Regenerative fuel cell system and method of operating same

Abstract

To provide a solution to the problem that electric energy is consumed in a heating and drying process using a heater and in a dehumidifying process using a dehumidifier and replacement of an adsorbent is required when the adsorbent is used.SOLUTION: A regenerative fuel cell system (10) comprises a water electrolysis apparatus (12), a hydrogen boosting apparatus (18), and a fuel cell (22), wherein external release valves (81 to 84) are provided between an oxygen supply line (43), which supplies oxygen gas from the water electrolysis apparatus (12) to the fuel cell (22), and a vacuum space, and between a second hydrogen supply line (44), which supplies hydrogen gas from the hydrogen boosting apparatus (18) to the fuel cell (22), a hydrogen discharge line (35) through which hydrogen gas that has not contributed to pressure boosting in the hydrogen boosting apparatus (18) flows, and a first hydrogen supply line (32) through which hydrogen gas supplied from the water electrolysis apparatus (12) to the hydrogen boosting apparatus (18) flows, and the vacuum space.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a regenerative fuel cell system and an operating method thereof. [Background technology]

[0002] In recent years, research and development into fuel cells has been conducted to contribute to energy efficiency in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy.

[0003] Japanese Patent No. 7393450 discloses a regenerative fuel cell system that utilizes a water electrolysis device, a hydrogen booster device, and a fuel cell. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7393450 Summary of the Invention [Problem to be solved by the invention]

[0005] In such a regenerative fuel cell system, if condensation occurs inside the pipes through which hydrogen gas and oxygen gas flow, the condensed water may adhere to sensors and devices installed in the pipes, potentially impairing the function of the sensors, etc.

[0006] Therefore, in a regenerative fuel cell system, in order to remove moisture from the piping, a heater is used to warm and dry the air, and a dehumidifier or adsorbent is used to adsorb the moisture. However, there are issues with the use of heaters for warming and drying, and with the use of dehumidifiers for dehumidification, which consume electrical energy, and with the use of adsorbents, which require replacement.

[0007] The present invention aims to solve the above-mentioned problems. [Means for solving the problem]

[0008] An aspect of the present disclosure is a water electrolysis device that generates hydrogen gas from supplied water and generates pressurized oxygen gas and stores the pressurized oxygen gas in an oxygen tank through an oxygen supply channel; a hydrogen pressure boosting device that generates pressurized hydrogen gas from the hydrogen gas supplied from the water electrolysis device through a first hydrogen supply channel and stores the pressurized hydrogen gas in the hydrogen tank through a second hydrogen supply channel and returns hydrogen gas that did not contribute to the pressurization to the first hydrogen supply channel through a hydrogen discharge channel; and a hydrogen pressure boosting device that generates electricity by electrochemical reaction when the oxygen gas stored in the oxygen tank and the hydrogen gas stored in the hydrogen tank are supplied. and a fuel cell that generates the water and that supplies oxygen to the water electrolysis device, the regenerative fuel cell system comprising: a first external open valve provided between the oxygen supply channel communicating with the water electrolysis device and a vacuum space; a second external open valve provided between the second hydrogen supply channel communicating with the hydrogen booster device and the vacuum space; a third external open valve provided between the hydrogen discharge channel communicating with the hydrogen booster device and the vacuum space; and a fourth external open valve provided between the first hydrogen supply channel communicating with the hydrogen booster device and the vacuum space.

[0009] Another aspect of the present disclosure is a method for operating a regenerative fuel cell system, comprising: a gas accumulation step in which a water electrolysis device generates hydrogen gas and pressurized oxygen gas from supplied water and stores them in an oxygen tank through an oxygen supply channel; and a hydrogen booster device to which the hydrogen gas is supplied through a first hydrogen supply channel generates pressurized hydrogen gas and stores it in the hydrogen tank through a second hydrogen supply channel; a depressurization step in which, after gas accumulation, the oxygen supply channel and the second hydrogen supply channel are depressurized by power generation of a fuel cell to which the oxygen gas remaining in the oxygen supply channel and the hydrogen gas remaining in the second hydrogen supply channel are supplied; and a moisture removal step in which, after depressurization, the oxygen supply channel, the first hydrogen supply channel, a hydrogen discharge channel for the hydrogen gas not used for pressurization by the hydrogen booster device, and the second hydrogen supply channel are connected to a vacuum space, and condensed water remaining in the oxygen supply channel, the first hydrogen supply channel, the hydrogen discharge channel, and the second hydrogen supply channel is evaporated. [Effects of the Invention]

[0010] According to this invention, first to fourth external release valves capable of communicating with the vacuum spaces are provided between the oxygen supply channel communicating with the water electrolysis device and the vacuum space, between the second hydrogen supply channel communicating with the hydrogen booster device and the vacuum space, between the hydrogen discharge channel communicating with the hydrogen booster device and the vacuum space, and between the first hydrogen supply channel communicating with the hydrogen booster device and the vacuum space, respectively. Thus, by opening the first to fourth external release valves, the oxygen supply channel, the second hydrogen supply channel, the hydrogen discharge channel, and the first hydrogen supply channel can be communicated with the vacuum space, thereby removing moisture. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a regenerative fuel cell system according to an embodiment. [Figure 2] FIG. 2 is a time chart used to explain the operation of the regenerative fuel cell system. [Figure 3] FIG. 3 is an explanatory diagram of the oxygen decompression region and the hydrogen decompression region. [Figure 4] FIG. 4 is an explanatory diagram of the operation of converting oxygen and hydrogen that cross-leak from the high-pressure side to the low-pressure side during depressurization treatment into water using an oxygen removal catalyst. [Figure 5] FIG. 5 is an explanatory diagram of a moisture removal region that is connected to a vacuum space. [Figure 6] FIG. 6 is a time chart used to explain the operation of the modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 is a schematic diagram showing a regenerative fuel cell system (RFC) 10 according to an embodiment. The regenerative fuel cell system 10 may be used in a vacuum space such as outer space or the surface of the moon. The regenerative fuel cell system 10 includes a casing 11. The casing 11 surrounds the entire interior of the regenerative fuel cell system 10. This allows the casing 11 to isolate the interior of the regenerative fuel cell system 10 from the vacuum space, creating an airtight structure.

[0013] [Overall explanation of regenerative fuel cell system 10] The regenerative fuel cell system 10 basically comprises a water electrolysis device 12, a gas-liquid separator (hydrogen gas-liquid separator, hydrogen gas supply device) 14, an oxygen tank 16, a hydrogen pressure booster 18, a hydrogen tank 20, a fuel cell 22, a battery 23, a gas-liquid separator (oxygen exhaust gas gas-liquid separator) 24, a gas-liquid separator (hydrogen exhaust gas gas-liquid separator) 26, and a control device 28. A controller 28 controls all components of the regenerative fuel cell system 10 .

[0014] In this embodiment, the water electrolysis apparatus 12 is a high differential pressure water electrolysis stack apparatus (hereinafter abbreviated as EC) that generates electrochemically compressed high-pressure oxygen gas and unpressurized hydrogen gas (low-pressure hydrogen gas) by water electrolysis. Water for water electrolysis is supplied from the gas-liquid separator 14 to the water electrolysis device 12 via a water supply line 30 .

[0015] The water supply channel 30 communicates with the water electrolysis device 12 and the gas-liquid separator 14. A pump 31 is provided in the water supply channel 30. The pump 31 is on / off controlled by the control device 28. When turned on, the pump 31 imparts flow energy to the water in the gas-liquid separator 14, and supplies the water from the gas-liquid separator 14 to the water electrolysis device 12. When turned off, the pump 31 stops the supply of water. All other pumps described below similarly impart flow energy to fluids when turned on, and stop the flow of fluids when turned off.

