JP2010282929A - Fuel cell system - Google Patents

Abstract

A fuel cell system that prevents damage to an electrolyte membrane in a sub-freezing environment with a simple configuration.
A fuel cell system includes a fuel cell and a cooling medium supply device. The cooling medium supply device 18 includes a radiator 60, and a circulation channel 62 for circulating the cooling medium is provided between the fuel cell 12 and the radiator 60. A first branch channel 66 that bypasses the radiator 60 is connected to the circulation channel 62. A thermo valve 70 is disposed at a joining portion of the circulation channel 62 and the first branch channel 66, and a second branch channel 72 that bypasses the thermo valve 70 is provided. When the controller 20 determines that the generated water may freeze inside the fuel cell 12 when the fuel cell system 10 is stopped, the controller 20 drives the pump 64 in the reverse direction.
[Selection] Figure 1

Description

  The present invention includes a fuel cell in which fuel gas and oxidant gas react electrochemically to obtain electric energy, and a cooling medium supply device for supplying a cooling medium to the fuel cell and adjusting the temperature of the fuel cell. The present invention relates to a fuel cell system provided.

  A fuel cell supplies a fuel gas (a gas mainly containing hydrogen, for example, hydrogen gas) and an oxidant gas (a gas mainly containing oxygen, for example, air) to an anode side electrode and a cathode side electrode for electricity. It is a system that obtains direct-current electrical energy through chemical reaction.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) in which an anode side electrode and a cathode side electrode are disposed on both sides of an electrolyte membrane made of a polymer ion exchange membrane is provided by a pair of separators. The unit cell is sandwiched. This type of fuel cell is normally used as a fuel cell stack by stacking a predetermined number of unit cells.

  In the fuel cell, generated water is generated by the reaction between the fuel gas and the oxidant gas. For this reason, when the fuel cell is used below freezing point, it is necessary to prevent the generated water from freezing when the power generation of the fuel cell is stopped.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 has a refrigerant circulation system in which a refrigerant storage unit capable of storing a refrigerant in a warm state and supply of the refrigerant from the refrigerant storage unit to the fuel cell. A storage refrigerant supply control unit for controlling, and the storage refrigerant supply control unit supplies refrigerant from the refrigerant storage unit to the fuel cell before or during the scavenging process of the fuel cell.

  Thus, in Patent Document 1, since the fuel cell can be maintained at a temperature suitable for the scavenging process even after power generation is stopped without using an electric heater or the like, the fuel cell of the fuel cell by the scavenging process is suppressed while suppressing energy consumption. It is said that moisture removal can be performed efficiently.

JP 2008-218164 A

  However, in Patent Document 1 described above, it is difficult to completely remove the water inside the MEA even if the scavenging process is performed when power generation of the fuel cell is stopped. For this reason, in the sub-freezing environment, there is a problem that the water remaining inside the MEA freezes after the power generation of the fuel cell is stopped, and the MEA, particularly the polymer ion exchange membrane, is damaged by the growth of ice.

  An object of the present invention is to solve this kind of problem and to provide a fuel cell system capable of preventing damage to an electrolyte membrane in a sub-freezing environment as much as possible with a simple and economical configuration. To do.

  The present invention includes a fuel cell in which fuel gas and oxidant gas react electrochemically to obtain electric energy, and a cooling medium supply device for supplying a cooling medium to the fuel cell and adjusting the temperature of the fuel cell. The present invention relates to a fuel cell system provided.

  The cooling medium supply device includes a radiator, a circulation channel that circulates the cooling medium between the fuel cell and the radiator, a pump that is disposed on the circulation channel and that can send the cooling medium in both forward and reverse directions, The first branch channel provided in the circulation channel and bypassing the radiator, and arranged at the junction of the circulation channel and the first branch channel, and depending on the environmental temperature of the fuel cell, A flow rate adjusting valve that adjusts the flow rate of the circulation channel and the flow rate of the first branch channel, a second branch channel that is provided in the circulation channel and bypasses the flow rate adjustment valve, and the second branch flow When it is determined that the generated water may freeze inside the fuel cell when the fuel cell is stopped based on the check valve provided in the passage and the temperature detected by the temperature sensor, the pump is turned in the reverse direction. And a controller to be driven.

