JP6229925B2 - Charge / discharge system and method for drying charge / discharge system - Google Patents

Description

  The present invention relates to a charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated, and a method for drying the charge / discharge system.

  In a power storage system using a reversible cell, water (electrolytic power storage) is performed by electrolyzing the raw water, generating pure hydrogen and pure oxygen, and storing the pure hydrogen in a container. Is called. And discharge (power supply to the outside) is performed by operating the fuel cell with the stored hydrogen and air or oxygen sucked from the atmosphere. The water generated by the discharge is stored in a separate container and used again as a raw material during the water electrolysis operation.

  The polymer electrolyte reversible cell has a structure in which a polymer electrolyte water electrolysis cell and a fuel cell are integrated so that both functions can be selectively performed in one cell. In a water electrolysis cell, by controlling the pressure of pure hydrogen and pure oxygen generated by electrolysis of water, pure hydrogen and pure oxygen of several MPa to several tens of MPa are generated without using a booster such as a compressor. be able to. If this pressurized gas is stored in a separately provided container, it can be used as a fuel and an oxidant during fuel cell operation. In fuel cell operation, electricity and water are generated by a chemical reaction between pure hydrogen and pure oxygen. If the generated water is stored in a container, it can be used as a raw material for water electrolysis operation. That is, by collecting and reusing the reaction product, charging by water electrolysis operation and discharging by fuel cell operation can be repeated, so that it can be constructed as a power storage system.

  As a system using such a reversible cell, for example, there is one disclosed in Patent Document 1, but in this type of conventional system, the hydrogen generation electrode (cathode) during water electrolysis operation is used as the fuel cell operation time. It is used as a hydrogen electrode (anode), and an oxygen generation electrode (anode) during water electrolysis operation is used as an oxygen electrode (cathode) during fuel cell operation. The same electrode is used when hydrogen is generated and consumed. Oxygen generation and consumption were performed at the same pole.

JP 2006-127807 A

In the reversible cell in the conventional system, carbon can be used for the hydrogen generation electrode during water electrolysis operation, but water-repellent carbon cannot be used for the oxygen generation electrode. A mixed catalyst of iridium oxide and platinum black is used. This is because water is supplied to the oxygen electrode side during the water electrolysis operation, so that a hydrophilic material has better performance.
On the other hand, since iridium oxide and platinum black itself are hydrophilic, if they are used as they are, water generated on the oxygen electrode side during the operation of the fuel cell remains on the catalyst surface and power generation efficiency decreases. For this reason, conventionally, a catalyst made of iridium oxide and platinum black itself is subjected to a water repellent treatment using PTFE or the like, so that the performance during the water electrolysis operation is sacrificed to some extent while it is necessary for the fuel cell operation. The water repellency of the electrode catalyst is ensured.
However, if charging / discharging is repeated for a long period of time, the water repellent such as PTFE applied to the electrode catalyst may be physically removed or the original water repellent performance may not be exhibited due to contamination. It is conceivable that the performance degradation will accelerate, and there is room for further improvement.

  The present invention has been made in view of such points, and in such a charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated, the performance of the reversible cell is as follows. It aims to maintain the long-term.

To achieve the above object, the present invention provides a discharge system using a reversible cell integrating the fuel cell of a water electrolysis apparatus and solid high molecular form of solid high molecular type, raw material during water electrolysis operation Hydrogen is supplied to the oxygen generating electrode where water is supplied and oxygen is generated during fuel cell operation, and oxidant is supplied to the hydrogen generating electrode where hydrogen is generated during water electrolysis operation. In addition, a mixture of iridium oxide and platinum black not subjected to water repellent treatment is used as the electrode catalyst of the oxygen generating electrode of the reversible cell, and the electrode catalyst of the hydrogen generating electrode of the reversible cell is used. It is characterized in that platinum-supporting carbon is used .

  According to the present invention, hydrogen is supplied at the time of fuel cell operation and hydrogen is generated at the time of water electrolysis operation, while the raw water is supplied and oxygen is generated at the time of water electrolysis operation. Since the oxidant is supplied during fuel cell operation, platinum is supported on carbon that originally has water repellency on the oxidizer electrode that requires water repellency of the electrode catalyst during fuel cell operation. Since the electrocatalyst that has been used can be used, it is possible to avoid performance degradation due to a decrease in water repellency compared to conventional reversible cells. In addition, despite the use of reversible cells, the electrode catalyst on the oxidizer electrode side, which is used for high performance and high durability in ordinary cells dedicated to fuel cells, can be applied as is. The same performance and durability as the special fuel cell machine can be maintained.

A cell stack in which a plurality of the reversible cells are connected in series, ports A and B that communicate with the flow path of the reaction fluid on the oxygen generation electrode side of each reversible cell, and the reaction fluid on the hydrogen generation electrode side of each reversible cell Port C and Port D leading to the flow path are provided, port A is set as a raw water supply port during water electrolysis operation and hydrogen discharge port during fuel cell operation, and port B is a raw material during water electrolysis operation Port C is set as a water and pure oxygen discharge port and a hydrogen supply port during fuel cell operation, and a port for discharging hydrogen and water during water electrolysis operation and a discharge of oxidant and generated water during fuel cell operation. The outlet is set, the port D is set as an oxidant supply port during operation of the fuel cell, the oxidant supplied to the port D is air, the air supply channel, and the port B during the water electrolysis operation. The discharge flow path of pure oxygen discharged from As at least a humidity exchange or heat exchanger, it may be arranged via the least moisture exchanger or heat exchangers.

  In addition, it is preferable that the said reversible cell has a pressure difference resistance between electrodes when hydrogen side pressure> oxygen side pressure = atmospheric pressure. A reversible cell has resistance to inter-electrode differential pressure when hydrogen side pressure> oxygen side pressure = atmospheric pressure, such as a solid polymer electrolyte membrane used in a reversible cell. In the partitioning membrane, during water electrolysis operation, even when the pressure on the oxygen side is atmospheric pressure and the pressure on the hydrogen side is greater than the pressure on the oxygen side, the membrane does not break. It means having. That is, when the pressure on the oxygen side is atmospheric pressure, the solid polymer electrolyte membrane is not damaged even if the pressure on the hydrogen side of the solid polymer electrolyte membrane in the reversible cell is greater than atmospheric pressure and several tens of Pa. .

  As a reversible cell having such a resistance to pressure difference between electrodes, for example, a first current collector and a second current collector are arranged on both sides of a solid polymer electrolyte in which an electrode catalyst layer is formed on both sides, A separator disposed on each outer side of the first current collector and the second current collector, wherein the first current collector and the second current collector are sandwiched between the first current collector and the first current collector; The current collector is larger than the second current collector, and the edge of the first current collector is located outside the edge of the second current collector over the entire circumference. A seal member that has a convex shape with respect to the solid polymer electrolyte membrane and is in contact with the solid polymer electrolyte membrane is disposed on the outer periphery of the current collector, and the solid polymer electrolyte membrane of the seal member It is possible to propose a reversible cell in which the facing position via the inner side is located on the inner peripheral side from the edge of the first current collector. In such a case, the sealing member may be a convex portion formed on a sealing material provided so as to surround the outer periphery of the second current collector, or an O-ring provided in a groove of the separator.

  In a cell stack in which a plurality of reversible cells are connected in series, ports A and B connected to the flow path of the reaction fluid on the oxygen generation electrode side of each reversible cell, and the reaction fluid on the hydrogen generation electrode side of each reversible cell Ports C and D that lead to the flow path are provided, port A is set as a raw water supply port during water electrolysis operation and hydrogen discharge port during fuel cell operation, and port B is raw water during water electrolysis operation And a pure oxygen discharge port, a hydrogen supply port during fuel cell operation, and port C includes a hydrogen and water discharge port during water electrolysis operation, and an oxidant and generated water discharge port during fuel cell operation. In the above charging / discharging system set to the oxidant supply port during fuel cell operation, the port D is used to dry the charge / discharge system before switching from water electrolysis operation to fuel cell operation. Can be proposed.

