Regenerative fuel cell system

Abstract

To provide a technology capable of suppressing reduction of hydrogen and oxygen used for power generation of a fuel cell.SOLUTION: The regenerative fuel cell system includes a fuel cell, a water tank that stores water, a recombiner that combines hydrogen and oxygen to generate water, and a water electrolysis device that electrolyzes water supplied from the water tank to generate hydrogen and oxygen to be used in an electrochemical reaction of the fuel cell, wherein the water tank includes a first region that stores water containing hydrogen discharged from the fuel cell, a second region that stores water containing oxygen discharged from the fuel cell, and a communication portion that communicates the first region and the second region, the recombiner is disposed in the communication portion.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to regenerative fuel cell systems. [Background technology]

[0002] A regenerative fuel cell system is known that includes a fuel cell that generates electricity through an electrochemical reaction between hydrogen and oxygen, and a water electrolysis device that produces hydrogen and oxygen by electrolyzing water produced during power generation by the fuel cell (see, for example, Patent Document 1). In such a regenerative fuel cell system, the water produced during power generation by the fuel cell is temporarily stored in a water tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-117525 Summary of the Invention [Problem to be solved by the invention]

[0004] The water produced when a fuel cell generates electricity contains hydrogen and oxygen. When this hydrogen and oxygen evaporate inside the water tank, the pressure in the water tank increases. If the evaporated hydrogen and oxygen are released outside the system to maintain the water tank pressure below a certain level, the hydrogen and oxygen used to generate electricity in the fuel cell will decrease, which is a problem. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms.

[0006] (1) According to one aspect of the present disclosure, there is provided a regenerative fuel cell system comprising: a fuel cell; a water tank for storing water; a recombiner for combining hydrogen and oxygen to produce water; and a water electrolysis device for electrolyzing water supplied from the water tank to produce hydrogen and oxygen for use in an electrochemical reaction in the fuel cell, wherein the water tank comprises a first region for storing water containing hydrogen discharged from the fuel cell, a second region for storing water containing oxygen discharged from the fuel cell, and a communication part for communicating the first region with the second region, and the recombiner is disposed in the communication part. In this type of regenerative fuel cell system, the recombiner generates water, reducing the amount of hydrogen and oxygen in the water tank, preventing the water tank pressure from increasing. This reduces the amount of hydrogen and oxygen released outside the system to maintain the water tank pressure at a certain level or below. (2) In the regenerative fuel cell system of the above configuration, the water tank may include a hydrogen-side water tank having the first region and an oxygen-side water tank having the second region, and the communication portion may connect the hydrogen-side water tank and the oxygen-side water tank. (3) In the regenerative fuel cell system of the above configuration, the communication section may connect a portion of the hydrogen-side water tank above a first reference water level with a portion of the oxygen-side water tank above a second reference water level. In this regenerative fuel cell system, the recombiner combines the hydrogen vaporized in the hydrogen-side water tank with the oxygen vaporized in the oxygen-side water tank to produce water. The reaction efficiency of the reaction combining hydrogen and oxygen to produce water is higher in the gas phase than in the liquid phase. Therefore, compared to when the recombiner combines hydrogen dissolved in water in the hydrogen-side water tank with oxygen dissolved in water in the oxygen-side water tank to produce water, the pressure increase in the water tank can be more effectively suppressed. (4) In the regenerative fuel cell system of the above configuration, the communication section may connect a portion of the hydrogen-side water tank below a first reference water level with a portion of the oxygen-side water tank below a second reference water level. In this type of regenerative fuel cell system, the recombiner combines hydrogen dissolved in water inside the hydrogen-side water tank with oxygen dissolved in water inside the oxygen-side water tank to produce water. Because the recombiner is placed in water, the heat generated by combining hydrogen and oxygen to produce water can be dissipated into the water. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a lunar rover equipped with a regenerative fuel cell system. [Figure 2] FIG. 1 is a schematic diagram of a regenerative fuel cell system. [Figure 3] FIG. 2 is a diagram showing a schematic configuration of a water tank. [Figure 4] FIG. 10 is a diagram showing a schematic configuration of a water tank in a second embodiment. [Figure 5] FIG. 10 is a diagram showing a schematic configuration of a water tank in a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. First embodiment: FIG. 1 is a schematic diagram of a lunar rover 5 equipped with a regenerative fuel cell system 10. The lunar rover 5 is a vehicle configured to travel on the lunar surface MS. In this embodiment, the lunar rover 5 includes the regenerative fuel cell system 10, a solar power generation system 20, and a traction motor 30. The regenerative fuel cell system 10 can generate hydrogen and oxygen by electrolyzing water using power supplied from the solar power generation system 20 during the lunar daytime, and can generate electricity and water using the hydrogen and oxygen during the lunar nighttime. The regenerative fuel cell system 10 can also generate electricity and water using the hydrogen and oxygen during the lunar daytime. The lunar rover 5 travels on the lunar surface MS by driving the traction motor 30 using power supplied from the regenerative fuel cell system 10. Hereinafter, hydrogen will also be referred to as fuel gas, and oxygen will also be referred to as oxidant gas.

