Regenerative fuel cell system

Abstract

To suppress a decrease in production efficiency of oxygen by a water electrolyzer in a regenerative fuel cell system.SOLUTION: A regenerative fuel cell system includes a fuel cell, a water tank that stores water discharged from the fuel cell, a recombiner that is disposed in the water tank and generates water by combining hydrogen and oxygen, and a water electrolyzer that generates hydrogen and oxygen by electrolyzing the water supplied from the water tank. The internal pressure of the water tank storing the water is lower than the internal pressure of the fuel cell during power generation and the internal pressure of the water electrolyzer during electrolysis.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 using hydrogen and oxygen, and a water electrolysis device that generates hydrogen and oxygen by electrolyzing water produced during power generation by the fuel cell (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7260045 Summary of the Invention [Problem to be solved by the invention]

[0004] The water discharged from the fuel cell contains hydrogen. When water containing hydrogen is supplied to the anode of a water electrolysis device, the oxygen produced at the anode of the water electrolysis device reacts with the hydrogen and returns to water, reducing the efficiency of oxygen production by the water electrolysis device. [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. The regenerative fuel cell system includes a fuel cell, a water tank for storing water discharged from the fuel cell, a recombiner disposed in the water tank for combining hydrogen and oxygen to produce water, and a water electrolysis device for producing hydrogen and oxygen by electrolyzing water supplied from the water tank. The internal pressure of the water tank while storing water is lower than the internal pressure of the fuel cell while generating electricity and the internal pressure of the water electrolysis device while electrolyzing water. This regenerative fuel cell system can reduce the amount of hydrogen contained in the water supplied from the water tank to the water electrolysis device, thereby preventing a decrease in the efficiency of oxygen production by the water electrolysis device. (2) In the regenerative fuel cell system of the above aspect, the recombiner may be disposed in an upper portion of the water tank. In this type of regenerative fuel cell system, the hydrogen and oxygen separated from the water and moved to the upper part of the water tank can be recombined into water by the recombiner, thereby effectively reducing the amount of hydrogen contained in the water in the water tank. (3) The regenerative fuel cell system of the above aspect may further include a temperature regulator that adjusts the temperature of the water tank. This type of regenerative fuel cell system can prevent the saturated vapor pressure in the water tank from changing, and can also prevent the water in the water tank from freezing. (4) The regenerative fuel cell system of the above form is mounted on a lunar rover that travels on the surface of the moon, and further comprises a valve that switches the state of the water tank between a connected state in which the water tank is connected to the external space of the lunar rover, and a disconnected state in which the water tank is not connected to the external space, and the valve may switch the state of the water tank to the connected state when the lunar rover is located on the lunar surface, and switch the state of the water tank to the disconnected state before water flows from the fuel cell into the water tank. With this type of regenerative fuel cell system, the internal pressure of the water tank can be reduced by opening and closing the valve on the lunar surface, making it possible to reduce the internal pressure of the water tank with a simple configuration. The present disclosure can be realized in various forms other than a regenerative fuel cell system, such as a lunar rover. [Brief explanation of the drawings]

[0007] [Figure 1] Schematic of a lunar rover equipped with a regenerative fuel cell system. [Figure 2] Schematic diagram of a regenerative fuel cell system. [Figure 3]Schematic diagram of a water tank. 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 according to a first embodiment of the present disclosure. 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.

[0009] Figure 2 is a schematic diagram of the regenerative fuel cell system 10. Figure 3 is a schematic diagram of the water tank 300. As shown in Figure 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.

[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 water tank 300 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 in the hydrogen-side drainage channel 131 from the fuel cell 200 toward the water tank 300. 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 in 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 water tank 300. 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 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 water tank 300. The hydrogen-side check valve 134 prevents water from flowing back from the water tank 300 into the hydrogen-side gas-liquid separator 132.

[0014] The oxygen outlet of the fuel cell 200 is connected to the water tank 300 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 water tank 300. 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 water tank 300. 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 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 water tank 300. The oxygen-side check valve 144 prevents water from flowing back from the water tank 300 into the oxygen-side gas-liquid separator 142.

