 120 of the multiple water electrolysis cells 70. If the determination unit 204 determines that the water volume in the anode-side reservoir 174 is less than the first water volume threshold (YES in step S2), the process proceeds to step S3.

[0075] In step S3, water is supplied to the anode-side reservoir 174. Specifically, the control unit 200 controls the on-off valve 182 to open the water introduction channel 160. Then, the water stored in the reservoir 44 of the fuel cell system 14 is pushed by the oxygen exhaust gas in the gas-liquid separator 36 and introduced into the anode-side reservoir 174 via the water introduction channel 160. The water introduced into the anode-side reservoir 174 is pure water from which impurities have been removed by the ion exchange device 180. When water is introduced into the anode-side reservoir 174, the hydrogen gas in the pressurizing chamber 176 is pushed by the piston 170 and discharged to the outside via the discharge channel 166. The hydrogen gas flowing through the discharge channel 166 is diluted with nitrogen gas before being discharged. For example, when the amount of water in the anode-side reservoir 174 reaches a first water amount threshold, the control unit 200 controls the on-off valve 182 to close the water introduction channel 160. This allows the amount of water in the anode-side reservoir 174 to be equal to or greater than the first water amount threshold. After this, the process proceeds to step S6.

[0076] If the determining unit 204 determines that the amount of water in the anode-side reservoir 174 is equal to or greater than the first water amount threshold (NO in step S2), the process proceeds to step S4.

[0077] In step S4, the determination unit 204 determines whether the water volume in the cathode-side reservoir 58 is less than the second water volume threshold. The water volume in the cathode-side reservoir 58 is acquired by the information acquisition unit 202 based on the detection signal of the sensor 192. The second water volume threshold is set appropriately based on the size of the water electrolysis stack 60, the size of the reservoir 44, etc. If the determination unit 204 determines that the water volume in the cathode-side reservoir 58 is less than the second water volume threshold (YES in step S4), the process proceeds to step S5.

[0078] In step S5, water is supplied to the cathode-side reservoir 58. Specifically, the control unit 200 controls the on-off valve 56 to open the connecting path 54. As a result, the water stored in the reservoir 44 of the fuel cell system 14 is pushed by the oxygen exhaust gas in the gas-liquid separator 36 and guided to the cathode-side reservoir 58 via the connecting path 54. For example, when the water volume in the cathode-side reservoir 58 reaches the second water volume threshold, the control unit 200 controls the on-off valve 56 to close the connecting path 54. This allows the water volume in the cathode-side reservoir 58 to be equal to or greater than the second water volume threshold. After this, the process proceeds to step S6.

[0079] In step S6, the determination unit 204 determines whether the anode electrode 90 of the water electrolysis cell 70 is dry or in a state where it can dry. Specifically, the determination unit 204 determines whether the anode electrode 90 of the water electrolysis cell 70 is dry or in a state where it can dry, for example, based on the voltage or resistance between the cathode power supply 96 and the anode power supply 102 of the water electrolysis cell 70. When water is not introduced into the anode-side reservoir 174, water is easily supplied to the cathode electrode 88 of the water electrolysis cell 70, while only water that has permeated the electrolyte membrane 86 is supplied to the anode electrode 90. Therefore, the anode electrode 90 is the cause of an increase in the voltage or resistance between the cathode power supply 96 and the anode power supply 102 of the water electrolysis cell 70. This makes it easy to determine whether the anode electrode 90 of the water electrolysis cell 70 is dry or in a state where it can dry. The determination unit 204 may also determine whether the anode electrode 90 of the water electrolysis cell 70 is dry or in a state that may dry out, for example, based on the operation time of the water electrolysis stack 60. The anode electrode 90 being dry refers to a state in which the amount of moisture in the anode electrode 90 is less than a predetermined moisture threshold.

