JP2010135174A - Fuel cell system and operation method of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system and a fuel cell operation method capable of suppressing a decrease in durability of the fuel cell.
A fuel cell system (100) includes a plurality of terminals (21, 22) arranged on both sides of a membrane-electrode assembly (10) and a membrane-electrode assembly for taking out a generated current of the membrane-electrode assembly. , 41, 42) on the outer peripheral portion and a fuel cell (110) having a current collector (20, 40) having conductivity and gas permeability, and a current collector by selecting one of a plurality of terminals Switching means (121, 122) for switching the current collecting position from.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system and a fuel cell operating method.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. Since this fuel cell is excellent in terms of the environment and can realize high energy efficiency, it has been widely developed as a future energy supply system.

  The fuel cell includes, for example, an electrolyte membrane having proton conductivity, a cathode catalyst layer and an anode catalyst layer disposed along the electrolyte membrane, and a separator disposed on the opposite side of each catalyst layer from the electrolyte membrane. Prepare. In such a fuel cell, an oxidant gas is supplied to the cathode catalyst layer, and a fuel gas is supplied to the anode catalyst layer. Thereby, power generation is performed. Patent Document 1 discloses a fuel cell in which electric power is recovered from a current collector through an external output terminal.

JP 2004-031026 A

  The fuel cell disclosed in Patent Document 1 has a structure in which current is taken out from one side of the current collector. In this case, power generation tends to concentrate on the side from which current is extracted. As a result, the current distribution varies, which may reduce the durability of the fuel cell.

  An object of the present invention is to provide a fuel cell system and a fuel cell operation method capable of suppressing a decrease in durability of the fuel cell.

  The fuel cell system according to the present invention has a plurality of terminals arranged on both sides of the membrane-electrode assembly and the membrane-electrode assembly on the outer peripheral portion for taking out the generated current of the membrane-electrode assembly. A fuel cell comprising a current collector and a switching means for switching a current collecting position from the membrane-electrode assembly by selecting one of a plurality of terminals. . In the fuel cell system according to the present invention, current concentration in the surface of the membrane-electrode assembly can be suppressed. As a result, a decrease in the durability of the fuel cell can be suppressed.

  The switching means may switch the current collection position from the current collector regularly or irregularly. In this case, the current concentration region moves regularly or irregularly. Thereby, current concentration in the plane of the membrane-electrode assembly can be suppressed.

  Current distribution detection means for detecting current distribution in the membrane-electrode assembly may be provided, and the switching means may switch the current collection position from the current collector according to the detection result of the current distribution detection means. In this case, current concentration can be suppressed.

  The current distribution detection means may be a temperature detection means for detecting the temperature of the cooling medium flowing in the fuel cell. When the temperature detected by the temperature detection means is equal to or higher than the threshold value, the switching means may select a terminal closer to the oxidant gas inlet than the oxidant gas outlet in the current collector. In this case, current concentration near the oxidant gas outlet is suppressed. Thereby, a decrease in durability of the fuel cell can be suppressed.

  When the temperature detected by the temperature detection means is not more than the threshold value, the switching means may select the terminal closer to the oxidant gas outlet than the oxidant gas inlet in the current collector. In this case, current concentration near the oxidant gas inlet is suppressed. Thereby, a decrease in durability of the fuel cell can be suppressed.

  The current distribution detecting means may be a potential difference detecting means for detecting a potential difference between two points in the plane of the membrane-electrode assembly. The switching means may switch the current collection position from the current collector as long as the potential difference detected by the potential difference detection means is equal to or greater than a threshold value. In this case, current concentration in the surface of the membrane-electrode assembly can be suppressed. A plurality of fuel cells may be stacked.

  A fuel cell operating method according to the present invention comprises a plurality of terminals arranged on both sides of a membrane-electrode assembly and a membrane-electrode assembly on the outer peripheral portion for taking out a power generation current of the membrane-electrode assembly, A fuel cell having a gas permeable current collector includes a switching step of switching a current collecting position from the membrane-electrode assembly by selecting one of a plurality of terminals. is there. In the fuel cell operating method according to the present invention, current concentration in the surface of the membrane-electrode assembly can be suppressed. As a result, a decrease in the durability of the fuel cell can be suppressed.