[0016] The water electrolysis device 12 has one or more unit cells each having an electrolyte membrane 15. The unit cell includes a membrane electrode assembly (MEA) in which the electrolyte membrane 15 is sandwiched between an anode electrode and a cathode electrode. In this embodiment, the electrolyte membrane 15 used in the water electrolysis device 12 is an anion exchange membrane. It may also be a proton exchange membrane.

[0017] The water electrolysis apparatus 12 supplies water from a gas-liquid separator 14 to the cathode electrode of each unit cell. Each unit cell performs water electrolysis based on a voltage applied to the anode electrode and cathode electrode from a power supply 13. In this case, pressurized high-pressure (for example, in the range of 1 to 100 MPa) oxygen gas is produced at the anode electrode, and unpressurized hydrogen gas is produced at the cathode electrode. The reaction formula on the anode electrode side of the water electrolysis device 12 is shown below. 2OH - →(1 / 2)O2+H2O+2e - The reaction formula on the cathode electrode side of the water electrolysis device 12 is shown below. 2H2O+2e - →H2+2OH -

[0018] The control device 28 can vary the voltage applied between the anode electrode and the cathode electrode by the power supply 13. The power of the power supply 13 may be power from a battery 23.

[0019] The water electrolysis device 12 collects high-pressure oxygen gas generated in each unit cell and outputs a release gas containing the oxygen gas to the oxygen supply mechanism 17A through the oxygen supply path 43. The release gas contains water vapor vaporized by the heat of the water electrolysis device 12 or the like.

[0020] At the same time, the water electrolysis device 12 collects hydrogen gas produced in each unit cell and excess water that has not been electrolyzed (unreacted water), and outputs a discharge fluid containing the hydrogen gas and unreacted water to the first hydrogen supply channel 32. The discharge fluid also contains water vapor vaporized by the heat of the water electrolysis device 12, etc.

[0021] The discharge fluid (hydrogen gas and unreacted water) output from the water electrolysis device 12 to the first hydrogen supply channel 32 flows into the gas-liquid separator 14. The gas-liquid separator 14 separates the discharge fluid into a gas component (hydrogen gas and water vapor) and a liquid component (liquid water). The gas component is supplied to the hydrogen booster 18 through the first hydrogen supply channel 32 by turning on a pump 34 of the first hydrogen supply channel 32 provided on the outlet side of the gas-liquid separator 14. The hydrogen gas supplied to the hydrogen booster 18 through the first hydrogen supply passage 32 passes through a pipe (not shown) and stored water in the gas-liquid separator 14 before being supplied from the gas-liquid separator 14 to the first hydrogen supply passage 32.

[0022] A pressure sensor 60 is provided on the first hydrogen supply line 32 near the outlet of the gas-liquid separator 14 . Furthermore, between the outlet of the gas-liquid separator 14 and the inlet of the hydrogen booster 18, the pressure sensor 60, the pump 34, the shutoff valve 94, a fourth humidity sensor 99, the oxygen remover 33, and the inlet seal valve 93 are provided in this order from the outlet. The fourth humidity sensor 99 may be a dew point meter.

[0023] A fourth external release path 104 communicating with an external vacuum space is provided at a communication part between the oxygen remover 33 and the shutoff valve 94 on the first hydrogen supply path 32. A fourth external release valve 84 (external release valve, on-off valve) is provided on the fourth external release path 104.

[0024] The oxygen remover 33 reacts oxygen gas discharged from the water electrolysis device 12 to the gas-liquid separator 14 during depressurization treatment with hydrogen gas discharged from the hydrogen booster device 18 to the gas-liquid separator 14 through the hydrogen discharge path 35 using an oxygen removal catalyst to generate water.

[0025] A second outlet seal valve 92, a third humidity sensor 98, and a check valve 36 are provided in this order from the outlet of the hydrogen discharge passage 35 of the hydrogen booster device 18 toward the inlet side of the gas-liquid separator 14. The third humidity sensor 98 may be a dew point meter.

[0026] A third external release path 103 communicating with the external vacuum space is provided in the communicating part between the second outlet sealing valve 92 and the check valve 36 on the hydrogen discharge path 35. A third external release valve 83 (external release valve, on-off valve) is provided on the third external release path 103.

[0027] The hydrogen booster 18 has a membrane electrode assembly (MEA) in which an electrolyte membrane 21 is sandwiched between an anode electrode and a cathode electrode. The electrolyte membrane 21 used in the hydrogen booster 18 is a proton exchange membrane. A power source 19 is connected to the anode electrode and the cathode electrode.

[0028] The control device 28 can vary the voltage applied between the anode electrode and the cathode electrode by the power supply 19. The power of the power supply 19 may be powered by the battery 23.

[0029] The hydrogen booster 18 supplies hydrogen gas flowing in from the first hydrogen supply channel 32 to the anode electrode. The hydrogen booster 18 ionizes the hydrogen gas based on a voltage applied from a power source 19. Protons obtained by the ionization of the hydrogen gas are accompanied by water vapor and reach the cathode electrode through an electrolyte membrane 21 (proton exchange membrane). The protons that reach the cathode electrode combine with electrons (electrons generated during the ionization) supplied from the power source 19 and return to hydrogen gas.

[0030] The hydrogen pressure booster 18 generates pressurized hydrogen gas by transferring protons from the anode electrode to the cathode electrode. For example, the hydrogen gas is compressed to a pressure range of 1 to 100 MPa. In this way, the hydrogen pressure booster 18 is an electrochemical hydrogen compressor (EHC) that electrochemically compresses hydrogen gas. The reaction formula on the cathode electrode side of the hydrogen booster 18 is shown below. 2H + +2e - →H2 The reaction formula on the anode electrode side of the hydrogen boosting device 18 is shown below. H2→2H + +2e -

[0031] The hydrogen booster 18 outputs excess hydrogen gas that has not been ionized to the hydrogen discharge path 35. The hydrogen discharge path 35 is a flow path (pipe) for discharging hydrogen gas from the hydrogen booster 18 to the gas-liquid separator 14.

[0032] The hydrogen pressure booster 18 outputs a release gas containing pressurized hydrogen gas to the hydrogen supply mechanism 17 B. The release gas contains water vapor vaporized by the heat of the hydrogen pressure booster 18 or the like.

[0033] The oxygen supply mechanism 17A and the hydrogen supply mechanism 17B constitute the gas supply mechanism 17. The gas supply mechanism 17 is a mechanism for supplying gases (hydrogen gas and oxygen gas) to the fuel cell 22.

[0034] The oxygen supply mechanism 17A supplies the oxygen gas produced in the water electrolysis device 12 to the fuel cell 22. The hydrogen supply mechanism 17B supplies the hydrogen gas produced in the hydrogen booster device 18 to the fuel cell 22.

[0035] The shutoff valves 47 to 50, the first external release valve 81, the second external release valve 82, the third external release valve 83, the fourth external release valve 84, the first outlet sealing valve 91, the second outlet sealing valve 92, the inlet sealing valve 93, and the shutoff valve 94 are each an on-off valve. In this embodiment, solenoid valves are used as the on-off valves, and the valves are opened (when driven on) and closed (when driven off) by on-off drive control of the control device 28.

[0036] [Explanation of oxygen supply mechanism 17A] The oxygen supply mechanism 17A includes an oxygen supply path 43, an oxygen tank 16, a bypass path 45, a shutoff valve 47, a shutoff valve 49, a pressure reducing valve 51, a pressure reducing valve 58, a back pressure valve 57, a pressure sensor 61, a temperature sensor 63, and a first humidity sensor 79. The first humidity sensor 79 may be a dew point meter.