[0009] Fig. 2 is a schematic diagram of a regenerative fuel cell system 10. As shown in Fig. 2, the regenerative fuel cell system 10 includes a hydrogen tank 110, an oxygen tank 120, a fuel cell 200, a water tank 300, a water electrolysis device 400, and a control device 500. The water tank 300 includes a hydrogen-side water tank 310, an oxygen-side water tank 320, and a communication part 330 that communicates between the hydrogen-side water tank 310 and the oxygen-side water tank 320.

[0010] Hydrogen is stored in the hydrogen tank 110. The hydrogen tank 110 is connected to the hydrogen inlet of the fuel cell 200 via a hydrogen supply path 111. The hydrogen supply path 111 is provided with a hydrogen supply valve 112 that adjusts the amount of hydrogen supplied from the hydrogen tank 110 to the fuel cell 200. The hydrogen supply valve 112 is configured, for example, as an electric valve or a solenoid valve. The hydrogen supply valve 112 is opened and closed under the control of the control device 500.

[0011] Oxygen is stored in the oxygen tank 120. The oxygen tank 120 is connected to the oxygen inlet of the fuel cell 200 via an oxygen supply path 121. The oxygen supply path 121 is provided with an oxygen supply valve 122 that adjusts the amount of oxygen supplied from the oxygen tank 120 to the fuel cell 200. The oxygen supply valve 122 is configured by, for example, an electric valve or a solenoid valve. The oxygen supply valve 122 is opened and closed under the control of the control device 500.

[0012] The fuel cell 200 generates electricity using hydrogen and oxygen. In this embodiment, a polymer electrolyte fuel cell is used for the fuel cell 200. The fuel cell 200 includes a fuel cell stack in which a plurality of fuel cell cells are stacked. Each fuel cell includes a membrane electrode assembly in which electrode catalyst layers are provided on both sides of an electrolyte membrane, and separators that sandwich the membrane electrode assembly. The fuel cell 200 generates electricity by supplying hydrogen to the electrode catalyst layer on the anode side and oxygen to the electrode catalyst layer on the cathode side. Water is produced as the fuel cell 200 generates electricity. The electricity generated by the fuel cell 200 is used to drive the traction motor 30.

[0013] The hydrogen outlet of the fuel cell 200 is connected to the hydrogen-side water tank 310 via a hydrogen-side drainage channel 131. A hydrogen-side gas-liquid separator 132, a hydrogen-side drainage valve 133, and a hydrogen-side check valve 134 are provided in this order on the hydrogen-side drainage channel 131 from the fuel cell 200 toward the hydrogen-side water tank 310. Hydrogen and water are discharged from the hydrogen outlet of the fuel cell 200. The hydrogen-side gas-liquid separator 132 stores the hydrogen and water discharged from the hydrogen outlet of the fuel cell 200 and separates the hydrogen from the water. In this embodiment, the hydrogen-side gas-liquid separator 132 is connected to the hydrogen supply channel 111 via a hydrogen circulation channel 135. A hydrogen circulation pump 136 is provided on the hydrogen circulation channel 135. The hydrogen circulation pump 136 pumps hydrogen from the hydrogen-side gas-liquid separator 132 to the hydrogen supply channel 111 via the hydrogen circulation channel 135. The hydrogen circulation pump 136 is driven under the control of the control device 500. The hydrogen-side drain valve 133 adjusts the amount of water discharged from the hydrogen-side gas-liquid separator 132 to the hydrogen-side water tank 310. The hydrogen-side drain valve 133 is configured, for example, as an electric valve or a solenoid valve. The hydrogen-side drain valve 133 is opened and closed under the control of the control device 500. Although not shown in the figures, in this embodiment, the hydrogen-side gas-liquid separator 132 is provided with a water level sensor that detects the water level of the hydrogen-side gas-liquid separator 132. The control device 500 opens the hydrogen-side drain valve 133 when the water level of the hydrogen-side gas-liquid separator 132 detected by the water level sensor is equal to or higher than a predetermined value, and closes the hydrogen-side drain valve 133 when the water level of the hydrogen-side gas-liquid separator 132 detected by the water level sensor is lower than the predetermined value. This prevents hydrogen separated from water from flowing from the hydrogen-side gas-liquid separator 132 into the hydrogen-side water tank 310. The hydrogen-side check valve 134 prevents water from flowing back from the hydrogen-side water tank 310 to the hydrogen-side gas-liquid separator 132 .