  In the switching step, the current collecting position from the current collector may be switched regularly or irregularly. In this case, the current concentration region moves regularly or irregularly. Thereby, current concentration in the plane of the membrane-electrode assembly can be suppressed.

  A current distribution detection step for detecting a current distribution in the membrane-electrode assembly may be included, and in the switching step, the current collection position from the current collector may be switched according to the detection result of the current distribution detection step. In this case, current concentration can be suppressed.

  The current distribution detection step may be a temperature detection step of detecting the temperature of the cooling medium flowing in the fuel cell. When the detected temperature in the temperature detection step is equal to or higher than the threshold value, a terminal closer to the oxidant gas inlet than the oxidant gas outlet may be selected in the current collector in the switching step. In this case, current concentration near the oxidant gas outlet is suppressed. Thereby, a decrease in durability of the fuel cell can be suppressed.

  When the detected temperature in the temperature detecting step is equal to or lower than the threshold value, a terminal closer to the cathode gas outlet than the fuel cell cathode gas inlet may be selected in the switching step. In this case, current concentration near the oxidant gas inlet is suppressed. Thereby, a decrease in durability of the fuel cell can be suppressed.

  The current distribution detection step may be a potential difference detection step for detecting a potential difference between two points in the plane of the membrane-electrode assembly. In the switching step, the current collecting position from the current collector may be switched if the potential difference detected in the potential difference detecting step is equal to or greater than a threshold value. In this case, current concentration in the surface of the membrane-electrode assembly can be suppressed. A plurality of fuel cells may be stacked.

  According to the present invention, current concentration in the plane of the membrane-electrode assembly is suppressed. Thereby, a decrease in durability of the fuel cell can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a diagram for explaining a fuel cell system 100 according to the first embodiment. FIG. 1A is a schematic diagram showing the overall configuration of the fuel cell system 100. FIG. 1B is a plan view of current collectors 20 and 40 to be described later.

  As shown in FIG. 1A, the fuel cell system 100 includes a fuel cell 110, changeover switches 121 and 122, fuel gas supply means 130, oxidant gas supply means 140, and control means 150. The fuel cell 110 is depicted in a schematic cross-sectional view in FIG. The fuel cell 110 has a structure in which the current collector 20 and the separator 30 are stacked on one surface of the membrane-electrode assembly 10 and the current collector 40 and the separator 50 are stacked on the other surface.

  The membrane-electrode assembly 10 has a structure in which the anode catalyst layer 12 is joined to the current collector 20 side of the electrolyte membrane 11 and the cathode catalyst layer 13 is joined to the current collector 40 side of the electrolyte membrane 11. For example, a solid polymer electrolyte having proton conductivity can be used as the electrolyte membrane 11. The anode catalyst layer 12 and the cathode catalyst layer 13 are made of a conductive material containing a catalyst. The catalyst of the anode catalyst layer 12 promotes protonation of hydrogen. The catalyst of the cathode catalyst layer 13 promotes the reaction between protons and oxygen. As the anode catalyst layer 12 and the cathode catalyst layer 13, for example, platinum-supported carbon can be used.

  The current collector 20 is disposed along the anode catalyst layer 12. At least a part of the current collector 20 may be embedded in the anode catalyst layer 12. As shown in FIG. 1B, terminals 21 and 22 for taking out a generated current from the membrane-electrode assembly 10 without using the separator 30 are provided on the outer peripheral portion of the current collector 20. For example, the terminals 21 and 22 are disposed at positions facing each other along the flow direction of the oxidant gas. The terminals 21 and 22 are provided outside the separator 30.

  The current collector 40 is disposed along the cathode catalyst layer 13. At least a part of the current collector 40 may be embedded in the cathode catalyst layer 13. As shown in FIG. 1B, terminals 41 and 42 for taking out a generated current from the membrane-electrode assembly 10 without using the separator 50 are provided on the outer periphery of the current collector 40. For example, the terminals 41 and 42 are arranged at positions facing each other along the flow direction of the oxidant gas. The terminals 41 and 42 are provided outside the separator 50. In this embodiment, the terminals 21 and 41 are disposed on the oxidant gas inlet side, and the terminals 22 and 42 are disposed on the oxidant gas outlet side.

