JP2007227162A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which prevents the freeze of generated water without a large decline in the efficiency of the fuel cell system. <P>SOLUTION: The fuel cell system includes a fuel cell stack consisting of a plurality of laminated cells among which a cell with a high voltage loss is located at an end of the lamination, and a controlling means that when the cells have a temperature equal to or lower than a prescribed temperature, reduces the amount of a fuel gas supplied to the fuel cell stack to an amount smaller than an amount of the gas that is supplied when the cells have a temperature exceeding the prescribed temperature. This encourages water electrolysis at the end cell that is easy to freeze, thus prevents the freeze of generated water without a large decline in the efficiency of the fuel cell system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  The cell constituting the fuel cell stack has a structure in which an anode and a cathode are arranged with an electrolyte membrane interposed therebetween. When a reactive gas is supplied to each electrode, an electrochemical reaction occurs between the electrodes to generate an electromotive force. Specifically, the reaction occurs when hydrogen (fuel gas) is in contact with the anode and oxygen (oxidant gas) is in contact with the cathode.

  In general, in a fuel cell system, fuel gas supplied from a high-pressure hydrogen tank is supplied to the anode of the fuel cell, while air taken in from outside air by a compressor is supplied to the cathode.

Further, the fuel cell system includes a humidifier in order to make the electrolyte membrane in a wet state. As a result, water is replenished to the electrolyte membrane to facilitate the movement of H ⁺ from the anode side.

  The above will be described in more detail as follows.

At the anode,
H ₂ → 2H ⁺ + 2e ⁻
H ⁺ produced by this reaction becomes H ₃ O ⁺ and moves through the electrolyte membrane, and then (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O at the cathode.
The reaction of

That is, between both electrodes,
H ₂ + (1/2) O ₂ → H ₂ O
An electromotive force is generated by the occurrence of the electrochemical reaction. At this time, water is generated on the cathode side.

  However, in such a fuel cell system, when the fuel cell is started in a low-temperature environment, the generated water freezes, thereby inhibiting the reaction between hydrogen and oxygen and lowering the output voltage of the fuel cell. There was a problem. In addition, there has been a problem that physical destruction occurs in a membrane-electrode-gas diffusion layer assembly (MEGA) due to freezing of water.

  On the other hand, a fuel cell system provided with power supply means for supplying power capable of electrolyzing water has been proposed (see Patent Document 1). According to this fuel cell system, since water is gasified and removed by electrolysis, the reaction between hydrogen and oxygen is prevented and the fuel cell can be started even in a low temperature environment.

JP 2005-50749 A JP 2004-22503 A JP-A-6-310161 JP 2003-197240 A JP 2004-311348 A

  The fuel cell system described in Patent Document 1 has a motor connected to the fuel cell and driven by electric power. The power supply means has a battery connected to the motor and the fuel cell to store electromotive force. And while supplying electric power from a battery to a motor, the high voltage is applied to a fuel cell from a battery, and the water produced | generated with the electric power generation is electrolyzed.

  Thus, in the fuel cell system described in Patent Document 1, power is consumed by the battery to cause electrolysis. Therefore, when power is not supplied from the battery to the fuel cell, charging from the fuel cell to the battery is required. For this reason, the efficiency of the fuel cell system may be greatly reduced.

  The present invention has been made in view of these problems. That is, an object of the present invention is to provide a fuel cell system that can prevent the generated water from freezing without greatly reducing the efficiency of the fuel cell system.

  Other objects and advantages of the present invention will become apparent from the following description.

A first fuel cell system of the present invention includes a fuel cell stack in which a plurality of cells are stacked, and an end cell in the stacking direction is a cell having a higher pressure loss than a central cell,
Control means for reducing the amount of fuel gas supplied to the fuel cell stack when the cell is below a predetermined temperature compared to when the cell is higher than the predetermined temperature. .
In this case, it is preferable that at least a part of the cells are arranged so that the pressure loss gradually increases toward the end.