[0014] The oxygen outlet of the fuel cell 200 is connected to the oxygen-side water tank 320 via an oxygen-side drainage channel 141. An oxygen-side gas-liquid separator 142, an oxygen-side drainage valve 143, and an oxygen-side check valve 144 are provided in this order in the oxygen-side drainage channel 141 from the fuel cell 200 toward the oxygen-side water tank 320. Oxygen and water are discharged from the oxygen outlet of the fuel cell 200. The oxygen-side gas-liquid separator 142 stores the oxygen and water discharged from the oxygen outlet of the fuel cell 200 and separates the oxygen from the water. In this embodiment, the oxygen-side gas-liquid separator 142 is connected to the oxygen supply channel 121 via an oxygen circulation channel 145. An oxygen circulation pump 146 is provided in the oxygen circulation channel 145. The oxygen circulation pump 146 pumps oxygen from the oxygen-side gas-liquid separator 142 to the oxygen supply channel 121 via the oxygen circulation channel 145. The oxygen circulation pump 146 is driven under the control of the control device 500. The oxygen-side drain valve 143 adjusts the amount of water discharged from the oxygen-side gas-liquid separator 142 to the oxygen-side water tank 320. The oxygen-side drain valve 143 is configured, for example, as an electric valve or a solenoid valve. The oxygen-side drain valve 143 is opened and closed under the control of the control device 500. Although not shown in the drawings, in this embodiment, the oxygen-side gas-liquid separator 142 is provided with a water level sensor that detects the water level of the oxygen-side gas-liquid separator 142. The control device 500 opens the oxygen-side drain valve 143 when the water level of the oxygen-side gas-liquid separator 142 detected by the water level sensor is equal to or higher than a predetermined value, and closes the oxygen-side drain valve 143 when the water level of the oxygen-side gas-liquid separator 142 detected by the water level sensor is lower than the predetermined value. This prevents oxygen separated from water from flowing from the oxygen-side gas-liquid separator 142 into the oxygen-side water tank 320. The oxygen-side check valve 144 prevents water from flowing back from the oxygen-side water tank 320 to the oxygen-side gas-liquid separator 142 .

[0015] FIG. 3 is a diagram showing a schematic configuration of the water tank 300. The water tank 300 stores water discharged from the fuel cell 200. As described above, the water tank 300 includes a hydrogen-side water tank 310, an oxygen-side water tank 320, and a communication unit 330. Water flows into the hydrogen-side water tank 310 from the hydrogen-side gas-liquid separator 132 via the hydrogen-side drainage channel 131. The water flowing from the hydrogen-side gas-liquid separator 132 into the hydrogen-side water tank 310 contains dissolved hydrogen that could not be separated by the hydrogen-side gas-liquid separator 132. Therefore, the hydrogen-side water tank 310 stores water containing hydrogen. Water flows into the oxygen-side water tank 320 from the oxygen-side gas-liquid separator 142 via the oxygen-side drainage channel 141. The water flowing from the oxygen-side gas-liquid separator 142 into the oxygen-side water tank 320 contains dissolved oxygen that could not be separated by the oxygen-side gas-liquid separator 142. For this reason, water containing oxygen is stored in the oxygen-side water tank 320. In this specification, the region that stores water containing hydrogen discharged from the fuel cell 200 is called the first region R1, and the region that stores water containing oxygen discharged from the fuel cell 200 is called the second region R2. That is, the hydrogen-side water tank 310 has the first region R1, and the oxygen-side water tank 320 has the second region R2. In addition, the water tank 300 has the first region R1 and the second region R2.

