Regenerative fuel cell system

Abstract

This regenerative fuel cell system is provided with: a fuel cell; a water tank for storing water discharged from the fuel cell; a recombiner which is disposed in the water tank and generates water by combining hydrogen and oxygen; and a water electrolysis device that generates hydrogen and oxygen by electrolyzing the water supplied from the water tank. The internal pressure of the water tank for storing water is lower than the internal pressure of the fuel cell for power generation and the internal pressure of the water electrolysis device for electrolysis.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a regenerative fuel cell system. BACKGROUND

[0002] A regenerative fuel cell system is known, which includes a fuel cell that generates electricity using hydrogen and oxygen, and a water electrolysis device that generates hydrogen and oxygen by electrically decomposing water generated at the time of electricity generation in the fuel cell (for example, Japanese Patent No. 7260045).

[0003] Water discharged from the fuel cell contains hydrogen. If water containing hydrogen is supplied to the anode of the water electrolysis device, oxygen generated at the anode of the water electrolysis device reacts with hydrogen to be restored to water, and thus the oxygen generation efficiency of the water electrolysis device decreases. SUMMARY

[0004] The present disclosure can be implemented as follows.

[0005] According to one embodiment of the present disclosure, a regenerative fuel cell system is provided. The 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 causes hydrogen and oxygen to combine to generate water, and a water electrolysis device that electrically decomposes water supplied from the water tank to generate hydrogen and oxygen. The internal pressure of the water tank that stores water is lower than the internal pressure of the fuel cell during electricity generation and the internal pressure of the water electrolysis device during electrical decomposition. According to the regenerative fuel cell system of this embodiment, the amount of hydrogen contained in water supplied from the water tank to the water electrolysis device can be reduced. Thus, the oxygen generation efficiency of the water electrolysis device can be suppressed from decreasing. The regenerative fuel cell system of the above embodiment can be configured such that the recombiner is disposed in an upper portion of the water tank. According to the regenerative fuel cell system of this embodiment, hydrogen separated from water and moved to the upper portion of the water tank can be caused to become water by the recombiner. Thus, the amount of hydrogen contained in water in the water tank can be effectively reduced. The regenerative fuel cell system of the above embodiment can further include a temperature regulator that regulates the temperature of the water tank. According to the regenerative fuel cell system of this embodiment, the saturation vapor pressure in the water tank can be suppressed from changing. In addition, water in the water tank can be suppressed from freezing. The regenerative fuel cell system of the above embodiment can be mounted on a lunar rover that travels on the moon, and can further include a valve that switches the state of the water tank between a communication state in which the water tank communicates with an external space of the lunar rover and a non-communication state in which the water tank does not communicate with the external space. The valve switches the state of the water tank to the communicating state before water flows from the fuel cell to the water tank, and switches the state of the water tank to the non-communicating state after water flows from the fuel cell to the water tank. According to the regenerative fuel cell system of this aspect, the internal pressure of the water tank can be reduced by opening and closing the valve on the moon. Therefore, the internal pressure of the water tank can be reduced with a simple structure. The present disclosure can also be implemented in various ways other than the regenerative fuel cell system. For example, it can be implemented in a moon rover or the like. Features, advantages, and technical and industrial significance of exemplary embodiments of the application will be described below with reference to the accompanying drawings, wherein the same reference numerals in different drawings denote the same element. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 is a diagram of a moon rover equipped with a regenerative fuel cell system. Figure 2 is a diagram of a regenerative fuel cell system. Figure 3 is a diagram of a water tank. DETAILED DESCRIPTION A. First Embodiment:

[0007] Figure 1 is a diagram of a moon rover 5 equipped with the regenerative fuel cell system 10 in the first embodiment of the present disclosure. The moon rover 5 is a vehicle configured to be able to travel on the moon MS. In the present embodiment, the moon rover 5 is provided with the regenerative fuel cell system 10, a solar power generation system 20, and a travel motor 30. The regenerative fuel cell system 10 is able to generate hydrogen and oxygen by using electric power supplied from the solar power generation system 20 to split water during the day on the moon, is able to generate electric power using the hydrogen and oxygen and generate water during the night on the moon, and is also able to generate electric power using the hydrogen and oxygen and generate water during the day on the moon. The moon rover 5 drives the travel motor 30 using electric power supplied from the regenerative fuel cell system 10, thereby traveling on the moon MS.

