JP2007042375A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system heating air supplied to a fuel cell to warm up the fuel cell in an early stage while suppressing increase of an overvoltage of the fuel cell. <P>SOLUTION: This fuel cell system is provided with: the fuel cell 10 obtaining power by electrochemically reacting hydrogen and oxygen; a gas compressor 21 adiabatically compressing air containing oxygen and supplying it to the fuel cell 10 through an air supply path 20a; and a heater 26 for heating the air on the upstream side of the compressor 21 in the air gas supply path 20a. The heater 26 is supplied with power from the fuel cell 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric energy by an electrochemical reaction between hydrogen and oxygen, and is effective when applied to a mobile generator such as a vehicle, a ship, and a portable generator. .

A polymer electrolyte fuel cell that is considered as a driving source for vehicles or the like has a problem that power generation efficiency is low at low temperatures, so that sufficient power generation capacity cannot be obtained at low temperature startup. In order to solve such a problem, in a fuel cell system that supplies air to the fuel cell at normal pressure, a method has been proposed in which the supplied air is heated to warm up the fuel cell to improve the power generation efficiency at the start ( Patent Document 1).
JP 2002-093445 A

  However, in the configuration described in Patent Document 1, since air is supplied to the fuel cell at normal pressure, there is a problem that the overvoltage of the fuel cell increases and the power generation characteristics deteriorate.

  In view of the above, the present invention provides a fuel cell system that can quickly warm up a fuel cell by heating air supplied to the fuel cell while suppressing an increase in overvoltage of the fuel cell. With the goal.

  In order to achieve the above object, the first feature of the present invention is that a fuel cell (10) that obtains electric power by electrochemically reacting hydrogen and oxygen contained in air and a fuel via an air supply path (20a). A gas compressor (21) that supplies air to the battery (10) after adiabatic compression, and air that is provided upstream of the gas compressor (21) in the air gas supply path (20a) and is sucked into the gas compressor And a heating device (26) for heating.

  Thus, in the fuel cell system that supplies air to the fuel cell (10) by the compressor (21), the heating device (26) is provided on the upstream side of the compressor (21), and the intake air of the compressor (21) is provided. Is heated, the temperature of air supplied to the fuel cell (10) can be raised efficiently, and the temperature of the catalyst layer on the cathode side of the fuel cell (10) can be raised quickly. Then, high-temperature compressed air can be supplied to the fuel cell 10, the cathode overvoltage can be reduced, the power generation characteristics of the fuel cell 10 can be improved, and the self-heating of the fuel cell 10 can be promoted. Thus, the temperature of the fuel cell (10) can be raised quickly.

  When the compressed air is heated on the downstream side of the compressor (21), the heat exchange efficiency is poor because there is no air flow rate, whereas the upstream side of the compressor (21) is heated as in the present invention. By arranging the device (26), heat exchange is performed in a state where there is a flow velocity of air, so that heat exchange efficiency is good and air is easily heated. Furthermore, the air supplied to the fuel cell (10) can be raised to a higher temperature by increasing the discharge pressure of the compressor (21) simultaneously with the heating by the heating device (26).

  Moreover, a heating apparatus (26) can be made compact by using what an electric heater and a heat exchanger are comprised integrally.

  The second feature of the present invention is that the heating device (26) is supplied with power from the fuel cell (10). Thereby, the electric power generation amount of a fuel cell (10) can be increased, and the self-heating amount can be increased. Furthermore, by heating the air supplied to the fuel cell (10) by the heating device (26), the generated power increased by the fuel cell (10) can be recovered as heat.

  A third feature of the present invention includes a first temperature sensor (17) for detecting the temperature of the fuel cell (10), and is based on the temperature of the fuel cell (10) detected by the first temperature sensor (17). And controlling the heating of the air by the heating device (26). Thereby, the temperature of the air supplied to the fuel cell (10) can be appropriately adjusted according to the fuel cell temperature.

  The fourth feature of the present invention includes a second temperature sensor (18) for detecting the outside air temperature, and heating the air by the heating device (26) based on the outside air temperature detected by the second temperature sensor (18). Is to control. Thereby, the temperature of the air supplied to the fuel cell (10) can be appropriately adjusted according to the outside air temperature.

  A fifth feature of the present invention is that the fuel cell (10), the gas compressor (21), and the heating device (26) are mounted on a vehicle, the fuel cell (10) is used as a driving source for the vehicle, and the gas The air discharged from the compressor (21) is configured to be supplied into the vehicle compartment. Thereby, even when the air heating temperature by the air conditioner is low, the passenger compartment can be heated.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In this embodiment, the fuel cell system is mounted on an electric vehicle (fuel cell vehicle) that travels using the fuel cell as a drive source for travel.