First, as a reversible cell, for a charge / discharge system using the above-mentioned hydrogen side pressure> oxygen side pressure = atmospheric pressure differential pressure tolerance, when the water electrolysis operation ends, port B A step of introducing hydrogen at a pressure higher than atmospheric pressure (pressure at which hydrogen can flow through the flow path) into the reversible cell of the cell stack to discharge the remaining water in the cell from port A; The process of exhausting the residual hydrogen in the cell is performed in any order, and then, after the inside of the reversible cell reaches atmospheric pressure, air is supplied from the port D into the cell to dry the cell. It is possible to propose a method for drying a charge / discharge system. Thereby, when switching from the water electrolysis operation to the fuel cell operation, the operation can be quickly switched with a simple operation.
In addition, at the end of the water electrolysis operation, the high-pressure hydrogen remaining in the hydrogen generation electrode is exhausted from the system until it reaches atmospheric pressure, and the electrical circuit connected to the cell stack is short-circuited, After the hydrogen and oxygen are consumed and the voltage of each reversible cell is reduced to 0 V, the electric circuit is shut off. Then, hydrogen is supplied from the port B into the reversible cell of the cell stack, and the oxygen generation electrode side is hydrogenated It is possible to propose a drying method for a charge / discharge system, in which the replacing step and the step of supplying air from the port D into the cell are performed in any order to dry the cell.
According to such a drying method, when switching from water electrolysis operation to fuel cell operation, the possibility of abnormal heat generation (thermal runaway) when hydrogen and oxygen are mixed at the same extreme can be minimized. It is.

In addition, as a reversible cell, a charge / discharge system using a conventional reversible cell that does not have an inter-electrode differential pressure resistance in the case of hydrogen side pressure> oxygen side pressure = atmospheric pressure, as described above, at the end of water electrolysis operation In order to prevent damage to the solid polymer electrolyte membrane of the reversible cell, the pressure on the hydrogen generation electrode side and the oxygen generation electrode side is controlled so that the high-pressure hydrogen remaining on the hydrogen generation electrode is maintained from the port C until it reaches atmospheric pressure. Exhausting out of the system and discharging residual water and oxygen in the cell from port A, and then supplying hydrogen from the port B into the reversible cell of the cell stack to replace the oxygen generation electrode side with hydrogen; It is possible to propose a drying method for a charge / discharge system, in which the step of supplying air from the port D into the cell is performed in any order and the inside of the cell is dried. According to such a drying method, when switching from the water electrolysis operation to the fuel cell operation, the operation can be quickly switched with a simple operation.
As another drying method, at the end of the water electrolysis operation, the pressure on the hydrogen generation electrode side and the oxygen generation electrode side was controlled so that the solid polymer electrolyte membrane of the reversible cell was not damaged, and remained in the hydrogen generation electrode. The high-pressure hydrogen is exhausted from the system until it reaches atmospheric pressure, and the residual water and oxygen in the cell are exhausted from the port A, and the electrical circuit connected to the cell stack is short-circuited. After the hydrogen and oxygen are consumed and the voltage of each reversible cell is reduced to 0 V, the electric circuit is shut off, and then hydrogen is supplied from the port B into the reversible cell of the cell stack, A method for drying the charge / discharge system can be proposed, in which the step of replacing in step S3 and the step of supplying air from the port D into the cell are performed in any order to dry the cell. According to such a drying method, when switching from water electrolysis operation to fuel cell operation, it is possible to minimize the possibility of abnormal heat generation (thermal runaway) when hydrogen and oxygen are mixed at the same extreme. , Safe.

  According to the present invention, in this type of charge / discharge system employing a conventional reversible cell, the expected performance and durability can be maintained over a longer period than before.

It is explanatory drawing which showed the outline | summary of the structure of the charging / discharging system concerning embodiment. It is explanatory drawing which showed typically the flow-path cross section of the reversible cell used for the charging / discharging system of FIG. It is a front view of the separator used for the reversible cell of FIG. It is explanatory drawing which showed typically the reaction at the time of the water electrolysis driving | operation of the reversible cell employ | adopted with the charging / discharging system concerning embodiment. It is explanatory drawing which showed typically the reaction at the time of the fuel cell driving | operation of the reversible cell employ | adopted with the charging / discharging system concerning embodiment. It is explanatory drawing which showed typically the flow-path cross section of the reversible cell concerning another structure. It is explanatory drawing which showed typically the flow-path cross section of the reversible cell concerning another structure. It is explanatory drawing which showed the outline | summary of the structure of the charging / discharging system using the reversible cell which does not have inter-electrode differential pressure tolerance.

  Referring to an embodiment of the present invention, FIG. 1 schematically shows the configuration of a charge / discharge system 1 according to the embodiment. In the charge / discharge system 1, the reversible cell 10 shown in FIGS. A cell stack 2 in which a plurality of, for example, several tens to several hundreds are stacked.

  FIG. 2 schematically shows the inside (plane cross section) of the reversible cell 10, and FIG. 3 shows the front of a separator 15 used in the reversible cell 10 described later. In this reversible cell 10, a rectangular first current collector 12 and a second current collector 13 are arranged on both surfaces of a solid polymer electrolyte membrane 11 having electrode catalyst layers formed on both surfaces. A separator 15 that forms the flow path 14 is disposed outside the first current collector 12, and a separator 17 that forms the flow path 16 is disposed outside the second current collector 13. .

  In the solid polymer electrolyte membrane 11, a mixed catalyst of iridium oxide and platinum black is used for the electrode catalyst 11a provided on the surface on the first current collector 12 side, which becomes the oxygen generation side during water electrolysis. . The first current collector 12 is made of a sintered product of titanium fibers or titanium particles and subjected to platinum plating. The separator 15 forming the flow path 14 may be a metal plate made of SUS, titanium, or the like, grooved by cutting or photochemical etching, a metal thin plate pressed, or a metal mesh. In order to prevent metal oxidation and dissolution and hydrogen embrittlement, it is preferable to use a metal surface that has been subjected to surface treatment such as platinum plating, diamond-like carbon (DLC), or the like. The first current collector 12, the electrode catalyst 11a, and the separator 15 constitute the oxygen generating electrode of the present invention.

  On the other hand, the electrode catalyst 11b on the surface of the second current collector 13 in the solid polymer electrolyte membrane 11 on the hydrogen generation side during water electrolysis has the same platinum support as that used in ordinary fuel cell dedicated machines. Carbon is used. Carbon paper or carbon cloth is used for the second current collector 13. In this case, the second current collector 13 may be subjected to a water repellent treatment or may be provided with a microporous layer as necessary. The separator 17 that forms the flow path 16 is obtained by molding carbon resin, SUS, titanium or other metal plate cut or photochemically etched, or metal thin plate pressed. Metal mesh can be used. When a metal plate is used, platinum plating, DLC, or the like is preferably applied to the metal surface in order to prevent oxidation or hydrogen embrittlement of the metal surface. The second current collector 13, the electrode catalyst 11b, and the separator 17 constitute the hydrogen generating electrode of the present invention.

  In addition, although cooling water is distribute | circulated to the back side of each flow path 14 and 16, the cooling flow path does not need to be provided for every single cell, and may be provided for every 2 or 3 cells.

  In the present embodiment, as shown in FIG. 3, the first current collector 12 is larger (the area is larger) than the second current collector 13, and the first current collector 12 The edge is located outside the edge of the second current collector 13 over the entire circumference.

  A rectangular recess 15a is formed on the inner surface side (solid polymer electrolyte membrane 11 side) of the separator 15, and the first current collector 12 is provided in the recess 15a. A groove 15b is formed on the outer peripheral side of the recess 15a in the separator 15, that is, on the outer side of the first current collector 12, so as to surround the first current collector 12, and in the groove 15b, A seal member 21 such as an O-ring is provided.

  On the other hand, a rectangular recess 17a is also formed on the inner surface side (solid polymer electrolyte membrane 11 side) of the separator 17, and the second current collector 13 is provided in the recess 17a. A groove 17b is formed on the outer peripheral side of the recess 17a in the separator 17, that is, on the outer side of the second current collector 13, so as to surround the second current collector 13, and in the groove 17b, A seal member 22 such as an O-ring is provided.

  The shapes of the separators 15 and 17 shown in FIGS. 2 and 3 have a thickness of several millimeters, but the material of the separators 15 and 17 forms the flow paths 14 and 16 for allowing the reaction fluid to flow on the separator surface. What can provide the recessed parts 15a and 17a for inserting a member by a mold, cutting, etc. is preferable, for example, a resin separator and a metal plate separator can be used. The shape of the separator is not limited to the example shown in FIGS. 2 and 3 and may be a known shape.

  And the position of the sealing member 22 provided in the separator 17 is set to a position facing the surface of the first current collector 12 through the solid polymer electrolyte membrane 11 as shown in FIG. . That is, the position of the seal member 22 is set so as to be located on the inner side of the edge of the first current collector 12 with the solid polymer electrolyte membrane 11 interposed therebetween.

  In FIG. 3, the cooling water manifolds 24 and 25 are positioned on the left and right sides of the seal member 21 in the separator 15, and the reaction fluid manifold is also positioned above the seal member 21. 26 and 27, which are also located on the lower side of the seal member 21 are reaction fluid manifolds 28 and 29. Sealing members 30 such as O-rings are provided on the outer circumferences of the manifolds 24 to 29 so as to surround the manifolds 24 to 29, respectively.

