JP2006164681A - Temperature control unit for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature control unit for a fuel cell capable of shortening a start-up time at a low temperature, and improving power generation efficiency. <P>SOLUTION: At both end of a fuel cell stack 1, an anode-side end plate 2 and a cathode-side end plate 3 are provided, and in the end plates 2, 3, in-end-plate coolant flow channels 2a, 3a are formed, respectively. A coolant sent under compression from a coolant pump 11 is supplied to the in-end-plate coolant flow channels 2a, 3a through a coolant supply tube 12, and, after heat exchange with the end plates 2, 3, is cooled by a heat exchanger 14 and returned to the coolant pump 11. During an operation stop below a freezing point, a coolant control valve 15 is throttled, and a large volume of a coolant is made to flow in the cathode-side end plate 3 from the anode-side end plate 2, so that the fall of a temperature at stoppage at the cathode-side end plate 3 gets slower than that at the anode-side end plate 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell temperature adjustment device for adjusting the temperature of a fuel cell stack.

  Solid polymer fuel cells, which extract electrical energy from the chemical reaction between hydrogen and oxygen, are not only used for power generation but also as a power source for automobiles because they emit only harmless water and are highly efficient. Is also considered. In such an application, a cell having a minimum configuration capable of generating electric power cannot secure necessary power, and therefore, it is used in the form of a fuel cell stack in which cells are stacked.

  FIG. 6 shows a typical configuration of the fuel cell system. A plurality of unit fuel cells (cells) are stacked to form a fuel cell stack 1. At both ends of the fuel cell stack 1, an end plate 2 on the anode side and an end plate 3 on the cathode side are disposed in order to apply a fastening load by bolts or the like to the stack. High-pressure hydrogen as fuel gas stored in the fuel tank 8 is pressure-reduced and flow-controlled by the hydrogen pressure regulating valve 9 and supplied to the anode via the intake pipe 4. Excess hydrogen gas is discharged from the exhaust pipe 5. The An oxidant (air) compressed by the pump 10 is supplied to the cathode via the intake pipe 6, and unreacted air is discharged from the exhaust pipe 7 on the cathode side. Moreover, although not shown in figure, the cooling device which cools a fuel cell stack by circulating a refrigerant | coolant through the refrigerant | coolant flow path formed in each cell is provided.

  In a fuel cell stack in which a number of cells as described above are stacked and connected in series, there is a difference in heat dissipation between the stack center and the stack edge, so the temperature of the cell near the stack edge is higher than that of the cell in the stack center. Lower. When the temperature is lowered, the rate of chemical reaction is reduced, so that the efficiency and power generation capacity of the cell near the end of the stack is lowered, and as a result, the output current of the entire fuel cell stack is lowered.

As a countermeasure against the above-described phenomenon, a technique of providing a heat medium chamber in which a heat medium circulates between the fuel cell stack body 1 and the end plates 2 and 3 is known as Patent Document 1. According to this technology, the end of the fuel cell stack, which is lower in temperature than the center of the fuel cell stack, can be heated and the temperature distribution inside the fuel cell stack can be made uniform, so the efficiency and power generation performance as the fuel cell stack Can be improved.
JP-A-11-097048 (page 3, FIG. 1)

  However, when a fuel cell is used as a power source for an automobile, the fuel cell must be able to start even when it is left below freezing point. There was a point.

  When the conventional fuel cell stack is stopped and left under freezing, the stack end near the end plates 2 and 3 is more affected by the cooling by the outside air than the center of the stack. Thus, the distribution is high at the center of the stack and low at the end of the stack. If a temperature distribution exists as a stack, a temperature distribution is also formed in each cell, but the water in each cell moves from a high temperature region to a low region. Thereafter, the water in each cell is frozen while forming an uneven distribution in the cell.

  In the cell located on the anode side of the stack from the center of the stack, the water in the cell moves to the anode side of the cell as shown in FIG. 8, and in the cell located on the cathode side of the stack from the center of the stack, FIG. Thus, the water in the cell moves to the cathode side of the cell. Therefore, at the start of the temperature below freezing point, at the cathode of the cell on the cathode side of the stack rather than the center of the stack, the water generated by the reaction and the water that has been kept frozen are combined, so there is an excess of water. A flooding phenomenon occurs in which the gas flow path is blocked by water. Therefore, the generation of flooding has a problem in that the efficiency of power generation of the fuel cell stack is reduced, and the start-up time is below freezing point.

