JPH04242075A - Heating and cooling device of fuel cell - Google Patents

Abstract

PURPOSE:To drive the circulating pump of a heating and cooling device at a constant speed for reducing a loss of a drive motor which is large hitherto, and for avoiding an empty burning accident of a heat exchanger. CONSTITUTION:To a circulating pump 4 to circulate a cooling medium to a cooling plate 1A laminated to a fuel cell 1 through a heat exchanger 5, and a blower 7 to blow the air to the above heat exchanger 5 through an auxiliary burner 6, one common set of motive power device 11 such as a variable speed motor or a prime mover is provided, and the motive power device 11 is controlled in a variable speed made by a drive current generated by a controller 9 detecting the temperature of the fuel cell, and both the circulating amount of the cooling medium and the air blowing amount are increased or decreased proportionally to the heat exchange amount necessary for a heating and cooling device 20. And a motive power transmitting device 12 is provided when necessary, and the difference of revolution between the circulating pump 4 and the blower 7 is absorbed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention controls the temperature of the cooling medium circulating through the cooling plate of a liquid-cooled fuel cell, thereby raising the temperature of the fuel cell at startup, maintaining an appropriate operating temperature, and stopping the fuel cell. The present invention relates to a fuel cell heating and cooling device that lowers the temperature over time.

0002

[Prior Art] A fuel cell is constructed as a stack of single cells consisting of a matrix impregnated with an electrolyte, such as phosphoric acid, and a fuel electrode and an oxidizer electrode sandwiching the matrix. It supplies hydrogen-rich fuel gas and air as an oxidizing agent to directly generate electricity based on an electrochemical reaction, and eliminates the heat generated by the electrode reaction, which is an exothermic reaction, to maintain the fuel cell at a specified temperature. Operating temperature, e.g. 190°C to 195°C
In order to maintain the temperature, a cooling plate is laminated together with the unit cells in the stack, and a heating/cooling device is provided to control the temperature of the cooling medium flowing through the cooling plate. Additionally, as the current supplied by a fuel cell to its load increases, the internal resistance of the fuel cell, the diffusion resistance of fuel gas and oxidant gas (together referred to as reactant gas) to the electrodes, and energy loss due to electrode reactions increase. The voltage drop increases accordingly, and the energy loss due to this voltage drop also increases the heat produced by power generation. In addition, a voltage drop due to deterioration of electrode characteristics also causes an increase in heat generation. Therefore, a fuel cell heating and cooling device has a heating function to raise the temperature of the fuel cell to the appropriate operating temperature when starting the fuel cell, and a heating function to raise the temperature of the fuel cell to the appropriate operating temperature during power generation operation in response to load fluctuations. A cooling function is required to quickly lower the temperature of the fuel cell to below its storage temperature of 100°C when power generation operation is stopped.

FIG. 2 is a configuration diagram showing a conventional fuel cell heating/cooling device, in which fuel gas is supplied from a fuel reformer 2 to a fuel electrode, and reaction air is supplied to an oxidizer electrode to generate electricity in a fuel cell. The (stack) 1 is provided with a heating and cooling device 10 including a cooling plate 1a stacked together with the unit cells. That is, a cooling medium circulation system 3 is connected to the cooling pipe of the cooling plate 1a, and the circulation system 3 uses a circulation pump 4 to circulate the internal cooling medium through the corrugated pipes in the heat exchangers 5 and 8 to the cooling plate 1a. configured. Auxiliary burner 6
When starting up the fuel cell 1, high-temperature combustion gas is supplied to the heat exchanger 5 to heat the cooling medium, and while the primary combustion air is supplied by the blower 7, it is supplied to the burner by the source fuel pump 6a. By burning source fuel,
The high temperature combustion gas is radiated towards the heat exchanger 5. on the other hand,
Another heat exchanger 8 is provided in the circulation system 3 to utilize the heat generated by the power generation of the fuel cell 1 as waste heat, and is used as a heater or vaporizer for a source fuel such as methane gas, liquefied natural gas, or methanol. The heated source fuel gas or vaporized gas is supplied to a fuel reformer 2 that reforms the source fuel into hydrogen-rich fuel gas and supplies it to the fuel cell 1 . On the other hand, the circulation pump 4 and the blower 7 are each equipped with drive motors 4a and 7a as power devices, and the drive motors are activated by a drive signal or drive current generated by the control unit 9 upon receiving a detection signal from the temperature sensor 9a of the cooling plate 1a. By controlling the rotational speed, the flow rate of the cooling medium and the amount of air blown by the blower are controlled.