[0016] The communication part 330 connects the first region R1 and the second region R2. In this embodiment, the communication part 330 is a pipe connecting the hydrogen-side water tank 310 and the oxygen-side water tank 320. The communication part 330 connects the hydrogen-side water tank 310 and the oxygen-side water tank 320, thereby connecting the first region R1 and the second region R2. The communication part 330 in this embodiment is also referred to as a communication passage. The communication part 330 connects a portion of the hydrogen-side water tank 310 above a first reference water level S1 with a portion of the oxygen-side water tank 320 above a second reference water level S2. Here, the first reference water level S1 is the reference water level in the hydrogen-side water tank 310, and the second reference water level S2 is the reference water level in the oxygen-side water tank 320. In other words, the first reference water level S1 is the reference water level in the first region R1, and the second reference water level S2 is the reference water level in the second region R2. The first reference water level S1 is located within a first range, which is a predetermined range of water levels in the hydrogen-side water tank 310. The first range is preferably, for example, a range equal to or greater than the water level when the hydrogen-side water tank 310 is 20% filled with water and equal to or less than the water level when the hydrogen-side water tank 310 is 80% filled with water. In this embodiment, the position of the first reference water level S1 is equal to the water level when the hydrogen-side water tank 310 is 50% filled with water. In other words, in this embodiment, the first reference water level S1 is located at the center of the hydrogen-side water tank 310 in the direction of gravity. The second reference water level S2 is located within a second range, which is a predetermined range of water levels in the oxygen-side water tank 320. The second range is preferably, for example, a range above the water level when 20% of the oxygen-side water tank 320 is filled with water and below the water level when 80% of the oxygen-side water tank 320 is filled with water. The position of the second reference water level S2 in this embodiment is equal to the position of the water surface when 50% of the oxygen-side water tank 320 is filled with water. In other words, in this embodiment, the second reference water level S2 is located at the center of the oxygen-side water tank 320 in the direction of gravity.

[0017] The regenerative fuel cell system 10 further includes a recombiner 340 that combines hydrogen and oxygen to generate water. The recombiner 340 is disposed in the communication section 330. The recombiner 340 is fixed to the inner wall of the communication section 330, for example, so that the first region R1 and the second region R2 are in communication with each other. The recombiner 340 is a catalytic recombiner. Examples of catalysts that can be used include platinum and platinum alloys. Examples of alloy elements that can be used for platinum alloys include Co, Ni, Fe, Mn, Ta, Ti, Hf, W, Zr, Nb, Al, Sn, Mo, and Si. The recombiner 340 may be a recombiner that converts hydrogen and oxygen into water through an oxidation reaction, rather than a catalytic recombiner.

[0018] Inside the hydrogen-side water tank 310, i.e., the first region R1, hydrogen-containing water and a mixed gas containing water vapor evaporated from the hydrogen-containing water coexist. Inside the oxygen-side water tank 320, i.e., the second region R2, oxygen-containing water and a mixed gas containing water vapor evaporated from the oxygen-containing water and oxygen coexist. In this embodiment, the portion of the hydrogen-side water tank 310 above the first reference water level S1 and the portion of the oxygen-side water tank 320 above the second reference water level S2 are connected by the communication section 330. Therefore, the recombiner 340 located in the communication section 330 combines the hydrogen vaporized in the first region R1 with the oxygen vaporized in the second region R2 to generate water. The generated water is stored in the first region R1 or the second region R2.

[0019] As shown in FIG. 2 , the hydrogen-side water tank 310 is connected to the water inlet of the water electrolysis device 400 via the hydrogen-side water supply channel 151 and the water supply channel 150. The water supply channel 150 connects the junction of the hydrogen-side water supply channel 151 and the oxygen-side water supply channel 161 (described later) to the water inlet of the water electrolysis device 400. The hydrogen-side water supply channel 151 is provided with a hydrogen-side water supply valve 152 and a hydrogen-side water supply check valve 153 extending from the hydrogen-side water tank 310 to the water electrolysis device 400. The hydrogen-side water supply valve 152 adjusts the amount of water supplied from the hydrogen-side water tank 310 to the water electrolysis device 400. The hydrogen-side water supply valve 152 is, for example, an electric valve or a solenoid valve. The hydrogen-side water supply valve 152 opens and closes under the control of the control device 500. Although not shown in the figures, in this embodiment, the hydrogen-side water tank 310 is provided with a water level sensor that detects the water level within the hydrogen-side water tank 310, and the control device 500 opens the hydrogen-side water supply valve 152 when the water level in the hydrogen-side water tank 310 detected by the water level sensor is equal to or greater than a predetermined value, and closes the hydrogen-side water supply valve 152 when the water level in the hydrogen-side water tank 310 detected by the water level sensor is below the predetermined value. This prevents hydrogen separated from water from flowing from the hydrogen-side water tank 310 into the water electrolysis device 400. The hydrogen-side water supply check valve 153 prevents water from flowing back from the water electrolysis device 400 into the hydrogen-side water tank 310.

[0020] In this embodiment, the hydrogen-side water tank 310 is connected to the external space of the lunar rover 5, in other words, the external space of the regenerative fuel cell system 10, via a hydrogen-side exhaust path 191. A hydrogen-side exhaust valve 192 is provided in the hydrogen-side exhaust path 191. The hydrogen-side exhaust valve 192 switches the state of the hydrogen-side water tank 310 between a communication state in which the hydrogen-side water tank 310 is connected to the external space of the lunar rover 5, and a non-communication state in which the hydrogen-side water tank 310 is not connected to the external space of the lunar rover 5. The hydrogen-side exhaust valve 192 is configured, for example, as an electric valve or a solenoid valve. The hydrogen-side exhaust valve 192 is opened and closed under the control of the control device 500.