  The check valve preferably allows the flow of the cooling medium only when the pump is driven in the reverse direction.

  Further, it is preferable that a check valve that allows the flow of the cooling medium only when the pump is driven in the forward direction is disposed in the first branch flow path.

  According to the present invention, when it is determined that the generated water may freeze inside the fuel cell when the fuel cell is stopped, the pump is driven in the reverse direction. For this reason, the cooling medium flows in the reverse direction in the circulation channel. At that time, since the cooling medium flows through the second branch flow path by bypassing the flow rate adjusting valve, the cooling medium is not influenced by the flow rate adjusting valve and is introduced into the radiator. Therefore, the cooling medium is cooled well by exchanging heat with the external atmosphere via the radiator, and the fuel cell can be rapidly cooled.

  Moreover, the flow rate adjusting valve is not used when the cooling medium is backflowed. For this reason, it is not necessary to use a relatively expensive three-way solenoid valve or the like as a flow rate adjusting valve, and it is possible to prevent damage to the electrolyte membrane in a sub-freezing environment as much as possible with a simple and economical configuration. .

1 is an explanatory diagram of a schematic configuration of a fuel cell system according to an embodiment of the present invention. FIG. 4 is a relationship diagram between an outside air temperature and a fuel cell internal temperature in the fuel cell system. It is explanatory drawing of the flow control of a cooling medium. It is explanatory drawing at the time of making the said cooling medium flow backward.

  As shown in FIG. 1, a fuel cell system 10 according to an embodiment of the present invention includes a fuel cell 12 in which a fuel gas and an oxidant gas react electrochemically to obtain electric energy, and the fuel cell 12 is subjected to the oxidation. An oxidant gas supply device 14 for supplying the agent gas, a fuel gas supply device 16 for supplying the fuel gas to the fuel cell 12, and a cooling medium to the fuel cell 12 to adjust the temperature of the fuel cell 12. A cooling medium supply device 18 to be performed and a controller (control unit) 20 to control the entire fuel cell system 10 are provided.

  A plurality of fuel cells 12 are usually stacked to constitute a fuel cell stack. Each fuel cell 12 includes, for example, an electrolyte membrane / electrode structure (MEA) 28 in which a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode side electrode 24 and an anode side electrode 26. The electrolyte membrane / electrode structure 28 is sandwiched between a pair of separators 30a and 30b.

  The cathode side electrode 24 and the anode side electrode 26 are uniformly coated on the surface of the gas diffusion layer with a gas diffusion layer (not shown) made of carbon paper or the like and porous carbon particles carrying platinum alloy on the surface. An electrode catalyst layer (not shown). The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  Between the electrolyte membrane / electrode structure 28 and the separator 30a, a cathode gas channel 32 for supplying an oxidant gas to the cathode electrode 24 is formed, and the electrolyte membrane / electrode structure 28 and the separator 30b In the meantime, an anode gas flow path 34 for supplying fuel gas to the anode electrode 26 is formed. Between the separators 30a and 30b constituting the fuel cells 12 adjacent to each other, a cooling medium flow path 36 for supplying a cooling medium is formed.

  At one end of the fuel cell 12 in the stacking direction, an oxidizing gas inlet communication hole 38a for supplying an oxidizing gas such as air (oxygen-containing gas) to the cathode gas flow path 32 and the oxidizing gas are supplied to the cathode gas. An oxidant gas outlet communication hole 38b for discharging from the flow path 32, a fuel gas inlet communication hole 40a for supplying a fuel gas such as a hydrogen-containing gas to the anode gas flow path 34, and the fuel gas to the anode gas A fuel gas outlet communication hole 40b for discharging from the flow path 34 is formed.

