Regenerative fuel cell system

Abstract

The present application relates to a regenerative fuel cell system, the regenerative fuel cell system (10) is equipped with: supply mechanism (16) for supplying the gas generated in the pressure increasing device (14) to the fuel cell (12); And control device (18). The supply mechanism (16) is equipped with: flow regulating valve (60), which is arranged in the gas supply path (40);And pressure sensor (62), which detects the pressure of the gas supplied to the gas supply path (40), in the case of starting the pressure increasing stop action, the control device (18) adjusts the flow of the flow regulating valve (60) in the form of the target pressure reducing speed, and makes the fuel cell generate the power corresponding to the flow.

Description

Technical Field

[0001] This invention relates to regenerative fuel cell systems. Background Technology

[0002] Patent Document 1 discloses a regenerative fuel cell system comprising a fuel cell, a water electrolysis device, and a gas storage tank. The fuel cell uses hydrogen and oxygen to generate electricity. The water electrolysis device decomposes water to produce high-pressure hydrogen and oxygen. In the regenerative fuel cell system of Patent Document 1, the water supplied to the water electrolysis device is circulated to improve the water supply efficiency to the water electrolysis device.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-015282 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Generally, when a water electrolysis device transitions from the pressurization phase to the pressurization-stop phase, the generated gas is discharged during this stop phase. Furthermore, the pressurization phase involves decomposing water to generate high-pressure hydrogen and oxygen. The pressurization-stop phase is the process from the start of the pressurization phase until its complete cessation.

[0008] If the generated gas can be supplied to the fuel cell during the pressurization and shutdown process, the gas generated in the water electrolysis unit will be eliminated by exhaust, thus allowing the gas to be utilized efficiently.

[0009] However, immediately after the pressurization stop operation, the gas pressure generated in the water electrolysis unit is high. Therefore, when the high-pressure gas generated during the pressurization stop operation is supplied to the fuel cell, there is a concern that bubbles may form in the electrolyte membrane of the water electrolysis unit, leading to its deterioration.

[0010] The purpose of this invention is to solve the above-mentioned problems.

[0011] Solution for solving the problem

[0012] One aspect of the present invention is a regenerative fuel cell system having a fuel cell that generates electricity through the electrochemical reaction of oxygen and hydrogen. The regenerative fuel cell system includes: a booster device that generates either pressurized oxygen or pressurized hydrogen; a supply mechanism for supplying the gas to the fuel cell; and a control device. The supply mechanism includes: a gas supply path that supplies the gas from the booster device to the fuel cell; a flow regulating valve disposed in the gas supply path; and a pressure sensor that detects the pressure of the gas supplied to the gas supply path. When the booster device begins to stop pressurizing, the control device adjusts the flow rate of the flow regulating valve based on the pressure to a target depressurization rate, and causes the fuel cell to generate electricity corresponding to the flow rate.

[0013] The effects of the invention

[0014] According to the above method, it is possible to suppress the generation of bubbles in the electrolyte membrane of the booster device while enabling the fuel cell to generate electricity. As a result, the fuel cell can generate electricity stably.

[0015] The above-described objectives, features, and advantages should be readily understood from the following description of embodiments with reference to the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating an embodiment of a regenerative fuel cell system.

[0017] Figure 2 This is a timing diagram showing the predetermined sequence of operations performed by the control unit of a regenerative fuel cell system.

[0018] Figure 3 Showing according to Figure 2 A timeline diagram showing the operation of oxygen, hydrogen, water, and electricity generation under predetermined operating conditions. Detailed Implementation

[0019] Figure 1 This is a schematic diagram illustrating a regenerative fuel cell system 10 according to an embodiment. The regenerative fuel cell system 10 includes a fuel cell 12, a booster device 14, a supply mechanism 16, and a control device 18.

[0020] Fuel cell 12 generates electricity through the electrochemical reaction of oxygen and hydrogen. Fuel cell 12 has multiple individual cells. Each individual cell has a membrane electrode assembly (MEA), the electrolyte membrane of which is sandwiched between an anode electrode and a cathode electrode. Fuel cell 12 supplies hydrogen to the anode electrode of each individual cell. Fuel cell 12 supplies oxygen to the cathode electrode of each individual cell. Fuel cell 12 collects the electricity generated in each individual cell due to the electrochemical reaction of oxygen and hydrogen and stores it in battery 20.

[0021] Fuel cell 12 collects any remaining oxygen that has not undergone an electrochemical reaction with hydrogen and discharges oxygen-containing exhaust gas. Most of this oxygen-containing exhaust gas is recycled back into fuel cell 12 for reuse. Similarly, fuel cell 12 collects any remaining hydrogen that has not undergone an electrochemical reaction with oxygen and discharges hydrogen-containing exhaust gas. Most of this hydrogen-containing exhaust gas is also recycled back into fuel cell 12 for reuse.

[0022] The booster unit 14 is a device that generates either pressurized oxygen or pressurized hydrogen. The regenerative fuel cell system 10 of this embodiment includes a water electrolysis unit 22 and a hydrogen booster unit 24 as the booster unit 14. The water electrolysis unit 22 is the booster unit 14 that generates pressurized oxygen. The hydrogen booster unit 24 is the booster unit 14 that generates pressurized hydrogen.

[0023] The water electrolysis device 22 generates pressurized oxygen through the electrolysis of water. Water is supplied from the water supply device 26 via the water supply path 28. The water supply path 28 is the path for supplying water from the water supply device 26 to the water electrolysis device 22. A gas-liquid separator 30 is installed on the water supply path 28. A pump 31 is installed between the gas-liquid separator 30 and the water electrolysis device 22 in the water supply path 28. The pump 31 supplies water stored in the gas-liquid separator 30 to the water electrolysis device 22.