[0021] The oxygen-side water tank 320 is connected to the water inlet of the water electrolysis device 400 via an oxygen-side water supply channel 161 and a water supply channel 150. An oxygen-side water supply valve 162 and an oxygen-side water supply check valve 163 are provided in the oxygen-side water supply channel 161 from the oxygen-side water tank 320 toward the water electrolysis device 400. The oxygen-side water supply valve 162 adjusts the amount of water supplied from the oxygen-side water tank 320 to the water electrolysis device 400. The oxygen-side water supply valve 162 is configured by, for example, an electric valve or a solenoid valve. The oxygen-side water supply valve 162 opens and closes under the control of the control device 500. Although not shown in the figures, in this embodiment, the oxygen-side water tank 320 is provided with a water level sensor that detects the water level in the oxygen-side water tank 320, and the control device 500 opens the oxygen-side water supply valve 162 when the water level in the oxygen-side water tank 320 detected by the water level sensor is equal to or higher than a predetermined value, and closes the oxygen-side water supply valve 162 when the water level in the oxygen-side water tank 320 detected by the water level sensor is below the predetermined value. This prevents oxygen separated from water from flowing from the oxygen-side water tank 320 into the water electrolysis device 400. The oxygen-side water supply check valve 163 prevents water from flowing back from the water electrolysis device 400 into the oxygen-side water tank 320.

[0022] In this embodiment, the oxygen-side water tank 320 is in communication with the external space of the lunar rover 5 via an oxygen-side exhaust path 196. An oxygen-side exhaust valve 197 is provided in the oxygen-side exhaust path 196. The oxygen-side exhaust valve 197 switches the state of the oxygen-side water tank 320 between a communication state in which the interior of the oxygen-side water tank 320 is in communication with the external space of the lunar rover 5, and a non-communication state in which the interior of the oxygen-side water tank 320 is not in communication with the external space of the lunar rover 5. The oxygen-side exhaust valve 197 is configured by, for example, an electric valve or an electromagnetic valve. The oxygen-side exhaust valve 197 is opened and closed under the control of the control device 500.

[0023] The water electrolysis device 400 generates hydrogen and oxygen by electrolyzing water supplied from the water tank 300. In this embodiment, a solid polymer water electrolysis device is used for the water electrolysis device 400. The water electrolysis device 400 includes a water electrolysis stack in which a plurality of water electrolysis cells are stacked, and a pump that pressure-feeds water from the water supply channel 150 to the water electrolysis stack. Each water electrolysis cell includes a membrane electrode assembly in which electrode catalyst layers are provided on both sides of an electrolyte membrane, and separators that sandwich the membrane electrode assembly. The water electrolysis device 400 electrolyzes water supplied to the anode-side electrode catalyst layer to generate oxygen at the anode-side electrode catalyst layer and hydrogen at the cathode-side electrode catalyst layer. In this embodiment, the water electrolysis device 400 electrolyzes water using power supplied from the solar power generation system 20. However, the water electrolysis device 400 may also electrolyze water using power supplied from a power supply source other than the solar power generation system 20, such as a lithium-ion secondary battery.

[0024] The hydrogen outlet of the water electrolysis device 400 is connected to the hydrogen tank 110 via a hydrogen filling path 171. A hydrogen filling pump 172, a hydrogen filling valve 173, and a hydrogen filling check valve 174 are provided in this order on the hydrogen filling path 171 from the water electrolysis device 400 toward the hydrogen tank 110. The hydrogen filling pump 172 pumps hydrogen from the water electrolysis device 400 to the hydrogen tank 110. The hydrogen filling pump 172 is driven under the control of a control device 500. The hydrogen filling valve 173 adjusts the amount of hydrogen supplied from the water electrolysis device 400 to the hydrogen tank 110. The hydrogen filling valve 173 is configured, for example, as an electric valve or a solenoid valve. The hydrogen filling valve 173 is opened and closed under the control of the control device 500. The hydrogen filling check valve 174 prevents hydrogen from flowing back from the hydrogen tank 110 to the water electrolysis device 400. The regenerative fuel cell system 10 may further include a gas-liquid separator that separates the hydrogen and water discharged from the hydrogen outlet of the water electrolysis device 400, and a circulation path and pump for circulating the water separated from the hydrogen by the gas-liquid separator to the water supply path 150.