A second fuel cell system of the present invention includes a fuel cell stack in which a plurality of cells are stacked,
A supply manifold for supplying fuel gas to the fuel cell stack;
A discharge manifold for discharging fuel off-gas discharged from the fuel cell stack,
The supply manifold includes a first supply manifold portion for supplying fuel gas to one end of the fuel cell stack and cells arranged in the vicinity thereof, and a second supply manifold portion for supplying fuel gas to other cells. The first supply manifold portion is shut off when the fuel cell stack is generating power and the cell is at a predetermined temperature or lower.

A third fuel cell system of the present invention includes a fuel cell stack in which a plurality of cells are stacked,
A supply manifold for supplying fuel gas to the fuel cell stack;
A discharge manifold for discharging fuel off-gas discharged from the fuel cell stack,
The supply manifold is arranged at one end of the fuel cell stack and a first supply manifold portion for supplying fuel gas to cells arranged in the vicinity thereof, and at the other end of the fuel cell stack and in the vicinity thereof. A second supply manifold portion for supplying fuel gas to the cells and a third supply manifold portion for supplying fuel gas to the other cells; When the temperature is equal to or lower than a predetermined temperature, the first supply manifold portion and the second supply manifold portion are shut off.

  In the second and third fuel cell systems of the present invention, when the cell is below the predetermined temperature, the amount of fuel gas supplied to the fuel cell stack is compared with that when the cell is higher than the predetermined temperature. It is preferable to further have a control means for reducing the number of control means.

  In the first, second and third fuel cell systems of the present invention, the predetermined temperature may be 0 ° C.

  According to the first fuel cell system of the present invention, when a cell with high pressure loss is located at the end of the fuel cell stack, and when the cell is below a predetermined temperature, the amount of fuel gas supplied to the fuel cell stack is Since the number of the cells is smaller than when the temperature is higher than the predetermined temperature, the electrolysis of water in the cell at the end that is easily frozen can be promoted. As a result, it is possible to prevent the generated water from freezing without greatly reducing the efficiency of the fuel cell system.

  According to the second fuel cell system of the present invention, when the cell is at a predetermined temperature or lower, the first supply manifold portion for supplying the fuel gas to one end portion of the fuel cell stack and the cells arranged in the vicinity thereof is provided. Since it interrupts | blocks, the electrolysis of the water in the cell of the edge part which is easy to freeze can be promoted. As a result, it is possible to prevent the generated water from freezing without greatly reducing the efficiency of the fuel cell system.

  According to the third fuel cell system of the present invention, when the cell is at a predetermined temperature or lower, the first supply manifold portion for supplying the fuel gas to the both ends of the fuel cell stack and the cells arranged in the vicinity thereof, and Since the two supply manifold portions are cut off, it is possible to promote electrolysis of water in the cells at both ends that are easily frozen. As a result, it is possible to prevent the generated water from freezing without greatly reducing the efficiency of the fuel cell system.

Embodiment 1 FIG.
FIG. 1 is a schematic cross-sectional view of cells constituting a fuel cell stack. As shown in this figure, a cell 1 is composed of a membrane-electrode-gas diffusion layer assembly (MEGA) 2 and separators 3 and 4 in which a reaction gas flow path is formed. Become. The membrane-electrode-gas diffusion layer assembly 2 is provided on an electrolyte membrane 5 made of an ion exchange resin, an anode 6 made of a catalyst layer provided on one surface of the electrolyte membrane 5, and the other surface of the electrolyte membrane 5. The cathode 7 is formed of a catalyst layer, and gas diffusion layers 8 and 9 are provided on the anode side and the cathode side, respectively. The separators 3 and 4 are provided on the anode side and the cathode side via the gas diffusion layers 8 and 9, respectively.

As described above, in the fuel cell, H ₂ + (1/2) O ₂ → H ₂ O between the hydrogen supplied to the anode 6 and the oxygen supplied to the cathode 7.
An electromotive force is generated by the occurrence of this reaction.

  The fuel gas supplied to the anode 6 may be hydrogen gas itself, or may be hydrogen-rich reformed gas generated by a reforming reaction of a hydrocarbon compound. On the other hand, the oxidant gas supplied to the cathode 7 can be air taken in from the outside air by a compressor (not shown).

