JP2009266689A - Operation method of fuel cell, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve power generation performance in startup below zero by executing a scavenging operation while keeping a wet condition of an electrolyte membrane after stopping a power generation operation of a fuel cell. <P>SOLUTION: When a power generation operation is stopped, a control unit 70 of this fuel cell system 10 starts scavenging operation control. In the scavenging operation control, when the temperature T of a fuel cell stack 20 is set below a predetermined value Th1, the scavenging operation for the fuel stack 20, a fuel gas system apparatus 30 and an oxidation gas system apparatus 40 by using dry air. When the surface resistance value Rs of the fuel cell stack 20 is set above a predetermined value TH2, the scavenging operation is stopped. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of operating a fuel cell using an electrolyte membrane that conducts protons through water.

  In a polymer electrolyte fuel cell, water is generated with an electrochemical reaction, and a part of the generated water remains inside the fuel cell even after power generation is stopped. When starting up a fuel cell in a low-temperature environment such as below freezing with such residual water remaining, the residual water freezes on the catalyst surface, gas flow path, etc., and the reaction gas is supplied to the electrode. Therefore, it is necessary to remove residual water. On the other hand, the electrolyte membrane constituting the solid polymer fuel cell needs to be kept wet to a certain level or more in order to conduct protons through water. Such a problem is not limited to a polymer electrolyte fuel cell, and is a problem common to various fuel cells using an electrolyte membrane that conducts protons through water. For example, the following techniques are known for such problems.

JP 2007-200779 A Japanese Patent Laid-Open No. 2004-199988

  In Patent Document 1, in the scavenging operation, the impedance of the fuel cell that correlates with the wet state of the electrolyte membrane is measured, and when the impedance exceeds a predetermined value, the scavenging operation is stopped, so that excess electrolyte membrane is present. Disclosed is a scavenging operation stop control technique that can prevent excessive drying. However, the impedance of the fuel cell changes abruptly when the state of the electrolyte membrane changes from a wet state to a dry state to some extent, so that the scavenging operation is performed in a timely manner, aiming at the point where the impedance reaches a predetermined value. It has been difficult in practice to perform control to stop.

  In view of the above-mentioned various problems, the problem to be solved by the present invention is that after the power generation operation of the fuel cell is stopped, the scavenging operation is performed while keeping the electrolyte membrane in a wet state. It is to improve.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A method for operating a fuel cell using an electrolyte membrane that conducts protons through water,
After the fuel cell stops the power generation operation, an inert gas is circulated through the fuel cell in a state where the temperature of the fuel cell is equal to or lower than a predetermined temperature, so that at least one of the moisture remaining in the fuel cell. A scavenging operation step of performing a scavenging operation to remove the part;
A scavenging operation end step of ending the scavenging operation based on a parameter that can estimate a wet state of the electrolyte membrane in the scavenging operation.

  In such a fuel cell operation method, since the scavenging operation is performed after the temperature of the fuel cell is decreased, the saturated vapor pressure is reduced as compared with the case where the scavenging operation is performed before the temperature is decreased. The amount of water evaporated into the gas can be suppressed, and excessive drying of the electrolyte membrane can be suppressed. This also slows the evaporation rate of moisture contained in the electrolyte membrane, that is, the rate of change in the wet state of the electrolyte membrane is slow, so based on the parameters that can estimate the wet state of the electrolyte membrane, The scavenging operation can be stopped with high accuracy at a timing at which the electrolyte membrane does not dry excessively.

Application Example 2 The fuel cell operating method according to Application Example 1, wherein the parameter is an internal resistance value of the fuel cell.
Such a fuel cell operating method uses the fact that the internal resistance value of the fuel cell varies greatly depending on the wet state of the electrolyte membrane, and thus terminates the scavenging operation based on the internal resistance value of the fuel cell. The scavenging operation can be reliably stopped before the water is excessively dried.