  The current collectors 20 and 40 are made of a conductive material having gas permeability in the thickness direction. For example, the current collectors 20 and 40 are made of a porous conductive material. As the current collectors 20 and 40, for example, a metal mesh, a metal foam sintered body, an expanded metal, a carbon fiber, a carbon sintered body, or the like is used.

  Separator 30,50 has a contact part which protrudes and contacts with membrane-electrode assembly 10 in an outer peripheral part. Thereby, a space 31 for fuel gas flow is defined between the separator 30 and the membrane-electrode assembly 10. A space 51 for flowing an oxidant gas is defined between the separator 50 and the membrane-electrode assembly 10. In addition, the separators 30 and 50 may have a contact portion that contacts the membrane-electrode assembly 10 in addition to the outer peripheral portion as long as the flow of the reaction gas is not hindered. However, in consideration of the diffusibility of the reaction gas into the membrane-electrode assembly 10, it is preferable that a reaction gas flow space is formed over the entire surface or almost the entire surface of the membrane-electrode assembly 10.

  The fuel gas supply means 130 is means for supplying a fuel gas containing hydrogen to the space 31 for flowing the fuel gas. The fuel gas supply means 130 is, for example, a hydrogen tank. The oxidant gas supply means 140 is a means for supplying an oxidant gas containing oxygen to the space 51 for flowing the oxidant gas. The oxidant gas supply means 140 is, for example, an air pump. The control means 150 includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory) and the like.

  Next, an outline of the operation of the fuel cell system 100 will be described. The fuel gas supply means 130 supplies fuel gas to the space portion 31 in accordance with an instruction from the control means 150. The fuel gas supplied to the space 31 passes through the current collector 20 and diffuses into the anode catalyst layer 12. In the anode catalyst layer 12, hydrogen in the fuel gas is separated into protons and electrons. Protons are conducted through the electrolyte membrane 11 and reach the cathode catalyst layer 13. The electrons are collected by the current collector 20 and supplied to the load via the terminal 21 or terminal 22, and then reach the current collector 40 via the terminal 41 or terminal 42.

  The oxidant gas supply unit 140 supplies the oxidant gas to the space 51 in accordance with an instruction from the control unit 150. The oxidant gas supplied to the space 51 passes through the current collector 40 and diffuses into the cathode catalyst layer 13. In the cathode catalyst layer 13, water is generated from oxygen in the oxidant gas, protons conducted through the electrolyte membrane 11, and electrons supplied from the load to the terminal 41 or the terminal 42. Through the above process, the fuel cell 110 generates power.

  The change-over switches 121 and 122 switch between a circuit that connects the terminal 21 and the terminal 41 via a load and a circuit that connects the terminal 22 and the terminal 42 via a load in accordance with an instruction from the control unit 150.

  In the fuel cell 110 according to the present embodiment, the current is collected through the terminals 21, 22, 41, and 42, so that the separators 30 and 50 do not require conductivity. Thereby, as the separators 30 and 50, a material that is lighter and lower in cost than a conductive member such as metal may be used. For example, by using a resin, the separators 30 and 50 can be reduced in weight and cost, and the separators 30 and 50 can have corrosion resistance.

  Further, since the contact between the separators 30 and 50 for current collection and the membrane-electrode assembly 10 is not necessary, the electrical connection between the separators 30 and 50 and the membrane-electrode assembly 10 such as a groove channel is made. A contact part is unnecessary. Thereby, the pressure loss when the reaction gas flows through the reaction gas flow path is reduced. As a result, the power generation performance of the fuel cell 110 is improved.

  In the fuel cell 110, good power generation is performed in a region near the current collecting position, and power generation is suppressed in a region far from the current collecting position due to the resistance of the current collector. For example, when current is collected at the terminals 21 and 41, power generation is better in a region closer to the terminals 21 and 41 than in other regions. In this case, current concentration occurs in the plane of the membrane-electrode assembly 10.

  Therefore, in the present embodiment, the occurrence of current concentration is suppressed by switching the current collecting position regularly or irregularly. For example, the control unit 150 controls the changeover switches 121 and 122 to switch the circuit via the terminals 21 and 41 and the circuit via the terminals 22 and 42 regularly or irregularly. In this case, the current collection position from the membrane-electrode assembly 10 is switched. Thereby, current concentration in the surface of the membrane-electrode assembly 10 can be suppressed. As a result, the durability of the fuel cell 110 is improved.