[0015] The water tank 300 stores water discharged from the fuel cell 200. As shown in FIG. 3 , at least one recombiner 350 is disposed within the water tank 300. In this embodiment, three recombiners 350 are disposed within the water tank 300. The recombiners 350 combine hydrogen and oxygen to produce water. In this embodiment, catalytic recombiners are used as the recombiners 350. In the following description, to distinguish between the three recombiners 350, the first recombiner 350 may be referred to as the first recombiner 350A, the second recombiner 350 as the second recombiner 350B, and the third recombiner 350 as the third recombiner 350C. When the three recombiners 350 are described without any particular distinction, they will simply be referred to as recombiners 350.

[0016] The first recombiner 350A is disposed in the upper part of the water tank 300 so as to be located above the water. The upper part of the water tank 300 refers to the part above the center of the water tank 300 in the vertical direction. The first recombiner 350A is fixed, for example, to the ceiling surface or a side wall surface of the water tank 300. The second recombiner 350B is disposed near the center of the water tank 300 in the vertical direction so as to be located near the water surface. The second recombiner 350B is fixed, for example, to the side wall surface of the water tank 300. However, the second recombiner 350B does not have to be fixed to the water tank 300. The second recombiner 350B may be configured, for example, to float on water and move up and down within the water tank 300. The third recombiner 350C is disposed in the lower part of the water tank 300 so as to be located underwater. The lower part of the water tank 300 refers to the part below the center in the vertical direction of the water tank 300. The third recombiner 350C is fixed, for example, to the floor surface or the side wall surface of the water tank 300. However, the third recombiner 350C does not have to be fixed to the water tank 300.

[0017] The water tank 300 is provided with a temperature regulator 360 that regulates the temperature inside the water tank 300. The temperature regulator 360 regulates the temperature inside the water tank 300 under the control of the control device 500. In this embodiment, the temperature regulator 360 is composed of a pipe through which the heat medium flows, a heat exchanger that exchanges heat with the heat medium, a pump that pressure-feeds the heat medium, etc. However, the temperature regulator 360 may also be composed of a heater that generates heat when supplied with electric power.

[0018] As shown in FIG. 2 , the water tank 300 is connected to the water inlet of the water electrolysis device 400 via a water supply channel 151. A water supply valve 152 and a water supply check valve 153 are provided in the water supply channel 151, extending from the water tank 300 toward the water electrolysis device 400. The water supply valve 152 adjusts the amount of water supplied from the water tank 300 to the water electrolysis device 400. The water supply valve 152 is configured, for example, as an electric valve or a solenoid valve. The water supply valve 152 opens and closes under the control of a control device 500. Although not shown in the figures, in this embodiment, the water tank 300 is provided with a water level sensor that detects the water level in the water tank 300. The control device 500 opens the water supply valve 152 when the water level in the water tank 300 detected by the water level sensor is equal to or greater than a predetermined value, and closes the water supply valve 152 when the water level in the water tank 300 detected by the water level sensor is below the predetermined value. This prevents hydrogen and oxygen separated from water from flowing from the water tank 300 into the water electrolysis device 400. The water supply check valve 153 prevents water from flowing back from the water electrolysis device 400 to the water tank 300.

[0019] In this embodiment, the water tank 300 is in communication with the external space of the lunar rover 5, in other words, the external space of the regenerative fuel cell system 10, via an exhaust path 191. An exhaust valve 192 is provided in the exhaust path 191. The exhaust valve 192 switches the state of the water tank 300 between a communication state in which the interior of the water tank 300 is in communication with the external space of the lunar rover 5, and a non-communication state in which the interior of the water tank 300 is not in communication with the external space of the lunar rover 5. When the exhaust valve 192 is opened, the water tank 300 is in a communication state, and when the exhaust valve 192 is closed, the water tank 300 is in a non-communication state. The exhaust valve 192 is configured, for example, as an electric valve or a solenoid valve. The exhaust valve 192 is opened and closed under the control of the control device 500.