[Application Example 3] The operation method according to Application Example 1 or Application Example 2, wherein the inert gas is a gas in a non-humidified state.
Such a fuel cell operation method performs scavenging operation with a gas in a non-humidified state, and thus is efficient in removing moisture.

Application Example 4 The fuel cell operating method according to any one of Application Examples 1 to 3, wherein the inert gas is air.
In such a fuel cell operation method, the air used for the scavenging operation can be taken in from the outside air, and no scavenging gas storage facility or the like is required. Therefore, the equipment configuration can be simplified. Further, since it is not necessary to prepare or generate scavenging gas, the running cost can be reduced.

  The present invention can also be realized as a fuel cell system, a computer program, etc., in addition to a fuel cell operation method.

A. Example:
A-1. General configuration of the fuel cell system:
FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system 10 as an embodiment of the present invention. The fuel cell system 10 includes a fuel cell stack 20 that generates power by an electrochemical reaction, a fuel gas system device 30 that supplies and discharges fuel gas to the fuel cell stack 20, and an oxidizing gas that supplies and discharges oxidizing gas to the fuel cell stack 20 A system device 40, a cooling system device 50 for cooling the fuel cell stack 20, and a control unit 70 for controlling the fuel cell system 10 are provided.

  The fuel cell stack 20 is a fuel cell in which a plurality of laminate assemblies each including an anode, a cathode, an electrolyte membrane, a separator, and the like are stacked. In this embodiment, the fuel cell stack 20 is a polymer electrolyte fuel cell, and polytetrafluoroethylene is used for the electrolyte membrane.

  In addition, a temperature sensor 22 for grasping the operating temperature of the fuel cell stack 20 and an impedance meter 24 for measuring the impedance of the fuel cell stack 20 are attached to the fuel cell stack 20. In this embodiment, the thermistor is used for the temperature sensor 22, but the method is not particularly limited, and various known methods such as a thermocouple can be used. Similarly, although the high frequency impedance type is used for the impedance meter 24, the method is not particularly limited, and various known methods of current interruption type can be used.

  The fuel gas system device 30 includes a hydrogen tank 31, a shut valve 32, a regulator 33, a gas-liquid separator 36, a circulation pump 37, a purge valve 39, and pipes 34, 35, and 38. The high-pressure hydrogen stored in the hydrogen tank 31 is adjusted in pressure and supply amount by the shut valve 32 and the regulator 33 and is supplied as fuel gas to the anode of the fuel cell stack 20 via the pipe 34. Then, the exhaust gas from the anode (hereinafter referred to as anode off gas) is led to the gas-liquid separator 36 through the pipe 35 to separate the water contained in the anode off gas from the residual hydrogen that has not been consumed in power generation. . The hydrogen separated by the gas-liquid separator 36 is recirculated to the fuel cell stack 20 via the circulation pump 37 and the pipe 38.

  A pipe 38 between the gas-liquid separator 36 and the circulation pump 37 is branched, and a purge valve 39 is provided at the branch destination. During the recirculation of the anode off gas described above, the purge valve 39 is normally closed. However, when the anode off gas is opened at a predetermined timing, the anode off gas is supplied via a pipe 38 to a diluter 46 described later. By introducing it into the system and discharging it outside the system, the increase in impurity concentration is suppressed.

  The oxidizing gas system device 40 includes an air cleaner 41, an air compressor 42, a diluter 46, pipes 43, 45 and 47, and a gate valve 44. The air drawn from the air cleaner 41 is compressed by the air compressor 42 and supplied as an oxidizing gas to the cathode of the fuel cell stack 20 via the pipe 43. Exhaust gas from the cathode (hereinafter referred to as cathode off gas) is introduced into the diluter 46 via the pipe 45.

  In the diluter 46, the concentration of hydrogen contained in the anode off gas is diluted by mixing the cathode off gas and the anode off gas introduced into the diluter 46 at the predetermined timing described above. The exhaust gas discharged from the diluter 46 is discharged out of the fuel cell system 10 through the pipe 47.