[0008] Figure 2 is a diagram of the regenerative fuel cell system 10. Figure 3 is a diagram of a water tank 300. As Figure 2 shown, the regenerative fuel cell system 10 is provided with a hydrogen tank 110, an oxygen tank 120, a fuel cell 200, the water tank 300, a water electrolysis device 400, and a control device 500.

[0009] Hydrogen is stored in a hydrogen tank 110. The hydrogen tank 110 is connected to a hydrogen inlet of the fuel cell 200 via a hydrogen supply path 111. A hydrogen supply valve 112 that adjusts the supply amount of hydrogen supplied from the hydrogen tank 110 to the fuel cell 200 is provided in the hydrogen supply path 111. The hydrogen supply valve 112 is constituted by, for example, an electrically driven valve or a solenoid valve. The hydrogen supply valve 112 is opened and closed under the control of a control device 500.

[0010] Oxygen is stored in an oxygen tank 120. The oxygen tank 120 is connected to an oxygen inlet of the fuel cell 200 via an oxygen supply path 121. An oxygen supply valve 122 that adjusts the supply amount of oxygen supplied from the oxygen tank 120 to the fuel cell 200 is provided in the oxygen supply path 121. The oxygen supply valve 122 is constituted by, for example, an electrically driven valve or a solenoid valve. The oxygen supply valve 122 is opened and closed under the control of the control device 500.

[0011] The fuel cell 200 generates electric power using hydrogen and oxygen. In the present embodiment, the fuel cell 200 is a solid polymer type fuel cell. The fuel cell 200 is provided with a fuel cell stack in which a plurality of fuel cell units are stacked. Each fuel cell unit is provided with a membrane electrode assembly in which an electrode catalyst layer is provided on both surfaces of an electrolyte membrane, and a separator that sandwiches the membrane electrode assembly. The fuel cell 200 generates electric power by supplying hydrogen to the electrode catalyst layer on the anode side and supplying oxygen to the electrode catalyst layer on the cathode side. Water is generated along with the generation of electric power in the fuel cell 200. The electric power generated by the fuel cell 200 is used to drive the traveling motor 30.

[0012] The hydrogen outlet of the fuel cell 200 is connected to the water tank 300 via a hydrogen-side drain passage 131. In the hydrogen-side drain passage 131, a hydrogen-side gas-liquid separator 132, a hydrogen-side drain valve 133, and a hydrogen-side check valve 134 are provided in this order 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 accumulates the hydrogen and water discharged from the hydrogen outlet of the fuel cell 200 and separates the hydrogen from the water. In the present embodiment, the hydrogen-side gas-liquid separator 132 is connected to the hydrogen supply passage 111 via a hydrogen circulation passage 135. A hydrogen circulation pump 136 is provided in the hydrogen circulation passage 135. The hydrogen circulation pump 136 pressurizes the hydrogen from the hydrogen-side gas-liquid separator 132 toward the hydrogen supply passage 111 via the hydrogen circulation passage 135. The hydrogen circulation pump 136 is driven under the control of the control device 500. The hydrogen-side drain valve 133 adjusts the discharge amount of the water discharged from the hydrogen-side gas-liquid separator 132 toward the water tank 300. The hydrogen-side drain valve 133 is constituted by, for example, 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 present embodiment, a water level sensor that detects the water level of the hydrogen-side gas-liquid separator 132 is provided in the hydrogen-side gas-liquid separator 132. In a case where the water level of the hydrogen-side gas-liquid separator 132 detected by the water level sensor is equal to or greater than a prescribed value, the control device 500 opens the hydrogen-side drain valve 133, and in a case where the water level of the hydrogen-side gas-liquid separator 132 detected by the water level sensor is less than the prescribed value, the control device 500 closes the hydrogen-side drain valve 133. Thus, inflow of the hydrogen separated from the water from the hydrogen-side gas-liquid separator 132 toward the water tank 300 is suppressed. The hydrogen-side check valve 134 suppresses backflow of the water from the water tank 300 toward the hydrogen-side gas-liquid separator 132.