[0024] The water supply device 26 can be a tank capable of storing water or a water supply device. In this embodiment, the water supply device 26 is a tank. Alternatively, if the water supply device 26 is a tank, a pump can be installed between the water supply device 26 and the gas-liquid separator 30 in the water supply path 28.

[0025] The water electrolysis device 22 has multiple battery cells. Each battery cell has a membrane electrode assembly (MEA), and the electrolyte membrane of the MEA is sandwiched between an anode electrode and a cathode electrode. The electrolyte membrane used in the water electrolysis device 22 is an anion exchange membrane. A voltage application device 23 is connected to the anode and cathode electrodes of each battery cell. The voltage application device 23 is configured to change the voltage value applied between the anode and cathode electrodes. The voltage application device 23 can obtain the power source for the voltage applied between the anode and cathode electrodes from the battery 20, or it can obtain the power source for the voltage applied between the anode and cathode electrodes from a power source other than the battery 20. Alternatively, the electrolyte membrane used in the water electrolysis device 22 may be a proton exchange membrane.

[0026] The water electrolysis device 22 supplies water flowing from the water supply line 28 to the cathode electrodes of each cell. Each cell electrolyzes the water based on a voltage applied by the voltage application device 23. As a result, oxygen is generated at the anode electrode and hydrogen is generated at the cathode electrode. The oxygen generated in the water electrolysis device 22 is high-pressure oxygen. For example, the oxygen is compressed in the range of 1 to 100 MPa.

[0027] The water electrolysis device 22 collects the oxygen generated in each battery cell and outputs the exhaust gas containing the oxygen to the supply mechanism 16. Furthermore, the exhaust gas contains water vapor that has been vaporized by the heat of the water electrolysis device 22. On the other hand, the water electrolysis device 22 collects the hydrogen generated in each battery cell and the remaining water (unreacted water) that has not been electrolyzed, and outputs the exhaust fluid containing the hydrogen and unreacted water to the hydrogen supply path 32. Furthermore, the exhaust fluid contains water vapor that has been vaporized by the heat of the water electrolysis device 22.

[0028] Hydrogen supply path 32 is the path for supplying hydrogen from water electrolysis unit 22 to hydrogen booster unit 24. Hydrogen supply path 32 passes through gas-liquid separator 30. A pump 34 is installed between gas-liquid separator 30 and hydrogen booster unit 24 in hydrogen supply path 32.

[0029] Hydrogen gas and unreacted water output from water electrolysis unit 22 to hydrogen supply line 32 flow into gas-liquid separator 30. Gas-liquid separator 30 separates the discharged fluid into gaseous components (hydrogen gas and water vapor) and liquid components (liquid water). The gaseous components are supplied to hydrogen booster unit 24 by means of pump 34.

[0030] The hydrogen pressurization device 24 pressurizes the hydrogen flowing in from the hydrogen supply line 32 and generates pressurized hydrogen gas. The hydrogen flowing in from the hydrogen supply line 32 is generated by the water electrolysis device 22.

[0031] The hydrogen booster device 24 has a membrane electrode assembly (MEA) with an electrolyte membrane sandwiched between an anode and a cathode electrode. The electrolyte membrane used in the hydrogen booster device 24 is a proton exchange membrane. A voltage application device 25 is connected to the anode and cathode electrodes. The voltage application device 25 is configured to change the voltage value applied between the anode and cathode electrodes. The voltage application device 25 can obtain the power source for the voltage applied between the anode and cathode electrodes from the battery 20, or from a power source other than the battery 20.

[0032] The hydrogen booster device 24 supplies hydrogen gas from the hydrogen supply line 32 to the anode electrode. The hydrogen booster device 24 ionizes the hydrogen gas based on a voltage applied by the voltage application device 25. The protons generated by the ionization of the hydrogen gas travel through an electrolyte membrane (proton exchange membrane) to the cathode electrode to return to the hydrogen gas. The hydrogen booster device 24 moves protons from the anode electrode to the cathode electrode, thereby generating pressurized hydrogen gas. For example, the hydrogen gas is compressed in the range of 1–100 MPa. Thus, the hydrogen booster device 24 is an electrochemical hydrogen compressor (EHC) capable of electrochemically compressing hydrogen gas.

[0033] The hydrogen booster 24 outputs a discharge gas containing pressurized hydrogen to the supply mechanism 16. Furthermore, the discharge gas contains water vapor that has been vaporized by the heat of the hydrogen booster 24. On the other hand, the hydrogen booster 24 outputs the remaining hydrogen that has not undergone ionization to the hydrogen discharge path 35. The hydrogen discharge path 35 is the path for discharging hydrogen from the hydrogen booster 24 to the gas-liquid separator 30.

[0034] The supply mechanism 16 is a mechanism for supplying gas to the fuel cell 12. The regenerative fuel cell system 10 of this embodiment includes an oxygen supply mechanism 36 and a hydrogen supply mechanism 38 as the supply mechanism 16. The oxygen supply mechanism 36 is a supply mechanism 16 for supplying oxygen generated in the water electrolysis unit 22 to the fuel cell 12. The hydrogen supply mechanism 38 is a supply mechanism 16 for supplying hydrogen generated in the hydrogen booster unit 24 to the fuel cell 12.

[0035] The structure of the oxygen supply mechanism 36 is basically the same as that of the hydrogen supply mechanism 38. Therefore, except in special cases, the supply mechanism 16, which is common to both the oxygen supply mechanism 36 and the hydrogen supply mechanism 38, will be described.