  Further, the pipe 43 is branched between the air compressor 42 and the fuel cell stack 20, and this branch destination is connected to the pipe 34 of the fuel gas system device 30 via the gate valve 44. Normally, the gate valve 44 is closed, but the gate valve 44 is opened and supplies air to the fuel gas system device 30 during the scavenging operation described later.

  The cooling system device 50 includes a radiator 51, a circulation pump 52, and a pipe 54. The cooling water is circulated between the fuel cell stack 20 and the radiator 51 by the circulation pump 52 via the pipe 54. As a result, the heat generated by the electrochemical reaction is absorbed by the fuel cell stack 20 and is radiated by the radiator 51, whereby the temperature of the fuel cell stack 20 can be maintained appropriately.

  The above-described apparatus is controlled by the control unit 70. The control unit 70 is configured as a microcomputer having a CPU, a RAM, and a ROM therein. The program stored in the ROM is expanded in the RAM and executed, whereby the output request 76 and signals from the various sensors 78 are received. In response, drive signals are output to the regulator 33, the air compressor 42, and various actuators 77 of the fuel cell system 10 to control the entire operation of the fuel cell system 10. The control unit 70 also functions as a scavenging operation unit 72 and a scavenging operation end unit 74. Details of the scavenging operation unit 72 and the scavenging operation end unit 74 will be described later in “A-2. Scavenging operation control”.

A-2. Scavenging operation control:
The scavenging operation control in the fuel cell system 10 will be described with reference to FIG. The scavenging operation refers to the fuel cell stack 20, the fuel gas system device 30, and the oxidizing gas system by sending an inert gas to the fuel gas system device 30 and the oxidizing gas system device 40 after the power generation operation of the fuel cell system 10 is stopped. In this operation, residual water remaining in the device 40 is removed. The scavenging operation control in the present embodiment is started when the control unit 70 stops the fuel gas system device 30 and the oxidizing gas system device 40 and stops the power generation operation of the fuel cell stack 20.

  When the exhaust operation control is started, the control unit 70 detects the temperature T of the fuel cell stack 20 using the temperature sensor 22 and determines whether or not the temperature T has decreased to a predetermined value Th1 or less. (Step S110). As a result, if the temperature T is higher than the predetermined value Th1 (step S110: NO), the control unit 70 stands by until the temperature T becomes equal to or lower than the predetermined value Th1. In this embodiment, the predetermined value Th1 = 30 ° C.

  In the present embodiment, the temperature T of the fuel cell stack 20 is directly detected by the temperature sensor 22. However, the temperature T may be indirectly detected by another method. For example, the control unit 70 may grasp the temperature of the fuel cell stack 20 by operating the cooling system device 50 and detecting the temperature of the circulating cooling water.

  On the other hand, when the temperature T decreases to the predetermined value Th1 (step S110: YES), the control unit 70 starts the scavenging operation as a process of the scavenging operation unit 72 (step S120). Specifically, the control unit 70 opens the gate valve 44 with the regulator 33 closed and drives the air compressor 42 to perform scavenging with air. Thus, by performing scavenging, residual water remaining in the fuel cell stack 20, the fuel gas system device 30, and the oxidizing gas system device 40 can be removed.

  In this embodiment, the air used for scavenging was the same air taken from outside air. Moreover, you may use the dry air which reduced the water | moisture content (water vapor | steam) contained. By using dry air, the removal efficiency of residual water can be improved. In addition, air can be obtained from the outside air, and the oxidizing gas system device 40 can be used for the supply route to the fuel cell stack 20, so that it is not necessary to provide a scavenging gas storage facility, and the equipment configuration is simplified. Can be

  The scavenging gas is not limited to dry air, and may be a non-humidified inert gas such as nitrogen. The dry air supply route may be provided separately for the fuel gas system device 30 and the oxidizing gas system device 40 separately, or when the humidity of the air obtained from the outside air is high due to the influence of the weather, etc. In order to obtain dry air having a suitable humidity, a dehumidifying device such as a dehumidifying filter may be provided.