[0013] The oxygen outlet of the fuel cell 200 is connected to the water tank 300 via an oxygen-side drain passage 141. In the oxygen-side drain passage 141, from the fuel cell 200 toward the water tank 300, an oxygen-side gas-liquid separator 142, an oxygen-side drain valve 143, and an oxygen-side check valve 144 are sequentially arranged. 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 passage 121 via an oxygen circulation passage 145. An oxygen circulation pump 146 is provided in the oxygen circulation passage 145. The oxygen circulation pump 146 pressurizes oxygen from the oxygen-side gas-liquid separator 142 to the oxygen supply passage 121 via the oxygen circulation passage 145. The oxygen circulation pump 146 is driven under the control of the control device 500. The oxygen-side drain valve 143 regulates the discharge rate of water from the oxygen-side gas-liquid separator 142 to the water tank 300. The oxygen-side drain valve 143 is, for example, 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 figure, in this embodiment, a water level sensor is provided in the oxygen-side gas-liquid separator 142 to detect the water level. For the control device 500, when the water level in the oxygen-side gas-liquid separator 142 detected by the water level sensor is above a predetermined value, the oxygen-side drain valve 143 is opened; when the water level in the oxygen-side gas-liquid separator 142 detected by the water level sensor is below the predetermined value, the oxygen-side drain valve 143 is closed. Therefore, oxygen separated from water is prevented 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 to the oxygen-side gas-liquid separator 142.

[0014] Water tank 300 stores water discharged from fuel cell 200. For example... Figure 3 As shown, 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 generate water. In this embodiment, the recombiners 350 are catalyst-type recombiners. In the following description, to distinguish the three recombiners 350, the first recombiner 350 is sometimes 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. Unless specifically distinguished in the description of the three recombiners 350, they are simply referred to as recombiners 350.

[0015] The first rejoiner 350A is disposed in the upper part of the water tank 300, above the water surface. The upper part of the water tank 300 is the portion of the water tank 300 located above its center in the vertical direction. The first rejoiner 350A is fixed, for example, to the top surface or side wall of the water tank 300. The second rejoiner 350B is disposed near the center of the water tank 300 in the vertical direction, near the water surface. The second rejoiner 350B is fixed, for example, to the side wall of the water tank 300. Alternatively, the second rejoiner 350B may not be fixed to the water tank 300. The second rejoiner 350B may also be configured to float on the water and move vertically within the water tank 300. The third rejoiner 350C is disposed in the lower part of the water tank 300, underwater. The lower part of the water tank 300 is the portion of the water tank 300 located below its center in the vertical direction. The third rejoint 350C is fixed to, for example, the bottom surface of the water tank 300 or the side wall surface of the water tank 300. Alternatively, the third rejoint 350C may not be fixed to the water tank 300.

[0016] A temperature regulator 360 is provided in the water tank 300 to regulate 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 consists of piping for the flow of the heating medium, a heat exchanger for heat exchange of the heating medium, and a pump for pressurizing the heating medium. Alternatively, the temperature regulator 360 may also be a heater that receives electrical power and generates heat.

[0017] like Figure 2 As shown, the water tank 300 is connected to the water inlet of the water electrolysis device 400 via a water supply passage 151. A water supply valve 152 and a water supply check valve 153 are provided in the water supply passage 151, extending from the water tank 300 towards the water electrolysis device 400. The water supply valve 152 regulates the amount of water supplied from the water tank 300 to the water electrolysis device 400. The water supply valve 152 is, for example, an electric valve or a solenoid valve. The water supply valve 152 is opened and closed under the control of the control device 500. Although not shown in the figure, in this embodiment, a water level sensor is provided in the water tank 300 to detect the water level inside the water tank 300. For the control device 500, when the water level in the water tank 300 detected by the water level sensor is above a predetermined value, the water supply valve 152 is opened; when the water level in the water tank 300 detected by the water level sensor is below the predetermined value, the water supply valve 152 is closed. Therefore, the flow of hydrogen and oxygen separated from water from water tank 300 into water electrolysis unit 400 is prevented. Water supply check valve 153 prevents water from flowing back from water electrolysis unit 400 into water tank 300.