[0036] In the following description, "supply mechanism 16" refers to either the oxygen supply mechanism 36 or the hydrogen supply mechanism 38. Similarly, "gas" refers to either oxygen or hydrogen. Likewise, "pressurization device 14" refers to either the water electrolysis device 22 or the hydrogen pressurization device 24.

[0037] However, when "supply mechanism 16" refers to oxygen supply mechanism 36, please note that "gas" refers to oxygen, not hydrogen. Also, when "supply mechanism 16" refers to oxygen supply mechanism 36, please note that "pressurization device 14" refers to water electrolysis device 22, not hydrogen pressurization device 24. Similarly, when "supply mechanism 16" refers to hydrogen supply mechanism 38, please note that "gas" refers to hydrogen, not oxygen. Also, when "supply mechanism 16" refers to hydrogen supply mechanism 38, please note that "pressurization device 14" refers to hydrogen pressurization device 24, not water electrolysis device 22.

[0038] The supply mechanism 16 includes a gas supply path 40, a tank 42, a bypass path 44, a first on / off valve 46, a second on / off valve 48, a first pressure reducing valve 50, a second pressure reducing valve 52, a first check valve 54, a second check valve 56, a back pressure valve 58, a flow regulating valve 60, a pressure sensor 62, and a gas-liquid separator 64.

[0039] Gas supply path 40 is a path for supplying gas from booster 14 to fuel cell 12. One end of gas supply path 40 is connected to booster 14, and the other end of gas supply path 40 is connected to fuel cell 12.

[0040] Tank 42 is located on gas supply line 40. Gas generated by pressurization device 14 is stored in tank 42. This gas has been pressurized.

[0041] The bypass passage 44 branches off from the booster device 14 and tank 42 in the gas supply passage 40, and merges with the tank 42 and fuel cell 12 in the gas supply passage 40.

[0042] A first on / off valve 46 is provided in the bypass passage 44. The first on / off valve 46 is configured to be openable and closed. The first on / off valve 46 is opened and closed according to the control of the control device 18. In this embodiment, the first on / off valve 46 is a shut-off valve. When an abnormality is detected, the shut-off valve will cut off the bypass passage 44 regardless of the control of the control device 18.

[0043] The second on / off valve 48 is disposed between the confluence portion MP in the gas supply path 40 and the tank 42, wherein the confluence portion MP is the part where the bypass path 44 and the gas supply path 40 merge. The second on / off valve 48 is configured to be openable and closable. The second on / off valve 48 is opened and closed under the control of the control device 18. In this embodiment, the second on / off valve 48 is a shut-off valve.

[0044] The first pressure reducing valve 50 is located between the confluence section MP and the tank 42 in the gas supply line 40. The first pressure reducing valve 50 reduces the pressure of the gas supplied from the tank 42.

[0045] The second pressure reducing valve 52 is located between the confluence section MP and the fuel cell 12 in the gas supply path 40. The second pressure reducing valve 52 reduces the pressure of the gas supplied from the first pressure reducing valve 50 or the bypass passage 44.

[0046] The first check valve 54 is located between the branch section BP in the gas supply line 40 and the gas-liquid separator 64. The second check valve 56 is located between the confluence section MP in the bypass passage 44 and the first on / off valve 46.

[0047] A back pressure valve 58 is disposed between a branch BP in the gas supply path 40 and the tank 42, wherein the branch BP is the portion of the bypass path 44 that branches off from the gas supply path 40. The back pressure valve 58 applies pressure (back pressure) to the pressure boosting device 14. As a result, in the case where the pressure boosting device 14 is a water electrolysis device 22, the pressure of the oxygen generated at the anode electrode of each cell rises, becoming a high pressure higher than the pressure of the hydrogen generated at the cathode electrode.

[0048] That is, the water electrolysis device 22 generates oxygen at a higher pressure than the hydrogen generated at the cathode electrode. Therefore, it is possible to suppress the permeation of hydrogen from the cathode electrode to the anode electrode through the electrolyte membrane. As a result, it is possible to prevent a decrease in the amount of hydrogen supplied from the water electrolysis device 22 to the hydrogen booster device 24.

[0049] A flow regulating valve 60 is disposed between the confluence section MP in the gas supply path 40 and the fuel cell 12. The flow regulating valve 60 is configured to adjust the flow rate of the gas flowing to the fuel cell 12. The flow regulating valve 60 adjusts the flow rate according to the control of the control device 18.

[0050] Pressure sensor 62 detects the pressure of the gas supplied to gas supply path 40. Pressure sensor 62 outputs a signal indicating the detected pressure to control device 18. Preferably, pressure sensor 62 is located near water electrolysis device 22 in gas supply path 40. In this embodiment, pressure sensor 62 is located between water electrolysis device 22 and branch section BP in gas supply path 40.

[0051] A gas-liquid separator 64 is disposed between the back pressure valve 58 and the first check valve 54 on the gas supply path 40. As described above, the exhaust gas discharged from the pressurization device 14 to the gas supply path 40 contains water vapor in addition to gas. The gas-liquid separator 64 supplies the gas in the exhaust gas to the tank 42. This prevents the tank 42 from becoming wet. As a result, the durability of the tank 42 can be improved even without excessive rust prevention.

[0052] On the other hand, the gas-liquid separator 64 cools the water vapor in the exhaust gas to generate liquid water. The gas-liquid separator 64 is connected to the gas-liquid separator 30 via a liquid water supply path 65. The liquid water supply path 65 is a path for supplying the liquid water stored in the gas-liquid separator 64 to the gas-liquid separator 30. The liquid water obtained from the water vapor in the exhaust gas discharged from the water electrolysis unit 22 is supplied to the gas-liquid separator 30 via the liquid water supply path 65, where the gas-liquid separator 30 stores the water supplied to the water electrolysis unit 22. Therefore, water used in the water electrolysis unit 22 can be saved.