  When the fuel cell system is started in a low temperature environment, the water generated at the cathode 7 may freeze. In order to remove this water, it is preferable that the amount of fuel gas supplied to the fuel cell stack is reduced by the control means when the cell is below a predetermined temperature compared to when the cell is higher than the predetermined temperature. In other words, when starting the fuel cell system in a low temperature environment, the amount of fuel gas supplied to the fuel cell stack is made smaller than the amount of fuel gas supplied during normal operation, so that the anode has run out of hydrogen. It is good to be in a state. In this case, whether or not it is during normal operation can be determined from the temperature of the cell. For example, when the temperature of the cell is below freezing point, that is, 0 ° C. or lower, water freezes in the cell, so that the anode is depleted of hydrogen. On the other hand, when the temperature of the cell is higher than the freezing point, it is determined that the operation is normal, and a necessary amount of fuel gas is supplied.

  In the example of FIG. 1, the anode 6 is depleted in a state where oxygen is sufficiently present in the cathode 7. If the amount of hydrogen supplied to the anode 6 is reduced, the water in the cathode 7 moves to the anode 6 through the electrolyte membrane 5 to compensate for the shortage of hydrogen, and the electrolysis of water proceeds at the anode 6. Therefore, according to this method, electrolysis of water can proceed without requiring an external power source such as a battery.

  Incidentally, in general, the anode and the cathode are made of a carbon material. When the anode is deficient in hydrogen at room temperature, there is a risk that corrosion will occur at the anode or cathode due to the reaction of carbon and water. However, this embodiment has a problem of freezing water at a low temperature, specifically below freezing point. Therefore, the hydrogen deficiency may be performed at a low temperature and does not need to be performed at room temperature. Since the reaction between carbon and water is suppressed at a low temperature, it is considered that there is almost no possibility that the electrode corrodes due to this reaction in the present embodiment. Furthermore, it is possible to further reduce the deterioration of the electrode by using an electrode material that is less likely to react with water or using a water electrocatalyst.

Specifically, the hydrogen deficient state can be realized by reducing the stoichiometric ratio. Here, the stoichiometric ratio refers to a ratio (Q _H0 / Q _H1 ) between the amount of hydrogen (Q _H0 ) supplied to the fuel cell and the amount of hydrogen (Q _H1 ) consumed by the fuel cell. When the stoichiometric ratio is reduced, the amount of hydrogen supplied to the fuel cell is reduced, so that the anode can be in a hydrogen deficient state.

  FIG. 2 is a flowchart showing the operation method of the fuel cell system in the present embodiment.

  In the present embodiment, a temperature is monitored by providing a thermocouple or the like in the fuel cell system. If the temperature is below freezing, the process proceeds to step 1 in FIG. 1 so that the stoichiometric ratio is lower than that during normal operation. Specifically, the stoichiometric ratio according to the generated power required for the fuel cell is set in accordance with the stoichiometric ratio map in the low-temperature mode prepared in advance. The water freezing is a problem mainly when the fuel cell is started in a low temperature environment. Therefore, in a low temperature environment, it can be paraphrased that the fuel cell is started by reducing the stoichiometric ratio.

  On the other hand, when the temperature is higher than the freezing point, the process proceeds to step 2 in FIG. 1 to obtain the stoichiometric ratio during normal operation. Also in this case, the stoichiometric ratio according to the generated power required for the fuel cell is set in accordance with the stoichiometric ratio map in the normal mode prepared in advance.

  The location where the temperature is monitored is preferably in the vicinity of the membrane-electrode-gas diffusion layer assembly. Further, when a membrane-electrode assembly (MEA) is used, it is preferable to set the vicinity. However, the present invention is not limited to these, and monitors the temperature of the gas in the cell and the temperature of the cooling water circulating in the fuel cell system, and estimates the temperature in the cell from these temperatures. May be.

  By the way, the fuel cell stack has a structure in which a plurality of cells are stacked. The amount of hydrogen supplied to each cell varies. For example, in a cell where water remains in the interior, the pressure loss is high, so that it is difficult for hydrogen to enter the interior. Further, even when nitrogen contained in the air supplied to the cathode moves to the anode side through the electrolyte membrane and stays therein, it is difficult for hydrogen to enter the inside.