  At one end of the fuel cell 12 in the stacking direction, a cooling medium inlet communication hole 42a for supplying a cooling medium such as pure water, ethylene glycol, or oil to the cooling medium flow path 36, and the cooling medium through the cooling medium flow path. A cooling medium outlet communication hole 42b for discharging from 36 is formed.

  The oxidant gas supply device 14 includes a compressor 44 that compresses and supplies air from the atmosphere, and the compressor 44 is disposed in the air supply flow path 46. The air supply channel 46 communicates with the oxidant gas inlet communication hole 38 a of the fuel cell 12. The oxidant gas supply device 14 includes an air discharge channel 48 that communicates with the oxidant gas outlet communication hole 38b. The air discharge passage 48 is provided with a valve (back pressure control valve) 49 whose opening degree is adjustable for adjusting the pressure of air supplied from the compressor 44 to the fuel cell 12 through the air supply passage 46. It is done.

  The fuel gas supply device 16 includes a hydrogen tank 50 that stores high-pressure hydrogen (hydrogen-containing gas). The hydrogen tank 50 communicates with the fuel gas inlet communication hole 40 a of the fuel cell 12 through the hydrogen supply flow path 52. . An ejector 54 is provided in the hydrogen supply channel 52.

  The fuel gas supply device 16 includes an off-gas flow path 56 that communicates with the fuel gas outlet communication hole 40b. A hydrogen circulation path 58 communicates with the off gas channel 56. The ejector 54 supplies the hydrogen gas supplied from the hydrogen tank 50 to the fuel cell 12 through the hydrogen supply passage 52, and exhaust gas containing unused hydrogen gas that has not been used in the fuel cell 12. The gas is sucked from the hydrogen circulation path 58 and supplied again as fuel gas to the fuel cell 12.

  The cooling medium supply device 18 includes a radiator 60, and a circulation channel 62 for circulating the cooling medium is provided between the fuel cell 12 and the radiator 60. A pump 64 is provided on the circulation channel 62 so that the cooling medium can be sent out in both forward and reverse directions (arrow A direction and arrow B direction) under the forward and reverse rotation action of the motor 63. Note that an electric fan 65 may be disposed in the vicinity of the radiator 60.

  Both ends of a first branch channel 66 that bypasses the radiator 60 are connected to the circulation channel 62. A thermostat that adjusts the flow rate of the circulation flow channel 62 and the flow rate of the first branch flow channel 66 in accordance with the environmental temperature of the fuel cell 12 is provided at the junction of the circulation flow channel 62 and the first branch flow channel 66. A valve (flow regulating valve) 70 is disposed.

  Both ends of a second branch flow path 72 that bypasses the thermo valve 70 are connected to the circulation flow path 62, and a first check valve 74 a is disposed in the second branch flow path 72. The first check valve 74a allows the flow of the cooling medium in the arrow B direction only when the pump 64 is driven in the reverse direction.

  The first branch flow path 66 is provided with a second check valve 74b that allows the flow of the cooling medium only when the pump 64 is driven in the forward direction. The controller 20 may freeze the generated water inside the fuel cell 12 when the fuel cell 12 is stopped based on the detected temperatures of the temperature sensors 76a and 76b (particularly, the detected temperature of the temperature sensor 76a for detecting the external temperature). When it is determined that there is, the pump 64 is driven in the reverse direction.

  The operation of the fuel cell system 10 configured as described above will be described below.

  When the compressor 44 constituting the oxidant gas supply device 14 is driven, air is supplied to the oxidant gas inlet communication hole 38 a of the fuel cell 12 through the air supply passage 46. The air moves along the cathode gas flow path 32 of each fuel cell 12 and is then discharged from the oxidant gas outlet communication hole 38 b to the air discharge flow path 48.