[0004] In the heating/cooling device constructed as described above, the circulation pump 4 is continuously operated while maintaining a constant flow rate during operation of the fuel cell. When starting up the fuel cell, the heat exchanger 5 is heated by the auxiliary burner 6 to bring the fuel cell 1 close to the appropriate operating temperature. When the temperature of the fuel cell 1 and the heat exchanger 8 reaches the operating temperature, the fuel reformer 2 also reaches the operating temperature by the reformer burner, and the fuel cell starts power generation operation, the operation of the auxiliary burner 6 is stopped. After that, the operating temperature of the fuel cell and heat exchanger 8 is maintained by the self-heating of the fuel cell, but it is necessary to prevent overheating beyond the proper operating temperature. Therefore, during power generation operation, the cooling plate temperature is monitored and the drive current generated by the control unit 9 operates the drive motor 7a at variable speed to adjust the air flow rate of the blower 7, and the heat exchanger 5
Temperature control is performed to cool the cooling medium through. Furthermore, when stopping the operation of the fuel cell, a cooling operation is performed to maximize the amount of air blown by the blower 7 to maximize the cooling efficiency of the cooling medium of the heat exchanger 5.

[0005]

[Problems to be Solved by the Invention] In conventional heating and cooling systems, the circulation pump 4 is always operated at a constant flow rate, and the air flow rate of the blower 7 is varied to control the temperature. There is a problem in that the power consumption (auxiliary equipment loss) reaches 2% of the constant output power of the fuel cell, and the power generation efficiency of the fuel cell power generation device decreases, especially when the fuel cell has an output lower than its constant output. If the system is operated at Furthermore, since the drive motors for the circulation pump and blower are separate, if the drive system of the circulation pump breaks down while the burner 6 is burning, the heat exchanger 5 will be in an empty state and the heat exchanger 5 will be damaged by overheating. Occur.

[0006] An object of the present invention is to reduce auxiliary equipment loss;
The object of the present invention is to provide a heating and cooling device that can avoid an accident of dry heating of a heat exchanger.

[0007]

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a fuel cell consisting of a stack of unit cells includes a cooling plate laminated together with the unit cells, and a cooling medium is applied to the cooling plate. a heat exchanger having a circulation pump and an auxiliary burner disposed in a circulation system that recirculates the gas; a blower that blows hot combustion gas or cooling air to the heat exchanger via the auxiliary burner; The fuel cell is heated or cooled by controlling the power unit of the circulation pump and the blower based on the drive current generated by detecting the temperature of the cooling plate, wherein the power unit includes a common power unit that drives the circulation pump and the blower. shall be.

[0008] Furthermore, a power transmission device is provided between the power unit and at least one of the circulation pump and the blower to regulate the rotational speed ratio of the circulation pump and the blower as necessary.

It is further assumed that the common power device driving the circulation pump and blower is a variable speed motor.

0010

[Operation] By configuring the circulation pump and blower of the heating and cooling system to be driven by a single power unit, such as a variable speed motor, a large amount of heat exchange is required, such as when starting up a fuel cell or during high output operation. Sometimes, the drive motor is rotated at high speed to increase the heat exchange efficiency of the cooling plate and heat exchanger to increase the heating and cooling rate of the cooling medium, and to prevent the fuel cell from operating at low output or when there is a difference between the proper operating temperature and the detected temperature. When the drive motor is small, the rotation speed of the drive motor is lowered and the circulation pump and blower are operated at low output to control the power consumed by the drive motor in accordance with the required amount of heat exchange, reducing auxiliary equipment loss. is obtained. In addition, if the drive system breaks down while the burner is burning and the circulation of the cooling medium and air flow stop, the burner will become deficient in oxygen and will not be able to maintain combustion.This will automatically prevent damage caused by overheating of the heat exchanger. You can get the ability to avoid it.

Furthermore, by providing a power transmission device that regulates the rotational speed ratio between the circulation pump and the blower, the rotational speed ratio between the circulation pump and the blower can be maintained, and the speed can be controlled to change in proportion to the amount of heat exchange. can be performed smoothly with one power unit.

0012

EXAMPLES The present invention will be explained below based on examples. FIG. 1 is a block diagram showing a heating and cooling device for a fuel cell according to an embodiment of the present invention, and the same reference numerals are used for the same parts as in the conventional device, and redundant explanation will be omitted. In the figure, the heating and cooling device 20 includes a common power unit 11 that drives the circulation pump 4 and the blower 7. The power device 11 is preferably a variable speed motor whose rotational speed can be controlled, but if the fuel cell 1 is a mobile power supply device, it may be a prime mover such as a gasoline engine or a diesel engine. Further, if the constant rotation speeds of the circulation pump and the blower are the same, the rotating shaft of the power unit 11 may be directly connected to the shafts of the circulation pump and the blower, but if the constant rotation speeds of both are different, A transmission 12 as a power transmission device is provided between one of the two, for example, the circulation pump 4 and the power device. The power transmission device 12 can easily adjust the rotational speed ratio between the two by changing the diameter of the pulley if a belt drive is used, or by using a variable speed gearbox if a direct connection type is used. The difference can be corrected.