[0053] In addition to the structure of the aforementioned supply mechanism 16, the oxygen supply mechanism 36 also includes an oxygen exhaust flow path 66, a gas-liquid separator 68, and a circulation pump 70. The oxygen exhaust flow path 66 is a path for returning oxygen-containing exhaust gas discharged from the fuel cell 12 back to the fuel cell 12. One end of the oxygen exhaust flow path 66 is connected to the fuel cell 12. The other end of the oxygen exhaust flow path 66 is connected between the fuel cell 12 and the flow regulating valve 60 in the gas supply path 40.

[0054] A gas-liquid separator 68 and a circulation pump 70 are installed on the oxygen exhaust path 66. The gas-liquid separator 68 separates the oxygen-containing exhaust gas discharged from the fuel cell 12 into gaseous components (oxygen and water vapor) and liquid components (liquid water) in the oxygen exhaust path 66. The gaseous components are then supplied back to the fuel cell 12 by the circulation pump 70. On the other hand, the liquid components are supplied to the water supply device 26.

[0055] In addition to the structure of the aforementioned supply mechanism 16, the hydrogen supply mechanism 38 also includes a hydrogen exhaust flow path 72, a gas-liquid separator 74, and a circulation pump 76. The hydrogen exhaust flow path 72 is a path for returning hydrogen-containing exhaust gas discharged from the fuel cell 12 back to the fuel cell 12. One end of the hydrogen exhaust flow path 72 is connected to the fuel cell 12. The other end of the hydrogen exhaust flow path 72 is connected between the fuel cell 12 and the flow regulating valve 60 in the gas supply path 40.

[0056] A gas-liquid separator 74 and a circulation pump 76 are installed on the hydrogen exhaust flow path 72. The gas-liquid separator 74 separates the hydrogen-containing exhaust gas discharged from the fuel cell 12 into gaseous components (hydrogen and water vapor) and liquid components (liquid water) in the hydrogen exhaust flow path 72. The gaseous components are then supplied back to the fuel cell 12 by the circulation pump 76. On the other hand, the liquid components are supplied to the water supply device 26.

[0057] Figure 2 This is a timing diagram showing the predetermined sequence of operation performed by the control device 18 of the regenerative fuel cell system 10. Figure 3 It shows according to Figure 2 A timeline diagram showing the flow of oxygen, hydrogen, water, and electricity generation under predetermined operating sequence conditions. Figure 2 The time point "T1" in the text is related to... Figure 3 The time point "T1" in the text is consistent. Figure 2 and Figure 3 The same applies to "T2" through "T8".

[0058] in addition, Figure 2 The “O2 first opening and closing valve” refers to the first opening and closing valve 46 of the oxygen supply mechanism 36. Figure 2 The “O2 second on / off valve” refers to the second on / off valve 48 of the oxygen supply mechanism 36. Figure 2 The “H2 first on / off valve” refers to the first on / off valve 46 of the hydrogen supply mechanism 38. Figure 2 The “H2 second on / off valve” refers to the second on / off valve 48 of the hydrogen supply mechanism 38.

[0059] in addition, Figure 3 The “H2 gas pressure” refers to the gas pressure of hydrogen generated by the hydrogen booster device 24. Figure 3 The “O2 gas pressure” refers to the gas pressure of oxygen generated by the water electrolysis device 22. Figure 3 The “H2O storage capacity” refers to the amount of water stored in the gas-liquid separator 30. Figure 3 The “H2 storage capacity” refers to the amount of hydrogen stored in the gas-liquid separator 30. Figure 3 The “H2 tank storage capacity” refers to the amount of hydrogen stored in tank 42 of the hydrogen supply facility 38. Figure 3 The “O2 tank storage capacity” refers to the amount of oxygen stored in tank 42 of the oxygen supply unit 36.

[0060] The operation of the regenerative fuel cell system 10 is controlled by the control device 18. The control device 18 provides comprehensive control over the regenerative fuel cell system 10. When the regenerative fuel cell system 10 is stopped, the first on / off valve 46 and the second on / off valve 48 of the oxygen supply mechanism 36 and the hydrogen supply mechanism 38 are closed. In addition, the fuel cell 12, the water electrolysis device 22, and the hydrogen booster device 24 are also stopped.

[0061] When the regenerative fuel cell system 10 is started to operate, the control device 18 first controls the water supply device 26 to start outputting water. The water output from the water supply device 26 is supplied to the cathode electrode of each cell in the water electrolysis device 22 via the water supply path 28.

[0062] Then, the control device 18 controls the voltage application device 23 to cause the water electrolysis device 22 to perform a pressure boosting preparation operation. Figure 2 (A-1). In this case, the control device 18 supplies a predetermined electrolysis standby current to the cathode and anode electrodes of each cell in the water electrolysis device 22.

[0063] Subsequently, when the water electrolysis device 22 reaches a state capable of producing hydrogen and oxygen separately, the control device 18 causes the water electrolysis device 22 to perform a pressure boosting operation. Figure 2 (A-2). In this case, the control device 18 supplies a predetermined electrolysis operating current to the cathode and anode electrodes of each cell in the water electrolysis device 22.

[0064] When the water electrolysis device 22 begins its pressurization operation, pressurized oxygen is generated at the anode electrode through the electrolysis of water. This oxygen is supplied to the tank 42 of the oxygen supply mechanism 36 via the gas supply path 40. Conversely, when the water electrolysis device 22 begins its pressurization operation, hydrogen is generated at the cathode electrode through the electrolysis of water. This hydrogen is supplied to the anode electrode of each cell in the hydrogen pressurization device 24 via the hydrogen supply path 32.