  On the other hand, in the fuel gas supply device 16, high-pressure hydrogen stored in the hydrogen tank 50 is led out to the hydrogen supply passage 52 and supplied to the fuel gas inlet communication hole 40 a of the fuel cell 12 through the ejector 54. . The hydrogen gas moves along the anode gas flow path 34 and then is led out from the fuel gas outlet communication hole 40 b to the off gas flow path 56. In the off-gas flow path 56, exhaust gas containing unused hydrogen gas is sucked into the ejector 54 through the hydrogen circulation path 58 and supplied to the fuel cell 12 as fuel gas.

  Therefore, in the electrolyte membrane / electrode structure 28, the oxidant gas supplied to the cathode side electrode 24 and the hydrogen (fuel gas) supplied to the anode side electrode 26 are consumed by an electrochemical reaction in the electrode catalyst layer. And power generation is performed.

  In the cooling medium supply device 18, the pump 64 sends the cooling medium in the forward direction under the rotating action of the motor 63. This cooling medium is supplied from the cooling medium inlet communication hole 42 a of the fuel cell 12 to the cooling medium flow path 36. The cooling medium that has cooled the fuel cell 12 through the cooling medium flow path 36 is discharged from the cooling medium outlet communication hole 42 b to the circulation flow path 62.

  In the circulation flow path 62, when the temperature of the cooling medium is relatively high, a larger amount of cooling medium is supplied to the radiator 60 than the first branch flow path 66 under the action of the thermo valve 70. For this reason, the cooled cooling medium is supplied to the fuel cell 12 to lower the temperature of the fuel cell 12.

  Further, when the temperature of the cooling medium is relatively low, the flow rate of the cooling medium flowing through the first branch channel 66 is set to be larger than the flow rate of the cooling medium flowing through the radiator 60 under the action of the thermo valve 70. Is done. Therefore, the temperature of the cooling medium is increased, and the temperature of the fuel cell 12 is adjusted within a desired temperature range.

  Next, the controller 20 detects the operating environment temperature of the fuel cell system 10 via the temperature sensor 76a, and detects the internal temperature of the fuel cell 12 via the temperature sensor 76b. Then, the controller 20 determines whether or not generated water inside the fuel cell 12 is frozen when the operation of the fuel cell system 10 is stopped based on the detected temperature obtained from the temperature sensor 76a. It is determined whether or not to perform rapid cooling control.

  Specifically, when the operation of the fuel cell system 10 is stopped, the cooling medium supply device 18 drives the pump 64 in the forward direction to circulate and supply the cooling medium to the fuel cell 12. Therefore, when the controller 20 determines that the outside air temperature is a predetermined temperature or lower, for example, minus 10 ° C. or lower, based on the temperature detected from the temperature sensor 76a, the controller 20 shifts to the rapid cooling control.

  In the rapid cooling control, as shown in FIG. 4, the motor 63 is rotated in the reverse direction, and the cooling medium is sent through the circulation channel 62 in the reverse flow direction (see the arrow in FIG. 4) via the pump 64. For this reason, the cooling medium is introduced into the second branch flow path 72 that bypasses the thermo valve 70, and is supplied to the radiator 60 through the first check valve 74 a. As described above, the flow of the cooling medium does not occur in the first branch flow path 66 by the action of the second check valve 74b. The cooling medium cooled by exchanging heat with outside air by the radiator 60 moves in the reverse direction in the circulation flow path 62 and is supplied to the cooling medium flow path 36 from the cooling medium outlet communication hole 42 b of the fuel cell 12.

