JP2005183023A - Fuel cell system - Google Patents

Abstract

A fuel cell system that minimizes the output limitation of a fuel cell at the time of gas leakage is provided.
A membrane electrode assembly including a polymer electrolyte membrane, an anode separator having a fuel gas flow path through which fuel gas flows, a cathode separator having an oxidant gas flow path through which oxidant gas flows, and a porous structure Anode-side cooling plate with an anode-side cooling water channel for humidifying the fuel gas through the body, and a cathode-side cooling with a cathode-side cooling water channel for humidifying the oxidant gas through the porous body A fuel cell body in which the plates are laminated, an anode side differential pressure adjusting means for adjusting a differential pressure between the fuel gas in the fuel gas passage and the cooling water in the anode side cooling water passage, and an oxidant gas passage in the oxidant gas passage Cathode side differential pressure adjusting means for adjusting the differential pressure between the oxidant gas and the cooling water in the cathode side cooling water flow path, a pressure sensor for measuring the pressure of the cooling water in the cooling water system, and the concentration of the gas in the cooling water system Gas concentration sensor to measure A.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system in which a part of cooling water humidifies a reaction gas through a separator made of a porous material.

  A polymer electrolyte fuel cell (PEFC) using a polymer electrolyte membrane having hydrogen ion conductivity as an electrolyte membrane among the fuel cells must be compact and have a high output density and can be operated with a simple system. Therefore, it is attracting attention as a power source for mobile use such as space and vehicles.

  The polymer electrolyte membrane is hygroscopic and needs to be humidified to saturation in order to efficiently generate power. 2. Description of the Related Art Conventionally, a fuel cell using a porous type (porous and permeable) separator as a reaction gas (fuel gas and oxidant gas) separator is known (see, for example, Patent Document 1).

In Patent Document 1, a plurality of unit cells each having a polymer electrolyte membrane sandwiched between a fuel electrode (anode electrode) and an oxidant electrode (cathode electrode) are stacked, and a cooling plate is inserted into each unit cell. Fuel in which a part of the cooling water supplied to the cooling plate is supplied to the polymer electrolyte membrane via the humidified water permeable plate and the porous fuel electrode current collector plate to humidify the polymer electrolyte membrane There is disclosed a solid polymer fuel cell system comprising a battery body and a cooling water system for removing heat generated during power generation by circulating cooling water to the cooling plate by a pump.
JP-A-9-92310

  In the aforementioned polymer electrolyte fuel cell system, the reaction gas and the cooling water are separated by a porous body. Therefore, when the amount of the cooling water contained in the porous body is not sufficient, the fuel gas and / or the oxidant gas may leak into the cooling water system.

  In this case, if the operation is continued as it is, the amount of water in the porous body is further reduced, and the leakage amount of the fuel gas and / or the oxidant gas is further increased. Therefore, it is necessary to immediately stop the operation and lower the pressure of the fuel gas or the oxidant gas with respect to the pressure of the cooling water so that the cooling water is supplied again into the porous body.

  In addition, since the temperature of the porous body needs to be lowered in order for the cooling water to be resupplied into the porous body, the pressure of the fuel gas and the oxidant gas is lowered and the power generation of the fuel cell is stopped or the output is limited Thus, the heat of reaction must not be released.

  The present invention has been made in view of the above problems, and an object thereof is to provide a fuel cell system capable of minimizing the output limitation of the fuel cell at the time of gas leakage.

  A feature of the present invention is that a membrane electrode assembly including a polymer electrolyte membrane, an anode separator provided with a fuel gas channel for supplying fuel gas to the membrane electrode assembly, and an oxidant gas in the membrane electrode complex. Cathode separator with oxidant gas flow path for supplying, anode side cooling plate with anode side cooling water flow path for humidifying fuel gas through porous body, and oxidation through porous body Pressure difference between the fuel cell body in which the cathode side cooling plate provided with the cathode side cooling water flow path for humidifying the agent gas, and the fuel gas in the fuel gas flow path and the cooling water in the anode side cooling water flow path An anode side differential pressure adjusting means for adjusting the pressure, a cathode side differential pressure adjusting means for adjusting a differential pressure between the oxidant gas in the oxidant gas flow path and the cooling water in the cathode side cooling water flow path, and an anode side cooling water flow Cooling including the channel and cathode side cooling water channel A pressure sensor for measuring the pressure of the cooling water in the water system, and summarized in that a fuel cell system having a gas concentration sensor for measuring the concentration of gas in the cooling water system.