  As shown in FIG. 3, a part of the flow path 14 of the separator 15 communicates with the manifold 26 via the header portion 14 a and a communication hole 31 formed inside the separator 15. The other part of the flow path 14 of the separator 15 communicates with the manifold 29 through the header portion 14 b and a communication hole 32 formed in the separator 15.

  Similarly, a part of the flow path 16 of the separator 17 communicates with the manifold 27 through a header portion (not shown) and a communication hole (not shown) formed in the separator 17. The other part of the flow path 16 of the separator 17 communicates with the manifold 28 through a header portion (not shown) and a communication hole (not shown) formed inside the separator 17.

  Since the reversible cell 10 having such a configuration has an inter-electrode differential pressure tolerance, by adopting the reversible cell 10, in the charge / discharge system 1 according to the embodiment, for example, hydrogen side 1 MPa (abs), oxygen Water electrolysis operation at a side 0.1 MPa (abs) can be performed. Therefore, there is no need for a special pump, pressurizer or the like for pressure control on the oxygen electrode side.

  As shown in FIG. 1, this charge / discharge system 1 has a tank 41 for replenishing raw water (for example, pure water), and the bottom of the tank 41 is connected via a pipe 42 having an electromagnetic valve V1. The gas-liquid separation tank 43 on the oxygen side communicates. The raw water in the gas-liquid separation tank 43 (for example, pure water; hereinafter referred to as electrolyzed water) serves as a raw water inlet (for water electrolysis operation) and a hydrogen discharge port (for fuel operation) of the cell stack 2. Supplying to port A, water electrolysis operation is performed. That is, the water from the gas-liquid separation tank 43 is generated by the pump 46 provided in the pipe 44 via the pipe 44 connected to the bottom of the tank and the pipe 45 connected to the cell stack 2. It can be supplied to the port A on the pole side. The pressure of the gas entering and leaving the port A is measured by a pressure gauge P1 provided in the pipe 45.

  A return pipe 47 for returning a part of the water flowing in the pipe 44 to the gas-liquid separation tank 43 is connected to the pipe 44. The return pipe 47 is provided with an electromagnetic valve V2. The return pipe 47 may be provided with a heat exchanger, an ion exchange resin tower, a filter, etc., and the return water may be treated through these devices to maintain the water quality in the gas-liquid separation tank 43. . A liquid level sensor 48 for detecting the water level in the tank is provided in the gas-liquid separation tank 43.

  One end of a pipe 51 is connected to port B which is a raw water and pure oxygen discharge port (in water electrolysis operation) and a hydrogen (fuel) supply port (in fuel cell operation) in the cell stack 2. The other end portion of the pipe 51 is connected to the gas layer portion of the gas-liquid separation tank 43. The pipe 51 is provided with an electromagnetic valve V3. The pressure of the gas entering and exiting the port B is measured by a pressure gauge P <b> 2 provided in the pipe 51.

  A pipe 52 is connected between the pipe 51 and the cell stack 2 side of the pipe 51 relative to the solenoid valve V3. The piping 52 is provided with solenoid valves V4 and V5, and a pump 53 is provided between the solenoid valves V4 and V5.

  A power supply device 61 is connected to the cell stack 2, and DC power is supplied to each reversible cell 10. The power supply device 61 is controlled by the control device 62.

  A pipe 63 for circulating cooling water for cooling is connected to the cell stack 2, and the cooling water heat-exchanged by the heat exchanger 64 circulates in the cell stack 2 by driving the pump 65, and each reversible The cell 10 is cooled. Here, the heat exchanged by the heat exchanger 64 can be used as warm heat. When it is not necessary to use heat, heat is dissipated using a radiator in the heat exchanger 64, and the cooling water may be cooled.

  A pipe 71 is connected to a port C serving as a hydrogen outlet (during water electrolysis operation) and an outlet for oxidant and water (during fuel cell operation) of the cell stack 2, and this pipe 71 is connected to a gas-liquid separation on the hydrogen side. It leads to a gas-liquid separation tank 72 that performs the function. The bottom part of the gas-liquid separation tank 72 and the gas layer part in the gas-liquid separation tank 43 on the oxygen side (the part above the liquid level of water stored in the tank, even if the stored liquid level rises, A pipe 73 is connected to a portion where the surface does not reach. The piping 73 is provided with an electromagnetic valve V16 and a flow rate adjustment valve V6. A water level meter 74 for detecting the water level in the tank is provided in the gas-liquid separation tank 72.

  The gas layer part of the gas-liquid separation tank 72 communicates with the inlet side of the hydrogen storage part 76 via the pipe 75. The hydrogen storage unit 76 in this example is a hydrogen storage tank (high pressure vessel), and the pressure in the tank is measured by a pressure gauge P3. The piping 75 is provided with a back pressure valve V7 and a check valve V8.

  A pipe 81 is connected to the outlet side of the hydrogen storage unit 76, and the pipe 81 is connected to the pipe 52 described above. The piping 81 is provided with a pressure adjustment valve V10.

  Air serving as an oxidant during operation of the fuel cell is supplied from the pipe 83 to the port D of the cell stack 2 by the blower 82. The pressure in the pipe 83 is measured by the pressure gauge P4. The pipe 83 passes through the heat exchanger 84 and the humidity exchanger 85 on the way to the port D. As a type of the heat exchanger used for the heat exchanger 84, for example, a plate type heat exchanger is preferable, but of course, it is not limited to this. As the humidity exchanger 85, for example, a rotary total heat exchanger can be used. In addition, those used as static total heat exchangers and vaporizing humidifiers, especially those using hollow fiber membranes, porous membranes, and osmotic membranes are suitable, but the necessary function is to flow gas As long as it can easily absorb and desorb moisture in the gas.

  An electromagnetic valve V <b> 11 is provided between the humidity exchanger 85 and the port D in the pipe 83. A pipe 86 is connected between the pipe 81 and a portion of the pipe 83 near the port D of the electromagnetic valve V11. The pipe 86 is provided with an electromagnetic valve V12.

  A pipe 91 is connected to the upper gas layer portion of the gas-liquid separation tank 43, and this pipe 91 passes through the humidity exchanger 85 and the heat exchanger 84, and further passes through the heat exchanger 92 and is released to the outside of the system. A pipe 93 is connected. In the heat exchanger 92, for example, heat is exchanged with a refrigerant of a cooling chiller (not shown) that is separately installed.

  A branched pipe 94 is connected to the inlet side of the humidity exchanger 85 in the pipe 91, and this pipe 94 communicates with the upper gas layer portion of the gas-liquid separation tank 72. The piping 94 is provided with an electromagnetic valve V13.

  A branched pipe 95 is connected to the inlet side of the heat exchanger 92 in the pipe 91, and this pipe 95 leads to the upper part of the tank 41. A branch pipe 96 is connected to the discharge pipe 93, and this pipe 96 leads to the bottom of the tank 41.

  To the tank 41, pure water from the pure water production apparatus 97 is supplied as raw water. The tank 41 is provided with a liquid level sensor 98 that detects the water level in the tank.

  The charge / discharge system 1 according to the embodiment has the above-described configuration. Next, an example of the operation will be described.

  First, when starting the water electrolysis operation, the pump 46 is started after opening the electromagnetic valve V3. The electrolyzed water stored in the gas-liquid separation tank 43 on the oxygen side is supplied to the reversible cell 10 of the cell stack 2 from the pipes 44 and 45 through the port A by the pump 46 provided in the pipe 44.

  Next, the solenoid valves V12 and V13 are opened, and the air remaining in the flow path of the hydrogen generation electrode of the reversible cell 10 is purged at once with the hydrogen from the hydrogen storage unit 76. At this time, hydrogen from the hydrogen storage unit 76 flows in the order of the pipe 81, the pipe 86, the port D, the port C, the pipe 71, the pipe 94, the pipe 91, and the pipe 93. When the purge is completed, the solenoid valves V12 and V13 are closed.

  When power is supplied from the power supply device 61 to the reversible cell 10 in this state, water corresponding to the power is electrolyzed into hydrogen ions, oxygen atoms, and electrons on the oxygen electrode catalyst. The hydrogen ions move to the hydrogen electrode with accompanying water, combine with electrons on the hydrogen electrode catalyst (electrode catalyst 11b) to form hydrogen molecules, and are discharged from the port C through the pipe 71 to the outside of the cell. On the other hand, oxygen atoms become oxygen molecules on the oxygen electrode catalyst (electrode catalyst 11a) and are discharged out of the cell from the port B through the pipe 51 together with the circulating water. The state of the reversible cell 10 during the reaction is shown in FIG.