  In addition, when a current collection position switches regularly, the drying in the membrane-electrode assembly 10 is suppressed. In this case, the generated current in the surface of the membrane-electrode assembly 10 is substantially proportional to the oxygen partial pressure on the cathode side. In addition, the generated current may be biased due to the electrical resistance of the current collector 40. Therefore, the current collection switching time may be determined in consideration of these two effects. For example, if the power generation current in the region near the oxidant gas inlet is twice the power generation current in the region near the oxidant gas outlet, the current collection time from the terminals 22 and 42 is calculated at a time ratio of 2: 1. The current collection time from 21 and 41 may be longer.

  FIG. 2 is a diagram illustrating an example of a flowchart for periodically switching the current collection position. As shown in FIG. 2, the control means 150 controls the fuel gas supply means 130 and the oxidant gas supply means 140 so that the reaction gas is supplied to the fuel cell 110 (step S1). Next, the control means 150 controls the changeover switches 121 and 122 so that current is collected via the terminals 21 and 41 or the terminals 22 and 42 (step S2). Thereby, power generation is started.

  Next, the control means 150 determines whether or not a predetermined time has elapsed (step S3). If it is not determined in step S3 that the predetermined time has elapsed, the control unit 150 executes step S3 again. When it is determined in step S3 that the predetermined time has elapsed, the control unit 150 controls the changeover switches 121 and 122 so that the current collecting position is switched (step S4). Thereafter, the control means 150 executes Step S3 again.

  According to the flowchart of FIG. 2, the current collection position from the membrane-electrode assembly 10 is periodically switched. Thereby, current concentration in the membrane-electrode assembly 10 is suppressed. As a result, the durability of the fuel cell 110 is improved. In addition, when switching a current collection position irregularly, you may set the predetermined time in step S3 at random. In this embodiment, the selector switches 121 and 122 and the control unit 150 function as a switching unit.

  FIG. 3A is a schematic diagram for explaining the overall configuration of the fuel cell system 100a according to the second embodiment. The fuel cell system 100a is different from the fuel cell system 100 of FIG. 1 in that a cooling water pump 160 and a temperature sensor 161 are further provided. The cooling water pump 160 is a pump that supplies cooling water to the cooling water flow path in the fuel cell 110 in accordance with an instruction from the control means 150. The temperature sensor 161 is a sensor that detects the temperature of the cooling water after flowing in the fuel cell 110, and gives the detection result to the control means 150. In the present embodiment, the temperature of the fuel cell 110 can be indirectly acquired according to the detection result of the temperature sensor 161.

  FIG. 3B is a diagram showing a water balance in the fuel cell 110. In FIG. 3B, the horizontal axis represents the temperature of the fuel cell 110, and the vertical axis represents the water balance. Here, the water balance is an amount obtained by subtracting the amount of water discharged from the oxidant gas outlet from the amount of generated water generated by power generation in the fuel cell 110.

  When the temperature of the fuel cell 110 is low (temperature range A in FIG. 3B), the generated water generated by the power generation exists almost in a liquid state. In this case, the generated water stays at the oxidant gas outlet in the space 51 for flowing the oxidant gas. As a result, the generated current concentrates in a region other than the oxidant gas outlet. In addition, the water balance is positive. When the temperature of the fuel cell 110 increases (temperature range B in FIG. 3B), the generated water is mixed in a liquid and gas state. In this case, the water balance gradually decreases.

  Further, when the temperature of the fuel cell 110 becomes higher (temperature range C in FIG. 3B), the generated water exists almost in a gaseous state. In this case, the amount of water discharged from the fuel cell 110 increases. Thereby, the area near the oxidant gas inlet is dried. As a result, power generation concentrates in a region other than the oxidant gas inlet. In addition, the water balance is negative. As described above, the current distribution can be detected from the temperature of the fuel cell 110. The temperature ranges A to C can be acquired by causing the fuel cell 110 to generate power in advance.

  In the present embodiment, when the temperature T detected by the temperature sensor 161 is in the temperature range A, the control unit 150 controls the change-over switches 121 and 122 so that current is collected from the terminals 22 and 42. In this case, current concentration on the oxidant gas inlet side can be suppressed. In addition, when the temperature T is in the temperature range B, the control unit 150 controls the change-over switches 121 and 122 so that the current collection position is switched regularly or irregularly.