[0037] The oxygen supply channel 43 is a flow path for supplying high-pressure oxygen gas generated in the water electrolysis device 12 to the fuel cell 22 via the oxygen tank 16. One end of the oxygen supply channel 43 is connected to the water electrolysis device 12, and the other end of the oxygen supply channel 43 is connected to the fuel cell 22.

[0038] The oxygen tank 16 is provided on the oxygen supply line 43. In the oxygen tank 16, high-pressure oxygen gas generated by the water electrolysis device 12 is accumulated.

[0039] The bypass channel 45 branches off from a branch point Bpo (BP) of the oxygen supply channel 43 between the water electrolysis device 12 and the oxygen tank 16, and joins with the oxygen supply channel 43 at a joining point Mpo (MP) between the oxygen tank 16 and the fuel cell 22.

[0040] The shutoff valve 47 is provided in the bypass path 45. The shutoff valve 49 is provided in the oxygen supply path 43 between the confluence point Mpo and the oxygen tank 16.

[0041] The pressure reducing valve 51 is provided in the oxygen supply path 43 between the confluence part Mpo and the oxygen tank 16. The pressure reducing valve 51 reduces the pressure of the oxygen gas supplied from the oxygen tank 16 to a predetermined pressure.

[0042] The back pressure valve 57 is provided in the oxygen supply channel 43 between the branch point Bpo and the oxygen tank 16. The back pressure valve 57 applies pressure (back pressure) to the water electrolysis device 12 through the oxygen tank 16. This increases the pressure of oxygen gas generated at the anode electrode of the electrolyte membrane 15 of each unit cell of the water electrolysis device 12, and makes the pressure higher than the pressure of hydrogen gas generated at the cathode electrode.

[0043] The water electrolysis device 12 generates oxygen gas at the anode electrode at a pressure higher than that of hydrogen gas generated at the cathode electrode. This can suppress cross-leakage, in which hydrogen gas permeates through the electrolyte membrane 15 from the cathode electrode to the anode electrode. As a result, a decrease in the amount of hydrogen gas supplied from the water electrolysis device 12 to the hydrogen booster device 18 can be prevented.

[0044] The pressure sensor 61 is provided in the oxygen supply channel 43 between the water electrolysis device 12 and the branch point Bpo. The pressure sensor 61 detects the pressure of oxygen gas supplied from the water electrolysis device 12 to the oxygen supply channel 43. The pressure sensor 61 outputs a signal indicative of the detected pressure to the control device 28.

[0045] The temperature sensor 63 is provided in the oxygen supply channel 43 between the water electrolysis device 12 and the branch point Bpo. The temperature sensor 63 detects the temperature of the oxygen gas supplied from the water electrolysis device 12 to the oxygen supply channel 43. The temperature sensor 63 outputs a signal indicating the detected temperature to the control device 28.

[0046] The first humidity sensor 79 is provided near the outlet of the pressurized oxygen gas of the water electrolysis device 12. The first humidity sensor 79 detects the relative humidity in the oxygen supply channel 43 (on the anode electrode side of the electrolyte membrane 15 of the water electrolysis device 12). The first humidity sensor 79 outputs a signal indicating the detected humidity to the control device 28.

[0047] The pressurized oxygen gas released from the water electrolysis device 12 to the oxygen supply line 43 contains water vapor produced by the reaction at the anode electrode in addition to the oxygen gas.

[0048] A first external release passage 101 communicating with an external vacuum space is provided on the oxygen supply passage 43 communicating with the water electrolysis device 12. A first external release valve 81 (external release valve, on-off valve) is provided on the first external release passage 101.

[0049] The gas-liquid separator 14 stores water to be supplied to the water electrolysis device 12. A water supply channel 30 is provided between the gas-liquid separator 14 and the water electrolysis device 12. A pump 31 is provided on the water supply channel 30.

[0050] [Explanation of hydrogen supply mechanism 17B] The hydrogen supply mechanism 17B includes a second hydrogen supply path 44, a hydrogen tank 20, a bypass path 46, a shutoff valve 48, a shutoff valve 50, a first outlet sealing valve 91, a pressure reducing valve 52, a pressure reducing valve 56, a back pressure valve 59, a pressure sensor 62, a temperature sensor 69, and a second humidity sensor 78. The second humidity sensor 78 may be a dew point meter.

[0051] The second hydrogen supply path 44 is a flow path for supplying hydrogen gas pressurized by the hydrogen pressure booster 18 to the fuel cell 22 via the hydrogen tank 20. One end of the second hydrogen supply path 44 is connected to the hydrogen pressure booster 18, and the other end of the second hydrogen supply path 44 is connected to the fuel cell 22.

[0052] The hydrogen tank 20 is provided on the second hydrogen supply line 44. In the hydrogen tank 20, high-pressure hydrogen gas that has been pressurized by the hydrogen pressure booster 18 is stored.

[0053] The bypass path 46 branches off from a branch point Bph (BP) of the second hydrogen supply path 44 between the hydrogen booster 18 and the hydrogen tank 20, and merges at a junction Mph (MP) of the second hydrogen supply path 44 between the hydrogen tank 20 and the fuel cell 22.

[0054] An on-off valve (shutoff valve) 48 is provided in the bypass line 46. An on-off valve (shutoff valve) 50 is provided in the second hydrogen supply line 44 between the confluence point Mph and the hydrogen tank 20. A first outlet seal valve 91 is provided near the outlet of the hydrogen pressure booster 18 for pressurized hydrogen gas.

[0055] The pressure reducing valve 52 is provided in the second hydrogen supply passage 44 between the junction Mph and the hydrogen tank 20. The pressure reducing valve 52 reduces the pressure of the hydrogen gas supplied from the hydrogen tank 20 to a predetermined pressure.

[0056] The back pressure valve 59 is provided in the second hydrogen supply passage 44 between the branch point Bph and the hydrogen tank 20. The back pressure valve 59 applies pressure (back pressure) to the hydrogen booster 18. This increases the pressure of the hydrogen gas generated at the cathode electrode of each unit cell of the hydrogen booster 18, anode The pressure is higher than the pressure of the hydrogen gas supplied to the electrodes.

[0057] The hydrogen booster 18 generates hydrogen gas at the cathode electrode at a pressure higher than that of hydrogen gas supplied to the anode electrode, thereby suppressing cross-leakage, which is the permeation of hydrogen gas through the electrolyte membrane 21 from the cathode electrode to the anode electrode.

[0058] The pressure sensor 62 is provided in the second hydrogen supply line 44 near the hydrogen pressure booster 18. The pressure sensor 62 detects the pressure of the pressurized hydrogen gas supplied to the second hydrogen supply line 44. The pressure sensor 62 outputs a signal indicating the detected pressure to the control device 28.

[0059] The temperature sensor 69 is provided near the branch point Bph. The temperature sensor 69 detects the temperature of the hydrogen supplied from the hydrogen booster 18 to the second hydrogen supply line 44. hydrogen The temperature sensor 69 detects the temperature of the gas and outputs a signal indicating the detected temperature to the control device 28.

[0060] The second humidity sensor 78 , th 2 is provided in the hydrogen supply channel 44.

[0061] The second humidity sensor 78 detects the relative humidity of the second hydrogen supply path 44. More specifically, the second humidity sensor 78 detects the relative humidity on the cathode electrode side of the electrolyte membrane 21 of the hydrogen booster device 18. The second humidity sensor 78 outputs a signal indicating the detected humidity to the control device 28.