  FIG. 1 shows the overall configuration of the fuel cell system of the present embodiment. As shown in FIG. 1, the fuel cell system of the present embodiment includes a fuel cell (FC stack) 10 that generates electric power by utilizing an electrochemical reaction between hydrogen and oxygen. The fuel cell 10 is configured to supply electric power to electric devices such as a motor generator 11, a secondary battery 12, and an auxiliary machine 15 for driving the vehicle.

  In the present embodiment, a solid polymer electrolyte fuel cell is used as the fuel cell 10, and a plurality of fuel cells 100 serving as a basic unit are stacked. Each fuel cell 100 is composed of an electrolyte membrane made of a proton conductive ion exchange membrane and electrodes arranged on both side surfaces thereof. The electrode is composed of a catalyst layer and a gas diffusion layer. One electrode is configured as an air electrode (cathode) to which air as an oxidant gas is supplied, and the other electrode is configured as a hydrogen electrode (anode) to which hydrogen as a fuel gas is supplied.

  In the fuel cell 10, the following electrochemical reaction between hydrogen and oxygen occurs to generate electric energy.

(Hydrogen electrode side) H ₂ → 2H ⁺ + 2e ⁻
(Oxygen electrode side) 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
The fuel cell 10 and the secondary battery 12 are electrically connected via a DC-DC converter 13 capable of transmitting power in both directions. The DC-DC converter 13 controls the flow of electric power from the fuel cell 10 to the secondary battery 12 or from the secondary battery 12 to the fuel cell 10.

  A first inverter 14 is arranged between the fuel cell 10 and the secondary battery 12 and the motor generator 11. The function of the motor generator 11, that is, the function as an electric motor and the function as a generator are switched by the first inverter 14.

  When the DC-DC converter 13 and the first inverter 14 are operated, for example, when a large amount of electric power is suddenly required during sudden acceleration, the motor is driven not only from the fuel cell 10 but also from the secondary battery 12. Electric power can be supplied to the generator 11. Further, the surplus power during the power generation of the fuel cell 10 and the power regenerated by the motor generator 11 can be stored in the secondary battery 12.

  A second inverter 16 is arranged between the fuel cell 10 and the secondary battery 12 and the auxiliary machine 15. The auxiliary machine 15 is a power device necessary for operating the fuel cell 10, and includes an electric motor 22 that drives a compressor 21, which will be described later, and an electric motor 42 that drives a water pump 41.

  The fuel cell system is provided with a first temperature sensor 17 that detects the temperature of the fuel cell 10 and a second temperature sensor 18 that detects the outside air temperature.

  The fuel cell system includes an air supply path 20a for supplying air (oxidant gas) to the oxygen electrode side of the fuel cell 10, an air discharge path 20b for discharging air from the fuel cell 10, and a fuel cell. A hydrogen supply path 30a for supplying hydrogen (fuel gas) to the hydrogen electrode side of 10 and a hydrogen discharge path 30b for discharging unreacted hydrogen gas and the like from the fuel cell 10 are provided.

  The air supply path 20a is provided with a blower 21 for air pressure feeding. The blower 21 is driven by an electric motor 22. The air discharge path 20b is provided with an air discharge path opening / closing valve 24 that opens and closes the air discharge path 20b. When supplying air to the fuel cell 10, the air discharge path opening / closing valve 24 is opened and the compressor 21 is driven by the electric motor 22. The electric motor 22 as an auxiliary machine is connected to the secondary battery 12 via the inverter 23.

  A humidifier 25 is provided in the air supply path 20a and the air discharge path 20b. The humidifier 25 humidifies the air discharged from the compressor 21 using moisture contained in the humid exhaust air discharged from the fuel cell 10, whereby the solid polymer in the fuel cell 10 is obtained. The electrolyte membrane is in a wet state containing moisture so that an electrochemical reaction can be satisfactorily performed during power generation operation.

  A heating device 26 is provided on the upstream side of the compressor 21 in the air supply path 20a. The heating device 26 heats the air sucked into the compressor 21 and raises the temperature of the air supplied to the fuel cell 10. The heating device 26 operates by supplying power from the fuel cell 10 or the secondary battery 12. In addition, the heating device 26 has a compact configuration in which an electric heater and a heat exchanger are integrally formed.

  FIG. 2 shows the temperature of the air before and after being compressed by the compressor 21. The outside temperature is -30 ° C. Since the compressor 21 performs adiabatic compression, the air temperature after compression is proportional to the compression rate, and the higher the air temperature before compression, the higher the air temperature after compression. For this reason, the air temperature after compression can be made high by heating the air sucked into the compressor 21 by the heating device 26.

  When heating the compressed air on the downstream side of the compressor 21, the heat exchange efficiency is poor because there is no air flow rate. In contrast, by arranging the heating device 26 on the upstream side of the compressor 21 as in the present embodiment, heat exchange is performed in a state where there is a flow rate of air, so heat exchange efficiency is good and air is heated. Cheap. Moreover, since the air before compression is low temperature (-30 degreeC in this example) and the temperature difference with the heating temperature by the heating apparatus 26 is large, heat exchange efficiency is good.