  Such cells that are difficult for hydrogen to enter can be found in the cells arranged at the end of the fuel cell stack. On the other hand, the cells arranged at the ends are more likely to freeze at low temperatures. If the stoichiometric ratio is reduced, the amount of hydrogen supplied to each cell is generally reduced, but the cells arranged at the end are originally cells that are difficult for hydrogen to enter, so the amount of hydrogen supplied is particularly reduced. Therefore, only by reducing the stoichiometric ratio, a cell that is prone to freezing can be made deficient in hydrogen. As a result, the electrolysis of water is particularly promoted in the cells that are easily frozen, and it is possible to effectively suppress freezing in the fuel cell stack.

  Further, the amount of hydrogen supplied to the cell varies depending on the difference in the cell structure. However, the “difference in cell structure” mentioned here refers to a difference in the range allowed as a non-defective product, which occurs in the manufacturing process of the cell, and does not include a difference provided intentionally. Further, the difference in cell structure is reflected in the cell pressure loss.

  Therefore, the present embodiment is characterized in that cells with high pressure loss are arranged in advance at the positions of the cells that are likely to freeze. For example, it arrange | positions so that a cell with a high pressure loss may be located in an order from the edge part of a fuel cell stack. Further, at least a part of the cells may be arranged so that the pressure loss gradually increases toward the end. By doing so, when the stoichiometric ratio is reduced, the end cell is more likely to be deficient in hydrogen. Therefore, it is possible to further promote the electrolysis of water in the cell that is likely to freeze.

  By the way, when the amount of hydrogen supplied to the cell decreases, the generated voltage decreases. If the stoichiometric ratio is reduced and the voltage of all the cells becomes negative, the fuel cell cannot be started. Therefore, it is preferable to monitor the cell voltage and adjust the stoichiometric ratio so that the cell as a whole becomes positive even if the voltage of the cell located at the end of the fuel cell stack becomes negative.

  In addition, the above-described variation in the amount of hydrogen supplied to each cell is also seen on the cathode side. That is, in the cell in which the water generated at the cathode remains, the pressure loss is high, so that it is difficult for air to enter the inside. Further, when nitrogen in the air stays in the cell, it becomes difficult for air to enter. For this reason, oxygen necessary for the cathode is not supplied, and oxygen deficiency is likely to occur at the cathode. Therefore, if the stoichiometric ratio is reduced and the anode is deficient in hydrogen, the reaction gas may be insufficient at both electrodes.

Therefore, in this embodiment, the voltage of the entire cell is monitored, and power generation is stopped when the voltage becomes lower than a predetermined value. For example, when the current density is 0.1 A / cm ² , power generation can be stopped when the voltage becomes lower than −2.1V.

  Further, in the present embodiment, the voltage of each cell is individually monitored, and the voltage is lower than the predetermined value by means such as taking out the current from the fuel cell stack by bypassing the cell whose voltage is lower than the predetermined value. You may make it stop electric power generation only about the cell which became.

  As described above, freezing of water can be prevented by reducing the stoichiometric ratio and promoting electrolysis of water. Moreover, if this state is continued, the temperature of the fuel cell stack gradually increases. This is because in a fuel cell, heat is also generated when an electromotive force is generated. Then, when the temperature rises to a temperature at which water does not freeze, specifically, to a temperature higher than the freezing point, it is determined that the start of the fuel cell system has ended, and the stoichiometric ratio during normal operation is set.

Embodiment 2. FIG.
FIG. 3 is a conceptual diagram showing the configuration of the fuel cell stack in the present embodiment. As shown in this figure, the fuel cell stack has a structure in which a plurality of cells 11 are stacked. Here, the structure of the cell 11 is omitted in FIG. 3, but is the same as that of FIG. 1 described in the first embodiment. The total number of cells is not limited to the example of FIG. 3 and can be set as appropriate according to the specifications of the fuel cell stack.