[0062] A second external release path 102 communicating with the external vacuum space is provided on the second hydrogen supply path 44 near the branch point Bph. A second external release valve 82 is provided on the second external release path 102.

[0063] [Explanation of Fuel Cell 22] The oxygen supply mechanism 17A further includes an oxygen exhaust gas passage 76, a gas-liquid separator 24, a circulation pump 70, and a drain valve 72.

[0064] The hydrogen supply mechanism 17B further includes a hydrogen exhaust gas passage 77, a gas-liquid separator 26, a circulation pump 71, and a drain valve 73.

[0065] The fuel cell 22 has a stack of unit cells electrically connected in series. Each unit cell includes a membrane electrode assembly (MEA) in which an electrolyte membrane is sandwiched between an anode electrode and a cathode electrode.

[0066] The fuel cell 22 supplies oxygen gas, which is supplied from the oxygen tank 16 via a pressure reducing valve 51, to the cathode electrode of each unit cell. The fuel cell 22 supplies hydrogen gas, which is supplied from the hydrogen tank 20 via a pressure reducing valve 52, to the anode electrode of each unit cell. Each unit cell of the fuel cell 22 generates electricity through an electrochemical reaction between the oxygen gas and the hydrogen gas. The reaction formula on the anode electrode side of the fuel cell 22 is shown below. H2→2H + +2e - The reaction formula on the cathode electrode side of the fuel cell 22 is shown below. 2H + +(1 / 2)O2+2e - →H2O

[0067] The power generated by the fuel cell 22 is supplied to loads (not shown) (such as external actuators or electrical appliances) and also to auxiliary loads including the control device 28. Excess generated power is charged into the battery 23. The generated current Ifc of the fuel cell 22 is detected by a current sensor 27 and acquired by the control device 28. The stored voltage of the battery 23 and the generated voltage of the fuel cell 22 are each detected by voltage sensors (not shown) and acquired by the control device 28.

[0068] The oxygen-containing exhaust gas containing unreacted oxygen gas in each unit cell of the fuel cell 22 is supplied to the oxygen supply channel 43 via the oxygen circulation channel 66. The oxygen circulation channel 66 is a flow path for returning the oxygen-containing exhaust gas discharged from the fuel cell 22 to the oxygen supply channel 43.

[0069] The gas-liquid separator 24 and the circulation pump 70 are provided on the oxygen circulation path 66. The gas-liquid separator 24 separates the oxygen-containing exhaust gas discharged from the fuel cell 22 to the oxygen exhaust gas path 76 into a gas component (oxygen gas and water vapor) and a liquid component (liquid water). The gas component is supplied again to the fuel cell 22 by the circulation pump 70. Meanwhile, the liquid component is supplied to the gas-liquid separator 14 via a drain valve 72, which is an on-off valve, and a pump 25, which is provided on the water supply path 29 and turned on.

[0070] Meanwhile, hydrogen-containing exhaust gas containing unreacted hydrogen gas in each unit cell of the fuel cell 22 is supplied to the second hydrogen supply path 44 via the hydrogen circulation path 67. The hydrogen circulation path 67 is a flow path for returning the hydrogen-containing exhaust gas discharged from the fuel cell 22 to the second hydrogen supply path 44.

[0071] The gas-liquid separator 26 and the circulation pump 71 are provided on the hydrogen circulation path 67. The gas-liquid separator 26 separates the hydrogen-containing exhaust gas discharged from the fuel cell 22 to the hydrogen exhaust gas path 77 into a gas component (hydrogen gas and water vapor) and a liquid component (liquid water). The gas component is supplied again to the fuel cell 22 by the circulation pump 71.

[0072] On the other hand, the liquid component is supplied to the gas-liquid separator 14 via the drain valve 73, which is an on-off valve, and the pump 25, which is turned on.

[0073] Water produced in the fuel cell 22 is supplied to the gas-liquid separator 14 via a gas-liquid separator 24 , a gas-liquid separator 26 , a drain valve 72 , a drain valve 73 and a pump 25 on a water supply line 29 .

[0074] [Explanation of the control device 28] The controller 28 controls all the components of the regenerative fuel cell system 10 and executes the operation of the regenerative fuel cell system 10 .

[0075] The control device 28 is a computer that controls the regenerative fuel cell system 10. The control device 28 includes one or more processors and a storage medium. The storage medium may be composed of a volatile memory and a non-volatile memory. Examples of the processor include a CPU, an MCU, etc. Examples of the volatile memory include a RAM, etc. Examples of the non-volatile memory include a ROM, a flash memory, etc.

[0076] The control device 28 turns on the power supply 13 of the water electrolysis device 12 to apply a voltage to the anode and cathode electrodes of the unit cell. In addition, the control device 28 turns on the pump 31 to supply water from the gas-liquid separator 14 to the water electrolysis device 12.

[0077] As a result, the water electrolysis device 12 enters an operating state (pressure-boosting state, water electrolysis state) and performs water electrolysis (water electrolysis).

[0078] When the control device 28 stops the application of voltage from the power source 13 to the unit cells and the supply of water to the water electrolysis device 12, the water electrolysis device 12 enters a non-operating state (a depressurized state and then a stopped state).

[0079] The control device 28 also turns on the power supply 19 of the hydrogen booster 18 to apply a voltage to the anode and cathode electrodes of the unit cell. In addition, the control device 28 turns on the pump 34 to supply hydrogen gas from the water electrolysis device 12 to the hydrogen booster 18 via the first hydrogen supply path 32 and the gas-liquid separator 14.

[0080] This puts the hydrogen booster 18 into an operating state (pressurizing state) and boosts the hydrogen gas. When the control device 28 stops the application of voltage from the power source 19 to the unit cell and the supply of hydrogen gas to the hydrogen booster 18, the hydrogen booster 18 goes into a non-operating state (a stopped state after passing through a depressurizing state).

[0081] [Operation of regenerative fuel cell system 10] The operation of the regenerative fuel cell system 10 configured as above during continuous operation will be basically described below with reference to the time chart of FIG. 2 (operation sequence during continuous operation).

[0082] In FIG. 2, EC denotes the water electrolysis device 12, EHC denotes the hydrogen booster device 18, and FC denotes the fuel cell 22.

[0083] The relative humidity in Figure 2 is shown by straight lines, which schematically represent changes in the relative humidity on the second hydrogen supply channel 44 detected by the second humidity sensor 78 and obtained by the control device 28 (the relative humidity on the cathode electrode side of the electrolyte membrane 21 of the hydrogen booster device 18 when the first outlet shut-off valve 91 is open), the relative humidity on the first hydrogen supply channel 32 detected by the fourth humidity sensor 99 and obtained by the control device 28, the relative humidity on the hydrogen discharge channel 35 detected by the third humidity sensor 98, and the relative humidity on the oxygen supply channel 43 of the water electrolysis device 12 detected by the first humidity sensor 79 and obtained by the control device 28 (the relative humidity on the anode electrode side of the electrolyte membrane 15).