  Further, when the intake air temperature of the compressor 21 is the same, the higher the compression rate by the compressor 21, the higher the air temperature after compression. For this reason, the temperature rise of the air supplied to the fuel cell 10 is assisted by increasing the discharge pressure of the compressor 21 as necessary.

  In addition, an air conditioning air supply path 27 for supplying air into the vehicle interior is connected between the compressor 21 and the humidifier 25 in the air supply path 20a. The air conditioning air supply path 27 is provided with a flow rate adjusting valve 28, and the other end of the air conditioning air supply path 27 is connected to an air conditioner 29 that air-conditions the passenger compartment. The heated air supplied to the air conditioner 29 is used as blown air into the passenger compartment.

  The hydrogen supply path 30a includes a hydrogen cylinder 31 filled with hydrogen gas, a hydrogen pressure regulating valve 32 for adjusting the pressure of hydrogen supplied to the fuel cell 10, and a hydrogen supply path opening / closing valve 33 for opening and closing the hydrogen supply path 30a. Is provided. The hydrogen discharge path 30b is provided with a hydrogen discharge path opening / closing valve 34 that opens and closes the hydrogen discharge path 30b.

  When supplying hydrogen to the fuel cell 10, the hydrogen supply path opening / closing valve 33 is opened and adjusted to a desired hydrogen pressure by the hydrogen pressure regulating valve 32. The hydrogen discharge path 30b is opened and closed by a hydrogen discharge path opening / closing valve 34 in accordance with operating conditions. The hydrogen discharge path 30b discharges unreacted hydrogen gas, steam (or water), nitrogen, oxygen, and the like mixed through the solid polymer electrolyte membrane from the oxygen electrode.

  The fuel cell 10 generates heat with power generation. For this reason, the fuel cell system is provided with cooling systems 40 to 44 that cool the fuel cell 10 so that the operating temperature becomes a temperature suitable for the electrochemical reaction (for example, about 80 ° C.).

  The cooling system includes a cooling water path 40 that circulates cooling water (heat medium) in the fuel cell 10, a water pump 41 that circulates the cooling water, an electric motor 42 that drives the water pump 41, and a radiator 43 that includes a fan 44. Is provided. The heat generated in the fuel cell 10 is discharged out of the system by the radiator 43 through the cooling water. With such a cooling system, the cooling amount control of the fuel cell 10 can be performed by the flow rate control by the water pump 41 and the air volume control by the fan 44. Although not shown, the electric motor 42 as an auxiliary machine is connected to the secondary battery 12 via an inverter, like the blower electric motor 22.

  The fuel cell system is provided with a control unit (ECU) 50 that performs various controls. The control unit 50 is configured by a known microcomputer including a CPU, a ROM, a RAM, an I / O, and the like, and executes processing such as various calculations according to a program stored in the ROM. The controller 50 is input with required power signals from various loads, temperature detection signals from the temperature sensors 17 and 18, and the like. The control unit 50 includes a secondary battery 12, a DC-DC converter 13, a first inverter 14, a second inverter 16, an electric motor 22, an air discharge path on / off valve 23, a heating device 26, a hydrogen pressure regulating valve 32, and a hydrogen supply. A control signal is output to the path opening / closing valve 33, the hydrogen discharge path opening / closing valve 34, the electric motor 42, the fan 44, and the like.

  Next, the operation of the fuel cell system of this embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a flow of control performed by the CPU of the control unit 50 based on a control program stored in the ROM.

First, the outside temperature T _OUT is detected by the second temperature sensor 18 (S10), and it is determined whether or not the outside temperature T _OUT is lower than the first predetermined temperature T1 (S11). As a result, when it is determined that the outside air temperature T _OUT is not lower than the first predetermined temperature T1, the process returns to S10. The first predetermined temperature T1 is a reference value as to whether or not heating by the heating device 26 is performed, and can be arbitrarily set.

On the other hand, when it is determined that the outside air temperature T _OUT is lower than the first predetermined temperature T1, the first temperature sensor 17 detects the temperature T _FC of the fuel cell 10 (S12), and the fuel cell temperature T _FC. Is lower than the second predetermined temperature T2 (S13). As a result, when the fuel cell temperature T _FC is determined to not lower than the second predetermined temperature T2, the process returns to S10, It should be noted that the second predetermined temperature T2, whether performing heating by the heating device 26 It is a reference value and can be set arbitrarily.

On the other hand, when the fuel cell temperature T _FC is determined to below a second predetermined temperature T2 is energized heating device 26, for heating the intake air of the compressor 21 by the heating device 26 (S14). Thereby, heated air is supplied to the fuel cell 10.