[0080] If the determination unit 204 determines that the anode electrode 90 of the water electrolysis cell 70 is dry or capable of drying (YES in step S6), the process proceeds to step S7. On the other hand, if the determination unit 204 determines that the anode electrode 90 of the water electrolysis cell 70 is not dry or capable of drying (NO in step S6), the process proceeds to step S8.

[0081] In step S7, water is supplied to the anode electrode 90 of the water electrolysis cell 70. Specifically, the control unit 200 controls the on-off valve 186 to open the hydrogen gas inlet channel 164 and also controls the on-off valve 184 to open the water supply channel 162. Then, high-pressure hydrogen gas pressurized by the booster stack 134 flows from the hydrogen gas inlet channel 164 into the pressurization chamber 176 and presses the piston 170 toward the anode-side reservoir 174. Water pushed by the piston 170 flows from the anode-side reservoir 174 through the water supply channel 162 to the anode chamber 120 of the water electrolysis cell 70. This supplies water to the anode electrode 90. That is, the anode chamber 120 is filled with water. Note that when the hydrogen gas pressurized by the booster stack 134 has a higher pressure than the oxygen gas in the anode chamber 120 of the water electrolysis cell 70, the pressure of the hydrogen gas in the pressurization chamber 176 can move the piston 170. When the pressure of the hydrogen gas boosted by the booster stack 134 and the pressure of the oxygen gas in the water electrolysis cell 70 are similar to each other, a pressure difference can be generated by slowing down the electrolysis rate in the water electrolysis cell 70.

[0082] When the supply of water to the anode electrode 90 of the water electrolysis cell 70 is completed, the control unit 200 controls the on-off valve 186 to close the hydrogen gas introduction channel 164, and also controls the on-off valve 184 to close the water supply channel 162. Then, the process proceeds to step S8.

[0083] In step S8, the determination unit 204 determines whether the operation of the water electrolysis system 10 has stopped. When the control unit 200 receives a signal to stop the operation of the water electrolysis system 10, it stops the operation of the water electrolysis system 10. If the determination unit 204 determines that the operation of the water electrolysis system 10 has not stopped (NO in step S8), the process proceeds to step S2. If the determination unit 204 determines that the operation of the water electrolysis system 10 has stopped (YES in step S8), the process proceeds to step S9.

[0084] In step S9, the determination unit 204 determines whether the anode chamber 120 is filled with water. Specifically, the determination unit 204 determines whether the anode chamber 120 of the water electrolysis cell 70 is filled with water based on the voltage value or resistance value between the cathode power supply 96 and the anode power supply 102 of the water electrolysis cell 70. The determination unit 204 may also determine whether the anode chamber 120 of the water electrolysis cell 70 is filled with water based on, for example, the operation time of the water electrolysis stack 60. Note that the anode chamber 120 not being filled with water refers to a state in which the amount of water in the anode chamber 120 is less than a predetermined water volume threshold.

[0085] If the determination unit 204 determines that the anode chamber 120 is not filled with water (NO in step S9), the process proceeds to step S10. On the other hand, if the determination unit 204 determines that the anode chamber 120 is filled with water (YES in step S9), the process proceeds to step S11.

[0086] When the operation of the water electrolysis system 10 is stopped, the pressure of hydrogen gas cannot be increased by the pressure booster 50, and therefore the water stored in the anode-side reservoir 174 may not be pressed by the piston 170. Note that oxygen gas is not generated in the anode chamber 120 of the water electrolysis cell 70. In such a case, in step S10, potential energy is used to supply water to the anode chamber 120 of the water electrolysis cell 70. Specifically, the control unit 200 controls the on-off valve 184 to open the water supply channel 162. This allows the water stored in the anode-side reservoir 174 to fall to the anode chamber 120 via the water supply channel 162 due to potential energy (gravity). This allows the anode chamber 120 to be filled with water. After this, the process proceeds to step S11.

[0087] In step S11, the control unit 200 stops operation of the fuel cell system 14. This configuration prevents the anode 90 from coming into contact with oxygen gas during the shutdown, and prevents the anode 90 of the water electrolysis cell 70 from being corroded by oxygen gas even during the shutdown. After this, the process shown in FIG. 4 is completed.