[0025] The oxygen outlet of the water electrolysis device 400 is connected to the oxygen tank 120 via an oxygen filling path 181. An oxygen filling pump 182, an oxygen filling valve 183, and an oxygen filling check valve 184 are provided in this order on the oxygen filling path 181 from the water electrolysis device 400 to the oxygen tank 120. The oxygen filling pump 182 pumps oxygen from the water electrolysis device 400 to the oxygen tank 120. The oxygen filling pump 182 is driven under the control of a control device 500. The oxygen filling valve 183 adjusts the amount of oxygen supplied from the water electrolysis device 400 to the oxygen tank 120. The oxygen filling valve 183 is configured by, for example, an electric valve or a solenoid valve. The oxygen filling valve 183 is opened and closed under the control of the control device 500. The oxygen filling check valve 184 prevents oxygen from flowing back from the oxygen tank 120 to the water electrolysis device 400. The regenerative fuel cell system 10 may further include a gas-liquid separator that separates the oxygen and water discharged from the oxygen outlet of the water electrolysis device 400, and a circulation path and pump for circulating the water separated from the oxygen by the gas-liquid separator to the water supply path 150.

[0026] In this way, the hydrogen tank 110 stores hydrogen produced in the water electrolysis device 400, and the oxygen tank 120 stores oxygen produced in the water electrolysis device 400. That is, the fuel cell 200 generates electricity through an electrochemical reaction between the hydrogen and oxygen produced in the water electrolysis device 400. Note that the regenerative fuel cell system 10 may be supplied with hydrogen as a fuel gas, oxygen as an oxidant gas, or water from outside the regenerative fuel cell system 10. In this case, the fuel cell 200 generates electricity through an electrochemical reaction between the fuel gas containing hydrogen produced in the water electrolysis device 400 and the oxidant gas containing oxygen produced in the water electrolysis device 400.

[0027] The control device 500 is configured by a computer including a CPU 501, a memory 502 including ROM, RAM, etc., an input / output interface 503, and an internal bus 504. The CPU 501, memory 502, and input / output interface 503 are connected via the internal bus 504 to enable bidirectional communication. The input / output interface 503 is connected via wired or wireless communication to the various valves, pumps, sensors, etc. of the regenerative fuel cell system 10 described above. The CPU 501 executes computer programs pre-stored in the memory 502 to perform various functions, including a function to control power generation by the fuel cell 200 and a function to control water electrolysis by the water electrolysis device 400.

[0028] The control device 500 controls each part of the regenerative fuel cell system 10 so that the internal pressure of the water tank 300 while storing water is lower than the internal pressure of the fuel cell 200 while generating power and lower than the internal pressure of the water electrolysis device 400 while electrolyzing water. Specifically, the control device 500 opens the hydrogen-side exhaust valve 192 and the oxygen-side exhaust valve 197 after the lunar rover 5 arrives on the lunar surface MS. Because the external space of the lunar rover 5 is in a vacuum state while on the lunar surface MS, opening the hydrogen-side exhaust valve 192 and the oxygen-side exhaust valve 197 while on the lunar surface MS discharges the air inside the water tank 300 into the external space, creating a vacuum inside the water tank 300. After the water tank 300 has been vacuumed, the control device 500 closes the hydrogen-side exhaust valve 192 and the oxygen-side exhaust valve 197. The hydrogen-side exhaust valve 192 and the oxygen-side exhaust valve 197 may be opened before the lunar rover 5 arrives at the lunar surface MS, rather than after the lunar rover 5 arrives at the lunar surface MS. After closing the hydrogen-side exhaust valve 192 and the oxygen-side exhaust valve 197, the control device 500 starts power generation by the fuel cell 200 for the first time after the lunar rover 5 arrives at the lunar surface MS. After starting power generation by the fuel cell 200, the control device 500 opens the hydrogen-side exhaust valve 192 when the internal pressure of the hydrogen-side water tank 310 exceeds a predetermined upper limit, and opens the oxygen-side exhaust valve 197 when the internal pressure of the oxygen-side water tank 320 exceeds a predetermined upper limit.