[0020] 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 151 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.

[0021] 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 151.

[0022] 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 151.

[0023] 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.

[0024] 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 exhaust valve 192 after the lunar rover 5 arrives at the lunar surface MS. The lunar rover 5 is transported from Earth to the lunar surface MS with the water tank 300 empty, in other words, with no liquid such as water present in the water tank 300. On the lunar surface MS, the external space of the lunar rover 5 is in a vacuum state, so by opening the exhaust valve 192 on the lunar surface MS, the air inside the water tank 300 is exhausted to the external space, creating a vacuum inside the water tank 300. The control device 500 closes the exhaust valve 192 after the water tank 300 has been vacuumed. Although not shown in the drawings, in this embodiment, the water tank 300 is provided with a pressure sensor that detects the pressure inside the water tank 300, and the control device 500 can use the pressure sensor to determine whether a vacuum has been created inside the water tank 300. In this embodiment, while the exhaust valve 192 is open, the hydrogen-side drain valve 133, the oxygen-side drain valve 143, and the water supply valve 152 are closed. However, while the exhaust valve 192 is open, the hydrogen-side drain valve 133, the oxygen-side drain valve 143, and the water supply valve 152 may be open. Note that the exhaust valve 192 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.

[0025] After closing the exhaust valve 192, the control device 500 starts power generation by the fuel cell 200 for the first time. "First time" means the first time since the lunar rover 5 arrives on the lunar surface MS. In this embodiment, the internal pressure of the fuel cell 200 during power generation is higher than atmospheric pressure on Earth. When power generation by the fuel cell 200 starts, water containing hydrogen and water containing oxygen flow from the fuel cell 200 into the water tank 300, which is in a vacuum. When the water containing hydrogen and water containing oxygen flow into the water tank 300, which is in a vacuum, the water, hydrogen, and oxygen vaporize inside the water tank 300, causing the internal pressure of the water tank 300 to rise. Because the internal pressure of the water tank 300 does not exceed the saturated vapor pressure, the increase in the internal pressure of the water tank 300 stops when the internal pressure of the water tank 300 reaches the saturated vapor pressure. When the internal pressure of the water tank 300 reaches the saturated vapor pressure, a gas mixture containing water vapor, hydrogen, and oxygen, and water in which hydrogen and oxygen are dissolved, coexist within the water tank 300. The saturated vapor pressure varies depending on the temperature. In this embodiment, the control device 500 controls the temperature regulator 360 to maintain a constant temperature within the water tank 300. This makes it possible to suppress changes in the saturated vapor pressure within the water tank 300.

[0026] Here, the nighttime temperature on the lunar surface MS drops to approximately minus 170 degrees Celsius, which could cause the water to freeze in the water tank 300. Furthermore, if water flows into the water tank 300, which is in a vacuum state, the water will evaporate, and the heat of vaporization could cause the temperature in the water tank 300 to drop, potentially causing the water to freeze in the water tank 300. If the water in the water tank 300 freezes, it could become impossible to supply water to the water electrolysis device 400. However, in this embodiment, the control device 500 controls the temperature regulator 360 to keep the temperature in the water tank 300 constant, which could prevent the temperature in the water tank 300 from dropping due to the heat of vaporization when the water evaporates, thereby preventing the water in the water tank 300 from freezing.

[0027] Between the time when power generation by the fuel cell 200 is stopped and the time when water electrolysis by the water electrolysis device 400 starts, the hydrogen-side drain valve 133, the oxygen-side drain valve 143, and the water supply valve 152 are closed, and the water tank 300 is kept sealed. Because a recombiner 350 is disposed in the water tank 300, vaporized hydrogen and oxygen combine to reduce the hydrogen and oxygen partial pressures of the mixed gas in the water tank 300. Here, hydrogen and oxygen dissolve in water according to Henry's law. According to Henry's law, only an amount of a gas that is proportional to its partial pressure can dissolve in water. Therefore, as the hydrogen and oxygen partial pressures in the water tank 300 decrease, the hydrogen and oxygen concentrations in the water in the water tank 300 decrease.