  Furthermore, when the temperature T is in the temperature range C, the control unit 150 controls the changeover switches 121 and 122 so that current is collected from the terminals 21 and 41. In this case, current concentration on the oxidant gas outlet side is suppressed. Thereby, power generation deterioration in a region near the oxidant gas inlet can be suppressed. With the above control, the current collection position can be switched according to the current distribution in the plane of the membrane-electrode assembly 10. As a result, the durability of the fuel cell 110 is improved.

FIG. 4 is a diagram illustrating an example of a flowchart in the case where the current collecting position is switched according to the temperature of the fuel cell 110. The flowchart of FIG. 4 is executed when power generation is performed in the fuel cell 110. As shown in FIG. 4, the control means 150, the temperature T of the temperature sensor 161 detects and determines whether temperature _{T 1} of less than (step S11). In this case, it is determined whether or not the temperature T is in the temperature range A.

If the temperature T in step S11 is determined to be smaller than the temperature _{T 1,} the control unit 150, as will be the current collector from the terminal 22 and 42, controls the selector switch 121 and 122 (step S12). Thereby, the current collection position is switched to the oxidant gas outlet side. Thereafter, the control unit 150 ends the execution of the flowchart.

If the temperature T in step S11 is not determined to be smaller than the temperature _{T 1} of, control unit 150 determines whether or not the temperature T is a temperature above _{T 1} and temperature _{T 2} below (step S13). In this case, it is determined whether or not the temperature T is in the temperature range B. If the temperature T is determined to be a temperature above _{T 1} and temperature _{T 2} less in step S13, the control means 150, current collecting position controls the selector switch 121 to switch to periodically (step S14) . Thereafter, the control unit 150 ends the execution of the flowchart.

If the temperature T is not determined to be the temperature T1 or higher and temperature _{T 2} less in step S13, the control unit 150, as will be the current collector from the terminal 21, 41, controls the selector switch 121 (step S15). Thereby, the current collecting position is switched to the oxidant gas inlet side. Thereafter, the control unit 150 ends the execution of the flowchart.

  According to the flowchart of FIG. 4, the current collection position can be switched according to the current distribution in the plane of the membrane-electrode assembly 10. Thereby, current concentration in the membrane-electrode assembly 10 is suppressed. As a result, the durability of the fuel cell 110 is improved. In addition, in the present Example, although the temperature range B was provided, it is not restricted to it. You may switch a current collection position between a high temperature range and a low temperature range. In this embodiment, the selector switches 121 and 122 and the control unit 150 function as a switching unit.

  FIG. 5 is a schematic diagram for explaining the overall configuration of the fuel cell system 100b according to the third embodiment. The fuel cell system 100b is different from the fuel cell system 100 of FIG. 1 in that a voltage sensor 162 is further provided. The voltage sensor 162 is a sensor that detects an in-plane potential difference of the membrane-electrode assembly 10. In the present embodiment, the voltage sensor 162 detects a potential difference between the region on the terminal 21 side and the region on the terminal 22 side in the current collector 20 and gives the detection result to the control means 150.

  Here, if no current distribution is generated in the plane of the membrane-electrode assembly 10, the potential difference V detected by the voltage sensor 162 is small. However, if a current distribution occurs in the direction between the terminals 21 and 22, the potential difference V increases. In this embodiment, when the potential difference V exceeds a threshold value, the current collecting position is switched. In this case, the current collection position can be switched according to the current distribution in the plane of the membrane-electrode assembly 10. Thereby, current concentration in the surface of the membrane-electrode assembly 10 is suppressed. As a result, the durability of the fuel cell 110 is improved.

  Note that the potential difference may be detected in either the current collector 20 or the current collector 40.

  FIG. 6 is a diagram illustrating an example of a flowchart in the case where the current collecting position is switched according to the magnitude of the potential difference V. The flowchart of FIG. 6 is executed when power generation is performed in the fuel cell 110. As shown in FIG. 6, the control means 150 determines whether or not the absolute value | V | of the potential difference V detected by the voltage sensor 162 exceeds a threshold value (step S21).