[0065] The control device 18 confirms the supply of hydrogen to the hydrogen supply line 32 based on sensors or the like installed near the hydrogen booster device 24 in the hydrogen supply line 32. When the supply of hydrogen to the hydrogen supply line 32 is confirmed, the control device 18 controls the voltage application device 25 to cause the hydrogen booster device 24 to perform a boosting preparation operation. Figure 2 (B-1). In this case, the control device 18 supplies a predetermined ionization standby current to the cathode and anode electrodes of each cell in the hydrogen booster device 24.

[0066] Subsequently, when the hydrogen booster 24 reaches a state capable of ionizing hydrogen, the control device 18 causes the hydrogen booster 24 to perform a boosting operation. Figure 2 (B-2). In this case, the control device 18 supplies a predetermined ionization operating current to the cathode and anode electrodes of each cell in the hydrogen booster device 24.

[0067] When the hydrogen pressurization device 24 starts pressurization, hydrogen gas is generated at the cathode electrode due to the pressurization of hydrogen gas caused by ionization. This hydrogen gas is supplied to the tank 42 of the hydrogen supply mechanism 38 via the gas supply path 40 of the hydrogen supply mechanism 38.

[0068] The control device 18 monitors the electrical power stored in the battery 20 based on sensors installed on the battery 20. When the electrical power falls below a predetermined lower limit, the control device 18 causes the fuel cell 12 to perform a first start-up action. Figure 2 (C-1).

[0069] That is, the control device 18 opens the first on / off valve 46 of the oxygen supply mechanism 36. Figure 2 (D-1). Thus, oxygen is supplied from the water electrolysis unit 22 to the fuel cell 12. Similarly, the control unit 18 opens the first on / off valve 46 of the hydrogen supply mechanism 38 (D-1). Figure 2 (E-1). Thus, hydrogen is supplied from the hydrogen booster 24 to the fuel cell 12.

[0070] When the first on / off valve 46 of the oxygen supply mechanism 36 is opened, oxygen pressurized by water electrolysis in the water electrolysis device 22 is supplied to the fuel cell 12 via the bypass passage 44 of the oxygen supply mechanism 36. On the other hand, when the first on / off valve 46 of the hydrogen supply mechanism 38 is opened, hydrogen pressurized by ionization in the hydrogen booster device 24 is supplied to the fuel cell 12 via the bypass passage 44 of the hydrogen supply mechanism 38. In the fuel cell 12, electricity generation begins due to the electrochemical reaction between the oxygen supplied from the oxygen supply mechanism 36 and the hydrogen supplied from the hydrogen supply mechanism 38, and power corresponding to the amount of gas is obtained.

[0071] As described above, the exhaust gas discharged from the water electrolysis unit 22 to the gas supply path 40 includes water vapor in addition to oxygen. Therefore, the water vapor is supplied to the fuel cell 12 along with the oxygen. Similarly, the exhaust gas discharged from the hydrogen booster unit 24 to the gas supply path 40 includes water vapor in addition to hydrogen. Therefore, the water vapor is supplied to the fuel cell 12 along with the hydrogen. As a result, the drying of the electrolyte membrane of the membrane electrode assembly of the fuel cell 12 can be suppressed, and consequently, the reduction in the power generation efficiency of the fuel cell 12 can be suppressed.

[0072] Additionally, the control device 18 causes the booster device 14 to begin the boost-stop operation. The timing for initiating the boost-stop operation can be the same as, or later than, the start-up timing for the fuel cell 12 to perform the first start-up operation. Figure 2 The timing for initiating the boost stop action is the same as the timing for initiating the first start action of the fuel cell 12.

[0073] In this embodiment, the control device 18 controls the voltage application device 23 to cause the water electrolysis device 22 to begin the pressure boosting and stopping operation (pressure relief operation). Figure 2 (A-3). In this case, the control device 18 gradually reduces the current supplied to the cathode and anode electrodes of each cell in the water electrolysis unit 22. As a result, the high-pressure oxygen generated by the water electrolysis unit 22 gradually decreases. Similarly, the control device 18 controls the voltage application device 25 to initiate the pressure-reducing stop operation (pressure relief operation) of the hydrogen booster device 24. Figure 2 (B-3). In this case, the control device 18 gradually reduces the current supplied to the cathode and anode electrodes of each cell in the hydrogen booster device 24. As a result, the high-pressure hydrogen generated by the hydrogen booster device 24 gradually decreases.

[0074] If the pressure boosting device 14 (water electrolysis device 22 or hydrogen boosting device 24) depressurizes too quickly due to the pressure boosting device stopping, bubbles may form in the electrolyte membrane of the membrane electrode assembly of the boosting device 14, and the boosting device 14 may deteriorate.

[0075] Therefore, the control device 18 adjusts the flow rate of the flow regulating valve 60 based on the pressure detected by the pressure sensor 62 to achieve a target decompression rate, and causes the fuel cell 12 to generate electricity (generator voltage) corresponding to this flow rate. In this case, the control device 18 measures the decompression rate per unit time based on the pressure detected by the pressure sensor 62 and calculates the difference between this decompression rate and the target decompression rate. The target decompression rate is a target value for the decompression rate used to suppress the generation of bubbles, etc., and is preset in the memory of the control device 18. The control device 18 sets the flow rate of the flow regulating valve 60 in a way that reduces the difference from the target decompression rate. The larger the difference from the target decompression rate, the smaller the flow rate of the flow regulating valve 60 is set.