  Pure hydrogen with accompanying water discharged out of the cell from the port C through the pipe 71 is gas-liquid separated in the gas-liquid separation tank 72, and then passes through the pipe 75 through the back pressure valve V7 and the check valve V8, and then into the hydrogen storage section. 76 is supplied and stored.

  Pure oxygen discharged from the port B is sent from the pipe 51 to the gas-liquid separation tank 43, where gas-liquid separation is performed. The high-temperature and high-humidity pure oxygen after the gas-liquid separation is sent from the pipe 91 to the humidity exchanger 85 used for air humidification when the fuel cell is operated, and the humidity exchanger 85 is heated and humidified. . Thereafter, the heat exchanger 84 is sent to the heat exchanger 84 used for air heating during the fuel cell operation, and the heat exchanger 84 is heated. Thereafter, the water is sent to the heat exchanger 92 for dehumidification, and the water condensed so far is sent to the tank 41 via the pipe 95. The water cooled and dehumidified and condensed by the heat exchanger 92 is returned to the tank 41 through the pipe 96, while pure oxygen is discharged out of the system through the discharge pipe 93.

  Although the water level in the gas-liquid separation tank 43 on the oxygen side is reduced by electrolysis, while the water level in the gas-liquid separation tank 72 on the hydrogen side is increased, the reversible cell 10 has the resistance to the differential pressure between the electrodes as described above. Since the cell structure is included, the hydrogen side pressure is always higher than the oxygen side pressure (approximately atmospheric pressure). Therefore, when the water level meter 74 in the gas-liquid separation tank 72 reaches the predetermined upper limit value 74a, the electromagnetic valve V16 is opened, so that the water in the gas-liquid separation tank 72 is passed through the pipe 73 by the pressure difference. Water can be returned to the gas-liquid separation tank 43.

  When the pressure of the hydrogen storage unit 76 indicated by the pressure gauge P3 reaches a preset charge end pressure (fully charged state) or when a charge end signal is sent from a control circuit (not shown), The power supply by the power supply device 61 is cut off and the charging (water electrolysis operation) is terminated. The control circuit may be incorporated in the control device 62, for example. In addition, it may be a circuit that monitors the opening and closing of the valve and various measurement values, outputs a certain control signal, and instructs on / off of the devices.

  At the end of the water electrolysis operation, the pump 46 is first stopped, the solenoid valve V2 is opened, the solenoid valve V3 is closed, and then the solenoid valve V5 is opened. Then, hydrogen is supplied from the hydrogen storage unit 76 to the pipe 81 and the pipe 52, hydrogen is introduced from the pipe 51 and port B into the reversible cell 10, and the port A passes through the pipes 45, 44, 47 and enters the system. The remaining electrolyzed water is returned to the gas-liquid separation tank 43. The hydrogen used for returning water is exhausted from the gas-liquid separation tank 43 through the pipe 91 and the discharge pipe 93 to the outside of the system. When the electrolyzed water remaining in the system can be returned to the gas-liquid separation tank 43 in this way, the electromagnetic valve V2 is closed.

  Next, the solenoid valve V13 is opened, and the high-pressure hydrogen remaining in the hydrogen electrode in the cell is exhausted from the system through the pipes 71, 94, 91 and the discharge pipe 93 to near atmospheric pressure. . Then, when the value of the pressure gauge P4 becomes close to atmospheric pressure (for example, after the atmospheric pressure +50 kPa (G) or less), the solenoid valve V11 is opened, the blower 82 is activated, and air is immediately discharged from the port D into the cell. First, the hydrogen in the system, particularly the hydrogen in the hydrogen electrode channel portion, is immediately replaced with air, and the reversible cell 10 is dried by continuing to supply air as it is. Here, the cooling water circulation pump 65 is activated immediately before the air is supplied. A known method may be used as a criterion for determining the dry state of the cell. When the drying is completed, all the solenoid valves are closed and the operation is ended, or the operation is switched to the fuel cell operation. The pump 65 is continuously operated even during the fuel cell operation.

  The order of supplying the hydrogen to the oxygen electrode in the cell and discharging the remaining water outside the cell and exhausting the remaining hydrogen from the hydrogen electrode to the outside of the system are not particularly limited. For example, in the system configuration shown in FIG. 1, the exhaust system from the port C to the outside of the system and the exhaust system from the port A to the outside of the system are joined to the pipe 91. It is possible to carry out the above-mentioned process of supplying hydrogen to the oxygen electrode and the process of exhausting the remaining hydrogen from the hydrogen electrode simultaneously or in the reverse order by configuring the system with completely separate systems. In addition, a check valve is provided on the gas-liquid separation tank 43 side from the junction of the pipe 91 with the pipe 94 and on the pipe 91 side from the electromagnetic valve V13 of the pipe 94, respectively. The above steps can be carried out in any order by adopting a configuration that prevents hydrogen from flowing backward from the pipe 91 to the gas-liquid separation tank 43, the pipe 47, and the pipe 45 to the oxygen electrode side.

  As another drying method, the pump 46 is stopped, the solenoid valve V3 is closed, the solenoid valve V13 is opened, and the high-pressure hydrogen remaining in the hydrogen electrode is supplied from the port C through the pipe 91 until it becomes close to the atmospheric pressure. Exhaust outside the system. Thereafter, the electrical circuit connected to the cell is once short-circuited to consume hydrogen and oxygen in the vicinity of the electrode, and it is confirmed that the voltage of each cell has dropped to near 0 V (for example, less than 0.05 V). Thereafter, when the short-circuited electric circuit is cut off, the pump 65 is started for slow heating. After confirming the voltage drop of each cell, the electric circuit is shut off. First, with respect to the oxygen electrode, the solenoid valve V2 is opened and then the solenoid valve V5 is opened, so that the oxygen electrode flow path is immediately replaced with hydrogen. When completed, the solenoid valve V2 is closed. Next, for the hydrogen electrode, the solenoid valve V11 may be opened and the blower 82 may be activated to immediately replace the hydrogen electrode flow path with air, and the air may continue to be supplied to dry the cell. The electric circuit here is, for example, a connection circuit between the cell stack 2 and the power supply device 61 or a connection circuit with a power load (not shown).

  Further, the order of the step of supplying and replacing hydrogen to the oxygen electrode in the cell and the step of supplying air to the hydrogen electrode and drying the inside of the cell are not particularly limited. In FIG. 1, hydrogen is supplied to the oxygen electrode by configuring the exhaust system from the port C to the outside of the system and the exhaust system from the port A to the outside of the system without being joined together. The process and the process of supplying air to the hydrogen electrode can be performed simultaneously or in the reverse order. In addition, a check valve is provided on the gas-liquid separation tank 43 side from the junction point of the pipe 91 with the pipe 94 and on the pipe 91 side of the solenoid valve V13 of the pipe 94, respectively. The above steps can be performed in any order by adopting a configuration that prevents backflow from the pipe 91 to the tank 43, the pipe 47, and the pipe 45 to the oxygen electrode side.

  As another drying method, the pump 46 is stopped, the solenoid valve V3 is closed, the solenoid valve V13 is opened, and the high-pressure hydrogen remaining in the hydrogen electrode is exhausted to the vicinity of the atmospheric pressure. Thereafter, the electromagnetic valve V2 is opened, and the electromagnetic valve V13 is dried by electrolysis while being opened. That is, in this drying operation, a direct current is supplied from the power supply device 61 to the reversible cell 10 without turning water to the oxygen side during water electrolysis, whereby the electrodes in the reversible cell 10 are supplied. Water remaining in the catalyst can be removed by electrolysis and the cell can be dried.

  Once dry, the electrical circuit connected to the cell is once shorted to consume hydrogen and oxygen near the electrodes, confirm that the voltage of each cell has dropped to near 0V, and activate the pump 65 for slow heating To do. The pump 65 may be started immediately before the direct current is supplied from the power supply device 61 to the reversible cell 10. After confirming the voltage drop of each cell, the electric circuit is shut off. First, regarding the oxygen generation electrode, the solenoid valve V2 is opened and then the solenoid valve V5 is opened, so that the flow path 14 on the oxygen generation electrode side is immediately replaced with hydrogen. When the replacement is completed, the solenoid valve V2 is closed. Next, regarding the hydrogen generation electrode, the solenoid valve V11 may be opened and the blower 82 may be activated to immediately replace the flow path 16 on the hydrogen generation electrode side with air.