[0084] 2, the lower limit of the relative humidity indicates the lower limit humidity that should be ensured (observed) on the anode electrode side of the electrolyte membrane 15 or the cathode electrode side of the electrolyte membrane 21, and the upper limit of the relative humidity indicates the upper limit humidity that should be ensured (observed) during the boosting operation of the water electrolysis device 12 and the hydrogen boosting device 18. During the boosting operation of the water electrolysis device 12 and the hydrogen boosting device 18, the electrolyte membrane 15 and the electrolyte membrane 21 can fully function within the range between the upper and lower limits. As shown in FIG. 2, during the pressure-boosting operation of the water electrolysis device 12 and the hydrogen pressure-boosting device 18, the relative humidity is measured by the third humidity sensor 98 (hydrogen discharge path 35: high humidity), the fourth humidity sensor 99 (first hydrogen supply path 32: medium humidity), and the first humidity sensor 79 (oxygen supply path 4). 3) and a second humidity sensor 78 (Second hydrogen supply channel 44) The relative humidity obtained by

[0085] [Pressure increase process] At time t0, the water electrolysis device 12 starts the oxygen pressure boosting (water electrolysis) process. Immediately before time t0, the fuel cell 22, the water electrolysis device 12, and the hydrogen booster device 18 are stopped, and the regenerative fuel cell system 10 is stopped. When the regenerative fuel cell system 10 is stopped, the shut-off valves 47 to 50, which are shut-off valves for supplying oxygen gas and hydrogen gas to the fuel cell 22, are closed. Furthermore, when the regenerative fuel cell system 10 is stopped, the first external open valve 81, the second external open valve 82, the third external open valve 83, the fourth external open valve 84, the outlet seal valves 91 and 92, the inlet seal valve 93, and the shut-off valve 94 are closed.

[0086] At time t0, operation of the regenerative fuel cell system 10 is started. In this case, the controller 28 first changes the outlet seal valves 91 and 92, the inlet seal valve 93, and the shutoff valve 94 from a closed state to an open state. The controller 28 then turns on the pump 31 to supply water stored in the gas-liquid separator 14 to the cathode electrode of the electrolyte membrane 15 of each unit cell of the water electrolysis device 12 through the water supply path 30.

[0087] The control device 28 then supplies a predetermined current from the power source 13 to the cathode and anode electrodes of each unit cell of the water electrolysis device 12, causing the water electrolysis device 12 to start a voltage boosting operation.

[0088] In this case, oxygen gas pressurized by electrolysis of water is generated at the anode electrode, and this oxygen gas is supplied to the oxygen tank 16 of the oxygen supply mechanism 17A via the oxygen supply path 43 of the oxygen supply mechanism 17A.

[0089] When the water electrolysis device 12 starts the boosting operation, hydrogen gas is produced at the cathode electrode by electrolysis of water. This hydrogen gas is supplied from the water electrolysis device 12 to the anode electrode of the electrolyte membrane 21 of each unit cell of the hydrogen boosting device 18 via the first hydrogen supply path 32 by the pump 34 that has been turned on.

[0090] The control device 28 confirms the supply of hydrogen gas to the first hydrogen supply channel 32 based on the pressure detected by the pressure sensor 60 .

[0091] When the supply of hydrogen gas to the first hydrogen supply path 32 is confirmed, the control device 28 controls the power supply 19 to cause the hydrogen pressure booster 18 to perform a pressure boosting operation. When the hydrogen pressure booster 18 starts the pressure boosting operation, hydrogen gas is ionized and pressurized to produce hydrogen gas at the cathode. This pressurized, high-pressure hydrogen gas is supplied to the hydrogen tank 20 via the second hydrogen supply path 44 of the hydrogen supply mechanism 17B.

[0092] When a predetermined amount of hydrogen and oxygen is accumulated in the hydrogen tank 20 and the oxygen tank 16, respectively, at time t1 due to the water electrolysis process and the hydrogen pressure boosting process between time t0 and time t1, the control device 28 starts the depressurization (depressurization and power generation) process at time t1.

[0093] [Depressurization (depressurization and power generation) process] FIG. 3 is an explanatory diagram that schematically shows the regions to be subjected to depressurization treatment (oxygen depressurization region 181 and hydrogen depressurization region 182, each surrounded by a broken line).

[0094] On the oxygen supply side, the oxygen depressurization region 181 includes the oxygen supply path 43 from the anode electrode of the electrolyte membrane 15 of the water electrolysis device 12 to the primary side of the back pressure valve 57 communicating with the anode electrode, the flow path from the anode electrode of the water electrolysis device 12 to the primary side of the pressure reducing valve 58, and the region from the anode electrode of the water electrolysis device 12 to the flow path on the inlet side of the first external open valve 81.

[0095] The oxygen depressurization region 181 is a region where high-pressure oxygen gas remains when the water electrolysis apparatus 12 stops the pressure boosting operation.

[0096] On the hydrogen supply side, the second hydrogen supply passage 44 up to the primary side of the back pressure valve 59 communicating with the cathode electrode of the hydrogen booster 18, the region up to the primary side of the pressure reducing valve 56 communicating with the cathode electrode of the hydrogen booster 18, and the flow path up to the primary side of the second external release valve 82 communicating with the cathode electrode of the hydrogen booster 18 correspond to the hydrogen decompression region 182. The hydrogen decompression region 182 is the region where high-pressure hydrogen gas remains when the boosting operation of the hydrogen booster 18 is stopped.

[0097] Between time t1 and time t2, the control device 28 opens all of the shutoff valves 47 to 50. In this case, the control device 28 adjusts the pressure reducing valve 51 and the pressure reducing valve 58 so that the set pressure Psc of the pressure reducing valve 51 is lower than the set pressure Psd of the pressure reducing valve 58 on the oxygen decompression region 181 side (Psc <Psd)。

[0098] With this setting, only the high-pressure oxygen gas remaining in the oxygen decompression region 181 flows into the fuel cell 22 through the pressure reducing valve 58 and the bypass path 45, as shown by the thick dashed line in Figure 3, and no oxygen gas flows into the oxygen supply path 43 in which the pressure reducing valve 51 is installed.

[0099] At the same time, the control device 28 adjusts the pressure reducing valve 52 and the pressure reducing valve 56 on the hydrogen decompression region 182 side so that the set pressure Psa of the pressure reducing valve 52 is lower than the set pressure Psb of the pressure reducing valve 56 (Psa <Psb)。

[0100] With this setting, only the high-pressure hydrogen remaining in the hydrogen decompression region 182 flows into the fuel cell 22 through the pressure reducing valve 56 and the bypass path 46, as shown by the thick dashed line in Figure 3, and no hydrogen flows into the second hydrogen supply path 44 in which the pressure reducing valve 52 is installed.

[0101] In this state, only the oxygen gas in the oxygen depressurization region 181, which is the region requiring depressurization treatment, is supplied to the fuel cell 22, and only the hydrogen gas in the hydrogen depressurization region 182, which is the region requiring depressurization treatment, is supplied to the fuel cell 22, and is consumed in the power generation process due to the electrochemical reaction of the fuel cell 22.

[0102] During this depressurization treatment, the control device 28 controls the oxygen depressurization region 181 and the hydrogen depressurization region 182 so that they are depressurized at predetermined depressurization rates.

[0103] Since the depressurization speed is the change over time in the pressure values ​​measured by the pressure sensors 61 and 62, the control device 28 adjusts the set pressure of the pressure reducing valve 56 and the set pressure of the pressure reducing valve 58 to feedback control the power generation current Ifc so that the change over time in each pressure value becomes a predetermined value.

[0104] During the depressurization process, the control device 28 charges the battery 23 with the power generated from the oxygen gas and hydrogen gas consumed in the fuel cell 22.

[0105] When depressurization processing is performed, the hydrogen in the hydrogen depressurization region 182 is all consumed before the oxygen in the oxygen depressurization region 181 due to the electrochemical reaction in the fuel cell 22 consuming 2 moles of hydrogen for every 1 mole of oxygen.

[0106] In this case, the control device 28 adjusts the set pressure Psa of the pressure reducing valve 52 so that the set pressure Psa of the pressure reducing valve 52 becomes the pressure measured by the pressure sensor 62 of the hydrogen depressurization region 182 .