[0018] In the present embodiment, the water tank 300 communicates with the outside of the lunar vehicle 5, in other words, with the outside of the regenerative fuel cell system 10, via the exhaust passage 191. An exhaust valve 192 is provided in the exhaust passage 191. The exhaust valve 192 switches the state of the water tank 300 to either a communication state in which the inside of the water tank 300 communicates with the outside of the lunar vehicle 5 or a non-communication state in which the inside of the water tank 300 does not communicate with the outside of the lunar vehicle 5. The water tank 300 becomes the communication state by opening the exhaust valve 192, and the water tank 300 becomes the non-communication state by closing the exhaust valve 192. The exhaust valve 192 is constituted by, for example, an electric valve or a solenoid valve. The exhaust valve 192 is opened and closed under the control of the control device 500.

[0019] The water electrolysis device 400 generates hydrogen and oxygen by electrolyzing water supplied from the water tank 300. In the present embodiment, the water electrolysis device 400 uses a solid polymer type water electrolysis device. The water electrolysis device 400 is provided with a water electrolysis cell stack in which a plurality of water electrolysis cells are stacked, and a pump that pressurizes and feeds water to the water electrolysis cell stack from the water supply passage 151. Each water electrolysis cell is provided with a membrane electrode assembly in which an electrode catalyst layer is provided on both surfaces of an electrolyte membrane, and a separator that sandwiches the membrane electrode assembly. The water electrolysis device 400 generates oxygen at the electrode catalyst layer on the anode side and hydrogen at the electrode catalyst layer on the cathode side by electrolyzing water supplied to the electrode catalyst layer on the anode side. In the present embodiment, the water electrolysis device 400 electrolyzes water using electric power supplied from the solar power generation system 20. Incidentally, the water electrolysis device 400 may, for example, also electrolyze water using electric power supplied from an electric power supply source other than the solar power generation system 20, such as a lithium ion secondary battery.

[0020] The hydrogen outlet of the water electrolysis device 400 is connected to the hydrogen tank 110 via the hydrogen filling passage 171. In the hydrogen filling passage 171, a hydrogen filling pump 172, a hydrogen filling valve 173, and a hydrogen filling check valve 174 are provided in this order from the water electrolysis device 400 toward the hydrogen tank 110. The hydrogen filling pump 172 pressurizes and feeds hydrogen from the water electrolysis device 400 to the hydrogen tank 110. The hydrogen filling pump 172 is driven under the control of the control device 500. The hydrogen filling valve 173 adjusts the supply amount of hydrogen supplied from the water electrolysis device 400 to the hydrogen tank 110. The hydrogen filling valve 173 is constituted by, for example, 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 inhibits backflow of hydrogen from the hydrogen tank 110 to the water electrolysis device 400. In addition, the regenerative fuel cell system 10 can also be provided with a gas-liquid separator that separates hydrogen and water discharged from the hydrogen outlet of the water electrolysis device 400, and a circulation passage and a pump for circulating water separated from hydrogen by the gas-liquid separator to the water supply passage 151.