  In order to solve the above-described problems, the present invention provides a temperature adjustment device for a fuel cell that adjusts the temperature of the fuel cell stack, from the cathode side to the anode side of the fuel cell stack when the operation of the fuel cell stack is stopped. The gist is to form a negative temperature gradient.

  According to the present invention, when the fuel cell stack is stopped below the freezing point, the temperature on the stack cathode side is higher than that on the stack anode side, so that the water in each cell flows from the high temperature cell cathode side to the low temperature cell anode side. Move to freeze. For this reason, when the fuel cell system is restarted, water is not retained on the cell cathode side where the water content tends to increase due to the generated water, so flooding at the cathode of each cell can be suppressed, and the fuel cell stack Therefore, there is an effect that the startup time under the freezing point of the fuel cell stack can be shortened and the efficiency of power generation can be improved.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. Although not particularly limited, the following embodiments are fuel cell temperature control devices suitable for a fuel cell vehicle that can be parked even below freezing.

  FIG. 1 is a system configuration diagram showing the configuration of Embodiment 1 of the fuel cell system according to the present invention. In FIG. 1, an anode side end plate 2 and a cathode side end plate 3 are provided at both ends of the fuel cell stack 1. Inside the anode-side end plate 2 and the cathode-side end plate 3, there are formed end-plate refrigerant flow paths 2a and 3a, respectively.

  Hydrogen as a fuel gas is stored in the hydrogen tank 8 at a high pressure. The high-pressure hydrogen in the hydrogen tank 8 is reduced to the fuel cell operating pressure by the hydrogen pressure regulating valve 9 and supplied to the anode via the hydrogen supply pipe 4. Hydrogen that has not reacted at the anode is discharged through the hydrogen discharge pipe 5.

  Air as the oxidant gas is supplied to the compressor 10 via the air supply pipe 6, compressed to the operating pressure of the fuel cell, and supplied to the cathode. Air that has not reacted at the cathode is discharged through the air discharge pipe 7.

  The cooling system of the fuel cell system includes a refrigerant pump 11, a refrigerant supply pipe 12, a refrigerant discharge pipe 13, a heat exchanger 14, and a refrigerant control valve 15. As the cooling system refrigerant, for example, an antifreeze solution such as an ethylene glycol aqueous solution adjusted to a concentration corresponding to the minimum storage temperature of the fuel cell is used.

  The refrigerant pumped from the refrigerant pump 11 is supplied to the in-end plate refrigerant flow paths 2a and 3a via the refrigerant supply pipe 12, exchanges heat with the end plates 2 and 3, and then heats via the refrigerant discharge pipe 13. Enter the exchanger 14. The refrigerant that exchanges heat with the outside air in the heat exchanger 14 returns to the refrigerant pump 11.

  The refrigerant supply pipe 12 is branched into two systems, and a refrigerant control valve 15 for controlling the flow rate of the refrigerant is provided in the branch pipe connected to the end plate 2 on the stack anode side.

  In the first embodiment, during the operation of the fuel cell system, the refrigerant pump 11 is operated to allow the refrigerant to flow through the end plates 2 and 3 in order to cool the fuel cell stack 1. At this time, the refrigerant has a relatively high temperature of, for example, about 90 [° C.] in order to dissipate reaction heat due to the operation of the fuel cell to the outside. When the operation of the fuel cell system below freezing is stopped, the refrigerant control valve 15 is throttled so that a larger amount of refrigerant flows in the stack cathode side end plate 3 than in the stack anode side end plate 2.

  Thus, when the refrigerant is circulated when the operation is stopped, the end plate 3 on the cathode side of the fuel cell stack 1 comes into contact with the high-temperature refrigerant having a larger flow rate than the end plate 2 on the anode side, so that the temperature drop at the time of the stop is reduced. Become slow. For this reason, as shown in FIG. 2, the temperature distribution of the entire fuel cell stack becomes higher on the stack cathode side than on the stack anode side. The temperature distribution of the fuel cell stack 1 is a temperature distribution in which the cell cathode side is higher in temperature than the cell anode side when viewed for each cell.