[0029] According to the regenerative fuel cell system 10 of the first embodiment described above, a recombiner 340 is disposed in the communication section 330 that connects the first region R1 and the second region R2 of the water tank 300. The recombiner 340 combines the hydrogen stored in the first region R1 with the oxygen stored in the second region R2 to generate water. This reduces the amount of hydrogen and oxygen in the water tank 300, thereby preventing an increase in the pressure in the water tank 300. Therefore, in order to maintain the pressure in the water tank 300 at a certain value or less, the amount of hydrogen and oxygen released outside the system can be reduced, preventing a decrease in the amount of hydrogen and oxygen used for power generation in the fuel cell 200. Furthermore, if the recombiner 340 were not disposed inside the water tank 300, the volume of the water tank 300 would need to be increased to maintain the pressure in the water tank 300 at a certain value or less without releasing hydrogen and oxygen outside the system. In this embodiment, the recombiner 340 is disposed inside the water tank 300, allowing the water tank 300 to be made smaller.

[0030] In this embodiment, the communication unit 330 connects the portion of the hydrogen-side water tank 310 above the first reference water level S1 with the portion of the oxygen-side water tank 320 above the second reference water level S2. The recombiner 340 disposed in the communication unit 330 combines vaporized hydrogen in the hydrogen-side water tank 310 with vaporized oxygen in the oxygen-side water tank 320 to produce water. The reaction efficiency of the reaction combining hydrogen and oxygen to produce water is higher in the gas phase than in the liquid phase. Therefore, compared to when the recombiner 340 combines hydrogen dissolved in water in the hydrogen-side water tank 310 with oxygen dissolved in water in the oxygen-side water tank 320 to produce water, the pressure increase in the water tank 300 can be more effectively suppressed.

[0031] B. Second embodiment: 4 is a diagram showing a schematic configuration of a water tank 300b in the second embodiment. In the second embodiment, the position of the communication part 330b is different from that in the first embodiment. The configuration of each part of the regenerative fuel cell system 10 other than the communication part 330b is the same as that in the first embodiment.

[0032] In the second embodiment, the communication part 330b communicates between a portion of the hydrogen-side water tank 310 below the first reference water level S1 and a portion of the oxygen-side water tank 320 below the second reference water level S2. The recombiner 340 combines hydrogen dissolved in water inside the hydrogen-side water tank 310, i.e., in the first region R1, with oxygen dissolved in water inside the oxygen-side water tank 320, i.e., in the second region R2, to produce water.

[0033] The recombiner 340 generates heat by combining hydrogen and oxygen to generate water. In the second embodiment, the recombiner 340 is placed underwater, so the generated heat can be released into the water. If the recombiner 340 is not placed underwater, it is preferable that a structure for releasing the heat generated by the recombiner 340 be provided in the water tank 300b. However, if the recombiner 340 is placed underwater, it is not necessary to provide the above-mentioned structure. This simplifies the structure of the water tank 300b.

[0034] C. Third embodiment: 5 is a diagram showing a schematic configuration of a water tank 300c in the third embodiment. In the third embodiment, the structure of the water tank 300c is different from that in the first embodiment. The configuration of each part of the regenerative fuel cell system 10 other than the water tank 300c is the same as that in the first embodiment.

[0035] In the third embodiment, the water tank 300c is composed of a single tank. The first region R1 and the second region R2 are formed within the water tank 300c by dividing the interior of the water tank 300c by a wall portion 331. The wall portion 331 has a through-hole 332 that is a hole that connects the first region R1 and the second region R2. In the third embodiment, the through-hole 332 corresponds to the communication portion 330c. The through-hole 332 is provided above the first reference water level S1 and above the second reference water level S2. A recombiner 340 is arranged within the through-hole 332.

[0036] The regenerative fuel cell system 10 of the third embodiment described above can prevent a decrease in the hydrogen and oxygen used for power generation by the fuel cell 200, similar to the first embodiment. The through-hole 332 may be provided below the first reference water level S1 and below the second reference water level S2. In this case, similar to the second embodiment, it is possible to prevent a decrease in the hydrogen and oxygen used for power generation by the fuel cell 200.

[0037] D. Other Embodiments: (D-1) In the above embodiment, the regenerative fuel cell system 10 is mounted on the lunar rover 5 and used on the lunar surface MS. In contrast, the regenerative fuel cell system 10 may also be used, for example, on Earth. In this case, simply opening the hydrogen-side exhaust valve 192 and the oxygen-side exhaust valve 197 is not enough to create a vacuum inside the water tank 300. Therefore, the regenerative fuel cell system 10 may be provided with a vacuum pump connected to the water tank 300 via the hydrogen-side exhaust path 191 or the oxygen-side exhaust path 196, and the control device 500 may use the vacuum pump to create a vacuum inside the water tank 300.