[0021] The oxygen outlet of the water electrolysis device 400 is connected to the oxygen tank 120 via an oxygen filling path 181. In the oxygen filling path 181, from the water electrolysis device 400 toward the oxygen tank 120, an oxygen filling pump 182, an oxygen filling valve 183, and an oxygen filling check valve 184 are provided in this order. The oxygen filling pump 182 pressurizes oxygen from the water electrolysis device 400 to the oxygen tank 120. The oxygen filling pump 182 is driven under the control of the control device 500. The oxygen filling valve 183 adjusts the supply amount of oxygen supplied from the water electrolysis device 400 to the oxygen tank 120. The oxygen filling valve 183 is constituted 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 inhibits backflow of oxygen from the oxygen tank 120 to the water electrolysis device 400. In addition, the regenerative fuel cell system 10 can further include a gas-liquid separator that separates oxygen discharged from the oxygen outlet of the water electrolysis device 400 from water, and a circulation path and a pump for circulating water separated from oxygen by the gas-liquid separator to the water supply path 151.

[0022] The control device 500 is constituted by a computer including a CPU 501, a memory 502 including a ROM, a RAM, and the like, an input-output interface 503, and an internal bus 504. The CPU 501, the memory 502, and the input-output interface 503 are connected via the internal bus 504 so as to be able to communicate bidirectionally. To the input-output interface 503, the various valves, the various pumps, the various sensors, and the like of the regenerative fuel cell system 10 described above are connected via wired communication or wireless communication. The CPU 501 exercises various functions including a function of controlling power generation by the fuel cell 200 and a function of controlling electrolysis of water by the water electrolysis device 400 by executing a computer program stored in advance in the memory 502.

[0023] The control device 500 controls the respective units 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 during power generation, and is lower than the internal pressure of the water electrolysis device 400 during electrical decomposition of water. Specifically, after the lunar rover 5 reaches the moon MS, the control device 500 opens the exhaust valve 192. The lunar rover 5 is transported to the moon MS from the earth in a state where the water tank 300 is empty, in other words, in a state where no liquid such as water exists in the water tank 300. The outside space of the lunar rover 5 is in a vacuum state on the moon MS, and thus, by opening the exhaust valve 192 on the moon MS, the air in the water tank 300 is exhausted to the outside space, and the water tank 300 becomes in a vacuum state. After the water tank 300 becomes in the vacuum state, the control device 500 closes the exhaust valve 192. Although not shown, in the present embodiment, a pressure sensor that detects the pressure in the water tank 300 is provided in the water tank 300, and the control device 500 can determine whether the water tank 300 becomes in the vacuum state using the pressure sensor. In the present embodiment, the hydrogen-side water drain valve 133, the oxygen-side water drain valve 143, and the water supply valve 152 are closed during the period when the exhaust valve 192 is opened. Of course, the hydrogen-side water drain valve 133, the oxygen-side water drain valve 143, and the water supply valve 152 can be opened during the period when the exhaust valve 192 is opened. Further, the exhaust valve 192 can be opened before the lunar rover 5 reaches the moon MS, instead of being opened after the lunar rover 5 reaches the moon MS.

[0024] After the control device 500 closes the exhaust valve 192, the control device 500 starts the first power generation by the fuel cell 200. The first means the first after the lunar rover 5 reaches the moon MS. In the present embodiment, the internal pressure of the fuel cell 200 during power generation is higher than the atmospheric pressure on the earth. If the power generation by the fuel cell 200 is started, water containing hydrogen, and water containing oxygen flow from the fuel cell 200 to the water tank 300 in the vacuum state. If the water containing hydrogen, and the water containing oxygen flow to the water tank 300 in the vacuum state, the water, hydrogen, and oxygen vaporize in the water tank 300, and the internal pressure of the water tank 300 rises. In order to avoid the internal pressure of the water tank 300 exceeding the saturated vapor pressure, if the internal pressure of the water tank 300 reaches the saturated vapor pressure, the rise of the internal pressure of the water tank 300 is stopped. After the internal pressure of the water tank 300 reaches the saturated vapor pressure, in the water tank 300, a mixed gas containing water vapor, hydrogen, and oxygen, and water in which hydrogen and oxygen are dissolved coexist. Here, the saturated vapor pressure varies depending on the temperature. In the present embodiment, the control device 500 controls the temperature regulator 360 to keep the temperature in the water tank 300 constant. Thus, the variation of the saturated vapor pressure in the water tank 300 can be suppressed.