When the scavenging operation is started, the control unit 70 uses the impedance meter 24 to apply a high-frequency AC voltage to the fuel cell stack 20, measures the impedance of the fuel cell stack 20, and calculates the surface resistance value calculated from the impedance Z. It is determined whether or not Rs (mΩ · cm ² ) has increased to a predetermined value Th2 (step S130). The impedance Z used for the determination here is an instantaneous value. The reason for monitoring the impedance Z in this way is that the wet state of the electrolyte membrane can be estimated from the resistance value of the fuel cell stack 20. For example, when the wet state of the electrolyte membrane constituting the fuel cell stack 20 changes to the dry side, the proton conductivity of the electrolyte membrane decreases, and as a result, the resistance value of the fuel cell stack 20 increases.

  As a result, if the sheet resistance value Rs is smaller than the predetermined value Th2 (step S130: NO), this means that the electrolyte membrane is still in a sufficiently wet state, and the control unit 70 started in step S120. While continuing the scavenging operation, the system waits until the sheet resistance value Rs becomes equal to or greater than the predetermined value Th2.

  On the other hand, if the sheet resistance value Rs is larger than the predetermined value Th2 (step S130: YES), this means that the electrolyte membrane is shifting from the wet state to the dry state, and the control unit 70 performs the scavenging operation end unit 74. As the process, the scavenging operation is stopped (step S140), and the scavenging operation control is ended.

  In the present embodiment, the surface resistance value Rs is calculated using the instantaneous value of the impedance Z in the determination in step S130. However, the present invention is not limited to this, and a statistical value such as an average value within a predetermined time. It may be. In this way, the wet state of the electrolyte membrane can be determined with higher accuracy.

A-3. Effect of scavenging operation control:
Since the fuel cell system 10 having such a configuration performs a scavenging operation with an inert gas in a non-humidified state, the removal efficiency of residual water can be improved as compared with a case in which a scavenging operation is performed with an inert gas in a humidified state. Further, by performing the scavenging operation after the temperature of the fuel cell stack 20 is decreased, the saturated vapor pressure is reduced as compared with the case where the scavenging operation is performed before the temperature is decreased, so that evaporation from the electrolyte membrane into the scavenging gas occurs. It is possible to suppress the amount of moisture to be generated, and to suppress excessive drying of the electrolyte membrane. In addition, since the stop of the scavenging operation is controlled based on the surface resistance value Rs of the fuel cell stack 20 that is correlated with the wet state of the electrolyte membrane, excessive drying of the electrolyte membrane can be suppressed. From the above, the fuel cell system 10 performs the scavenging operation efficiently while suppressing excessive drying of the electrolyte membrane, so that the fuel cell stack 20, the fuel gas system device 30, and the oxidizing gas system device 40 remain. Since water can be efficiently removed, the power generation performance at the time of starting below freezing point can be improved.

  A specific example of such an effect will be described with reference to FIG. FIG. 3 is an explanatory diagram illustrating an example of an experimental result regarding the relationship between the scavenging conditions and the limit current value during sub-freezing power generation. Here, during sub-freezing power generation, after scavenging operation is performed after stopping the power generation operation of the fuel cell system 10, the fuel cell system 10 is stopped, and then the fuel cell system 10 is cold-started under sub-freezing conditions to generate power. Time to do. Further, the limit current value here means a current value when the voltage is 0.2 V in the IV characteristic of the fuel cell stack 20 cold-started under the condition where the temperature is −20 ° C.