  According to the present invention, the reaction gas (fuel gas / oxidant gas) leaking into the cooling water flow path is determined with reference to the gas concentration in the cooling water flow path, and the cooling water only on the leaking side is determined. By reducing the pressure of the gas relative to the pressure, it is possible to provide a fuel cell system that minimizes the output limitation of the fuel cell at the time of gas leakage.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

(First embodiment)
As shown in FIG. 1, the fuel cell system according to the first embodiment of the present invention generates power by supplying a fuel gas such as hydrogen and an oxidant gas such as air, and generates heat generated by the power generation. A fuel cell main body 30 that discharges the coolant through the cooling water, and anode-side differential pressure adjusting means (for example, a fuel gas pressure adjusting valve 6) that adjusts the differential pressure between the fuel gas and the cooling water in the fuel cell main body 30; The cathode side differential pressure adjusting means (for example, the oxidant gas pressure adjusting valve 7) for adjusting the differential pressure between the oxidant gas and the cooling water in the fuel cell main body 30 and the cooling in the cooling water system through which the cooling water circulates. It has a pressure sensor 22 for measuring the pressure of water, a gas concentration sensor (for example, a hydrogen concentration sensor 23) for measuring the concentration of gas in the cooling water system, and a cooling water tank 21 for storing cooling water.

  The fuel cell main body 30 includes a membrane electrode assembly 33 including a polymer electrolyte membrane, an anode separator 32 having a fuel gas passage for supplying fuel gas to the membrane electrode assembly 33, and a membrane electrode assembly 33. A cathode separator 34 having an oxidant gas flow path for supplying an oxidant gas; an anode side cooling plate 31 having an anode side cooling water flow path for humidifying the fuel gas through the porous body; A cathode side cooling plate 35 provided with a cathode side cooling water flow path for humidifying the oxidant gas through the material is laminated.

  In the first embodiment, the anode side differential pressure adjusting means includes a fuel gas pressure adjusting valve 6 that adjusts the pressure of the fuel gas in the fuel gas flow path. The cathode side differential pressure adjusting means includes an oxidant gas pressure adjusting valve 7 for adjusting the pressure of the oxidant gas in the oxidant gas flow path. Further, the gas concentration sensor is a hydrogen concentration sensor 23 that measures the hydrogen concentration of the leaking gas.

  As shown in FIG. 2, the fuel cell main body 30 of FIG. 1 includes a membrane electrode assembly 33 in which both surfaces of a polymer electrolyte membrane are sandwiched between a catalyst and a gas diffusion layer, and a first main surface of the membrane electrode assembly 33. An anode separator 32 having a fuel gas channel 37 in contact therewith, a cathode separator 34 having an oxidant gas channel 38 in contact with a second main surface facing the first main surface of the membrane electrode assembly 33, and an anode separator 32 An anode side cooling plate 31 having an anode side cooling water flow path 36 in contact with the cathode separator, and a cathode side cooling plate 35 having a cathode side cooling water flow path 39 in contact with the cathode separator 34.

  As shown in FIGS. 1 and 2, the fuel gas is supplied to the fuel gas flow path 37 in the anode separator 32 through a predetermined fuel gas pipe. The oxidant gas is supplied to the oxidant gas flow path 38 in the cathode separator 34 through a predetermined oxidant gas pipe. The cooling water stored in the cooling water tank 21 is supplied to the anode side cooling water flow path 36 in the anode side cooling plate 31 and the cathode side cooling water flow path 39 in the cathode side cooling plate 35 through a predetermined pump and cooling water supply piping. Supplied. The “cooling water system” includes a portion in which the cooling water circulates. Specifically, the cooling water tank 21, a predetermined pump, a cooling water supply pipe, an anode side cooling water channel 36, and a cathode side cooling water channel. 39 is included.

  At least a portion of the anode separator 32 sandwiched between the fuel gas passage 37 and the anode-side cooling water passage 36 is made of a porous body (porous plate) that allows the cooling water to pass therethrough. Similarly, at least a portion of the cathode separator 34 sandwiched between the oxidant gas flow path 38 and the cathode side cooling water flow path 39 is made of a porous body that allows cooling water to pass therethrough.