[0025] Here, the temperature at night on the moon MS decreases to about -170 degrees Celsius, and thus there is a possibility that water freezes in the water tank 300. In addition, if water flows into the water tank 300 in a vacuum state, the water vaporizes, the temperature in the water tank 300 decreases due to the heat of vaporization, and there is a possibility that water freezes in the water tank 300. If water freezes in the water tank 300, there is a possibility that water cannot be supplied to the water electrolysis device 400. However, in the present embodiment, the control device 500 controls the temperature regulator 360 to keep the temperature in the water tank 300 constant, and thus it is possible to suppress a decrease in the temperature of the water tank 300 due to the heat of vaporization when water vaporizes and freezing of water in the water tank 300.

[0026] During a period from stopping power generation by the fuel cell 200 to starting the water electrolysis device 400 to perform electrolysis of water, the hydrogen-side drain valve 133, the oxygen-side drain valve 143, and the water supply valve 152 are closed, and the closed state of the water tank 300 is maintained. Since the recombiner 350 is provided in the water tank 300, hydrogen that vaporizes combines with oxygen, and thus the hydrogen partial pressure and the oxygen partial pressure of the mixed gas in the water tank 300 decrease. Here, hydrogen and oxygen dissolve in water according to Henry's law. According to Henry's law, a gas dissolves in water in an amount proportional to its partial pressure. Thus, the hydrogen concentration and the oxygen concentration of water in the water tank 300 decrease by the decrease in the hydrogen partial pressure and the oxygen partial pressure in the water tank 300.

[0027] Thereafter, the control device 500 supplies water stored in the water tank 300 to the water electrolysis device 400, and starts the water electrolysis device 400 to perform electrolysis of water. In the present embodiment, the internal pressure of the water electrolysis device 400 during electrolysis of water is higher than the atmospheric pressure on the earth. Here, if water containing hydrogen is supplied to the anode side of the water electrolysis device 400, a part of oxygen generated on the anode side by electrolysis of water combines with hydrogen and returns to water, and thus the efficiency of oxygen generation by the water electrolysis device 400 decreases. However, in the present embodiment, the hydrogen concentration of water supplied from the water tank 300 to the water electrolysis device 400 is made low by providing the recombiner 350 in the water tank 300, and thus it is possible to suppress a decrease in the efficiency of oxygen generation by the water electrolysis device 400.

[0028] According to the regenerative fuel cell system 10 of the present embodiment described above, the control device 500 controls each part 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. Therefore, hydrogen and oxygen dissolved in water can be easily vaporized in the water tank 300. Also, in the present embodiment, the recombiner 350 that combines hydrogen and oxygen to generate water is provided in the water tank 300. Therefore, the vaporized hydrogen and oxygen can be changed to water in the water tank 300, thereby reducing the amount of hydrogen contained in the water supplied from the water tank 300 to the water electrolysis device 400. Thus, the efficiency of the water electrolysis device 400 in generating oxygen can be suppressed from decreasing.

[0029] Here, a mixed gas containing a large amount of hydrogen and oxygen can burn violently, and thus it is not preferable that a mixed gas containing a large amount of hydrogen and oxygen exists in the regenerative fuel cell system 10. However, in the present embodiment, the internal pressure of the water tank 300 is lower than the internal pressure of portions other than the water tank 300 in the flow path of water from the fuel cell 200 to the water electrolysis device 400. Therefore, the generation of a mixed gas containing a large amount of hydrogen and oxygen in portions other than the water tank 300 can be suppressed.

[0030] Also, in the present embodiment, three recombiners 350A to 350C are provided in the water tank 300. The first recombiner 350A provided in the upper portion of the water tank 300 can change hydrogen and oxygen vaporized and accumulated in the upper portion of the water tank 300 to water. The second recombiner 350B provided between the first recombiner 350A and the third recombiner 350C can change hydrogen and oxygen to water in the vicinity of the water surface before the hydrogen and oxygen move to the upper portion of the water tank 300. The third recombiner 350C provided in the lower portion of the water tank 300 can change hydrogen and oxygen to water in water. Therefore, by providing the recombiners 350A to 350C at a plurality of portions in the water tank 300, the amount of hydrogen in the water tank 300 can be effectively reduced.