[0107] By this adjustment, as shown by the thick dashed line in FIG. 3, hydrogen gas that is insufficient in the hydrogen depressurization region 182 is supplied from the hydrogen tank 20 to the fuel cell 22. In this way, the high-pressure oxygen gas in the oxygen depressurization region 181 can be entirely consumed.

[0108] During the above-described depressurization process, a pressure difference occurs across each of the electrolyte membranes 15 of the water electrolysis device 12 and each of the electrolyte membranes 21 of the hydrogen booster device 18 .

[0109] As shown in Figure 4, this pressure difference causes gas cross-leakage (cross-leakage of oxygen permeating in the opposite direction through the electrolyte membrane 15 of the water electrolysis device 12 and cross-leakage of hydrogen permeating in the opposite direction through the electrolyte membrane 21 of the hydrogen booster device 18) indicated by the thick dashed lines in Figure 4 from the high-pressure side to the low-pressure side of each stack of the water electrolysis device 12 and the hydrogen booster device 18. This cross-leaked oxygen and cross-leaked hydrogen must be depressurized (disposed of).

[0110] Regarding oxygen cross-leak in the water electrolysis apparatus 12, as shown in FIG. 4 , hydrogen remaining in the gas-liquid separator 14 and cross-leaked hydrogen supplied from the hydrogen booster 18 to the gas-liquid separator 14 through a hydrogen discharge channel 35 are reacted with cross-leaked oxygen supplied from the water electrolysis apparatus 12 to the gas-liquid separator 14 through a first hydrogen supply channel 32 in an oxygen remover 33 equipped with an oxygen removal catalyst to produce water, thereby depressurizing the water.

[0111] Oxygen remover 33 When the reaction is carried out, the pump 34 is turned on to circulate the oxygen and hydrogen that have cross-leaked onto the first hydrogen supply path 32 .

[0112] Generally, oxygen cross-leakage and hydrogen cross-leakage are greater for hydrogen, which has smaller molecules. Therefore, hydrogen gas remains on the primary side of the hydrogen booster 18, which is connected to the hydrogen discharge channel 35, i.e., in the gas-liquid separator 14, and the pressure on the anode side of the electrolyte membrane 21 increases.

[0113] Therefore, regarding the remaining hydrogen gas, current is passed from the power source 19 to the hydrogen pressure booster 18 during depressurization control, and the hydrogen gas remaining at the anode electrode is pressurized and transferred to the cathode electrode side. The pressurized high-pressure hydrogen gas on the cathode electrode side can be consumed by the depressurization method in the hydrogen depressurization region 182 described above. At time t2, the depressurization process is completed.

[0114] [Water removal process during FC operation (power generation)] As described above, Figure 2 is a time chart used to explain the operation of the water removal process of the regenerative fuel cell system 10 during continuous operation, in which the water electrolysis device 12 and the hydrogen booster device 18 are operated (pressure is stored in the oxygen tank 16 and the hydrogen tank 20) ​​and then stopped, and then the fuel cell 22 is operated (power generation) repeatedly.

[0115] At time t2 when the above-described depressurization process is completed, the control device 28 first closes the shutoff valves 47 and 48 from their open states.

[0116] The control device 28 then opens the first external release valve 81, the second external release valve 82, the third external release valve 83 and the fourth external release valve 84 from their closed states, thereby connecting the external release paths 101-104, which are the valve passages of each external release valve 81-84, to the vacuum space and starting the evacuation process.

[0117] 5, when the evacuation process is initiated, on the hydrogen booster device 18 side, the second external release valve 82 opens, and the hydrogen decompression region 182, which is made up of the second hydrogen supply channel 44 and the bypass channel 46 and which are in communication with the primary side of the pressure reducing valve 56, the primary side of the back pressure valve 59, and the cathode electrode of the electrolyte membrane 21 of the hydrogen booster device 18, is connected to the vacuum space via the second external release channel 102. The connection to the vacuum space initiates a moisture removal process in which condensed water in the hydrogen decompression region 182 evaporates (time point t2 in FIG. 2).

[0118] At the same time, the third external opening valve 83 is opened, and the second outlet sealing valve 92, which is connected to the outlet side of the anode electrode of the hydrogen booster device 18, and the partial area 96 of the hydrogen discharge path 35, which is connected to the check valve 36, are connected to the vacuum space through the third external release path 103, and a moisture removal process is initiated to evaporate the condensed water in the partial area 96.

[0119] At the same time, by opening the fourth external opening valve 84, the partial region 97 of the first hydrogen supply path 32, which is connected to the inlet sealing valve 93 and the shut-off valve 94 and which are connected to the inlet side of the anode electrode of the hydrogen boosting device 18, is connected to the vacuum space through the fourth external release path 104, thereby starting a moisture removal process to evaporate the condensed water in the partial region 97.

[0120] On the water electrolysis device 12 side, the first external release valve 81 opens at time t2, connecting the primary side of the back pressure valve 57, the primary side of the pressure reducing valve 58, and an oxygen depressurization region 181, which is made up of the oxygen supply path 43 and the bypass path 45 leading to the anode electrode of the electrolyte membrane 15 of the water electrolysis device 12, to the vacuum space. By connecting the oxygen depressurization region 181 to the vacuum space, a moisture removal process is initiated to evaporate condensed water in the oxygen depressurization region 181.

[0121] At time t2a, the relative humidity detected by the second humidity sensor 78 reaches the lower limit, terminating the moisture removal process in the hydrogen decompression region 182 connected to the cathode electrode of the hydrogen booster 18. At time t2a, the second external release valve 82 and the first outlet shut-off valve 91 are closed. At time t2b, the relative humidity detected by the first humidity sensor 79 connected to the anode electrode of the water electrolysis device 12 reaches a lower limit value, and the moisture removal process in the oxygen depressurization region 181 is terminated. At time t2b, the first external release valve 81 is closed. At time t2c, the relative humidity detected by the fourth humidity sensor 99 reaches the lower limit value, and the process of removing moisture from the partial region 97 of the first hydrogen supply channel 32 is terminated. At time t2c, the fourth external opening valve 84, the inlet sealing valve 93, and the shutoff valve 94 are closed. At time t3, the relative humidity of the third humidity sensor 98, which is connected to the outlet side of the anode electrode of the hydrogen booster 18 via the second outlet sealing valve 92, reaches a lower limit value, and the moisture removal process for the partial region 96 is terminated. At time t3, the third external opening valve 83 and the second outlet sealing valve 92 are closed. Although the moisture removal process described above is terminated at the lower limit of the relative humidity (lower limit humidity), it is also possible to provide a margin and close each external release valve 81-84, each sealing valve 91-93 and shut-off valve 94 at a threshold value (threshold humidity) higher than the lower limit. On the other hand, the fuel cell 22 performs a power generating operation between time t2 and time t4.

[0122] The processes from time t4 to time 8, including time t5, time t6, time t6a to t6c, time t7, and time t8, correspond to the processes from time t0 to time 4, including time t1, time t2, time t2a to t2c, time t3, and time t4, and will therefore be omitted.

[0123] As shown in FIG. 2, when pressure accumulation processing (time t0 to time t2, time t4 to time t6) and power generation operation (time t2 to time t4, time t6 to time t8) in the oxygen tank 16 and the hydrogen tank 20 are repeated, a moisture removal processing (moisture removal step: time t2 to time t3, time t6 to time t7) is performed during operation (power generation) of the fuel cell 22.

[0124] According to the above embodiment, the following operating method for the regenerative fuel cell system 10 is carried out.