[0076] Therefore, it is possible to suppress the generation of bubbles or the like in the electrolyte membrane of the booster device 14 due to the high-pressure gas (oxygen or hydrogen) supplied from the booster device 14 (water electrolysis device 22 or hydrogen booster device 24). As a result, the deterioration of the booster device 14 is suppressed.

[0077] As the pressure boosting device 14 stops operating, the amount of gas supplied to the fuel cell 12 decreases, and the gas pressure decreases. When the pressure detected by the pressure sensor 62 falls below a predetermined pressure threshold, the control device 18 causes the fuel cell 12 to perform a second start-up action. Figure 2 (C-2).

[0078] That is, when the pressure detected by the pressure sensor 62 of the oxygen supply mechanism 36 is lower than a predetermined oxygen pressure threshold, the control device 18 opens the second on / off valve 48 of the oxygen supply mechanism 36. Figure 2 (F-1). Thus, oxygen is supplied from the tank 42 of the oxygen supply mechanism 36 to the fuel cell 12. Similarly, if the pressure detected by the pressure sensor 62 of the hydrogen supply mechanism 38 is lower than the hydrogen pressure threshold, the control device 18 opens the second on / off valve 48 of the hydrogen supply mechanism 38. Figure 2 (G-1). Thus, hydrogen is supplied from tank 42 of hydrogen supply unit 38 to fuel cell 12.

[0079] Therefore, even if the gas supplied from the booster 14 to the fuel cell 12 decreases as the booster 14 stops operating, a stable gas supply can still be provided to the fuel cell 12. As a result, the reduction in the power generation efficiency of the fuel cell 12 can be suppressed. Furthermore, the aforementioned pressure threshold (oxygen pressure threshold or hydrogen pressure threshold) is preset in the memory of the control device 18.

[0080] Subsequently, when the pressure detected by pressure sensor 62 falls below a predetermined pressure threshold, control device 18 causes fuel cell 12 to perform a power generation operation. Figure 2 (C-3). In this case, the control device 18 fixes the flow rate of the flow regulating valve 60 at a preset flow rate value to obtain a predetermined power (generator voltage). In addition, the control device 18 also closes the first on / off valve 46, and begins to supply gas to the fuel cell 12 only from the tank 42.

[0081] That is, when the pressure detected by the pressure sensor 62 of the oxygen supply mechanism 36 is lower than the oxygen pressure threshold, the control device 18 fixes the flow rate of the flow regulating valve 60 of the oxygen supply mechanism 36 to a predetermined oxygen flow rate value. Furthermore, the control device 18 also closes the first on / off valve 46 of the oxygen supply mechanism 36. Figure 2 (D-2). Thus, a stable supply of oxygen is initially provided to the fuel cell 12 solely from the tank 42 of the oxygen supply mechanism 36.

[0082] Similarly, when the pressure detected by the pressure sensor 62 of the hydrogen supply mechanism 38 is lower than the hydrogen pressure threshold, the control device 18 fixes the flow rate of the flow regulating valve 60 of the hydrogen supply mechanism 38 to a predetermined hydrogen flow rate value. Furthermore, the control device 18 also closes the first on / off valve 46 of the hydrogen supply mechanism 38. Figure 2 (E-2). Thus, a stable supply of hydrogen is initially provided to the fuel cell 12 solely from the tank 42 of the hydrogen supply unit 38.

[0083] When the first on / off valve 46 is closed, the gas pressure of the gas supplied from the tank 42 to the fuel cell 12 via the gas supply passage 40 is adjusted to a predetermined value by the first pressure reducing valve 50 and the second pressure reducing valve 52 provided in the gas supply passage 40. Moreover, the aforementioned pressure threshold (oxygen pressure threshold or hydrogen pressure threshold) is preset in the memory of the control device 18.

[0084] When the electrical power stored in the battery 20 due to the power generation generated by the fuel cell 12 exceeds a predetermined upper limit, the control device 18 closes the second on / off valve 48 of the oxygen supply mechanism 36 and the hydrogen supply mechanism 38. Figure 2 (F-2, G-2). As a result, the power generation operation of fuel cell 12 is stopped.

[0085] As described above, the control device 18 executes a predetermined operating sequence to comprehensively control the regenerative fuel cell system 10.

[0086] However, there is a tendency for the decompression rates of oxygen (depressurized by the pressure-boosting stop operation of the water electrolysis unit 22) and hydrogen (depressurized by the pressure-boosting stop operation of the hydrogen boosting unit 24) to differ. When the decompression rates of oxygen and hydrogen differ, there is a discrepancy between the oxygen supply mechanism 36 and the hydrogen supply mechanism 38 regarding the timing of the pressure of the gas reduced due to the pressure-boosting stop operation reaching the aforementioned pressure threshold.

[0087] Therefore, in this embodiment, the control device 18 controls the first on / off valve 46 and the second on / off valve 48 so that the timing deviation of reaching the above-mentioned pressure threshold will not occur in the oxygen supply mechanism 36 and the hydrogen supply mechanism 38.

[0088] For example, suppose that the timing of reaching the aforementioned pressure threshold in the oxygen supply mechanism 36 is earlier than the timing of reaching the aforementioned pressure threshold in the hydrogen supply mechanism 38. In this case, firstly, the control device 18 closes the first on / off valve 46 of the oxygen supply mechanism 36 and opens the second on / off valve 48 of the oxygen supply mechanism 36. On the other hand, the control device 18 opens the first on / off valve 46 of the hydrogen supply mechanism 38 and closes the second on / off valve 48 of the hydrogen supply mechanism 38. Then, if the pressure detected by the pressure sensor 62 of the hydrogen supply mechanism 38 is lower than the aforementioned pressure threshold, the control device 18 closes the first on / off valve 46 of the hydrogen supply mechanism 38 and opens the second on / off valve 48 of the hydrogen supply mechanism 38.