  When the porous body portion of the anode separator 32 holds sufficient water, the pressure magnitude relationship between the fuel gas in the fuel gas passage 37 and the cooling water in the anode-side cooling water passage 36 is properly maintained. If so, a part of the cooling water in the anode side cooling water flow path 36 can be supplied into the fuel gas flow path 37 to humidify the fuel gas. Similarly, when the porous body portion of the cathode separator 34 holds sufficient water, the magnitude relationship between the pressures of the oxidant gas in the oxidant gas flow path 38 and the cooling water in the cathode side cooling water flow path 39 is large. Is maintained properly, a part of the cooling water in the cathode-side cooling water channel 39 can be supplied into the oxidant gas channel 38 to humidify the oxidant gas.

  Next, a control method in the case where fuel gas and / or oxidant gas or both of them leak into the cooling water system in the fuel cell system of FIGS. 1 and 2 will be described with reference to the flowchart of FIG.

  (A) First, in step S01, the pressure sensor 22 detects from the pressure of the cooling water in the cooling water system that fuel gas and / or oxidant gas is leaking into the cooling water system. It is still unclear which gas is leaking in the S01 stage.

  (B) In step S02, the hydrogen concentration sensor 23 measures the concentration of gas in the cooling water system. Specifically, the hydrogen concentration of the gas leaking into the cooling water system is measured, and from the measured value (hydrogen concentration), the gas leaking into the cooling water system is fuel gas or oxidant gas or both. Determine if there is. More specifically, when the hydrogen concentration is less than 30%, the hydrogen concentration sensor 23 determines that only the oxidant gas has leaked and the fuel gas has not leaked, and proceeds to step S03. When the hydrogen concentration is higher than 70%, the hydrogen concentration sensor 23 determines that only the fuel gas leaks and the oxidant gas does not leak, and proceeds to step S04. When the hydrogen concentration is not less than 30% and not more than 70%, the hydrogen concentration sensor 23 determines that both the oxidant gas and the fuel gas have leaked, and proceeds to step S05.

  (C) In step S03, the pressure of only the oxidant gas in the oxidant gas flow path 38 is lowered using the oxidant gas pressure regulating valve 7, and the fuel gas in the fuel gas flow path 37 is maintained at a normal pressure. .

  (D) In step S04, the pressure of only the fuel gas in the fuel gas flow path 37 is lowered using the fuel gas pressure regulating valve 6, and the oxidant gas in the oxidant gas flow path 38 is maintained at a normal pressure.

  (E) In step S05, the pressures of both the fuel gas in the fuel gas channel 37 and the oxidant gas in the oxidant gas channel 38 are lowered using the oxidant gas pressure regulating valve 7 and the fuel gas pressure regulating valve 6. .

  In this way, when the pressure sensor 22 detects that fuel gas and / or oxidant gas has leaked into the cooling water system, the hydrogen concentration sensor 23 detects the concentration component of the gas leaking into the cooling water system. Determine whether the leaking gas is fuel gas, oxidant gas, or both, and lower the pressure of only the leaking gas using the pressure regulating valve related to the leaking gas, and not leaking Maintain gas at normal pressure.

  Thus, the leakage of gas can be stopped by lowering the pressure of the leaking gas. Further, by maintaining the gas that has not leaked at a normal pressure, the output limit of the fuel cell at the time of gas leak can be minimized.

  In addition, even if the fuel gas or oxidant gas leaks into the cooling water during operation of the fuel cell, the amount of leakage does not increase even if the operation is continued as it is. There is no need to limit the output or stop the operation of the fuel cell.

  FIG. 4 shows how much the output of the fuel cell is reduced by lowering the gas pressure by the control method shown in FIG. That is, how much the output decreases when the pressure of only the fuel gas, only the oxidant gas, and both the fuel gas and the oxidant gas of the fuel cell of FIG. The output that can be taken out under the original operating conditions is represented as 100. Conventionally, it has not been determined which of the fuel gas and the oxidant gas has leaked, and thus the pressure of both the fuel gas and the oxidant gas has to be lowered to limit the output by 25%. However, as shown in FIG. 4, by using the control method shown in FIG. 3, it is possible to suppress the output limit by 5% when the fuel gas leaks and by 20% even when the oxidant gas leaks.