[0125] The operating method of the regenerative fuel cell system 10 includes a gas accumulation step in which hydrogen gas is produced from supplied water by the water electrolysis device 12 and pressurized oxygen gas is produced and stored in the oxygen tank 16 through the oxygen supply line 43, and the hydrogen gas is supplied to the hydrogen pressure booster 18 through the first hydrogen supply line 32, whereupon pressurized hydrogen gas is produced and stored in the hydrogen tank 20 through the second hydrogen supply line 44; and a moisture removal process in which, after depressurization, the oxygen supply channel 43, the first hydrogen supply channel 32, the hydrogen discharge channel 35 for the hydrogen gas not used for pressure boosting in the hydrogen boosting device 18, and the second hydrogen supply channel 44 are connected to a vacuum space, and condensed water remaining in the oxygen supply channel 43, the first hydrogen supply channel 32, the hydrogen discharge channel 35, and the second hydrogen supply channel 44 is evaporated.

[0126] [Variations] The above embodiment can be modified as follows.

[0127] A modified example of the water removal process of the regenerative fuel cell system 10 will be described with reference to the time chart (operation sequence from operation to shutdown of the water electrolysis device 12 and hydrogen booster device 18, which are booster devices) shown in FIG.

[0128] The operations from time t0 to time t4 in FIG. 6 correspond to the operations from time t0 to time t4 in FIG. 2 described above, and will therefore be briefly described.

[0129] In the moisture removal process shown in Figure 6, instead of the moisture removal (time t2 to time t3) during the operation (FC operation (power generation)) period of the fuel cell 22 shown between time t2 and time t4 in Figure 2, the moisture removal process is performed when the fuel cell 22 is stopped (standby) as shown between time t2 and time t3 in Figure 6.

[0130] That is, between time t0 and time t1 in FIG. 6, the water electrolysis device 12 and the hydrogen booster device 18 are operated to boost pressure, and then between time t1 and time t2, depressurization processing is performed, and at time t2, the operation of the water electrolysis device 12 and the hydrogen booster device 18 is stopped.

[0131] At time t2, each external release valve 81 to 84 is opened to connect the oxygen supply path 43, the first hydrogen supply path 32, the second hydrogen supply path 44 and the hydrogen discharge path 35 of the regenerative fuel cell system 10 to the vacuum space, and moisture (condensed water) in the parts that connect to the vacuum space is evaporated and removed until a predetermined relative humidity is reached, and the corresponding external release valves 81 to 84 are closed at time t2a, time t2b, time t2c and time t3.

[0132] In the hydrogen booster 18, in order to prevent the interior, including the electrolyte membrane 21, from drying out, all of the sealing valves 91 to 93 are closed by time t3, and are maintained in the closed state thereafter. In the water electrolysis device 12, the first external opening valve 81 is closed at time t2b to prevent the inside, including the electrolyte membrane 15, from drying out.

[0133] [Effects of the embodiment and modified examples] As described above, according to the above embodiment and modified example, when the water electrolysis device 12 and the hydrogen booster device 18 are stopped, the following valves are opened: a first external open valve 81 provided between the vacuum space and the oxygen supply path 43 that supplies oxygen gas from the water electrolysis device 12 to the oxygen tank 16 and the fuel cell 22; a second external open valve 82 provided between the vacuum space and the second hydrogen supply path 44 that supplies hydrogen gas from the hydrogen booster device 18 to the hydrogen tank 20 and the fuel cell 22; a third external open valve 83 provided between the vacuum space and the hydrogen discharge path 35 for hydrogen gas that did not contribute to boosting in the hydrogen booster device 18; and a fourth external open valve 84 provided between the vacuum space and the first hydrogen supply path 32 that supplies hydrogen gas from the water electrolysis device 12 to the hydrogen booster device 18.

[0134] As a result, the oxygen supply channel 43, the second hydrogen supply channel 44, the hydrogen discharge channel 35, and the first hydrogen supply channel 32 communicate with the vacuum space, and moisture (condensed water) in the oxygen supply channel 43, the second hydrogen supply channel 44, the hydrogen discharge channel 35, and the first hydrogen supply channel 32 can be evaporated and removed by the vacuum state. After removal, the first external open valve 81, the second external open valve 82, the third external open valve 83, and the fourth external open valve 84 are closed.

[0135] Therefore, after the moisture is removed, even if the vacuum space outside the casing 11 of the regenerative fuel cell system 10 placed on the surface of the moon or the like becomes a freezing-prone environment below freezing, it is possible to prevent freezing of water in the piping within the oxygen supply path 43, the second hydrogen supply path 44, the hydrogen discharge path 35, and the first hydrogen supply path 32 of the regenerative fuel cell system 10.

[0136] According to the above embodiment and modified example, after the operation of the water electrolysis device 12 and the hydrogen booster device 18 is stopped, the first external release valve 81, the second external release valve 82, the third external release valve 83, and the fourth external release valve 84 are provided at locations that may freeze and require removal of moisture (condensed water), and the moisture (condensed water) is evaporated by communicating with the vacuum space via these valves. This eliminates the need for the heater, dehumidifier, and adsorbent described in the background art.

[0137] The following notes are further disclosed regarding the above-described embodiment and modified examples. For ease of understanding, reference numerals as examples are given in parentheses to the first-mentioned configurations.

[0138] (Appendix 1) The regenerative fuel cell system (10) of the present disclosure includes a water electrolysis device (12) that generates hydrogen gas from supplied water and generates pressurized oxygen gas, which is stored in an oxygen tank (16) through an oxygen supply line (43); a hydrogen pressure booster (18) that generates pressurized hydrogen gas from the hydrogen gas supplied from the water electrolysis device through a first hydrogen supply line (32), which is stored in a hydrogen tank (20) through a second hydrogen supply line (44), and which returns hydrogen gas that did not contribute to the pressurization to the first hydrogen supply line through a hydrogen discharge line (35); and a hydrogen pressure booster (18) that generates pressurized hydrogen gas from the hydrogen gas supplied from the water electrolysis device through a first hydrogen supply line (32), which is stored in a hydrogen tank (20) through a second hydrogen supply line (44), and which returns hydrogen gas that did not contribute to the pressurization to the first hydrogen supply line through a hydrogen discharge line (35). A regenerative fuel cell system having a fuel cell (22) that is supplied with gas and generates electricity through an electrochemical reaction while producing water, and the system is equipped with: a first external open valve (81) provided between the oxygen supply path communicating with the water electrolysis device and a vacuum space; a second external open valve (82) provided between the second hydrogen supply path communicating with the hydrogen booster device and the vacuum space; a third external open valve (83) provided between the hydrogen discharge path communicating with the hydrogen booster device and the vacuum space; and a fourth external open valve (84) provided between the first hydrogen supply path communicating with the hydrogen booster device and the vacuum space.

[0139] (Appendix 2) In the regenerative fuel cell system described in Appendix 1, the first to fourth external release valves may be closed when the water electrolysis device and the hydrogen booster device are operating, and may be opened when the water electrolysis device and the hydrogen booster device are not operating, thereby releasing moisture remaining in the oxygen supply path, the second hydrogen supply path, the hydrogen discharge path, and the first hydrogen supply path into the vacuum space.

[0140] (Appendix 3) In the regenerative fuel cell system described in Appendix 2, before opening the first to fourth external release valves during the shutdown, the fuel cell may be caused to generate electricity using the oxygen gas remaining in the oxygen supply path and the hydrogen gas remaining in the second hydrogen supply path, and the oxygen supply path and the second hydrogen supply path may be depressurized.