  Accordingly, in all the cells of the fuel cell stack, the water in the cells moves to the cell anode side and freezes, and flooding at the time of starting below freezing is suppressed.

  According to this embodiment, when the fuel cell stack is stopped below the freezing point, the temperature on the stack cathode side is higher than that on the stack anode side, so that the water in each cell flows from the high temperature cell cathode side to the low temperature cell anode. Since the water is no longer retained on the cell cathode side, which tends to increase the amount of water due to the generated water, the flooding at the time of restart is suppressed, and the power generation amount of the fuel cell stack increases. Therefore, there are effects that the start-up time of the fuel cell stack below the freezing point can be shortened and the efficiency of power generation can be improved.

  The means for controlling the temperature distribution of the fuel cell stack according to the present invention is not limited to the embodiment.

  FIG. 3 is a system configuration diagram showing the configuration of Embodiment 2 of the fuel cell system according to the present invention. In FIG. 3, an electric heater 16 for heating the stack cathode side end plate 3, a power source 17 for supplying electric power to the electric heater 16, and a control device 18 for adjusting electric power supplied to the electric heater 16 are provided. It has been. Other configurations are the same as those of the conventional example of FIG.

  In Example 2, when the fuel cell is stopped below the freezing point, power is supplied from the power source 17 to the electric heater 16 to heat the stack cathode side end plate 3. For example, the control device 18 stops energization to the electric heater 16 after a certain energization time. In addition to this, the end plates 2 and 3 of the fuel cell stack 1 are each provided with a temperature sensor (not shown), and when the difference between the temperatures detected by these two temperature sensors reaches a certain temperature, the power source 17 transfers to the electric heater 16. May be stopped.

  According to this embodiment, even when the operation is stopped during the warm-up of the fuel cell stack, the cathode side end plate 3 of the fuel cell stack 1 is arbitrarily heated, and the fuel cell stack as shown in FIG. As a whole, the temperature on the stack cathode side can be higher than that on the stack anode side. Therefore, in all the cells constituting the fuel cell stack 1, the water in the cells moves to the cell anode side and freezes, and the occurrence of flooding when the fuel cell stack starts below freezing is suppressed.

  According to the second embodiment, even when the warm-up of the fuel cell stack is not completed before the operation is stopped, the cathode side of the fuel cell stack is arbitrarily heated by the heating means, and the temperature on the stack cathode side is set to the stack anode side. Therefore, it is possible to perform stop processing to suppress flooding when the fuel cell stack starts below freezing without being affected by the state of the fuel cell stack before stopping operation. Become.

  The means for heating the stack cathode side end plate 3 in the present invention is not limited to the electric heater.

  FIG. 4 is a system configuration diagram showing the configuration of Embodiment 3 of the fuel cell system according to the present invention. In FIG. 4, the cathode side of the fuel cell stack 1 is covered with a heat insulating tank 19. The heat insulating tank 19 is a container in which a heat insulating material such as a synthetic resin foam, glass fiber, or synthetic resin fiber is placed in an outer case. Other configurations are the same as those of the conventional example of FIG.

  In Example 3, when the power generation of the fuel cell stack is stopped, the heat release from the cathode side of the fuel cell stack is suppressed by the heat insulating tank 19, and the temperature on the stack cathode side is lower than the stack anode side without consuming energy such as electric power. Will be maintained in a high state. Therefore, in all the cells constituting the fuel cell stack 1, the water in the cells moves to the cell anode side and freezes, and the occurrence of flooding when the fuel cell stack starts below freezing is suppressed.

  According to the third embodiment, since the cathode side of the fuel cell stack is insulated from the outside air, heat dissipation on the stack cathode side is suppressed, and the temperature on the stack cathode side is maintained higher than that on the stack anode side. There is an effect that it is possible to suppress energy consumption in the stop processing for suppressing flooding at the time of starting below the freezing point of the battery stack.