(Second Embodiment)
As shown in FIG. 5, the fuel cell system according to the second embodiment of the present invention includes a fuel cell main body 30 and other anode side differential pressure adjusting means for adjusting the differential pressure between the fuel gas and the cooling water. An anode side cooling water pressure adjusting valve 41 as an example, a cathode side cooling water pressure adjusting valve 42 as another example of a cathode side differential pressure adjusting means for adjusting a differential pressure between an oxidant gas and cooling water, and a pressure sensor 22, a hydrogen concentration sensor 23, a cooling water tank 21, a fuel gas pressure adjustment valve 6, and an oxidant gas pressure adjustment valve 7. The fuel cell main body 30 is a laminate of a membrane electrode assembly 33, an anode separator 32, a cathode separator 34, an anode side cooling plate 31, and a cathode side cooling plate 35.

  In the second embodiment, the anode side differential pressure adjusting means includes an anode side cooling water pressure adjusting valve 41 that adjusts the pressure of the cooling water in the anode side cooling water flow path. The cathode side differential pressure adjusting means includes a cathode side cooling water pressure adjusting valve 42 that adjusts the pressure of the cooling water in the cathode side cooling water flow path.

  The detailed configuration of the fuel cell body 30 in the second embodiment is the same as that shown in FIG.

  Next, a control method when fuel gas and / or oxidant gas or both leak into the cooling water system in the fuel cell system of FIG. 5 will be described. The control method in the fuel cell system of FIG. 5 is common to the S01 stage and the S02 stage as compared with the control method shown in FIG. Instead of the steps S03 to S05, the following procedure is performed.

  When the pressure sensor 22 detects that fuel gas or oxidant gas has leaked into the cooling water system (step S01), the hydrogen concentration sensor 23 detects the concentration component (hydrogen concentration) of the gas leaking into the cooling water system. Then, it is determined whether the leaking gas is a fuel gas or an oxidant gas (step S02). Then, using the pressure regulating valve related to the leaking gas, the pressure of only the cooling water in the cooling water flow path related to the leaking gas is increased, and the cooling water in the cooling water flow path related to the non-leaking gas is reduced. Maintain normal pressure.

  (A) Specifically, when the hydrogen concentration is less than 30%, the hydrogen concentration sensor 23 determines that only the oxidant gas leaks and the fuel gas does not leak, and the cathode-side cooling water pressure regulating valve 42 Is used to increase the pressure of only the cooling water in the cathode side cooling water flow path 39 and maintain the cooling water in the anode side cooling water flow path 36 at a normal pressure.

  (B) When the hydrogen concentration is higher than 70%, the hydrogen concentration sensor 23 determines that only the fuel gas leaks and the oxidant gas does not leak, and the anode side cooling water pressure regulating valve 41 is used for the anode side. The pressure of only the cooling water in the cooling water flow path 36 is increased, and the cooling water in the cathode side cooling water flow path 39 is maintained at a normal pressure.

  (C) When the hydrogen concentration is not less than 30% and not more than 70%, the hydrogen concentration sensor 23 determines that both the oxidant gas and the fuel gas have leaked, and the cathode side cooling water pressure adjustment valve 42 and the anode side The cooling water pressure regulating valve 41 is used to increase both pressures of the cooling water in the cathode side cooling water channel 39 and the anode side cooling water channel 36.

  As described above, by increasing the pressure in the flow path through which the cooling water humidifying the leaked gas flows, the relative pressure of the gas with respect to the cooling water decreases, and the leakage of the gas can be stopped. In addition, by maintaining the operating pressure up to that time without increasing the pressure of the cooling water on the side where no gas leakage has occurred, the cooling water permeates the porous body more than necessary and flows into the gas flow path. The flow of gas and oxidant gas is not hindered and power generation performance is not unstable.

  In addition, even if the fuel gas or oxidant gas leaks into the cooling water during operation of the fuel cell, the amount of leakage does not increase even if the operation is continued as it is. There is no need to limit the output or stop the operation of the fuel cell.

  FIG. 6 shows how the stability of the fuel cell output changes by increasing the coolant pressure by the control method of the fuel cell system shown in FIG. That is, in the fuel cell system shown in FIG. 5 operated under certain conditions, the pressure of only the anode side cooling water, the pressure of only the cathode pole side cooling water, and the pressure of both the cathode side and anode side cooling water are raised. In this case, it shows how much the output becomes unstable and how long the output that can be stably taken out under the original operating conditions can be taken out continuously.