[0088] According to this embodiment, water produced in conjunction with power generation by the fuel cell stack 16 is supplied to the anode electrode 90 of the water electrolysis cell 70, thereby increasing the contact area of ​​water with the anode electrode 90. In other words, the contact area of ​​oxygen gas with the anode electrode 90 can be reduced. This makes it possible to prevent the anode electrode 90 of the water electrolysis cell 70 from being corroded by oxygen gas. Therefore, a better water electrolysis system 10 and energy system 12 can be provided.

[0089] The following additional notes are further disclosed regarding the above embodiment.

[0090] (Appendix 1) The water electrolysis system (10) of the present disclosure includes a membrane electrode assembly (80) formed by sandwiching an electrolyte membrane (86) between an anode electrode (90) and a cathode electrode (88), and includes a water electrolysis device (48) that supplies water to the cathode electrode and electrolyzes the water to generate oxygen gas at the anode electrode, and a water supply device (52) that supplies water produced in conjunction with power generation by a fuel cell stack (16) to the anode electrode.

[0091] With this configuration, water produced in conjunction with power generation by the fuel cell stack is supplied to the anode electrode of the water electrolysis device, thereby increasing the contact area of ​​water with the anode electrode. In other words, the contact area of ​​oxygen gas with the anode electrode can be reduced. This makes it possible to prevent corrosion of the anode electrode of the water electrolysis device by oxygen gas. Therefore, a better water electrolysis system can be provided.

[0092] (Appendix 2) In the water electrolysis system according to Supplementary Note 1, the pressure of the oxygen gas in the anode electrode may be higher than the pressure of the water in the cathode electrode.

[0093] With this configuration, hydrogen generated on the cathode electrode side is less likely to permeate the electrolyte membrane and move to the anode electrode side, making it possible to generate oxygen with higher purity.

[0094] (Appendix 3) In the water electrolysis system according to Supplementary Note 1 or 2, the water supply device may include an anode-side reservoir (174) for storing water produced in association with power generation by the fuel cell stack, and may supply the water stored in the anode-side reservoir to the anode electrode during operation of the water electrolysis device.

[0095] With this configuration, deterioration due to an increase in resistance value caused by a shortage of moisture in the anode electrode, which occurs when moisture that has permeated the electrolyte membrane is pushed back to the cathode electrode side due to a pressure difference between the anode electrode side and the cathode electrode side during operation of the water electrolysis device, can be suppressed.

[0096] (Appendix 4) In the water electrolysis system according to Supplementary Note 3, the water supply device may include a water inlet channel (160) connecting a reservoir (44) configured to store water obtained by gas-liquid separation of the oxygen exhaust gas discharged from the fuel cell stack and the anode-side reservoir.

[0097] With this configuration, the water stored in the storage section of the fuel cell stack is led to the anode side storage section via the water inlet passage, thereby preventing the oxygen exhaust gas from the fuel cell stack from flowing into the anode side storage section along with the water.

[0098] (Appendix 5) The water electrolysis system according to Supplementary Note 3 or 4 may further include a booster device (50) having a booster cell (144) to which hydrogen gas generated at the cathode electrode is introduced and which boosts the pressure of the introduced hydrogen gas, wherein the water supply device may pressure-feed water stored in the anode-side reservoir to the anode electrode by the pressure of the hydrogen gas boosted by the booster device during operation of the water electrolysis system.

[0099] According to this configuration, the pressure of the hydrogen gas boosted by the booster can be used to supply the water stored in the anode-side reservoir to the anode electrode of the water electrolysis device.

[0100] (Appendix 6) In the water electrolysis system according to Supplementary Note 5, the pressure of the hydrogen gas that can be boosted by the booster device may be higher than the pressure of the oxygen gas that can be generated at the anode electrode.