[0028] The control device 500 then supplies water stored in the water tank 300 to the water electrolysis device 400, and starts electrolysis of water by the water electrolysis device 400. In this embodiment, the internal pressure of the water electrolysis device 400 during water electrolysis is higher than the Earth's atmospheric pressure. When water containing hydrogen is supplied to the anode side of the water electrolysis device 400, some of the oxygen generated at the anode side by water electrolysis combines with the hydrogen and returns to water, reducing the efficiency of oxygen production by the water electrolysis device 400. However, in this embodiment, the recombiner 350 is disposed in the water tank 300, thereby reducing the hydrogen concentration in the water supplied from the water tank 300 to the water electrolysis device 400, thereby preventing a decrease in the efficiency of oxygen production by the water electrolysis device 400.

[0029] According to the regenerative fuel cell system 10 of the present embodiment described above, the control device 500 controls each component of the regenerative fuel cell system 10 so that the internal pressure of the water tank 300 storing water is lower than the internal pressure of the fuel cell 200 and lower than the internal pressure of the water electrolysis device 400. This makes it easier to vaporize hydrogen and oxygen dissolved in water in the water tank 300. Furthermore, in this embodiment, a recombiner 350 that combines hydrogen and oxygen to generate water is disposed in the water tank 300. This makes it possible to convert the vaporized hydrogen and oxygen in the water tank 300 into water, thereby reducing the amount of hydrogen contained in the water supplied from the water tank 300 to the water electrolysis device 400. This prevents a decrease in the efficiency of oxygen production by the water electrolysis device 400.

[0030] Here, a mixed gas containing a large amount of hydrogen and oxygen may burn violently, and therefore it is undesirable for the mixed gas containing a large amount of hydrogen and oxygen to be present in the regenerative fuel cell system 10. However, in this embodiment, in the water flow path from the fuel cell 200 to the water electrolysis device 400, the internal pressure of the water tank 300 is lower than the internal pressure of the portions other than the water tank 300. Therefore, it is possible to prevent a mixed gas containing a large amount of hydrogen and oxygen from being generated in the portions other than the water tank 300.

[0031] In this embodiment, three recombiners 350A to 350C are disposed within the water tank 300. The first recombiner 350A disposed at the top of the water tank 300 can convert the vaporized hydrogen and oxygen that accumulate at the top of the water tank 300 into water. The second recombiner 350B disposed between the first recombiner 350A and the third recombiner 350C can convert the hydrogen and oxygen into water early near the water surface before the hydrogen and oxygen move to the top of the water tank 300. The third recombiner 350C disposed at the bottom of the water tank 300 can convert the hydrogen and oxygen into water early within the water. Therefore, by disposing the recombiners 350A to 350C at multiple locations within the water tank 300, the amount of hydrogen in the water tank 300 can be effectively reduced.

[0032] Furthermore, in this embodiment, an exhaust valve 192 is provided that switches between communication and non-communication between the inside of the water tank 300 and the space outside the lunar rover 5. Therefore, by opening the exhaust valve 192, the inside of the water tank 300 can be communicated with the space outside the lunar surface MS, creating a vacuum inside the water tank 300. Therefore, a vacuum can be created inside the water tank 300 with a simple configuration.

[0033] Furthermore, in this embodiment, a temperature regulator 360 is provided to adjust the temperature inside the water tank 300. Therefore, by maintaining a constant temperature inside the water tank 300, it is possible to suppress changes in the saturated vapor pressure inside the water tank 300. Furthermore, by maintaining a constant temperature inside the water tank 300, it is possible to suppress the freezing of water inside the water tank 300, which would prevent water from being supplied to the water electrolysis apparatus 400.