As shown in the drawing, under the scavenging conditions of condition 1 (temperature T of fuel cell stack 20 = 80 ° C., scavenging gas = humidified gas, scavenging time = 12 minutes), the limit current value is about 0.18 A / cm ² . On the other hand, under condition 4 (temperature T = 20 ° C., scavenging gas = non-humidified gas, scavenging time = 12 minutes), the limit current value is approximately the same as in condition 1. This is because, under condition 4, the use of non-humidified gas as the scavenging gas improved the residual water removal effect as compared to condition 1, and the scavenging at low temperature reduced the saturated vapor pressure, resulting in the electrolyte. This is due to the balance between the positive factor that controlled the drying of the membrane and the negative factor that reduced the saturated vapor pressure and reduced the residual water removal effect during the same scavenging time due to scavenging at a low temperature. Yes. In condition 2 and condition 3, which are lower temperature conditions than condition 4, the above-described negative factor is superior and the residual water removal effect is further reduced, so that the limit current value is further reduced.

On the other hand, under the condition 5 (temperature T = 30 ° C. of the fuel cell stack 20, scavenging gas = non-humidified gas, scavenging time = until the surface resistance value Rs increases by 26 mΩ · cm ² ), the above-mentioned positive factors win. In addition, by controlling the stop of scavenging by the surface resistance value Rs, drying of the electrolyte membrane can be suppressed at an exquisite timing, so the limit current value is about 0.24 A / cm ² , and power generation during sub-freezing power generation We were able to dramatically improve performance.

When the temperature T of the fuel cell stack 20 during the scavenging operation is 30 ° C., the optimum timing for stopping the scavenging in this embodiment is when the surface resistance value Rs has increased by 26 mΩ · cm ² (normally , sheet resistance Rs when the electrolyte membrane is a wet state, by applying the 100 m [Omega · cm ² degree. This predetermined value Th2 = 126mΩ · cm ² or so) is, to a predetermined value Th2 = 400mΩ · cm ² approximately If so, even if the scavenging operation is performed, the wettability of the electrolyte membrane can be secured to some extent. Further, the timing at which scavenging is stopped may be controlled as a point in time when the surface resistance value Rs has increased by about 1/3 to 1/5 of the rated operation, and preferably has been increased by about 1/4.

  Further, the fuel cell system 10 having such a configuration performs the scavenging operation after the temperature is lowered, so that the saturated vapor pressure is lowered, and the evaporation rate of water contained in the electrolyte membrane is slowed, that is, the electrolyte membrane is dried. As a result, the rising speed of the sheet resistance value Rs becomes slow. This phenomenon will be described in detail with reference to FIG. FIG. 4 shows the relationship between the scavenging time in the scavenging operation and the surface resistance value Rs of the fuel cell stack 20. When the scavenging operation is performed under a high temperature condition, the evaporation rate of the moisture contained in the electrolyte membrane is fast, so that the surface resistance value Rs increases rapidly with the passage of the scavenging time as shown by the curve C1. For this reason, at the timing when the scavenging time becomes time T1, the surface resistance value Rs becomes equal to or greater than the predetermined value Th2, but when the control unit 70 detects this and stops the scavenging operation, the surface resistance value Rs is a larger value. That is, the drying of the electrolyte membrane has progressed to a considerable extent.

  On the other hand, when the scavenging operation is performed under a low temperature condition, the evaporation rate of the water contained in the electrolyte membrane is slow, so that the surface resistance value Rs gradually increases as the scavenging time elapses as shown by the curve C2. To do. For this reason, at the timing when the scavenging time becomes time T2, the surface resistance value Rs becomes equal to or greater than the predetermined value Th2, but the control unit 70 stops the scavenging operation at a point where the surface resistance value Rs becomes approximately the predetermined value Th2. Can do. That is, the wet state of the electrolyte membrane can be accurately controlled. As described above, in the scavenging operation under the low temperature condition, by performing the stop control of the scavenging operation based on the surface resistance value Rs, the accuracy of the stop control can be improved, and the power generation performance at the time of starting below the freezing point is improved. It can contribute to.