[0101] With this configuration, the water stored in the anode-side reservoir can be smoothly pressure-fed to the anode electrode of the water electrolysis device by the pressure of the hydrogen gas boosted by the booster.

[0102] (Appendix 7) In the water electrolysis system according to Supplementary Note 5 or 6, the water supply device may include a tubular portion (168) having the anode-side reservoir, a piston (170) provided in the tubular portion and configured to pressurize the water stored in the anode-side reservoir, and a water supply path (162) for guiding the water stored in the anode-side reservoir to the anode electrode, wherein hydrogen gas pressurized by the pressure booster may pressurize the piston, thereby pressure-feeding the water stored in the anode-side reservoir to the anode electrode via the water supply path.

[0103] With this configuration, the water supply device can be made simple in structure.

[0104] (Appendix 8) The water electrolysis system according to any one of Supplementary Notes 3 to 7, further comprising a cathode-side reservoir (58) configured to store water to be supplied to the cathode electrode, wherein when the amount of water in the anode-side reservoir is less than a predetermined water amount threshold, water generated in association with power generation by the fuel cell stack may be supplied to the anode-side reservoir without being supplied to the cathode-side reservoir, and when the amount of water in the anode-side reservoir is equal to or greater than the water amount threshold, water generated in association with power generation by the fuel cell stack may be supplied to the cathode-side reservoir.

[0105] With this configuration, water generated by the power generation in the fuel cell stack can be used for water electrolysis in the water electrolysis device. Furthermore, because the water generated by the power generation in the fuel cell stack is supplied to the anode-side reservoir preferentially over the cathode-side reservoir, shortages of water to be supplied to the anode electrode of the water electrolysis device can be prevented.

[0106] (Appendix 9) In the water electrolysis system according to any one of Supplementary Notes 3 to 8, the water supply device may supply water stored in the anode-side reservoir to the anode electrode while the water electrolysis device is not operating.

[0107] With this configuration, corrosion of the anode electrode by oxygen gas can be suppressed while the water electrolysis device is not operating.

[0108] (Appendix 10) In the water electrolysis system according to any one of Supplementary Notes 5 to 7, the water supply device may supply water stored in the anode-side reservoir to the anode electrode by utilizing potential energy while the water electrolysis device is not operating.

[0109] With this configuration, even when hydrogen gas cannot be generated due to the shutdown of the water electrolysis device, the water stored in the anode-side reservoir can be supplied to the anode electrode by utilizing potential energy.

[0110] (Appendix 11) In the water electrolysis system according to Supplementary Note 9 or 10, the water supply device may, while operation of the water electrolysis device is stopped, supply water stored in the anode-side reservoir to the anode chamber (120) accommodating the anode electrode, thereby filling the anode chamber with water.

[0111] With this configuration, the anode electrode and other components housed in the anode chamber can be prevented from being corroded by oxygen gas while the water electrolysis apparatus is not operating.

[0112] (Appendix 12) An energy system (12) of the present disclosure includes the water electrolysis system according to any one of Supplementary Notes 1 to 11, and a fuel cell system (14) having the fuel cell stack.

[0113] Such a configuration can provide a better energy system.

[0114] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments. [Explanation of symbols]

[0115] 10...Water electrolysis system 12...Energy system 14...Fuel cell system 16...Fuel cell stack 44...storage unit 48...water electrolysis device 50...Pressure booster device 52...Water supply device 58... Cathode-side reservoir 80... Membrane electrode assembly 86...electrolyte membrane 88...cathode electrode 90...Anode electrode 120...Anode chamber 144... Booster cell 160... Water inlet 162...Water supply channel 168...Cylinder part 170: Piston; 174: Anode side reservoir;

Claims

1. a water electrolysis device having a membrane electrode assembly formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode, wherein water is supplied to the cathode electrode and electrolyzed to generate oxygen gas at the anode electrode; a water supply device that supplies water generated in association with power generation by the fuel cell stack to the anode electrode without passing through the electrolyte membrane while the water electrolysis device is not operating; A water electrolysis system comprising:

2. The water electrolysis system according to claim 1, a pressure of the oxygen gas in the anode electrode being higher than a pressure of the water in the cathode electrode.