[0089] Conversely, suppose that the timing of reaching the aforementioned pressure threshold in the hydrogen supply mechanism 38 is earlier than the timing of reaching the aforementioned pressure threshold in the oxygen supply mechanism 36. In this case, firstly, the control device 18 closes the first on / off valve 46 of the hydrogen supply mechanism 38 and opens the second on / off valve 48 of the hydrogen supply mechanism 38. On the other hand, the control device 18 opens the first on / off valve 46 of the oxygen supply mechanism 36 and closes the second on / off valve 48 of the oxygen supply mechanism 36. Subsequently, if the pressure detected by the pressure sensor 62 of the oxygen supply mechanism 36 is lower than the aforementioned pressure threshold, the control device 18 closes the first on / off valve 46 of the oxygen supply mechanism 36 and opens the second on / off valve 48 of the oxygen supply mechanism 36.

[0090] In this way, the control device 18 opens the second on / off valve 48 of the supply mechanism 16 when the pressure of the gas, which has decreased due to the pressurization stop operation, reaches the aforementioned pressure threshold earlier, to supply gas from the tank 42. Then, when the pressure of the supply mechanism 16, which has decreased due to the pressurization stop operation, reaches the aforementioned pressure threshold later, the control device 18 opens the second on / off valve 48 of that supply mechanism 16. The timing deviation of reaching the aforementioned pressure threshold will not occur in the oxygen supply mechanism 36 and the hydrogen supply mechanism 38. Therefore, the generation of bubbles or the like in the electrolyte membrane of the membrane electrode assembly in the pressurization device 14 (water electrolysis device 22 or hydrogen pressurization device 24) can be suppressed, resulting in stable power generation by the fuel cell 12.

[0091] The present invention is not particularly limited to the embodiments described above, and various modifications can be made without departing from its spirit.

[0092] For example, either the water electrolysis device 22 or the hydrogen booster device 24 may be omitted. If the hydrogen booster device 24 is omitted, a hydrogen supply assembly configured to supply depressurized hydrogen to the fuel cell 12 may be connected to the fuel cell 12, replacing the hydrogen booster device 24 and the hydrogen supply mechanism 38. Conversely, if the water electrolysis device 22 is omitted, an oxygen supply assembly configured to supply depressurized oxygen to the fuel cell 12 may be connected to the fuel cell 12, replacing the water electrolysis device 22 and the oxygen supply mechanism 36.

[0093] The inventions and their effects that can be understood based on the above description are described below.

[0094] (1) The present invention is a regenerative fuel cell system having a fuel cell 12 that generates electricity through the electrochemical reaction of oxygen and hydrogen. The regenerative fuel cell system 10 includes: a booster device 14 that generates either the boosted oxygen or the boosted hydrogen; a supply mechanism 16 for supplying the gas to the fuel cell; and a control device 18. The supply mechanism includes: a gas supply path 40 that supplies the gas from the booster device to the fuel cell; a flow regulating valve 60 disposed in the gas supply path; and a pressure sensor 62 that detects the pressure of the gas supplied to the gas supply path. When the booster device begins to stop pressurizing, the control device adjusts the flow rate of the flow regulating valve based on the pressure to a target depressurization rate, and causes the fuel cell to generate electricity corresponding to the flow rate.

[0095] Therefore, it is possible to suppress the generation of bubbles in the booster unit and enable the fuel cell to generate electricity. As a result, it is possible to suppress the deterioration of the booster unit. In addition, the gas generated during the booster shutdown operation can be output to the gas supply path along with water vapor. Therefore, water vapor and gas can be supplied to the fuel cell together. As a result, it is possible to suppress the deterioration of the fuel cell due to insufficient moisture.

[0096] (2) The present invention is a regenerative fuel cell system, which may also include: a water electrolysis device 22, which is a booster device that uses the decomposition of water to generate pressurized oxygen; and an oxygen supply mechanism 36, which is a supply mechanism for supplying the oxygen generated by the water electrolysis device. The water electrolysis device has a membrane electrode assembly, in which the electrolyte membrane is sandwiched between an anode electrode and a cathode electrode. Hydrogen is generated at the cathode electrode, and oxygen at a pressure higher than that of the hydrogen is generated at the anode electrode. This suppresses the permeation of hydrogen from the cathode electrode to the anode electrode through the electrolyte membrane. As a result, the efficiency of hydrogen and oxygen generation in the water electrolysis device can be improved.

[0097] (3) The present invention is a regenerative fuel cell system, which may also include: a hydrogen booster device 24, which is a booster device for pressurizing the hydrogen generated by the water electrolysis device, and a hydrogen supply mechanism 38, which is a supply mechanism for supplying the hydrogen generated by the hydrogen booster device. Thus, the hydrogen generated by the water electrolysis device can be effectively utilized without being discharged.

[0098] (4) The present invention is a regenerative fuel cell system. Alternatively, the supply mechanism may include: a tank 42 disposed on the gas supply line, storing the gas pressurized by the booster device; a bypass passage 44 branching from the booster device and the tank in the gas supply line, and merging with the tank and the fuel cell in the gas supply line; a first on / off valve 46 disposed on the bypass passage; and a second on / off valve 48 disposed between the merging portion MP in the gas supply line and the tank, wherein the merging portion MP is the part where the bypass passage and the gas supply line merge; and a flow regulating valve disposed between the merging portion in the gas supply line and the fuel cell. When the booster device performs a pressurization operation, the control device closes the first and second on / off valves to supply the gas from the booster device to the tank. After the pressurization stop operation begins, the first on / off valve is opened to supply the gas from the booster device to the fuel cell. This allows hydrogen to be stored in the tank at high pressure, resulting in longer fuel cell operation time. Furthermore, the gas generated during the pressurization-to-stop operation can be supplied to the fuel cell simply by cutting off the gas supply and exhaust using the first and second on / off valves.