  When it is determined in step S21 that the absolute value | V | has exceeded the threshold value, the control unit 150 controls the changeover switches 121 and 122 so that the current collection position is switched (step S22). Thereafter, the control unit 150 ends the execution of the flowchart. Even when it is not determined in step S21 that the absolute value | V | exceeds the threshold value, the control unit 150 ends the execution of the flowchart.

  According to the flowchart of FIG. 6, the current collection position can be switched according to the current distribution in the plane of the membrane-electrode assembly 10. Thereby, current concentration in the membrane-electrode assembly 10 is suppressed. As a result, the durability of the fuel cell 110 is improved. In this embodiment, the selector switches 121 and 122 and the control unit 150 function as a switching unit.

  In the above flowchart, the current collection position is switched based on the absolute value of the potential difference, but the present invention is not limited to this. For example, even if the absolute value of the potential difference increases, the current concentration may further increase by switching the current collecting position. Therefore, the selector switches 121 and 122 may be controlled so that the potential difference detected by the voltage sensor 162 is alleviated. In this case, current concentration in the membrane-electrode assembly 10 can be more effectively suppressed.

  FIG. 7 is a diagram for explaining the fuel cell system 100c according to the fourth embodiment. FIG. 7A is a schematic diagram showing the overall configuration of the fuel cell system 100c. As shown in FIG. 7A, in the fuel cell system 100c, a fuel cell stack is provided instead of the fuel cell 110. In the fuel cell stack, a plurality of fuel cells 110 in FIG. 1 are stacked.

  In the fuel cell stack, a bus bar 201 that connects the terminals 21 and 41 of each fuel cell 110 and a bus bar 202 that connects the terminals 22 and 42 of each fuel cell 110 are provided. The bus bar 201 connects the terminal 21 and the terminal 41 between the adjacent fuel cells 110, and includes a changeover switch 203 between the terminal 21 and the terminal 41. The bus bar 202 connects the terminal 22 and the terminal 42 between the adjacent fuel cells 110, and includes a changeover switch 204 between the terminal 22 and the terminal 42.

  FIG. 7B shows a schematic diagram of the bus bar 201. In the bus bar 201, the connection part that connects the terminal 21 and the terminal 41 has conductivity, and the connection part has insulation. Thereby, a short circuit in the fuel cell stack is prevented. Similarly, in the bus bar 202, the connection part that connects the terminal 22 and the terminal 42 has conductivity, and the connection part has insulation.

  For example, the control unit 150 switches the change-over switches 121, 122, 203, and 204 so that the circuit that connects the terminal 21 and the terminal 41 and the circuit that connects the terminal 22 and the terminal 42 are switched regularly or irregularly. To control. In this case, current concentration in each membrane-electrode assembly 10 is suppressed. As a result, the durability of each fuel cell 110 is improved. In addition, the control means 150 may switch a current collection position according to the coolant temperature as in the second embodiment. Furthermore, the control means 150 may switch the current collection position according to the potential difference in the plane of the membrane-electrode assembly 10 as in the third embodiment.

  Moreover, in each fuel cell 110, ON / OFF of the changeover switches 203 and 204 may be individually controlled. Therefore, in the bus bar 201, the changeover switch 203 controlled to be on and the changeover switch 203 controlled to be off may be mixed. In the present embodiment, the change-over switches 121, 122, 203, 204 and the control means 150 function as the switching means.

  In each of the above-described embodiments, a description has been given of the control for providing a plurality of current collecting positions and generating power while switching the current collecting positions. Here, when a plurality of current collecting positions are provided, it is conceivable to always collect current from a plurality of current collecting positions without switching the current collecting positions. However, in power generation by a fuel cell, the power generation distribution changes depending on operating conditions such as temperature, and the current concentration changes. Therefore, control according to the current concentration situation is required. By providing the means for switching the current collecting position as in the above embodiments, it is possible to control in consideration of the actual power generation distribution.