3. The water electrolysis system according to claim 1, the water supply device has an anode-side reservoir for storing water produced in association with power generation by the fuel cell stack, and supplies the water stored in the anode-side reservoir to the anode electrode during operation of the water electrolysis device.

4. The water electrolysis system according to claim 3, the water supply device has a water inlet passage connecting a reservoir that stores water obtained by gas-liquid separation of the oxygen exhaust gas discharged from the fuel cell stack and the anode-side reservoir.

5. A water electrolysis device having a membrane electrode structure formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode, which supplies water to the cathode electrode and electrolyzes the water to generate oxygen gas at the anode electrode; a water supply device that supplies water generated in conjunction with power generation by the fuel cell stack to the anode electrode; a booster device having a booster cell into which the hydrogen gas generated at the cathode electrode is introduced and which boosts the pressure of the introduced hydrogen gas; Equipped with the water supply device has an anode-side reservoir for storing water produced in association with power generation by the fuel cell stack, and during operation of the water electrolysis device, the water stored in the anode-side reservoir is pressure-fed to the anode electrode by the pressure of the hydrogen gas boosted by the booster.

6. The water electrolysis system according to claim 5, a pressure of the hydrogen gas that can be boosted by the booster device is higher than a pressure of the oxygen gas that can be generated at the anode electrode.

7. The water electrolysis system according to claim 5, The water supply device is a cylindrical portion having the anode-side reservoir; a piston provided in the cylindrical portion and configured to pressurize the water stored in the anode-side storage portion; a water supply channel for guiding water stored in the anode-side reservoir to the anode electrode; and the hydrogen gas pressurized by the pressure booster pressurizes the piston, causing the water stored in the anode-side reservoir to be pressure-fed to the anode electrode through the water supply channel.

8. A water electrolysis device having a membrane electrode structure formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode, wherein water is supplied to the cathode electrode and oxygen gas is generated at the anode electrode by electrolyzing the water; a water supply device that supplies water generated in conjunction with power generation by the fuel cell stack to the anode electrode; a cathode-side reservoir that stores water to be supplied to the cathode electrode; Equipped with the water supply device has an anode-side reservoir for storing water produced in association with power generation by the fuel cell stack, and supplies the water stored in the anode-side reservoir to the anode electrode during operation of the water electrolysis device; When the amount of water in the anode-side reservoir is less than a predetermined water amount threshold, water generated in association with power generation by the fuel cell stack is supplied to the anode-side reservoir without being supplied to the cathode-side reservoir; a water electrolysis system, wherein when the amount of water in the anode-side reservoir is equal to or greater than the water amount threshold, water generated as the fuel cell stack generates electricity is supplied to the cathode-side reservoir;

9. A water electrolysis device having a membrane electrode structure formed by sandwiching an electrolyte membrane between an anode electrode and a cathode electrode, which supplies water to the cathode electrode and electrolyzes the water to generate oxygen gas at the anode electrode; a water supply device that supplies water generated in conjunction with power generation by the fuel cell stack to the anode electrode; Equipped with the water supply device has an anode-side reservoir for storing water produced in association with power generation by the fuel cell stack, and supplies the water stored in the anode-side reservoir to the anode electrode during operation and while operation of the water electrolysis device is stopped.

10. The water electrolysis system according to claim 5, the water supply device supplies water stored in the anode-side reservoir to the anode electrode by utilizing potential energy while the water electrolysis device is not operating.

11. The water electrolysis system according to claim 9, wherein the water supply device supplies water stored in the anode-side reservoir to an anode chamber accommodating the anode electrode while operation of the water electrolysis device is stopped, thereby filling the anode chamber with water.

12. The water electrolysis system according to any one of claims 1 to 11; a fuel cell system having the fuel cell stack; An energy system comprising:

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