  In this case, at the time of the above rapid cooling control, the cooling medium bypasses the thermo valve 70, so that the flow rate adjusting function by the thermo valve 70 is interrupted. Therefore, a desired amount of the cooling medium can be supplied to the radiator 60, and the cooling medium can be quickly cooled. Therefore, as shown in FIGS. 2 and 3, when the outside air temperature becomes a predetermined temperature (for example, 0 ° C.) or less, the pump 64 is rotated reversely from time T1 to time T2. As a result, the cooling medium is rapidly cooled under the action of the radiator 60 and, if necessary, the electric fan 65. Therefore, by circulating the cooling medium to the fuel cell 12, the fuel cell 12 is, for example, 0 ° C. Is rapidly cooled to a temperature of minus 10 ° C. or lower.

  For this reason, the phenomenon in which the ice crystals grow while the generated water in the fuel cell 12 freezes, which is observed when the fuel cell 12 is gradually cooled from around 0 ° C., does not occur, and the solid polymer electrolyte Damage to the membrane 22 can be prevented as much as possible.

  Thus, in this embodiment, when it is determined that the generated water may freeze inside the fuel cell 12 when the fuel cell system 10 is stopped, the pump 64 is driven in the reverse direction so that the cooling medium circulates. It flows through the flow path 62 in the reverse direction. At this time, the cooling medium bypasses the thermo valve 70 which is a flow rate adjusting valve, flows through the second branch flow path 72, and is rapidly cooled by exchanging heat with the outside air by the radiator 60. It becomes possible to cool.

  Moreover, the thermo valve 70 is not used when the cooling medium is backflowed. Therefore, in order to realize a valve operation different from normal when there is a risk of freezing of the generated water inside the fuel cell 12, it is not necessary to use a relatively expensive three-way solenoid valve or the like as the flow rate adjustment valve. Therefore, it is possible to obtain an effect of preventing damage to the solid polymer electrolyte membrane 22 in a sub-freezing environment as much as possible with a simple and economical configuration. In addition, there is an advantage that the power consumption during normal operation is effectively reduced by using the thermo valve 70 during normal operation.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 18 ... Cooling medium supply device 20 ... Controller 22 ... Solid polymer electrolyte membrane 24 ... Anode side electrode 26 ... Cathode side electrode 28 ... Electrolyte membrane / electrode structure 30a, 30b ... Separator 32 ... Cathode gas flow path 34 ... Anode gas flow path 36 ... Cooling medium flow path 44 ... Compressor 50 ... Hydrogen tank 54 ... Ejector 60 ... Radiator 62 ... Circulation flow path 63 ... Motor 64 ... Pump 66 ... Branch channel 70 ... Thermo valve 72 ... Branch channel 74a, 74b ... Check valve 76a, 76b ... Temperature sensor

Claims (3)

A fuel cell in which fuel gas and oxidant gas react electrochemically to obtain electrical energy; and
A cooling medium supply device for supplying a cooling medium to the fuel cell and adjusting the temperature of the fuel cell;
A fuel cell system comprising:
The cooling medium supply device includes a radiator,
A circulation channel for circulating the cooling medium between the fuel cell and the radiator;
A pump disposed on the circulation flow path and capable of feeding the cooling medium in both forward and reverse directions;
A first branch channel provided in the circulation channel and bypassing the radiator;
A flow rate adjustment that is disposed at a junction of the circulation channel and the first branch channel and adjusts the flow rate of the circulation channel and the flow rate of the first branch channel according to the environmental temperature of the fuel cell. A valve,
A second branch channel provided in the circulation channel and bypassing the flow regulating valve;
A check valve provided in the second branch flow path;
A controller that drives the pump in the reverse direction when it is determined that the generated water may freeze inside the fuel cell when the fuel cell is stopped based on the temperature detected by the temperature sensor;
A fuel cell system comprising:   2. The fuel cell system according to claim 1, wherein the check valve allows the flow of the cooling medium only when the pump is driven in the reverse direction.   3. The fuel cell system according to claim 1, wherein the first branch flow path is provided with a check valve that allows the flow of the cooling medium only when the pump is driven in the forward direction. A fuel cell system.

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