Furthermore, the following procedure is mentioned as another stop method. First, the pump 46 is stopped, the solenoid valve V3 is closed, the solenoid valve V13 is opened, and the high-pressure hydrogen remaining in the hydrogen electrode is brought from the port C to the vicinity of the atmospheric pressure through the pipes 71, 94, 91 and the discharge pipe 93. Exhaust outside the system until When the value of the pressure gauge P4 becomes close to atmospheric pressure, the solenoid valve V13 is closed and the operation is terminated. Such a procedure may be used, but in order to be able to start immediately in either operation mode after storage, as described above, the blower 82 is started and the flow path of the hydrogen electrode is replaced with air. It is good.
The latter end method, that is, the pump 46 is stopped, the electromagnetic valve V3 is closed and then the electromagnetic valve V13 is opened, and the high-pressure hydrogen remaining in the hydrogen electrode is supplied from the port C to the pipes 71, 94, 91 and the discharge pipe. The system is exhausted to near atmospheric pressure through 93, and when the value of the pressure gauge P4 becomes near atmospheric pressure, the solenoid valve V13 is closed and the operation is terminated. When starting the battery mode, draining, air replacement, and drying may be performed in the same manner as the former method at the time of starting, and when starting the water electrolysis mode, the normal water electrolysis start flow is followed. Just start up.

  Next, the start of the fuel cell operation will be described. At the start of the fuel cell operation, the pumps 53 and 65 and the blower 82 are activated from the state where the solenoid valves V11, V13, V4 and V5 are open. As a result, air as an oxidant is supplied from the port D to the reversible cell 10, while hydrogen as a fuel is supplied from the port B to the reversible cell 10. In this state, when a load (for example, various electric devices that consume electric power) is connected to the reversible cell 10, the reversible cell 10 is discharged according to the load (electric power is supplied to the outside), and the reversible cell 10 discharges current. Hydrogen and oxygen corresponding to the consumption are consumed. An ejector may be used instead of the pump 53.

  The air that has not been consumed and the generated water that has been consumed are discharged from the port C, and the hydrogen that has not been consumed is discharged from the port A. The state of the reversible cell during the reaction is shown in FIG. In FIG. 5, 100 indicates a load.

  The air and water discharged from the port C are sent to the humidity exchanger 85 via the pipes 71 and 94, and after the humidity is exchanged with the supply air to be supplied to the reversible cell 10 by the blower 82, the heat exchanger 84. The heat exchanger 84 exchanges heat with the supply air. As a result, the condensed water and the water whose humidity has not been exchanged are returned to the tank 41 through the pipes 91 and 95, and the gas is sent to the heat exchanger 92. It is done. The water further cooled and dehumidified by the heat exchanger 92 and condensed is sent to the tank 41 via the pipe 96. On the other hand, the remaining gas is exhausted from the discharge pipe 93 to the atmosphere.

  Further, the hydrogen that has not been consumed is sent from the port A to the pump 53 via the pipes 45 and 52, and reversible again through the pipe 51 through the port B together with the hydrogen replenished through the pipe 81 from the hydrogen storage unit 76. It is supplied to the cell 10. The hydrogen to be replenished is the amount of hydrogen consumed in the reaction, and after being regulated from the hydrogen storage unit 76 by the pressure regulating valve V10, is supplied to the pipe 52 that is the hydrogen circulation path. Here, in the circulating hydrogen, there is a slight amount of moisture and impurities (nitrogen in the air) diffused from the air electrode side through the membrane. Therefore, by periodically opening the solenoid valve V2, moisture and Drain impurities.

  When the pressure of the hydrogen storage unit 76 reaches a preset discharge end pressure (hereinafter referred to as a complete discharge state) or when a discharge end signal is sent from the control circuit (not shown), the load is reduced. Shut off and finish discharge.

  At the end of the fuel cell operation, the pump 53 is stopped and the solenoid valves V4 and V5 are closed. On the oxygen electrode side, after supplying air until the cell internal substrate is properly dried, the blower 82 is stopped, all the solenoid valves are closed, and the operation is terminated. In addition, what is necessary is just to start according to the above-mentioned water electrolysis start flow, when switching to water electrolysis operation after that.

  As another method of switching to the water electrolysis operation, there is a method of short-circuiting an electric circuit connected to the cell before switching to the water electrolysis operation by the water electrolysis start flow method. In this case, the value of the pressure on the air electrode side (pressure indicated by the pressure gauge P4) gradually decreases, but starts to increase from a certain point. If it is confirmed that the pressure has risen by about 5 KPa from the lowest pressure during decompression, there is a method in which the electric circuit is cut off and started according to the above-described water electrolysis start flow. When such switching is performed, the above-described process of opening the solenoid valves V12 and V13 and purging the air remaining in the flow path of the hydrogen generation electrode at once with the hydrogen from the hydrogen storage unit 76. Can do this more safely.

  As described above, according to the present embodiment, since carbon that is originally water-repellent can be used for the electrode catalyst 11b of the oxygen-side electrode during the fuel cell operation, the conventional reversible cell is used. Not only is the performance improved over the charge / discharge system of the seed, but it is also possible to reduce performance degradation due to wetting of the catalyst surface over a long period of time. In addition, since a hydrophilic material can be used for the electrode catalyst of the oxygen generating electrode during water electrolysis, water repellent treatment as in the past is unnecessary, and water supply to the reaction field during water electrolysis is improved accordingly. Electrolytic performance is improved. Moreover, the amount of platinum used in the electrode catalyst of the oxygen generating electrode can be reduced.

By the way, platinum is required for both the oxygen electrode and the hydrogen electrode in the fuel cell operation. In particular, the oxygen electrode requires a larger amount of platinum than the hydrogen electrode. In other words, platinum-supported carbon that can achieve equivalent performance is used on both electrodes). On the other hand, iridium oxide is required for the reaction at the oxygen electrode during the water electrolysis operation, and high voltage (about 2 V) is applied, so platinum-supported carbon that cannot withstand this cannot be used. Under such circumstances, a conventional reversible cell uses a catalyst in which a large amount of platinum is mixed with iridium oxide.
However, in the above embodiment, the oxygen electrode (electrode catalyst 11a) during the water electrolysis operation of the reversible cell 10 becomes a hydrogen electrode during the fuel cell operation. Therefore, the amount of platinum used can be greatly reduced as compared with the oxygen electrode of a conventional reversible cell.
As described above, a relatively large amount of platinum is required for the oxygen electrode (electrode catalyst 11b) during fuel cell operation. However, in the above embodiment, the oxygen electrode (electrode catalyst 11b) during fuel cell operation is In addition, since a high-voltage is not applied during water electrolysis operation and iridium oxide is not required, platinum-supported carbon can be used, so that the amount of platinum used can be reduced.
Therefore, according to the present embodiment, the amount of platinum used can be reduced as compared with this type of apparatus using a conventional reversible cell.

  In the reversible cell 10 of the above-described embodiment, the flow paths 14 and 16 formed in the separators 15 and 17 include the grooves formed in the separators 15 and 17, the first current collector 12, and the second current collector. The reversible cell 201 having the structure shown in FIG. 6 can be proposed.

  This reversible cell 201 uses a thin metal plate separator as a separator, and FIG. 4 schematically shows an internal flow path cross section (planar cross section). In this reversible cell 201, a rectangular first current collector 12 and a second current collector 13 are disposed on both surfaces of a solid polymer electrolyte membrane 11 having electrode catalyst layers formed on both surfaces. Similar to the reversible cell 10 described above, the first current collector 12 is larger than the second current collector 13, and the edge of the first current collector 12 extends over the entire circumference of the second current collector 12. It is located outside the edge of the current collector 13.

  A separator 203 for forming the reaction channel 202 is disposed outside the first current collector 12, and a separator for forming the reaction channel 204 is formed outside the second current collector 13. 205 is arranged. In this example, a porous metal mesh is inserted into the space between the first current collector 12 and the separator 203 and the space between the second current collector 13 and the separator 205, respectively. Reaction channels 202 and 204 are formed. The formation region of each reaction channel 202, 204 is larger in the reaction channel 202 on the first current collector 12 side than in the reaction channel 204 of the second current collector 13. The outer end of the formation region is located on the outer side of the outer end of the reaction channel 204. The size of the reaction channels 202 and 204 in the formation region is not limited to this.

  It should be noted that portions such as the cooling water channel provided for removing the heat generated by the reaction on the reaction channel side may also be constituted by a metal mesh. Forming these channels with a porous metal mesh is expensive, but has the advantage of simplifying the separator mechanism and the seal shape.