  In FIG. 6, the anode side cooling water is not pressurized, and a stable operation can be continuously performed under the original conditions. That is, when only the anode side cooling water is pressurized at 20 kPa as shown in FIG. 6, the operation is stably continued. If the possible time is 100 and a bar graph is written for the original condition, the graph becomes infinitely long. Therefore, even when the anode side cooling water is pressurized, the anode side cooling water slightly flows into the fuel gas flow path 37 and has an effect of hindering the flow of the fuel gas, which is the second embodiment of the present invention. Therefore, it is possible to avoid such effects.

(Other embodiments)
As described above, the present invention has been described according to the first and second embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art.

  Instead of the hydrogen concentration sensor 23 shown in FIGS. 1 and 5, as another example of the gas concentration sensor, the oxygen concentration may be indirectly estimated using an oxygen concentration sensor or a nitrogen concentration sensor. That is, the gas concentration sensor may determine the leaking gas from the oxygen concentration or the nitrogen concentration of the leaking gas.

  In the first and second embodiments, the case where the polymer electrolyte membrane is humidified by humidifying both the oxidant gas and the fuel gas with cooling water has been described. However, the present invention is not limited to this. No. As disclosed in Patent Document 1, a polymer electrolyte membrane may be humidified by humidifying only the fuel gas using a humidified water transmission plate (porous body) only on the anode side. However, according to the first and second embodiments, water generated as a result of operating the fuel cell by using the humidified water permeable plates on both the anode side and the cathode side is supplied from the oxidant gas flow path 38. It becomes possible to remove to a cooling water system.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters according to the scope of claims reasonable from this disclosure.

  As described above, the fuel cell body formed by laminating a plurality of unit cells, the fuel cell body is cooled, and moisture is supplied to the solid polymer electrolyte membrane constituting the unit cells via the porous body. A fuel cell flow path and an oxidant in a fuel cell system comprising a cooling water flow path for supplying cooling water for supply and a reaction gas flow path for supplying reaction gas (fuel and oxidant gas) to the fuel cell stack. The gas flow path is equipped with a pressure regulating valve that regulates each pressure, a pressure sensor and a gas concentration sensor are installed at any position in the cooling water system, and the fuel gas or oxidant gas flows into the cooling water system by the pressure sensor. If it is determined, the leakage location (cathode side or anode side) is determined from the concentration of gas leaking into the cooling water flow path, and the leakage location (cathode side or anode side) is determined. Reducing the pressure of the de-side) only, to maintain the other normal pressure. By this, when only fuel gas or oxidant gas leaks into the cooling water system, the pressure of only the gas on the leaking side can be lowered, and other gases can be maintained at normal pressure, The output limit of the fuel cell at the time of gas leakage can be limited to the minimum.

  Further, the above-described fuel cell system includes a configuration capable of separately adjusting the pressure of the cooling water system on the fuel gas channel and the oxidant gas channel side, and a pressure sensor and a gas concentration sensor at an arbitrary position of the cooling water system. When the pressure sensor determines that the fuel gas or the oxidant gas has leaked into the cooling water system, the gas leakage point (cathode side or anode side) is determined from the concentration of the gas leaking into the cooling water flow path, The pressure of only the cooling water flow path on the leaking side (cathode side or anode side) is increased, and the other cooling water flow paths are maintained at normal pressure. As a result, if only fuel gas or oxidant leaks into the cooling water system, the amount of cooling water flowing into the fuel gas flow path or oxidant gas flow path can be reduced, minimizing output restrictions. It can be limited to.

  Furthermore, in the fuel cell system described above, the gas concentration sensor determines the oxygen concentration, nitrogen concentration, or hydrogen concentration in the gas leaking into the cooling water flow path. This makes it possible to determine whether the gas leaking into the cooling water system is fuel gas or oxidant gas from the concentration of oxygen, nitrogen, or hydrogen, so it is possible to select a sensor to be used for the system from a larger number of types. .