[0031] Also, in the present embodiment, the exhaust valve 192 that switches the communication and non-communication between the inside of the water tank 300 and the outside space of the lunar rover 5 is provided. Therefore, by opening the exhaust valve 192, the inside of the water tank 300 can be communicated with the outside space on the moon MS to be brought to a vacuum state. Thus, the inside of the water tank 300 can be brought to a vacuum state with a simple structure.

[0032] Also, in the present embodiment, the temperature regulator 360 that regulates the temperature in the water tank 300 is provided. Therefore, by keeping the temperature in the water tank 300 constant, the saturated vapor pressure in the water tank 300 can be suppressed from changing. Also, by keeping the temperature in the water tank 300 constant, water can be prevented from freezing in the water tank 300 and failing to supply water to the water electrolysis device 400. B. Other Embodiments

[0033] (B1) In the above-described first embodiment, the regenerative fuel cell system 10 is mounted on the lunar rover 5 and used on the moon MS. In contrast, the regenerative fuel cell system 10 can also be used on the earth, for example. In this case, the inside of the water tank 300 cannot be made into a vacuum state by merely opening the exhaust valve 192, and therefore a vacuum pump connected to the water tank 300 via the exhaust passage 191 can also be provided in the regenerative fuel cell system 10, and the control device 500 can use the vacuum pump to make the inside of the water tank 300 into a vacuum state.

[0034] (B2) In the above-described first embodiment, the recombiner 350 uses a catalyst-type recombiner. In contrast, the recombiner 350 can also use a recombiner in which oxygen and hydrogen become water through an oxidation reaction.

[0035] (B3) In the above-described first embodiment, the number of water tanks 300 into which water containing hydrogen and water containing oxygen flow is one. In contrast, the number of water tanks 300 can also be two or more. In this case, it is preferable that the recombiner 350 be provided in all of the water tanks 300.

[0036] (B4) In the above-described first embodiment, the temperature regulator 360 that adjusts the temperature in the water tank 300 is provided. In contrast, the temperature regulator 360 can also not be provided.

[0037] (B5) In the above-described first embodiment, the exhaust valve 192 is constituted by 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 can also be constituted by a manual valve. In this case, the exhaust valve 192 cannot be opened and closed by the control device 500, and therefore, for example, the exhaust valve 192 can be opened and closed by an occupant of the lunar rover 5.

[0038] The present disclosure is not limited to the above-described embodiments, and can be implemented in various structures without departing from the gist thereof. For example, in order to solve part or all of the above-described problems or in order to achieve part or all of the above-described effects, the technical features in the embodiments corresponding to the technical features in each of the modes recited in the summary of the application can be appropriately replaced, combined, or deleted, provided that the technical features are not described as essential in the specification.

Claims

1. A regenerative fuel cell system, wherein, The regenerative fuel cell system comprises: Fuel cells; A water tank for storing water discharged from the fuel cell; A recombiner, disposed within the water tank, allows hydrogen and oxygen to combine to generate water; as well as The water electrolysis device electrolyzes water supplied from the tank to produce hydrogen and oxygen. The internal pressure of the water tank storing water is lower than the internal pressure of the fuel cell used in power generation and the internal pressure of the water electrolysis device used in electrolysis.

2. The regenerative fuel cell system according to claim 1, wherein, The recombiner is located in the upper part of the water tank.

3. The regenerative fuel cell system according to claim 1, wherein, It also has a temperature regulator to adjust the temperature of the water tank.

4. The regenerative fuel cell system according to claim 1, wherein, The regenerative fuel cell system is mounted on a lunar rover traveling on the moon. The regenerative fuel cell system also includes a valve that can switch the state of the water tank to either a connected state where the water tank is connected to the external space of the lunar rover, or a non-connected state where the water tank is not connected to the external space. When the lunar rover is on the moon, the valve switches the state of the water tank to the connected state, 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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