  Further, the fuel cell stack is provided with a supply manifold 12 that distributes fuel gas to each cell 11 and a discharge manifold 13 that collectively discharges fuel off-gas from each cell 11. In the present embodiment, the supply manifold 12 further supplies fuel gas to the cells 11 arranged at the ends of the fuel cell stack and in the vicinity thereof (hereinafter referred to as the ends and the like in the present embodiment). The first supply manifold portion 12a and the second supply manifold portion 12b for supplying fuel gas to the other cells 11 are branched. Further, a valve 14 is provided in the first supply manifold portion 12a. By closing the valve 14, the first supply manifold portion 12a is shut off and fuel gas is supplied to the cells 11 such as the end portions. Can be stopped. In FIG. 3, the cells 11 such as the end portions are hatched. Moreover, the arrow has shown the direction through which fuel gas flows.

  The fuel gas may be hydrogen gas itself or a hydrogen-rich reformed gas generated by a reforming reaction of a hydrocarbon compound. On the other hand, the oxidant gas can be air taken from outside air by a compressor (not shown).

  Also in the present embodiment, a temperature is monitored by providing a thermocouple or the like in the fuel cell system. The location where the temperature is monitored is preferably in the vicinity of the membrane-electrode-gas diffusion layer assembly. Further, when a membrane-electrode assembly is used, it is preferable to set the vicinity. However, the present invention is not limited to these, and monitors the temperature of the gas in the cell and the temperature of the cooling water circulating in the fuel cell system, and estimates the temperature in the cell from these temperatures. May be.

  When the temperature is higher than a predetermined temperature, for example, below the freezing point (0 ° C. or lower), the valve 14 provided in the first supply manifold portion 12a is opened. As a result, the fuel gas is supplied to all the cells 11. The fuel gas supplied to the anode of each cell 11 causes an electrochemical reaction via an electrolyte film with an oxidizing gas such as air supplied to the cathode. Thereafter, the unreacted fuel gas is discharged from the discharge manifold 13 to the outside of the fuel cell stack.

  On the other hand, when the temperature is below freezing point, the valve 14 provided in the first supply manifold portion 12a is closed. Here, freezing of water becomes a problem mainly when the fuel cell is started in a low temperature environment. Therefore, in a low temperature environment, it can be said that the valve 14 is closed and the fuel cell is started.

  When the valve 14 is closed, the fuel gas is not supplied to the cells 11 such as the end portions, so that the anodes of these cells are in a hydrogen deficient state. On the other hand, the fuel gas is supplied to the other cells 11 from the second supply manifold portion 12b.

  As described in the first embodiment, the cells arranged at the ends of the fuel cell stack or the like are likely to freeze at low temperatures. Therefore, as shown in FIG. 3, if the fuel gas is not supplied to the cells such as the end portions at low temperatures, the water in the cathode moves to the anode through the electrolyte membrane in order to make up for the lack of hydrogen. Water electrolysis proceeds. Therefore, freezing of water can be prevented in these cells. In this method, power is consumed to open and close the valve, but the amount of consumption is much smaller than when water is electrolyzed using a battery or the like. Therefore, freezing of generated water can be prevented without greatly reducing the efficiency of the fuel cell system.

  When the anode is depleted in hydrogen, the reaction between carbon and water proceeds, which may cause corrosion at the anode or cathode. However, this embodiment has a problem of freezing water at a low temperature, specifically below freezing point. Since the reaction between carbon and water is suppressed at a low temperature, it is considered that there is almost no possibility that the electrode corrodes due to this reaction in the present embodiment. Furthermore, it is possible to further reduce the deterioration of the electrode by using a material that is less likely to react with water.

By the way, when the amount of hydrogen supplied to the cell decreases, the generated voltage decreases. On the other hand, in order to start the fuel cell, the voltage of the entire cell needs to be positive. Therefore, it is preferable to monitor the cell voltage so that the cell as a whole becomes positive even if the voltage of the cell located at the end of the fuel cell stack becomes negative. Specifically, it is preferable to adjust the stoichiometric ratio according to the generated power required for the fuel cell. However, when the cell voltage becomes lower than a predetermined value, power generation is stopped at that time. For example, when the current density is 0.1 A / cm ² , power generation can be stopped when the voltage becomes lower than −2.1V. In this case, the voltage of each cell may be individually monitored, and power generation may be stopped only for the cell whose voltage is lower than a predetermined value.