[0038] (D-2) In the above embodiment, the recombiner 340 is disposed inside the water tank 300. Alternatively, the recombiner 340 may be disposed outside the water tank 300. For example, in a regenerative fuel cell system 10 in which the water tank 300 is configured as a single tank, the hydrogen-side drainage channel 131 and the oxygen-side drainage channel 141 merge before the water tank 300, and the junction of the hydrogen-side drainage channel 131 and the oxygen-side drainage channel 141 is connected to the water tank 300 by a single drainage channel, the recombiner 340 may be disposed in the single drainage channel connecting the junction of the hydrogen-side drainage channel 131 and the oxygen-side drainage channel 141 to the water tank 300. According to this configuration, the amount of hydrogen and oxygen flowing into the water tank 300 is reduced, thereby suppressing an increase in pressure in the water tank 300.

[0039] (D-3) In the above embodiment, the recombiner 340 is disposed inside the water tank 300. However, the recombiner 340 may be disposed outside the water tank 300. For example, in a regenerative fuel cell system 10 having a hydrogen-side water supply channel 151 that is not provided with a hydrogen-side water supply valve 152 or a hydrogen-side water supply check valve 153, an oxygen-side water supply channel 161 that is not provided with an oxygen-side water supply valve 162 or an oxygen-side water supply check valve 163, and a water supply channel 150 that is provided with a water supply valve and a water supply check valve, the recombiner 340 may be disposed upstream of the water supply valve of the water supply channel 150. In this embodiment, when the water supply valve is closed, water is generated in the recombiner 340, thereby reducing the amount of hydrogen dissolved in the water in the hydrogen-side water tank 310 and the amount of oxygen dissolved in the water in the oxygen-side water tank 320. This prevents the pressure in the hydrogen-side water tank 310 and the oxygen-side water tank 320 from increasing.

[0040] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0041] 5... Lunar rover, 10... Regenerative fuel cell system, 20... Solar power generation system, 30... Drive motor, 110... Hydrogen tank, 111... Hydrogen supply line, 112... Hydrogen supply valve, 120... Oxygen tank, 121... Oxygen supply line, 122... Oxygen supply valve, 131... Hydrogen side drain line, 132... Hydrogen side gas-liquid separator, 133... Hydrogen side drain valve, 134... Hydrogen side check valve, 135... Hydrogen circulation line, 13 6...hydrogen circulation pump, 141...oxygen side drainage channel, 142...oxygen side gas-liquid separator, 143...oxygen side drainage valve, 144...oxygen side check valve, 145...oxygen circulation channel, 146...oxygen circulation pump, 150...water supply channel, 151...hydrogen side water supply channel, 152...hydrogen side water supply valve, 153...hydrogen side water supply check valve, 161...oxygen side water supply channel, 162...oxygen side water supply valve, 163...oxygen side water supply check valve, 171...hydrogen filling passage, 172...hydrogen filling pump, 173...hydrogen filling valve, 174...hydrogen filling check valve, 181...oxygen filling passage, 182...oxygen filling pump, 183...oxygen filling valve, 184...oxygen filling check valve, 191...hydrogen side exhaust passage, 192...hydrogen side exhaust valve, 196...oxygen side exhaust passage, 197...oxygen side exhaust valve, 200...fuel cell, 300, 300b, 300c...water tank, 310 ...hydrogen side water tank, 320...oxygen side water tank, 330, 330b, 330c...communicating portion, 331...wall portion, 332...through hole, 340...recombiner, 400...water electrolysis device, 500...control device, 501...CPU, 502...memory, 503...input / output interface, 504...internal bus, MS...lunar surface, R1...first region, R2...second region, S1...first reference water level, S2...second reference water level

Claims

1. 1. A regenerative fuel cell system, comprising: A fuel cell; a water tank for storing water; a recombiner that combines hydrogen and oxygen to produce water; a water electrolysis device that electrolyzes water supplied from the water tank to generate hydrogen and oxygen to be used in an electrochemical reaction in the fuel cell; The water tank is a first region for storing water containing hydrogen discharged from the fuel cell; a second region for storing oxygen-containing water discharged from the fuel cell; a communication portion that communicates the first region and the second region, The recombiner is disposed in the communication portion. Regenerative fuel cell system.

2. 10. The regenerative fuel cell system of claim 1, The water tank is a hydrogen-side water tank having the first region; an oxygen-side water tank having the second region; The communication part communicates the hydrogen-side water tank with the oxygen-side water tank. Regenerative fuel cell system.

3. 3. The regenerative fuel cell system according to claim 2, the communication portion communicates a portion of the hydrogen-side water tank above a first reference water level with a portion of the oxygen-side water tank above a second reference water level. Regenerative fuel cell system.

4. 3. The regenerative fuel cell system according to claim 2, the communication portion communicates a portion of the hydrogen-side water tank below a first reference water level with a portion of the oxygen-side water tank below a second reference water level. Regenerative fuel cell system.

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