1 is a block diagram showing a fuel cell system according to a first embodiment of the present invention. It is sectional drawing which shows the fuel cell main body shown in FIG. 1 in detail. 3 is a flowchart showing a control method in the case where fuel gas and / or oxidant gas or both leak into the cooling water system in the fuel cell system of FIGS. 1 and 2. FIG. 4 is a graph for explaining how much the output decrease of the fuel cell is caused by lowering the gas pressure by the control method shown in FIG. 3. It is a block diagram which shows the fuel cell system concerning the 2nd Embodiment of this invention. 6 is a graph for explaining how the stability of the fuel cell output changes by increasing the coolant pressure by the control method of the fuel cell system shown in FIG. 5.

Explanation of symbols

6 ... Fuel gas pressure regulating valve 7 ... Oxidant gas pressure regulating valve 21 ... Cooling water tank 22 ... Pressure sensor 23 ... Hydrogen concentration sensor 30 ... Fuel cell body 31 ... Anode-side cooling plate 32 ... Anode separator 33 ... Membrane electrode composite 34 ... Cathode separator 35 ... Cathode side cooling plate 36 ... Anode side cooling water passage 37 ... Fuel gas passage 38 ... Oxidant gas passage 39 ... Cathode side cooling water passage 41 ... Anode side cooling water pressure regulating valve 42 ... Cathode side Cooling water pressure adjustment valve

Claims (8)

A membrane electrode assembly including a polymer electrolyte membrane, an anode separator having a fuel gas flow path for supplying a fuel gas to the membrane electrode assembly, and an oxidant gas for supplying the membrane electrode assembly A cathode separator having an oxidant gas flow path, an anode side cooling plate having an anode side cooling water flow path for humidifying the fuel gas via a porous body, and the oxidant gas via a porous body A fuel cell main body laminated with a cathode side cooling plate having a cathode side cooling water flow path for humidifying
An anode side differential pressure adjusting means for adjusting a differential pressure between the fuel gas in the fuel gas channel and the cooling water in the anode side cooling water channel;
Cathode side differential pressure adjusting means for adjusting a differential pressure between the oxidant gas in the oxidant gas flow path and the cooling water in the cathode side cooling water flow path;
A pressure sensor for measuring a pressure of the cooling water in a cooling water system including the anode side cooling water flow path and the cathode side cooling water flow path;
A fuel cell system comprising: a gas concentration sensor for measuring a concentration of gas in the cooling water system.   The anode side differential pressure adjustment means includes a fuel gas pressure adjustment valve that adjusts the pressure of the fuel gas in the fuel gas flow path, and the cathode side differential pressure adjustment means includes the fuel gas pressure adjustment valve in the oxidant gas flow path. The fuel cell system according to claim 1, further comprising an oxidant gas pressure adjusting valve that adjusts the pressure of the oxidant gas.   When the pressure sensor detects that the fuel gas or the oxidant gas leaks into the cooling water system, the gas concentration sensor detects the leakage from the concentration component of the gas leaking into the cooling water system. It is determined whether the gas that is leaking is the fuel gas or the oxidant gas, and the pressure of the leaking gas is lowered using the pressure regulating valve related to the leaking gas, and the gas that has not leaked is removed. The fuel cell system according to claim 2, wherein the fuel cell system is maintained at a normal pressure.   The anode side differential pressure adjusting means includes an anode side cooling water pressure adjusting valve that adjusts the pressure of the cooling water in the anode side cooling water flow path, and the cathode side differential pressure adjusting means includes the cathode side cooling water flow path. The fuel cell system according to claim 1, further comprising a cathode side cooling water pressure adjusting valve that adjusts the pressure of the cooling water in the inside.   When the pressure sensor detects that the fuel gas or the oxidant gas leaks into the cooling water system, the gas concentration sensor detects the leakage from the concentration component of the gas leaking into the cooling water system. It is determined whether the gas that is leaking is the fuel gas or the oxidant gas, and only the cooling water in the cooling water flow path related to the leaking gas is used by using the pressure regulating valve related to the leaking gas. 5. The fuel cell system according to claim 4, wherein the cooling water in the cooling water flow path related to the gas that has not leaked is maintained at a normal pressure by increasing the pressure.   6. The fuel cell system according to claim 3, wherein the gas concentration sensor determines from the oxygen concentration of the leaked gas.   The fuel cell system according to claim 3 or 5, wherein the gas concentration sensor judges from the nitrogen concentration of the leaked gas.   6. The fuel cell system according to claim 3, wherein the gas concentration sensor determines from the hydrogen concentration of the leaking gas.

Images