  In the present embodiment, the predetermined value Th1 is set to 30 ° C., but the predetermined value Th1 is a predetermined temperature for relaxing the drying speed of the electrolyte membrane during the scavenging operation to a desired speed. Any temperature lower than the operating temperature of the battery stack 20 may be used. If the temperature decreases, the saturated vapor pressure decreases and the evaporation rate of moisture contained in the electrolyte membrane can be reduced compared to the case where the scavenging operation is started immediately after power generation. This is because drying can be suppressed. However, in the saturated vapor pressure curve, the rate of decrease in saturated vapor pressure decreases as the temperature goes to the lower temperature side, and the effect of decreasing saturated vapor pressure gradually decreases. Since the residual water removal effect of the system device 30 and the oxidizing gas system device 40 is also reduced, the predetermined value Th1 is preferably about 20 to 40 ° C.

B. Variations:
A modification of the above-described embodiment will be described.
B-1. Modification 1:
In the scavenging operation control of the embodiment, the surface resistance value Rs of the fuel cell stack 20 is used as a parameter for determining the stop timing of the scavenging operation, and the scavenging operation is performed when the surface resistance value Rs exceeds a predetermined value Th2. However, the present invention is not limited to such an example. The above-described parameter may be any parameter that can estimate the wet state of the electrolyte membrane, and may be, for example, a scavenging time.

  For example, the relationship between the scavenging operation condition, the surface resistance value Rs and the scavenging time is grasped in advance, and the relationship between the scavenging operation condition and the scavenging time when the surface resistance value Rs is equal to or greater than a predetermined value Th2 is determined by the control unit 70. It is possible to store the data in a memory as a table, and the control unit 70 refers to the corresponding table to perform scavenging for a scavenging time according to the conditions of the scavenging operation being performed, and then stops scavenging. Good. For example, as shown in the embodiment, when scavenging is performed when the temperature T of the fuel cell stack 20 is 30 ° C., the optimum scavenging time corresponding to the timing when the surface resistance value Rs increases by 26 mΩ · cm 2 is 10 minutes. Can be set. In this way, scavenging operation control can be performed with a simpler configuration.

B-2. Modification 2:
In the embodiment, the forced cooling process for the fuel cell stack 20 is not particularly performed in the scavenging operation control. That is, when the power generation operation of the fuel cell stack 20 is stopped and the scavenging operation control is started, in step S110, the control unit 70 reduces the temperature T of the fuel cell stack 20 to a predetermined value Th1 or less due to natural cooling. Judgment whether or not. However, the present invention is not limited to this configuration, and a process for forcibly cooling the fuel cell stack 20 may be added to the preceding stage of S110. For example, the fuel cell stack 20 may be forcibly cooled by circulating cooling water through the cooling system device 50. In this way, the time until the temperature T of the fuel cell stack 20 decreases can be shortened, and therefore the time until the fuel cell system 10 is completely stopped after the end of the power generation operation can be shortened. Can do.

B-3. Modification 3:
In the embodiment, the sheet resistance value Rs used in the determination of S130 is the sheet resistance value Rs of the entire fuel cell stack 20, but is the sheet resistance value Rs of a single fuel cell constituting the fuel cell stack 20. There may be. In such a case, as the fuel cell for measuring the impedance, a cell in which the electrolyte membrane easily dries, for example, a cell upstream of scavenging may be selected. In this way, the scavenging operation can be stopped in a state where none of the electrolyte membranes of the respective fuel cells constituting the fuel cell stack 20 is excessively dried.

  Also, the impedance measurement location is not limited to one location, and the impedance of a plurality of fuel cells is measured, and the scavenging operation stop determination is made based on statistical values such as the average value, maximum value, and minimum value. You may go. In this way, the scavenging operation can be stopped with higher accuracy in a state where the electrolyte membrane is not excessively dried.