[0141] (Appendix 4) In the regenerative fuel cell system described in Supplementary Note 3, a shutoff valve (94) may be provided on the water electrolysis device side of the first hydrogen supply path and an inlet seal valve (93) may be provided on the hydrogen booster device side, a first outlet seal valve (91) may be provided between an outlet of the pressurized hydrogen gas from the hydrogen booster device and the second hydrogen supply path, and a second outlet seal valve (92) may be provided in the hydrogen discharge path, and the shutoff valve, the inlet seal valve, the first outlet seal valve, and the second outlet seal valve may be opened during the operation and closed after the depressurization.

[0142] (Appendix 5) In the regenerative fuel cell system described in Supplementary Note 4, when setting the closing timings of the shutoff valve, the inlet seal valve, the first outlet seal valve, and the second outlet seal valve, a first humidity sensor (79) may be provided in the oxygen supply path communicating with the water electrolysis device, a second humidity sensor (78) may be provided in the second hydrogen supply path communicating with the hydrogen booster device, a third humidity sensor (98) may be provided in the hydrogen discharge path communicating with the hydrogen booster device, and a fourth humidity sensor (99) may be provided in the first hydrogen supply path communicating with the hydrogen booster device, and when the relative humidity detected by the first to fourth humidity sensors drops to a lower limit humidity or a threshold humidity, the corresponding shutoff valve, inlet seal valve, first outlet seal valve, and second outlet seal valve are closed, and the corresponding first to fourth external open valves are also closed.

[0143] (Appendix 6) The method for operating a regenerative fuel cell system disclosed herein includes a gas accumulation process in which a water electrolysis device generates hydrogen gas and pressurized oxygen gas from supplied water and stores them in an oxygen tank through an oxygen supply channel, and a hydrogen booster device to which the hydrogen gas is supplied through a first hydrogen supply channel generates pressurized hydrogen gas and stores it in the hydrogen tank through a second hydrogen supply channel; a depressurization process in which, after gas accumulation, the oxygen supply channel and the second hydrogen supply channel are depressurized by power generation of a fuel cell to which the oxygen gas remaining in the oxygen supply channel and the hydrogen gas remaining in the second hydrogen supply channel are supplied; and a moisture removal process in which, after depressurization, the oxygen supply channel, the first hydrogen supply channel, a hydrogen discharge channel for the hydrogen gas not used for pressurization by the hydrogen booster device, and the second hydrogen supply channel are connected to a vacuum space, and condensed water remaining in the oxygen supply channel, the first hydrogen supply channel, the hydrogen discharge channel, and the second hydrogen supply channel is evaporated.

[0144] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments. [Explanation of symbols]

[0145] 10...Regenerative fuel cell system 11...Casing 12...Water electrolysis device 15, 21...Electrolyte membrane 16...Oxygen tank 18...Hydrogen booster 20...Hydrogen tank 22...Fuel cell 28...Control device 30...Water supply line 32, 44...Hydrogen supply passage 33...Oxygen remover 35...Hydrogen discharge passage 43...Oxygen supply passage 45, 46...Bypass path 47~50, 94...Shut-off valve 51, 52, 56, 58...Reducing valves 57, 59...Back pressure valves 78, 79, 98, 99... Humidity sensors 81-84... External release valves 91, 92...Outlet sealing valve 93...Inlet sealing valve 96, 97...Partial area 101~104: External release path 181: Oxygen decompression area 182: Hydrogen decompression area

Claims

1. a hydrogen booster that generates pressurized hydrogen gas from supplied water and generates pressurized oxygen gas and stores the pressurized hydrogen gas in an oxygen tank through an oxygen supply channel; a hydrogen booster that generates pressurized hydrogen gas from the hydrogen gas supplied from the water electrolysis device through a first hydrogen supply channel and stores the pressurized hydrogen gas in the hydrogen tank through a second hydrogen supply channel and returns hydrogen gas that did not contribute to the pressurization to the first hydrogen supply channel through a hydrogen discharge channel; and a fuel cell that is supplied with the oxygen gas stored in the oxygen tank and the hydrogen gas stored in the hydrogen tank, generates electricity through an electrochemical reaction, and produces the water, a first external release valve provided between the oxygen supply path communicating with the water electrolysis device and a vacuum space; a second external release valve provided between the second hydrogen supply line communicating with the hydrogen pressure booster and the vacuum space; a third external release valve provided between the hydrogen discharge passage communicating with the hydrogen booster device and the vacuum space; a fourth external release valve provided between the first hydrogen supply passage communicating with the hydrogen pressure booster and the vacuum space; Equipped with Regenerative fuel cell system.

2. 2. The regenerative fuel cell system according to claim 1, the first to fourth external release valves are closed when the water electrolysis device and the hydrogen booster device are in operation, and are opened when the water electrolysis device and the hydrogen booster device are not in operation, to release moisture remaining in the oxygen supply channel, the second hydrogen supply channel, the hydrogen discharge channel, and the first hydrogen supply channel into the vacuum space. Regenerative fuel cell system.

3. 3. The regenerative fuel cell system according to claim 2, before opening the first to fourth external release valves during the shutdown, the fuel cell is caused to generate electricity using the oxygen gas remaining in the oxygen supply channel and the hydrogen gas remaining in the second hydrogen supply channel, and the oxygen supply channel and the second hydrogen supply channel are depressurized. Regenerative fuel cell system.

4. 4. The regenerative fuel cell system according to claim 3, Furthermore, a shutoff valve is provided on the water electrolysis device side of the first hydrogen supply channel and an inlet seal valve is provided on the hydrogen booster device side, a first outlet seal valve is provided between an outlet of the hydrogen booster device for the pressurized hydrogen gas and the second hydrogen supply channel, and a second outlet seal valve is provided in the hydrogen discharge channel; the shutoff valve, the inlet seal valve, the first outlet seal valve, and the second outlet seal valve are opened during the operation and closed after the depressurization. Regenerative fuel cell system.

5. 5. The regenerative fuel cell system according to claim 4, When setting the closing timings of the shutoff valve, the inlet seal valve, the first outlet seal valve, and the second outlet seal valve, moreover, a first humidity sensor is provided in the oxygen supply path communicating with the water electrolysis device; a second humidity sensor is provided in the second hydrogen supply passage communicating with the hydrogen pressure booster; a third humidity sensor is provided in the hydrogen discharge passage communicating with the hydrogen pressure booster; a fourth humidity sensor is provided in the first hydrogen supply passage communicating with the hydrogen pressure boosting device; when the relative humidity detected by the first to fourth humidity sensors drops to a lower limit humidity or a threshold humidity, the corresponding shutoff valve, the inlet seal valve, the first outlet seal valve, and the second outlet seal valve are closed, and the corresponding first to fourth external open valves are closed. Regenerative fuel cell system.

6. a gas storage step in which hydrogen gas is generated from the supplied water by a water electrolysis device and pressurized oxygen gas is generated and stored in an oxygen tank through an oxygen supply line, and pressurized hydrogen gas is generated by a hydrogen pressure booster to which the hydrogen gas is supplied through a first hydrogen supply line and stored in a hydrogen tank through a second hydrogen supply line; a depressurization step of depressurizing the oxygen supply channel and the second hydrogen supply channel by power generation of a fuel cell to which the oxygen gas remaining in the oxygen supply channel and the hydrogen gas remaining in the second hydrogen supply channel are supplied after gas accumulation; a moisture removal step of, after depressurization, communicating the oxygen supply channel, the first hydrogen supply channel, the hydrogen discharge channel for the hydrogen gas not supplied for pressurization in the hydrogen pressurization device, and the second hydrogen supply channel with a vacuum space, and evaporating condensed water remaining in the oxygen supply channel, the first hydrogen supply channel, the hydrogen discharge channel, and the second hydrogen supply channel, A method for operating a regenerative fuel cell system.

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