  FIG. 5 is a system configuration diagram showing the configuration of Embodiment 4 of the fuel cell system according to the present invention. In FIG. 5, the anode side end plate 2 of the fuel cell stack 1 is provided with an in-end plate refrigerant flow path 2a.

  The refrigerant pump 20 pressurizes the refrigerant and supplies the refrigerant to the in-end-plate refrigerant flow path 2a via the refrigerant supply pipe 21. In addition, the refrigerant that has flowed out of the end plate refrigerant flow path 2 a is radiated to the outside of the system by the heat exchanger 23 disposed on the refrigerant discharge pipe 22, the temperature drops, and the refrigerant pump 20 returns.

  In Example 4, when the fuel cell stack is stopped below the freezing point, the refrigerant pump 20 is operated to supply the refrigerant to the stack anode side end plate 2. When the refrigerant is circulated in this manner, the temperature distribution on the stack cathode side as shown in FIG. 2 is higher than the temperature on the stack anode side in the entire stack while promoting cooling of the anode side of the fuel cell stack. Can do. Therefore, even in the cell on the cathode side of the center of the fuel cell stack, the water in the cell moves to the cell anode side and freezes, and the occurrence of flooding when the fuel cell stack starts below freezing is suppressed. Further, the time until the water in the cell moves to the anode side of the cell and freezes is shortened.

  According to Example 4, the anode side of the fuel cell stack is cooled when the operation is stopped, thereby forming a temperature distribution in the fuel cell stack in which the temperature on the stack cathode side is higher than that on the stack anode side. Since the time until the cell moves to the anode side and freezes is shortened, there is an effect that a stop process for suppressing flooding when the fuel cell stack is started below the freezing point can be performed in a short time.

1 is a system configuration diagram illustrating the configuration of a first embodiment of a fuel cell system according to the present invention. FIG. 2 is a temperature distribution diagram inside a fuel cell stack in Example 1. FIG. It is a system block diagram explaining the structure of Example 2 of the fuel cell system which concerns on this invention. It is a system block diagram explaining the structure of Example 3 of the fuel cell system which concerns on this invention. It is a system configuration figure explaining the composition of Example 4 of the fuel cell system concerning the present invention. It is a block diagram of the fuel cell system of a prior art example. It is a temperature distribution inside a fuel cell stack in a conventional example. It is explanatory drawing of the water movement in a cell. It is explanatory drawing of the water movement in a cell.

Explanation of symbols

1: Fuel cell stack 2: Anode side end plate 3: Cathode side end plate 2a, 3a: Refrigerant flow path in end plate 4: Hydrogen supply pipe 5: Hydrogen discharge pipe 6: Air supply pipe 7: Air discharge pipe 8: Hydrogen Tank 9: Hydrogen pressure regulating valve 10: Compressor 11: Refrigerant pump 12: Refrigerant supply pipe 13: Refrigerant discharge pipe 14: Heat exchanger 15: Refrigerant control valve 16: Electric heater 17: Power supply 18: Controller 19: Heat insulation tank 20: Refrigerant pump 21: Refrigerant supply pipe 22: Refrigerant discharge pipe 23: Heat exchanger

Claims (4)

  A temperature adjustment device for a fuel cell that adjusts the temperature of the fuel cell stack, wherein a negative temperature gradient is formed from the cathode side to the anode side of the fuel cell stack when the operation of the fuel cell stack is stopped Battery temperature control device. A heating means for heating the cathode side of the fuel cell stack;
2. The fuel cell temperature control device according to claim 1, wherein when the operation of the fuel cell stack is stopped, the cathode side of the fuel cell stack is heated by the heating means.   2. The temperature adjustment device for a fuel cell according to claim 1, comprising a structure in which a heat exchange amount with outside air on a cathode side of the fuel cell stack is smaller than a heat exchange amount on an anode side of the fuel cell stack. . A cooling means for cooling the anode side of the fuel cell stack;
2. The fuel cell temperature control device according to claim 1, wherein when the operation of the fuel cell stack is stopped, the anode side of the fuel cell stack is cooled by the cooling means.

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