  Further, since the impedance of the fuel cell stack 20 and the like has temperature dependency, the predetermined value Th2 may be changed according to the temperature T of the fuel cell stack 20 during the scavenging operation. In this way, the scavenging operation can be stopped with higher accuracy in a state where the electrolyte membrane is not excessively dried.

B-4. Modification 4:
In the embodiment, the scavenging operation is performed using a non-humidified inert gas at a temperature lower than the operation temperature of the fuel cell stack 20, but the scavenging operation is not limited to such a form. However, the scavenging operation may be performed by setting the scavenging conditions that can alleviate the drying speed of the electrolyte membrane during the scavenging operation. For example, a humidified inert gas may be used instead of the non-humidified inert gas. Alternatively, the scavenging amount per time may be reduced. Even in this case, the evaporation rate of moisture contained in the electrolyte membrane can be slowed down, and the accuracy of stop control can be improved.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an example, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, the present invention is not limited to the polymer electrolyte fuel cell using hydrogen gas as a fuel shown in the examples, but various fuels using an electrolyte membrane that conducts protons through water, such as a direct methanol fuel cell. It can be applied to batteries.

1 is an explanatory diagram showing a schematic configuration of a fuel cell system 10. FIG. It is a flowchart which shows the procedure of scavenging operation control. It is explanatory drawing which shows the specific example of the relationship between the conditions of scavenging operation and the power generation performance of the fuel cell at the next startup. 4 is an explanatory diagram showing a specific example of a relationship between a scavenging operation condition and a rising speed of the surface resistance value Rs of the fuel cell stack 20. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 20 ... Fuel cell stack 22 ... Temperature sensor 24 ... Impedance meter 30 ... Fuel gas system equipment 31 ... Hydrogen tank 32 ... Shut valve 33 ... Regulator 34, 35, 38 ... Pipe 36 ... Gas-liquid separator 37 ... Circulating pump 39 ... Purge valve 40 ... Oxidizing gas system equipment 41 ... Air cleaner 42 ... Air compressor 43, 45, 47 ... Piping 44 ... Gate valve 46 ... Diluter 50 ... Cooling system equipment 51 ... Radiator 52 ... Circulating pump 54 ... Piping 70 ... Control unit 72 ... Scavenging operation part 74 ... Scavenging stop part 76 ... Output request 77 ... Various actuators 78 ... Various sensors

Claims (8)

A method of operating a fuel cell using an electrolyte membrane that conducts protons through water,
After the fuel cell stops the power generation operation, an inert gas is circulated through the fuel cell in a state where the temperature of the fuel cell is equal to or lower than a predetermined temperature, so that at least one of the moisture remaining in the fuel cell. A scavenging operation step of performing a scavenging operation to remove the part;
A scavenging operation end step of ending the scavenging operation based on a parameter that can estimate a wet state of the electrolyte membrane in the scavenging operation.   2. The fuel cell operating method according to claim 1, wherein the parameter is an internal resistance value of the fuel cell.     The operation method according to claim 1, wherein the inert gas is a gas in a non-humidified state.   The method for operating a fuel cell according to any one of claims 1 to 3, wherein the inert gas is air. A fuel cell system including a fuel cell using an electrolyte membrane that conducts protons through water,
Means for grasping the temperature of the fuel cell;
After the fuel cell stops the power generation operation, in a state where the grasped temperature is equal to or lower than a predetermined temperature, an inert gas is circulated through the fuel cell, and at least a part of moisture remaining in the fuel cell Scavenging operation means for performing scavenging operation to remove
Obtaining means for obtaining a parameter capable of estimating a wet state of the electrolyte membrane in the scavenging operation;
A scavenging operation end means for ending the scavenging operation based on the acquired parameter.   The fuel cell system according to claim 5, wherein the parameter is an internal resistance value of the fuel cell.   The fuel cell system according to claim 5 or 6, wherein the inert gas is a gas in a non-humidified state.   The fuel cell system according to claim 5, wherein the inert gas is air.

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