The temperature control of the fuel cell 1 by the heating/cooling device 20 configured as described above is carried out by the control section 9 controlling the cooling plate 1a.
In proportion to the temperature difference between the detected temperature and its proper operating temperature,
This is done by controlling the magnitude of the drive current I supplied to the variable speed motor 11 as a power device. That is,
When starting up the fuel cell, the variable speed motor 11 rotates at high speed due to the large temperature difference, and at the same time, the source fuel pump 6a also rotates at high speed, causing the auxiliary burner 6 to generate a large amount of high-temperature combustion gas toward the heat exchanger 5. As a result, the temperature of the cooling medium increases rapidly, and a large amount of cooling medium flows through the cooling plate 1a, allowing the fuel cell to be heated to its proper operating temperature, and the source heated or vaporized by the heat exchanger 8 to be heated. Fuel gas can be supplied to the fuel reformer 2 to facilitate startup of the fuel cell. Note that the maximum heat exchange amount of the heat exchanger 5 is determined by the heating operation described above, so the maximum circulation amount of the cooling medium of the circulation pump 4 and the maximum combustion amount of the source fuel of the burner 6 are within the range in which the cooling medium does not boil during the heating operation. It can be determined by

On the other hand, during power generation operation of the fuel cell, the generated heat of the fuel cell 1 is absorbed into the cooling medium via the cooling plate 1a, and the absorbed thermal energy is disposed of in the heat exchanger 8 to heat or vaporize the source fuel. In addition to utilizing the heat, it is necessary to dissipate surplus thermal energy from the heat exchanger 5 to the outside to cool and maintain the fuel cell at its proper operating temperature of 190 to 195°C, so the burner 6 is kept in the extinguished state. , the circulation pump 4 and the blower 7 are driven to cool the heat exchanger 5 by forced air. At this time, the heat generated by the fuel cell increases in proportion to the electric power supplied to the load, but the thermal energy used by the heat exchanger 8 as waste heat also increases in proportion to this.
The control unit 9 senses the amount of change in the detected temperature with respect to the appropriate operating temperature of the fuel cell, and supplies the variable speed motor 11 with a drive current corresponding to the change, so that the amount of circulating coolant and the amount of air blown are adjusted to the amount of the fuel cell. Changes in response to the heat generated by power generation,
Correspondingly, the amount of heat exchanged externally by the heat exchanger 5 also increases, so that the fuel cell can be maintained at its proper operating temperature. The variable speed motor 11 is configured to operate continuously at a low speed even when the fuel cell is under a light load, so that the source fuel can be heated or vaporized in the heat exchanger 8 without any trouble. Furthermore, when the fuel cell stops operating, if the set temperature of the control unit 9 is switched to the storage temperature of the fuel cell and the difference between the detected temperature and the detected temperature is increased, the rotational speed of the variable speed motor increases and the fuel cell is rapidly cooled. be able to.

[0015]

[Effects of the Invention] As described above, the present invention is configured such that the cooling medium circulation pump and the blower that blows air to the heat exchanger via the auxiliary burner are coaxially driven by one power device such as a variable speed motor. . As a result, it is now possible to drive the circulation pump, which conventionally was always driven at a constant speed, at a variable speed in response to the amount of heat exchange required for heating or cooling the fuel cell. It is possible to provide a fuel cell heating and cooling device that can significantly reduce the auxiliary equipment loss of the drive motor, which consumes as much as 2% of the constant output of the fuel cell, and improve the power generation efficiency of the fuel cell. . Also,
If the power unit stops when the fuel cell is started, the circulation of the cooling medium and the air blowing will stop at the same time, causing the burner to become deficient in oxygen and stop combustion. Damage situations can be avoided.

Furthermore, the power device requires only one variable speed motor, and the rotation speed ratio of the circulation pump and blower can be adjusted using a simple and inexpensive power transmission device such as a pulley or gear box, so the configuration of the heating and cooling device can be adjusted. It is possible to provide a heating and cooling device for a fuel cell that can reduce auxiliary equipment loss and improve the power generation efficiency of a fuel cell without becoming complicated or bulky.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a fuel cell heating and cooling device according to an embodiment of the present invention.

[Figure 2] Configuration diagram showing a conventional fuel cell heating and cooling device

[Explanation of symbols]

1 Fuel cell 1a Cooling plate 2 Fuel reformer 3 Coolant circulation system 4 Circulation pump 4a Drive motor 5 Heat exchanger (for cooling) 6 Auxiliary burner 6a Source fuel pump 7 Blower 7a Drive motor 8 Heat exchanger (vaporizer) ) 9 Control unit 10 Heating/cooling device 11 Common power unit (variable speed motor) 12
Power transmission device (transmission) 20 Heating and cooling device

Claims (3)

[Claims] 1. A heat exchanger comprising a fuel cell consisting of a stack of unit cells, a cooling plate stacked together with the unit cells, and a circulation pump and an auxiliary burner disposed in a circulation system that circulates a cooling medium to the cooling plate. a blower for blowing high-temperature combustion gas or cooling air to the heat exchanger via the auxiliary burner; What is claimed is: 1. A heating and cooling device for a fuel cell, which controls a power device to heat or cool the fuel cell, comprising a common power device that drives the circulation pump and the blower. 2. Claim 1, further comprising a power transmission device that regulates a rotational speed ratio between the circulation pump and the blower, between the power device and at least one of the circulation pump and the blower. The heating and cooling device for the fuel cell described above. 3. The heating and cooling device for a fuel cell according to claim 1, wherein the common power device for driving the circulation pump and the blower is a variable speed motor.