[0099] (5) The present invention is a regenerative fuel cell system, which may also include a gas-liquid separator 64 disposed between a branch portion BP in the gas supply path and the tank, and separates water vapor contained in the gas. The branch portion BP is the part of the bypass path that branches off from the gas supply path. This prevents the tank from becoming wet. As a result, the durability of the tank can be improved even without excessive rust prevention.

[0100] (6) This invention relates to a regenerative fuel cell system. Alternatively, the control device may open the second on / off valve of the oxygen supply mechanism and the hydrogen supply mechanism at an earlier timing when the pressure of the gas, which has decreased due to the pressurization stop operation, reaches a predetermined pressure threshold. When the pressure of the supply mechanism at a later timing reaches the pressure threshold, the second on / off valve of the supply mechanism at the later timing is opened. This reliably reduces the gas pressures of both oxygen and hydrogen to below a predetermined value. Consequently, it suppresses the generation of bubbles in the pressurization device.

Claims

1. A regenerative fuel cell system comprising a fuel cell that generates electricity through the electrochemical reaction of oxygen and hydrogen, wherein in the regenerative fuel cell system (10), It comprises: a booster device (14) for generating either the boosted oxygen or the boosted hydrogen; a supply mechanism (16) for supplying the gas to the fuel cell; and a control device (18). The supply organization possesses: Gas supply path (40) supplies the gas from the booster to the fuel cell; A flow regulating valve (60) is provided in the gas supply path; and A pressure sensor (62) detects the pressure of the gas supplied to the gas supply path. When the pressure boosting device begins its pressure boosting stop operation, the control device measures the depressurization rate per unit time based on the pressure, sets the flow rate of the flow regulating valve in such a way that the difference between the depressurization rate and the target depressurization rate is reduced, and causes the fuel cell to generate electricity corresponding to the set flow rate.

2. The regenerative fuel cell system according to claim 1, characterized in that, have: Water electrolysis device (22), which is a pressurizing device that utilizes the decomposition of water to generate pressurized oxygen; and Oxygen supply mechanism (36), which is a supply mechanism for supplying the oxygen generated by the water electrolysis device. The water electrolysis device has a membrane electrode assembly, in which the electrolyte membrane is held between an anode electrode and a cathode electrode, hydrogen is generated at the cathode electrode, and oxygen is generated at the anode electrode at a pressure higher than that of the hydrogen.

3. The regenerative fuel cell system according to claim 2, characterized in that, have: Hydrogen booster device (24), which is a booster device for boosting the pressure of the hydrogen gas generated by the water electrolysis device, and Hydrogen supply mechanism (38) is a supply mechanism for supplying the hydrogen generated by the hydrogen booster device.

4. The regenerative fuel cell system according to claim 1, characterized in that, The supply organization possesses: A tank (42) is provided on the gas supply line to store the gas that has been pressurized by the pressurizing device; A bypass (44) branches off from the booster in the gas supply line between the gas supply line and the tank, and merges with the gas supply line between the tank and the fuel cell; A first on / off valve (46) is provided in the bypass passage; as well as The second on / off valve (48) is located between the confluence portion of the gas supply path and the tank, wherein the confluence portion is the part where the bypass passage and the gas supply path merge. The flow regulating valve is located between the confluence section of the gas supply path and the fuel cell. When the pressurization device is activated, the control device closes the first and second on / off valves to supply gas from the pressurization device to the tank. After the pressurization stop operation is initiated, the first on / off valve is opened to supply the gas from the pressurization device to the fuel cell.

5. The regenerative fuel cell system according to claim 4, characterized in that, It includes a gas-liquid separator (64) disposed between a branch (BP) in the gas supply path and the tank, which separates water vapor contained in the gas. The branch (BP) is the portion of the bypass path that branches off from the gas supply path.

6. The regenerative fuel cell system according to claim 1, characterized in that, have: A water electrolysis device, which is a pressurization device that utilizes the decomposition of water to generate pressurized oxygen; An oxygen supply mechanism, which is a supply mechanism for supplying the oxygen generated in the water electrolysis device; A hydrogen pressurization device, which is a pressurization device for the hydrogen gas generated by the water electrolysis device; and A hydrogen supply mechanism, which is a supply mechanism for supplying the hydrogen generated by the hydrogen pressurization device. The oxygen supply mechanism and the hydrogen supply mechanism include: A tank, which is installed on the gas supply line, stores the gas that has been pressurized by the pressurizing device; A bypass passage branches off from the booster device and the tank in the gas supply line and merges with the tank and the fuel cell in the gas supply line; A first on / off valve is provided in the bypass passage; as well as A second on / off valve is disposed between the confluence portion of the gas supply path and the tank, wherein the confluence portion is the section where the bypass passage and the gas supply path merge. The control device opens the second on / off valve of the oxygen supply mechanism and the hydrogen supply mechanism when the pressure of the gas, which has decreased due to the pressure boosting stop operation, reaches a predetermined pressure threshold at an earlier time. When the pressure of the supply mechanism at a later time reaches the pressure threshold, the control device opens the second on / off valve of the oxygen supply mechanism and the hydrogen supply mechanism at the later time.

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