  In FIG. 3, the supply of fuel gas at a low temperature can be stopped only for one end of the fuel cell stack and the cells arranged in the vicinity thereof. However, in the present embodiment, the fuel gas supply at the low temperature is stopped for the cells arranged at both ends of the fuel cell stack and in the vicinity thereof (hereinafter referred to as both ends, etc. in the present embodiment). You may be able to do it.

  FIG. 4 is another example of a conceptual diagram showing the configuration of the fuel cell stack in the present embodiment. The total number of cells is not limited to the example of FIG. 4 and can be set as appropriate according to the specifications of the fuel cell stack.

  In FIG. 4, the fuel cell stack is provided with a supply manifold 22 that distributes the fuel gas to each cell 21 and a discharge manifold 23 that collectively discharges the fuel off-gas from each cell 21. The supply manifold 22 supplies fuel to the first supply manifold portion 22a for supplying fuel gas to the cells 21 arranged at one end of the fuel cell stack and the cells 21 arranged at the other end. The gas is branched into a second supply manifold portion 22 b that supplies gas and a third supply manifold portion 22 c that supplies fuel gas to the other cells 21. The first supply manifold portion 22a and the second supply manifold portion 22b are provided with a first valve 24 and a second valve 25, respectively. By closing these valves, the first supply manifold portion 22a and the second supply manifold portion 22b are provided. The fuel gas supply to the cells 11 at both ends and the like can be stopped by blocking the 22a and the second supply manifold portion 22b.

  When the temperature is below freezing point, the first valve 24 and the second valve 25 are closed. As a result, the fuel gas is not supplied to the cells 11 at both ends and the anodes of these cells are deficient in hydrogen. On the other hand, the fuel gas is supplied to the other cells 11 from the third manifold 22c.

  According to the configuration of FIG. 3, it is possible to prevent water from freezing not only in the cells such as one end but also in the cells such as the other end. However, since the configuration is slightly more complicated than that in FIG. 2, it is better to compare and consider the merits and demerits of both, and to select which configuration.

  In FIG. 3, the first valve 24 and the second valve 25 are not necessarily opened and closed simultaneously. For example, depending on the position of the vehicle on which the fuel cell is mounted, there may be a difference in cell temperature at both ends. In such a case, it is preferable to first close the valve provided in the supply manifold portion connected to the end portion or the like where freezing is likely to occur, and then close the other valve.

  By the way, in the example of FIG. 3 and FIG. 4, the cells from the end of the fuel cell stack to the third cell are treated as cells such as end portions. However, the present embodiment is not limited to this. For example, the tenth cell from the end may be a cell such as an end, and the 20th cell may be a cell such as an end. The range of cells that are prone to freezing varies depending on the structure of the fuel cell stack, the environment in which the vehicle normally travels (cold or warm regions), the minimum temperature assumed at startup, and so on. Thus, it is preferable to determine a range of cells such as an end portion.

  However, even if the cell range such as the edge is determined as described above, it is expected that cells that cause freezing will occur beyond this range. Therefore, also in the present embodiment, it is preferable to operate the fuel cell system according to the flowchart of FIG. 2 described in the first embodiment. That is, when the temperature is below the freezing point, the valve provided in the manifold connected to the cell such as the end is closed and the stoichiometric ratio is lower than that in the normal operation. Specifically, the stoichiometric ratio according to the generated power required for the fuel cell is set in accordance with the stoichiometric ratio map in the low-temperature mode prepared in advance.

  On the other hand, when the temperature is higher than below freezing point, a valve provided in a manifold connected to a cell such as an end is opened, and the stoichiometric ratio during normal operation is set. Also in this case, the stoichiometric ratio according to the generated power required for the fuel cell is set in accordance with the stoichiometric ratio map in the normal mode prepared in advance.