  In the reversible cell 201, the seal members 211, 212 corresponding to the outer end of the first current collector 12 and the outer end of the second current collector 13 between the separators 203, 205, respectively. Is arranged and is sandwiched between the separators 203 and 205. On the outer peripheral side of the end of the first current collector 12 in the seal member 211, a lip 211a that protrudes from the solid polymer electrolyte membrane 11 is formed so as to surround the first current collector 12. A lip 212 a protruding from the solid polymer electrolyte membrane 11 is formed on the outer peripheral side of the end of the second current collector 13 in the seal member 212 so as to surround the second current collector 13. Yes. The lip 212a faces the peripheral portion of the first current collector 12 through the solid polymer electrolyte membrane 11. Each lip 211a, 212a can be easily formed by integrally molding with the seal members 211, 212 using, for example, a mold.

  These seal members 211 and 212 are integrated with the separators 203 and 205 by baking, injection molding, or the like, or grooves are formed in the separators 203 and 205 by press working, and the seal members are embedded in the portions, whereby internal pressure is applied to the seal members. It is preferable to have a structure in which the seal member does not move outwards even when applied.

  According to the reversible cell 201 having such a configuration, the end positions of the reaction flow paths 202 and 204 and the end positions of the first current collector 12 and the second current collector 13 are determined in the overlapping direction of each member ( As seen from the vertical direction in FIG. 4, the first current collector 12 and the second current collector 12 are not overlapped with each other, and are smoother in cross section than the reaction channels 202 and 204 having uneven cross sections. The electric body 13 is one size larger as a whole, and the solid polymer electrolyte membrane 11 is sandwiched only by a smooth current collector and a seal member. Therefore, the seal members 211 and 212 are not deformed to enter the reaction flow paths 202 and 204 to cause a problem such as an increase in flow path pressure loss, or the seal surface pressure does not decrease by entering. Therefore, as with the reversible cell 10 described above, resistance to a positive pressure difference from the hydrogen side to the oxygen side can be ensured.

  Moreover, in the reversible cell 201 having the above-described configuration, the reaction channels 202 and 204 are formed by inserting a porous metal mesh in the space between the separator 205, so the thickness is uniform over the entire surface. Can be produced. In addition, since the contact with the current collector becomes uniform, the conductor resistance is lowered, and hydrogen can be produced with high efficiency. In addition, the thickness of the separator constituting the flow path can be made thin and light, and there is also an advantage that the initial cost is not required because a mold is not required.

  Furthermore, the reversible cell 251 shown in FIG. 7 can also be proposed. This reversible cell 251 uses separators 252 and 253 obtained by press-molding a thin metal plate into a corrugated plate shape, and seal members 211 and 212 are integrated with the separators 252 and 253 by baking or injection molding. . The space formed between the first current collector 12 and the separator 252 becomes the oxygen-side reaction flow path 14c, and the space formed outside the separator 252 (in fact, another reversible cell of the same shape). When the 251 is stacked, the other reversible cell 251 is formed by the separator of the other reversible cell 251) to be the cooling water flow path 14d flowing on the back surface on the oxygen side. Similarly, a space formed between the second current collector 13 and the separator 253 serves as a reaction channel 16c on the hydrogen side, and a space formed outside the separator 253 (actually, other spaces having the same shape). When the reversible cell 251 is stacked, the reversible cell 251 is formed by the separator of the other reversible cell 251). Of course, like the reversible cells 10 and 201 described above, the first current collector 12 is larger than the second current collector 13, and the edge of the first current collector 12 extends over the entire circumference. It is located outside the edge of the second current collector 13.

  Further, in this reversible cell 251, a lip 211b having the same shape that protrudes outward is provided at a position corresponding to the lip 211a outside the seal member 211. The lip 211b is for ensuring the airtightness of the flow path of the cooling water when the reversible cells 251 are stacked to form a stack structure.

  According to the reversible cell 251 having such a configuration, the separator that forms the flow path can be easily manufactured by press working, and therefore, it is suitable for mass production, whereby the unit price per sheet can be reduced. Of course, according to the reversible cell 251 of this type, like the reversible cells 10 and 201 described above, it has an inter-electrode differential pressure resistance, and even if a positive differential pressure is applied from the hydrogen side to the oxygen side. The solid polymer electrolyte membrane is not damaged, and the gas does not leak out of the cell.

  The reversible cell 10 used in the charge / discharge system 1 according to the above-described embodiment is the reversible cell 10 having resistance to inter-electrode differential pressure, but in the present invention, it has such inter-electrode differential pressure resistance. It is also possible to apply a known type reversible cell (for example, JP 2011-146395 A).

  The charge / discharge system 300 shown in FIG. 8 shows a configuration example in the case of using such a reversible cell 301 that does not have the resistance to differential pressure between electrodes, and is the same as the charge / discharge system 1 in FIG. The members indicated by the reference numerals indicate the same members and the like as those of the charge / discharge system 1 of FIG.

  In the charge / discharge system 300, a discharge pipe 302 is connected to an upper part of the gas-liquid separation tank 43 that serves as a gas layer part, and an electromagnetic valve V <b> 30 is provided in the discharge pipe 302. Further, a back pressure valve V31 is newly provided in the vicinity of the gas-liquid separation tank 43 side in the pipe 91. In the charge / discharge system 1 of FIG. 1, the gas-liquid separation tank 72 and the gas-liquid separation tank 43 are directly connected by the pipe 73. An open buffer tank 303 is provided, and a pipe 304 is connected between the buffer tank 303 and the gas-liquid separation tank 43. The pipe 304 is provided with a pump 305.

  According to the charge / discharge system 300 having such a configuration, when the water electrolysis operation is started, the pump 46 is started after the electromagnetic valve V3 is opened. The electrolyzed water stored in the gas-liquid separation tank 43 on the oxygen side is supplied to the reversible cell 301 of the cell stack 2 from the pipes 44 and 45 through the port A by the pump 46 provided in the pipe 44.

  Next, the electromagnetic valves V12 and V13 are opened, and the air remaining in the flow path of the hydrogen generation electrode of the reversible cell 301 is purged at once with hydrogen from the hydrogen storage unit 76. At this time, hydrogen from the hydrogen storage unit 76 flows in the order of the pipe 81, the pipe 86, the port D, the port C, the pipe 71, the pipe 94, the pipe 91, and the pipe 93. When the purge is completed, the solenoid valves V12 and V13 are closed.

  If power is supplied from the power supply device 61 to the reversible cell 301 in this state, water corresponding to the power is electrolyzed into hydrogen ions, oxygen atoms, and electrons on the oxygen electrode catalyst. The hydrogen ions move to the hydrogen electrode with accompanying water, combine with electrons on the hydrogen electrode catalyst (electrode catalyst 11b) to form hydrogen molecules, and are discharged from the port C through the pipe 71 to the outside of the cell. On the other hand, oxygen atoms become oxygen molecules on the oxygen electrode catalyst (electrode catalyst 11a) and are discharged out of the cell from the port B through the pipe 51 together with the circulating water. The state of the reversible cell 301 at the time of the reaction is as shown in FIG. 4, as in the charge / discharge system 1 of the reversible cell 10 having inter-electrode differential pressure resistance.

  Pure hydrogen with accompanying water discharged from the port C through the pipe 71 is separated from the gas and liquid in the gas-liquid separation tank 72, and then stored in the hydrogen via the pipe 75 via the back pressure valve V7 and the check valve V8. Supplied and stored in section 76.

Pure oxygen discharged from the port B is sent from the pipe 51 to the gas-liquid separation tank 43, where it is gas-liquid separated, and then the hot and humid pure oxygen passes through the back pressure valve V31 from the pipe 91 during fuel cell operation. Is sent to the humidity exchanger 85 used for air humidification, and the humidity exchanger 85 is heated and humidified. Thereafter, the heat exchanger 84 is sent to the heat exchanger 84 used for air heating during the fuel cell operation, and the heat exchanger 84 is heated. Thereafter, the water is sent to the heat exchanger 92 for dehumidification, and the water condensed so far is sent to the tank 41 via the pipe 95. The water cooled and dehumidified and condensed by the heat exchanger 92 is returned to the tank 41 through the pipe 96, while pure oxygen is discharged out of the system through the discharge pipe 93.
In addition, when a differential pressure more than a certain differential pressure (pressure difference between pressure gauge P2 and pressure gauge P4, generally 50 to 100 kPa) is generated between the poles, the solenoid valve of the pole that has become higher pressure By opening (V13 or V30) and opening the solenoid valve (V13 or V30) until the pressure difference between the electrodes becomes a predetermined value (generally 20 kPa) or less, Control is always performed so that the differential pressure between the electrodes is within a certain range. A known technique may be used for controlling the differential pressure.