[0034] B. Other Embodiments: (B1) In the first embodiment described above, 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 be used, for example, on Earth. In this case, since it is not possible to create a vacuum inside the water tank 300 simply by opening the exhaust valve 192, the regenerative fuel cell system 10 may be provided with a vacuum pump connected to the water tank 300 via the exhaust path 191, and the control device 500 may use the vacuum pump to create a vacuum inside the water tank 300.

[0035] (B2) In the first embodiment described above, a catalytic recombiner is used as the recombiner 350. Alternatively, a recombiner in which oxygen and hydrogen are converted into water by an oxidation reaction may be used as the recombiner 350.

[0036] (B3) In the first embodiment described above, the number of water tanks 300 into which hydrogen-containing water and oxygen-containing water flow is one. However, the number of water tanks 300 may be two or more. In this case, it is preferable that a recombiner 350 is provided in each of the water tanks 300.

[0037] (B4) In the first embodiment described above, a temperature regulator 360 is provided to regulate the temperature inside the water tank 300. However, the temperature regulator 360 does not necessarily have to be provided.

[0038] (B5) In the first embodiment described above, the exhaust valve 192 is configured as an electric valve or a solenoid valve that can be opened and closed under the control of the control device 500. In contrast, the exhaust valve 192 may be configured as a manual valve. In this case, since the exhaust valve 192 cannot be opened and closed by the control device 500, the exhaust valve 192 may be opened and closed by a crew member of the lunar rover 5, for example.

[0039] 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]

[0040] 5... Lunar rover, 10... Regenerative fuel cell system, 20... Solar power generation system, 30... Drive motor, 110... Hydrogen tank, 111... Hydrogen supply channel, 112... Hydrogen supply valve, 120... Oxygen tank, 121... Oxygen supply channel, 122... Oxygen supply valve, 131... Hydrogen side drain channel, 132... Hydrogen side gas-liquid separator, 133... Hydrogen side drain valve, 134... Hydrogen side check valve, 135... Hydrogen circulation channel, 136... Hydrogen circulation pump, 141... Oxygen side drain channel, 142... Oxygen side gas-liquid separator, 143... Oxygen side drain valve, 144... Oxygen side check valve, 145... Oxygen circulation channel, 146... Oxygen circulation pump Circulation pump, 151...water supply line, 152...water supply valve, 153...water supply check valve, 171...hydrogen filling line, 172...hydrogen filling pump, 173...hydrogen filling valve, 174...hydrogen filling check valve, 181...oxygen filling line, 182...oxygen filling pump, 183...oxygen filling valve, 184...oxygen filling check valve, 191...exhaust line, 192...exhaust valve, 200...fuel cell, 300...water tank, 350...recombiner, 360...temperature regulator, 400...water electrolysis device, 500...control device, 501...processor, 502...memory, 503...input / output interface, 504...internal bus

Claims

1. 1. A regenerative fuel cell system, comprising: A fuel cell; a water tank for storing water discharged from the fuel cell; a recombiner disposed within the water tank, the recombiner combining hydrogen and oxygen to produce water; a water electrolysis device that generates hydrogen and oxygen by electrolyzing the water supplied from the water tank; Equipped with A regenerative fuel cell system, wherein the internal pressure of the water tank while storing water is lower than the internal pressure of the fuel cell while generating power and the internal pressure of the water electrolysis device while electrolysis is being performed.

2. 10. The regenerative fuel cell system of claim 1, A regenerative fuel cell system, wherein the recombiner is disposed in an upper portion of the water tank.

3. 10. The regenerative fuel cell system of claim 1, The regenerative fuel cell system further comprises a temperature regulator that regulates the temperature of the water tank.

4. 10. The regenerative fuel cell system of claim 1, The regenerative fuel cell system is mounted on a lunar rover that travels on the surface of the moon, and further comprises a valve that switches the state of the water tank between a communication state in which the water tank is in communication with an external space of the lunar rover, and a non-communication state in which the water tank is not in communication with the external space; The valve switches the state of the water tank to the connected state when the lunar rover is located on the lunar surface, and switches the state of the water tank to the disconnected state before water flows from the fuel cell into the water tank.

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