1 is a diagram for explaining a fuel cell system according to Embodiment 1. FIG. It is a figure which shows an example of the flowchart in the case of switching a current collection position regularly. 6 is a diagram for explaining a fuel cell system according to Embodiment 2. FIG. It is a figure which shows an example of the flowchart in the case of switching a current collection position according to the temperature of a fuel cell. FIG. 6 is a schematic diagram for explaining an overall configuration of a fuel cell system according to Example 3. It is a figure which shows an example of the flowchart in the case of switching a current collection position according to the magnitude | size of the electric potential difference V. FIG. FIG. 6 is a schematic diagram showing an overall configuration of a fuel cell system according to Example 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Membrane-electrode assembly 11 Electrolyte membrane 12 Anode catalyst layer 13 Cathode catalyst layer 20 Current collector 21, 22 Terminal 30 Separator 31 Space 40 Current collector 41, 42 Terminal 50 Separator 51 Space 100 Fuel cell system 110 Fuel cell 121, 122 changeover switch 130 fuel gas supply means 140 oxidant gas supply means 150 control means 160 cooling water pump 161 temperature sensor 162 voltage sensor 201, 202 bus bar

Claims (18)

Membrane-electrode assembly, and a current collector having a plurality of terminals arranged on both sides of the membrane-electrode assembly for taking out the generated current of the membrane-electrode assembly on the outer periphery and having conductivity and gas permeability A fuel cell comprising:
A fuel cell system comprising: switching means for switching a current collecting position from the current collector by selecting one of the plurality of terminals.   2. The fuel cell system according to claim 1, wherein the switching unit switches a current collection position from the current collector at regular or irregular intervals. A current distribution detecting means for detecting a current distribution in the membrane-electrode assembly;
2. The fuel cell system according to claim 1, wherein the switching unit switches a current collection position from the current collector according to a detection result of the current distribution detection unit.   4. The fuel cell system according to claim 3, wherein the current distribution detection means is temperature detection means for detecting a temperature of a cooling medium flowing in the fuel cell.   The switching unit selects the terminal closer to the oxidant gas inlet than the oxidant gas outlet in the current collector when the temperature detected by the temperature detection unit is equal to or higher than a threshold value. 5. The fuel cell system according to 4.   The switching unit selects the terminal closer to the oxidant gas outlet than the oxidant gas inlet in the current collector when the temperature detected by the temperature detection unit is equal to or lower than a threshold value. 5. The fuel cell system according to 4.   4. The fuel cell system according to claim 3, wherein the current distribution detecting means is a potential difference detecting means for detecting a potential difference between two points in a plane of the membrane-electrode assembly.   8. The fuel cell system according to claim 7, wherein the switching means switches the current collecting position from the current collector when the potential difference detected by the potential difference detecting means is equal to or greater than a threshold value.   The fuel cell system according to claim 1, wherein a plurality of the fuel cells are stacked.   A membrane-electrode assembly, and a current collector having a plurality of terminals arranged on both sides of the membrane-electrode assembly for taking out the generated current of the membrane-electrode assembly on the outer periphery and having conductivity and gas permeability And a switching step of switching a current collecting position from the current collector by selecting one of the plurality of terminals.   The method for operating a fuel cell according to claim 10, wherein in the switching step, the current collecting position from the current collector is switched regularly or irregularly. A current distribution detecting step of detecting a current distribution in the membrane-electrode assembly,
The fuel cell operating method according to claim 10, wherein, in the switching step, a current collecting position from the current collector is switched in accordance with a detection result of the current distribution detecting step.   13. The fuel cell operating method according to claim 12, wherein the current distribution detecting step is a temperature detecting step of detecting a temperature of a cooling medium flowing in the fuel cell.   The terminal is selected in the current collector closer to the oxidant gas inlet than the oxidant gas outlet in the switching step when the detected temperature in the temperature detection step is equal to or higher than a threshold value. 14. A method for operating a fuel cell according to item 13.   The terminal selected in the current collector is closer to the oxidant gas outlet than the oxidant gas inlet in the switching step when the detected temperature in the temperature detection step is equal to or lower than a threshold value. 14. A method for operating a fuel cell according to item 13.   13. The fuel cell operating method according to claim 12, wherein the current distribution detecting step is a potential difference detecting step of detecting a potential difference between two points in a plane of the membrane-electrode assembly.   The method of operating a fuel cell according to claim 16, wherein, in the switching step, the current collecting position from the current collector is switched if the potential difference detected in the potential difference detecting step is equal to or greater than a threshold value.   The fuel cell operating method according to claim 10, wherein a plurality of the fuel cells are stacked.

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