  The water level in the gas-liquid separation tank 43 on the oxygen side decreases due to electrolysis, while the water level in the gas-liquid separation tank 72 on the hydrogen side rises, so that the water in the tank 72 needs to be returned to the tank 43. Therefore, the buffer tank 303 is provided in the middle of the pipe 73. When the water level of the water level gauge 74 in the gas-liquid separation tank 72 reaches a predetermined upper limit 74a, the electromagnetic valve V16 is opened, so that the water in the gas-liquid separation tank 72 is first supplied through the pipe 73 by the pressure difference. Water is returned to the buffer tank 303. Next, the water in the buffer tank 303 is returned to the gas-liquid separation tank 43 by the pump 305.

  When the pressure of the hydrogen storage unit 76 indicated by the pressure gauge P3 reaches a preset charge end pressure (fully charged state) or when a charge end signal is sent from a control circuit (not shown), The point that the power supply by the power supply device 61 is interrupted and the charging (water electrolysis operation) is terminated is the same as in the charge / discharge system 1 of FIG.

And in the charging / discharging system 300 provided with the reversible cell 301 which does not have an inter-electrode differential pressure tolerance, at the end of the water electrolysis operation, the pump 46 is first stopped, the electromagnetic valves V13, V2, V30 are opened, and the electromagnetic valve V3 is opened. The high-pressure hydrogen remaining in the hydrogen electrode in the cell is exhausted from the system to the vicinity of the atmospheric pressure through the pipes 71, 94, 91 and the discharge pipe 93 at the same time as the oxygen in the cell. The high-pressure oxygen remaining in the electrode is exhausted from the port A through the pipes 45, 44, 47 and the discharge pipe 302 to near atmospheric pressure, and the electrolyzed water remaining in the system is separated into gas and liquid. Return water to tank 43. At this time, the solenoid valves V13 and V30 are controlled so that the inter-electrode differential pressure does not exceed a predetermined value. When the values of the pressure gauges P1 and P4 are close to the atmospheric pressure, on the hydrogen electrode side, the solenoid valve V11 is opened, the blower 82 is activated, and air is supplied from the port D into the cell at a stroke. The reversible cell 301 is dried by immediately substituting the hydrogen of the hydrogen electrode, particularly the hydrogen in the hydrogen electrode channel, with air and continuing to supply the air as it is. On the oxygen electrode side, the solenoid valve V5 is opened, oxygen in the system is immediately replaced with hydrogen, and V2, V5, and V30 are closed when the replacement is completed. Here, the cooling water circulation pump 65 is activated immediately before the air is supplied. A known method may be used as a criterion for determining the dry state of the cell. When the drying is finished, all the solenoid valves are closed and the operation is finished, or the operation is switched to the fuel cell operation. The pump 65 is continuously operated even during the fuel cell operation.
In addition, the order of supplying air to the hydrogen electrode in the cell and drying the inside of the cell and supplying and replacing hydrogen in the oxygen electrode are not particularly limited, and they may be performed simultaneously. It is also possible to order.

  Further, in the other drying methods described above, in the charge / discharge system 300 including the reversible cell 301 that does not have the resistance to the differential pressure between the electrodes, the pumps 46 are stopped and the electromagnetic valves V3 and V2 are closed. , Until V30 is opened and the high-pressure hydrogen remaining in the hydrogen electrode is exhausted out of the system through the pipe 91 until the high-pressure hydrogen remaining in the hydrogen electrode is close to the atmospheric pressure, The electrolyzed water remaining in the system is returned to the gas-liquid separation tank 43 while being exhausted out of the system from the port A. At this time, control is performed so that the differential pressure between the electrodes does not exceed a predetermined value.

Thereafter, the electrical circuit connected to the cell is once short-circuited to consume hydrogen and oxygen in the vicinity of the electrode, and it is confirmed that the voltage of each cell has dropped to near 0V. Thereafter, when the short-circuited electric circuit is cut off, the pump 65 is started for slow heating. When the voltage drop in each cell is confirmed, the electric circuit is shut off. First, regarding the oxygen electrode, the solenoid valves V2 and V30 are opened, and then the solenoid valve V5 is opened, so that the oxygen electrode flow path is immediately replaced with hydrogen. When the replacement is completed, the solenoid valves V2 and V30 are closed. Next, for the hydrogen electrode, the solenoid valve V11 may be opened and the blower 82 may be activated to immediately replace the hydrogen electrode flow path with air, and the air may continue to be supplied to dry the cell. The electric circuit here is, for example, a connection circuit between the cell stack 2 and the power supply device 61 or a connection circuit with a power load (not shown).
The order of supplying hydrogen to the oxygen electrode in the cell and replacing it and the step of supplying air to the hydrogen electrode and drying the cell are not particularly limited. It is also possible to implement in this order.

  As another drying method, in the charge / discharge system 300 including the reversible cell 301 that does not have the resistance to the differential pressure between the electrodes, the pump 46 is stopped and the solenoid valve V3 is closed, and then the solenoid valves V13, V2, V30 is opened and the high-pressure hydrogen remaining in the hydrogen electrode is exhausted outside the system until it becomes close to atmospheric pressure (by the pressure inside the system). At the same time, the high-pressure oxygen remaining in the oxygen electrode is discharged outside the system until it becomes close to atmospheric pressure. The electrolyzed water remaining in the system is returned to the gas-liquid separation tank 43 while being exhausted. At this time, control is performed so that the differential pressure between the electrodes does not exceed a predetermined value. Thereafter, the electromagnetic valves V2, V30, and V13 are dried by electrolysis while being opened. That is, in this drying operation, a direct current is supplied from the power supply device 61 to the reversible cell 301 without turning water to the oxygen side during water electrolysis. Water remaining in the catalyst can be removed by electrolysis and the cell can be dried.

  Once dried, the electrical circuit connected to the cell is short-circuited to consume hydrogen and oxygen in the vicinity of the electrodes, confirm that the voltage of each cell has dropped to near 0 V, and turn off the pump 65 for slow heating. to start. The pump 65 may be started immediately before the direct current is supplied from the power supply device 61 to the reversible cell 301. After confirming the decrease in the voltage of each cell, the electric circuit is shut off. For the oxygen generation electrode, first, the solenoid valves V2 and V30 are opened, and then the solenoid valve V5 is opened. Immediate replacement is performed, and when the replacement is completed, the solenoid valves V2 and V30 are closed. Next, regarding the hydrogen generation electrode, the solenoid valve V11 may be opened and the blower 82 may be activated to immediately replace the flow path 16 on the hydrogen generation electrode side with air.

  In addition, as a method for stopping the charge / discharge system 300 including the reversible cell 301 that does not have the resistance to the differential pressure between electrodes, for example, the pump 46 is first stopped and the solenoid valve V3 is closed, and then the solenoid valves V13 and V2 are closed. , V30 is opened, and the high pressure hydrogen remaining in the hydrogen electrode is exhausted from the system to the vicinity of the atmospheric pressure through the pipes 71, 94, 91 and the discharge pipe 93 through the port C. At the same time, the high pressure remaining in the oxygen electrode The electrolyzed water remaining in the system is returned to the gas-liquid separation tank 43 while exhausting the oxygen from the system to near atmospheric pressure. At this time, control is performed so that the differential pressure between the electrodes does not exceed a predetermined value. When the values of the pressure gauges P1 and P4 reach atmospheric pressure, it is possible to close all the solenoid valves and finish the operation.

  The present invention is useful as a power storage system using a solid molecular cell having a water electrolysis function and a fuel cell function. In addition, it is possible to improve the performance and maintain the durability of a reversible cell that performs water electrolysis and a fuel cell in the same cell, regardless of the application, even if it is other than the power storage system.