  Even during operation at a low stoichiometric ratio, the temperature of the fuel cell stack gradually rises due to heat generated by power generation. Then, when the temperature rises to a temperature at which water does not freeze, specifically, to a temperature higher than the freezing point, it is determined that the start of the fuel cell system has ended, and the stoichiometric ratio during normal operation is set.

  In this way, by changing the stoichiometric ratio, the amount of fuel gas supplied to cells other than the cells arranged at the end portions or the like can be reduced. Thereby, since it becomes possible to accelerate | stimulate decomposition | disassembly of water in all the cells, it can suppress that water freezes in cells other than cells, such as an edge part.

In this case as well, it is preferable to adjust the stoichiometric ratio so that the voltage of the entire cell becomes positive. When the cell voltage becomes lower than a predetermined value, power generation is stopped at that time. For example, when the current density is 0.1 A / cm ² , power generation can be stopped when the voltage becomes lower than −2.1V. Alternatively, the voltage of each cell may be monitored individually, and power generation may be stopped only for cells whose voltage is lower than a predetermined value.

  The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, in any of the first to third embodiments, an electrode containing a catalyst capable of promoting electrolysis of water is used for the end portion or the end portion and a cell in the vicinity thereof, and an electrochemical reaction is performed in the electrode. Water electrolysis may be prevented from occurring in the region where the water vapor proceeds. As a result, it is possible to prevent the potential from rising due to the electrolysis of water and the deterioration of the characteristics of the fuel cell due to deterioration of the catalyst involved in the electrode reaction.

3 is a schematic cross-sectional view of a cell in the first embodiment. FIG. 4 is a flowchart of an operation method of the fuel cell system in the first embodiment. FIG. 3 is an example of a conceptual diagram showing a configuration of a fuel cell stack in a second embodiment. FIG. 10 is another example of a conceptual diagram showing the configuration of the fuel cell stack in the second embodiment.

Explanation of symbols

1,11,21 cell 2 membrane-electrode-gas diffusion layer assembly 3,4 separator 5 electrolyte membrane 6 anode 7 cathode 8,9 gas diffusion layer 12,22 supply manifold 13,23 discharge manifold 14 valve 24 first valve 25 Second valve

Claims (6)

A fuel cell stack in which a plurality of cells are stacked and the cell at the end in the stacking direction has a higher pressure loss than the center cell;
Control means for reducing the amount of fuel gas supplied to the fuel cell stack when the fuel cell stack is generating power and the cell is below a predetermined temperature compared to when the cell is higher than the predetermined temperature; A fuel cell system comprising:   2. The fuel cell system according to claim 1, wherein at least some of the cells are arranged so that pressure loss gradually increases toward the end portion. A fuel cell stack in which a plurality of cells are stacked;
A supply manifold for supplying fuel gas to the fuel cell stack;
A discharge manifold for discharging fuel off-gas discharged from the fuel cell stack,
The supply manifold includes a first supply manifold portion for supplying fuel gas to one end of the fuel cell stack and cells arranged in the vicinity thereof, and a second supply manifold portion for supplying fuel gas to other cells. The fuel cell system is characterized in that the first supply manifold portion is shut off when the fuel cell stack is generating power and the cell is at a predetermined temperature or lower. A fuel cell stack in which a plurality of cells are stacked;
A supply manifold for supplying fuel gas to the fuel cell stack;
A discharge manifold for discharging fuel off-gas discharged from the fuel cell stack,
The supply manifold is arranged at one end of the fuel cell stack and a first supply manifold portion for supplying fuel gas to cells arranged in the vicinity thereof, and at the other end of the fuel cell stack and in the vicinity thereof. A second supply manifold portion for supplying fuel gas to the cells and a third supply manifold portion for supplying fuel gas to the other cells; When the temperature is equal to or lower than a predetermined temperature, the fuel cell system is characterized in that the first supply manifold portion and the second supply manifold portion are shut off.   5. The control unit according to claim 3, further comprising a control unit configured to reduce an amount of fuel gas supplied to the fuel cell stack when the cell is equal to or lower than the predetermined temperature compared to when the cell is higher than the predetermined temperature. Fuel cell system.   The fuel cell system according to any one of claims 1 to 5, wherein the predetermined temperature is 0 ° C.

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