  Furthermore, when the temperature of the air supplied to the fuel cell 10 is not sufficiently raised only by heating by the heating device 26, the discharge pressure of the compressor 21 is increased as necessary (S15). Thereby, the temperature of the air supplied to the fuel cell 10 can be made higher.

  Next, it is determined whether heating of the passenger compartment is necessary (S16). The necessity of heating the passenger compartment can be determined, for example, based on whether or not the heating switch is turned on. As a result, when it is determined that heating of the passenger compartment is necessary, the opening degree of the flow rate adjustment valve 28 is increased, and hot air flowing through the air supply path 20a is supplied to the air conditioner 29 (S17).

  As described above, in the fuel cell system that supplies air to the fuel cell 10 by the compressor 21, the heating device 26 is provided on the upstream side of the compressor 21, and the intake air of the compressor 21 is heated, whereby the fuel cell 10 The temperature of the air supplied to can be increased efficiently. Thereby, high-temperature air is supplied to the cathode side of the fuel cell 10, and the temperature of the catalyst layer on the cathode side of the fuel cell 10 can be raised quickly. Furthermore, the diffusibility of air can be improved by supplying high-temperature compressed air to the fuel cell 10. As a result, the cathode overvoltage can be reduced to improve the power generation characteristics of the fuel cell 10, the self-heating of the fuel cell 10 can be promoted, and the temperature of the fuel cell 10 can be raised quickly. It is possible to prevent water existing in the water from freezing.

  In order to raise the temperature of the fuel cell 10, it is effective to increase the self-heating value. For this purpose, it is necessary to increase the amount of reaction hydrogen and extract a large amount of current from the fuel cell 10. Therefore, by supplying electric power from the fuel cell 10 to the heating device 26 using an electric heater, it is possible to increase the power generation amount of the fuel cell 10 and increase the amount of self-heating. Then, by heating the air supplied to the fuel cell 10 by the heating device 26, the generated power increased by the fuel cell 10 can be recovered as heat. Furthermore, it is also effective to supply power from the fuel cell 10 to the heating device 26 when the power generation efficiency is lowered by reducing the operating voltage of the fuel cell 10 and the self-heating value is increased.

  Further, by supplying high-temperature air from the outlet of the compressor 21 to the air conditioner 29, the vehicle interior can be heated even when the air heating temperature by the air conditioner 29 is low.

(Other embodiments)
In the above embodiment, to determine whether to perform heating by the heating device 26 based on the outside air temperature T _OUT, and configured to adjust the heating temperature by the heating device 26 based on the outside air temperature T _OUT Also good. For example, when the outside air temperature T _OUT is low, the heating temperature by the heating device 26 may be increased, and when the outside air temperature T _OUT is high, the heating temperature by the heating device 26 may be increased.

Similarly, in the above embodiment, to determine whether to perform heating by the heating device 26 based on the fuel cell temperature T _FC, configured to adjust the heating temperature by the heating device 26 based on the fuel cell temperature T _FC May be. For example, when the fuel cell temperature T _FC is low, the heating temperature by the heating device 26 may be increased, and when the fuel cell temperature T _FC is high, the heating temperature by the heating device 26 may be increased.

It is a conceptual diagram of the fuel cell system of the said embodiment. It is a graph which shows the temperature of the air before and behind compressed with a compressor. It is a flowchart which shows the action | operation of the fuel cell system of the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 17 ... 1st temperature sensor, 18 ... 2nd temperature sensor, 20a ... Air supply path, 21 ... Compressor, 26 ... Heating device, 50 ... Control part.

Claims (5)

A fuel cell (10) for obtaining electric power by electrochemical reaction of hydrogen and oxygen contained in air;
A gas compressor (21) for supplying air by adiabatic compression to the fuel cell (10) via an air supply path (20a);
A heating device (26) provided on the upstream side of the gas compressor (21) in the air gas supply path (20a) and heating air sucked into the gas compressor (21). Fuel cell system. The fuel cell system according to claim 1, wherein the heating device (26) is supplied with electric power from the fuel cell (10). A first temperature sensor (17) for detecting the temperature of the fuel cell (10) is provided, and the heating device (26) based on the temperature of the fuel cell (10) detected by the first temperature sensor (17). 3. The fuel cell system according to claim 1, wherein the heating of the air is controlled. A second temperature sensor (18) for detecting an outside air temperature is provided, and heating of air by the heating device (26) is controlled based on the outside air temperature detected by the second temperature sensor (18). The fuel cell system according to any one of claims 1 to 3. The fuel cell (10), the gas compressor (21), and the heating device (26) are mounted on a vehicle, and the fuel cell (10) is used as a driving source for the vehicle.
The fuel cell system according to any one of claims 1 to 4, wherein the air discharged from the gas compressor (21) is configured to be supplied into a passenger compartment.

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