DESCRIPTION OF SYMBOLS 1 Charging / discharging system 2 Cell stack 10, 201, 251, 301 Reversible cell 11 Solid polymer electrolyte membrane 11a, 11b Electrode catalyst 12 First current collector 13 Second current collector 14, 16 Flow path 15, 17 Separator 21, 22 Seal member 41 Tank 43, 72 Gas-liquid separation tank 46, 53 Pump 61 Power supply device 62 Control device 64, 84, 92 Heat exchanger 76 Hydrogen storage unit 82 Blower 85 Humidity exchanger A, B, C, D port V1 to V5, V9, V11 to V16 Solenoid valve V6 Flow control valve V7 Back pressure valve V8 Check valve V10 Pressure adjustment valve

Claims (6)

A charge and discharge system using a reversible cell with an integrated water electrolysis cell and fuel cell of a solid high molecular form,
Hydrogen is supplied during fuel cell operation to the oxygen generating electrode where raw water is supplied and oxygen is generated during water electrolysis operation,
For the hydrogen generation electrode that generates hydrogen during water electrolysis operation, an oxidant is supplied during fuel cell operation ,
As the electrode catalyst of the oxygen generating electrode of the reversible cell, a mixture of iridium oxide and platinum black not subjected to water repellent treatment is used,
A charge / discharge system , wherein platinum-supported carbon is used as an electrode catalyst of the hydrogen generating electrode of the reversible cell . A charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated,
Hydrogen is supplied during fuel cell operation to the oxygen generating electrode where raw water is supplied and oxygen is generated during water electrolysis operation,
For the hydrogen generation electrode that generates hydrogen during water electrolysis operation, an oxidant is supplied during fuel cell operation,
In a cell stack in which a plurality of the reversible cells are connected in series,
A port A and a port B communicating with the reaction fluid flow path on the oxygen generation electrode side of each reversible cell; and a port C and a port D communicating with the reaction fluid flow path on the hydrogen generation electrode side of each reversible cell;
Port A is set to the raw water supply port during water electrolysis operation and the hydrogen discharge port during fuel cell operation.
Port B is set as a raw water and pure oxygen discharge port during water electrolysis operation and a hydrogen supply port during fuel cell operation,
Port C is set as a hydrogen discharge port during water electrolysis operation and a discharge port of oxidant and generated water during fuel cell operation.
Port D is set to the oxidant supply port during fuel cell operation,
The oxidant supplied to the port D is air, and the air supply flow path and the pure oxygen discharge flow path discharged from the port B during the water electrolysis operation are at least fluids flowing through the flow paths. A charge / discharge system, wherein the charge / discharge system is arranged through at least a humidity exchanger or a heat exchanger so as to be exchanged for humidity or heat . In a charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated, the charge / discharge system is dried before switching from water electrolysis operation to fuel cell operation. ,
The charge / discharge system includes:
Hydrogen is supplied during fuel cell operation to the oxygen generating electrode where raw water is supplied and oxygen is generated during water electrolysis operation,
It is configured to supply oxidant during fuel cell operation to the hydrogen generation electrode that generates hydrogen during water electrolysis operation,
In a cell stack in which a plurality of the reversible cells are connected in series,
A port A and a port B communicating with the reaction fluid flow path on the oxygen generation electrode side of each reversible cell; and a port C and a port D communicating with the reaction fluid flow path on the hydrogen generation electrode side of each reversible cell;
Port A is set to the raw water supply port during water electrolysis operation and the hydrogen discharge port during fuel cell operation.
Port B is set as a raw water and pure oxygen discharge port during water electrolysis operation and a hydrogen supply port during fuel cell operation,
Port C is set as a hydrogen discharge port during water electrolysis operation and a discharge port of oxidant and generated water during fuel cell operation.
Port D is set to the oxidant supply port during fuel cell operation,
The reversible cell is a cell having a pressure resistance between electrodes when hydrogen pressure> oxygen pressure = atmospheric pressure,
At the end of water electrolysis operation,
Introducing hydrogen at a pressure higher than atmospheric pressure from the port B into the reversible cell of the cell stack and discharging the residual water in the cell from the port A; and exhausting the residual hydrogen in the cell from the port C; Conducted in any order,
Then, after the inside of the reversible cell becomes atmospheric pressure, air is supplied into the cell from the port D to dry the inside of the cell. In a charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated, the charge / discharge system is dried before switching from water electrolysis operation to fuel cell operation. ,
The charge / discharge system includes:
Hydrogen is supplied during fuel cell operation to the oxygen generating electrode where raw water is supplied and oxygen is generated during water electrolysis operation,
It is configured to supply oxidant during fuel cell operation to the hydrogen generation electrode that generates hydrogen during water electrolysis operation,
In a cell stack in which a plurality of the reversible cells are connected in series,
A port A and a port B communicating with the reaction fluid flow path on the oxygen generation electrode side of each reversible cell; and a port C and a port D communicating with the reaction fluid flow path on the hydrogen generation electrode side of each reversible cell;
Port A is set to the raw water supply port during water electrolysis operation and the hydrogen discharge port during fuel cell operation.
Port B is set as a raw water and pure oxygen discharge port during water electrolysis operation and a hydrogen supply port during fuel cell operation,
Port C is set as a hydrogen discharge port during water electrolysis operation and a discharge port of oxidant and generated water during fuel cell operation.
Port D is set to the oxidant supply port during fuel cell operation,
The reversible cell is a cell having a pressure resistance between electrodes when hydrogen pressure> oxygen pressure = atmospheric pressure,
At the end of water electrolysis operation,
The high-pressure hydrogen remaining in the hydrogen generating electrode is exhausted from the system until it reaches atmospheric pressure, the electrical circuit connected to the cell stack is short-circuited, hydrogen and oxygen in the vicinity of the electrode are consumed, and each reversible After the cell voltage drops to 0V, shut off the electrical circuit,
Thereafter, the steps of supplying hydrogen from the port B into the reversible cell of the cell stack and replacing the oxygen generation electrode side with hydrogen and supplying the air from the port D into the cell are performed in any order. A method for drying a charge / discharge system, wherein the cell is dried. In a charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated, the charge / discharge system is dried before switching from water electrolysis operation to fuel cell operation. ,
The charge / discharge system includes:
Hydrogen is supplied during fuel cell operation to the oxygen generating electrode where raw water is supplied and oxygen is generated during water electrolysis operation,
It is configured to supply oxidant during fuel cell operation to the hydrogen generation electrode that generates hydrogen during water electrolysis operation,
In a cell stack in which a plurality of the reversible cells are connected in series,
A port A and a port B communicating with the reaction fluid flow path on the oxygen generation electrode side of each reversible cell; and a port C and a port D communicating with the reaction fluid flow path on the hydrogen generation electrode side of each reversible cell;
Port A is set to the raw water supply port during water electrolysis operation and the hydrogen discharge port during fuel cell operation.
Port B is set as a raw water and pure oxygen discharge port during water electrolysis operation and a hydrogen supply port during fuel cell operation,
Port C is set as a hydrogen discharge port during water electrolysis operation and a discharge port of oxidant and generated water during fuel cell operation.
At the end of water electrolysis operation,
The pressure from the hydrogen generation electrode side and the oxygen generation electrode side is controlled so that the solid polymer electrolyte membrane of the reversible cell is not damaged, and the high-pressure hydrogen remaining in the hydrogen generation electrode is connected to the system from the port C until the atmospheric pressure is reached. While exhausting outside, the remaining water and residual oxygen in the cell are discharged from port A,
Thereafter, the steps of supplying hydrogen from the port B into the reversible cell of the cell stack and replacing the oxygen generation electrode side with hydrogen and supplying the air from the port D into the cell are performed in any order. A method for drying a charge / discharge system, wherein the cell is dried. In a charge / discharge system using a reversible cell in which a solid polymer water electrolysis cell and a fuel cell are integrated, the charge / discharge system is dried before switching from water electrolysis operation to fuel cell operation. ,
The charge / discharge system includes:
Hydrogen is supplied during fuel cell operation to the oxygen generating electrode where raw water is supplied and oxygen is generated during water electrolysis operation,
It is configured to supply oxidant during fuel cell operation to the hydrogen generation electrode that generates hydrogen during water electrolysis operation,
In a cell stack in which a plurality of the reversible cells are connected in series,
A port A and a port B communicating with the reaction fluid flow path on the oxygen generation electrode side of each reversible cell; and a port C and a port D communicating with the reaction fluid flow path on the hydrogen generation electrode side of each reversible cell;
Port A is set to the raw water supply port during water electrolysis operation and the hydrogen discharge port during fuel cell operation.
Port B is set as a raw water and pure oxygen discharge port during water electrolysis operation and a hydrogen supply port during fuel cell operation,
Port C is set as a hydrogen discharge port during water electrolysis operation and a discharge port of oxidant and generated water during fuel cell operation.
At the end of water electrolysis operation,
The pressure from the hydrogen generation electrode side and the oxygen generation electrode side is controlled so that the solid polymer electrolyte membrane of the reversible cell is not damaged, and the high-pressure hydrogen remaining in the hydrogen generation electrode is connected to the system from the port C until the atmospheric pressure is reached. While exhausting outside, the remaining water and residual oxygen in the cell are discharged from port A,
Short circuiting the electrical circuit connected to the cell stack, consuming hydrogen and oxygen in the vicinity of the electrodes, and after the voltage of each reversible cell has dropped to 0 V, shut off the electrical circuit,
Thereafter, the steps of supplying hydrogen from the port B into the reversible cell of the cell stack and replacing the oxygen generation electrode side with hydrogen and supplying the air from the port D into the cell are performed in any order. A method for drying a charge / discharge system, wherein the cell is dried.

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