JPH0447674A - Temperature control device for fuel cell - Google Patents

Abstract

PURPOSE:To control the supply amount of a thermo-medium from a heating tank in a wide range by divergence control using a three-way valve, by furnishing a bypass through which the thermo-medium flows divergently through the three-way valve in a position nearer the heating tank on a main circulation line, and thereby allowing the heating tank to function as a buffer tank. CONSTITUTION:A heating tank 11 having an upper space functions as a buffer tank and the ratio of the rate of thermo-medium flow heated to 170 deg.C from the heating tank 11, which converges with the suction side of a circulation pump 13, to the rate of thermo-medium flow from a bypass 27 becomes controllable as desired by the use of a three-way selector valve. When this fuel cell concerned 1 is to be held at a standby temp. around 130 deg.C, therefore, it is practicable to sink the temp. of thermo-medium flowing through the circulation line down to around 130 deg.C while the temp. of the thermo-medium 12 stored in the heating tank 11 is kept at 170 deg.C through utilization of the heat radiated from the circulation system leading via the bypass 27, and the fuel cell temp. can be maintained stably and accurately at the standby temp. by compensating the downward overshooting temp. of the thermo-medium with a high temp. thermo-medium fed from the heating tank 11.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to operating temperatures in liquid-cooled fuel cells.

It is related to the control device for the startup temperature and power generation standby temperature.

[Conventional technology]

A typical example is the cynic acid type, in which multiple layers of unit cells are stacked with fuel electrodes and air electrodes arranged with a matrix holding an electrolyte sandwiched between them, with a liquid-cooled cooling plate interposed between each unit cell. In a fuel cell, fuel gas or reaction air is supplied to an electrode catalyst layer supported on the matrix side of a gas-permeable electrode base material through a reaction gas passage formed on the opposite side of the matrix, and the fuel gas or reaction air is passed through the electrode base material. Electric power is generated by the reaction active material causing an electrochemical reaction in a pair of electrode catalyst layers.

In order to facilitate the diffusion of the reactive active material into the electrode catalyst layer and activate the electrochemical reaction, the operating temperature is maintained at, for example, 190° C. in the case of a cynic acid fuel cell. Therefore, when the fuel cell is out of operation for a long period of time, its temperature remains constant at mK.
If the fuel cell temperature has dropped, a start-up operation is required to bring the fuel cell temperature to the limit.

Further, when the power generation operation is stopped for a short time, it is necessary to maintain the temperature at a predetermined standby temperature lower than the operating temperature in preparation for restarting the operation.

FIG. 5 is a system 70 diagram showing a conventional temperature control device, in which one liquid-cooled fuel cell is composed of a stack of unit cells, each unit cell is equipped with liquid-cooled cooling plates 5, and The cooling pipe 5A is connected to the main circulation path 15 for the heat medium 12. The main circulation path 15 supplies the heat medium 12 from the heating tank 11 containing the heat medium 12 heated by the heater 11A to the cooling pipe 5A via the circulation pump 13, and the heat medium 12 exits from the cooling pipe 5A. The cooling pipe 5A is configured to return the heat to the heating tank 11 via a heat exchanger 14, and a side passage 17 having a control valve 16 is provided in parallel with the cooling pipe 5A at the inlet and outlet of the cooling pipe 5A.

The starting operation of the fuel cell 1 in the device configured as described above is carried out by circulating the heat medium 12 heated to, for example, 170° C. to the main circulation path 15 while the supply of refrigerant to the heat exchanger 14 is stopped. The temperature controller 19 detects the temperature of the cooling plate 5 with the temperature sensor 18 and fully controls the opening of the control valve 16, thereby increasing the temperature of the cooling plate 5 and the side passage. This is carried out by dividing the heat medium into 17 and 17. Furthermore, the standby temperature is maintained in a similar manner.

On the other hand, the operating temperature is maintained in the same way as during startup or standby by utilizing the difference between the temperature of the heat medium 12 contained in the heating tank 11, 170°C, and the operating temperature of 190°C. In a heavy load state with a large amount of heat, a part of the generated heat is absorbed by the heat exchanger 14 to maintain the operating temperature.

[Problem to be solved by the invention]

Figure 6 is a characteristic diagram showing the relationship between the temperature of the fuel cell in a no-load state and the deterioration rate of the electrode catalyst layer. If kept at high temperatures, the electrode catalyst particles become coarse and the electrode surface area decreases, or the carbon black that supports the catalyst particles corrodes, causing so-called high-temperature deterioration of the electrode, which reduces the power generation performance and remaining life of the battery. Failures such as Further, at a temperature of 130° C. or lower, the diffusion of reaction gas into the electrode catalyst layer and the rate of release of generated water to the outside of the electrode decrease.

Therefore, by keeping the standby temperature of the fuel cell at around 160°C and using the generated heat of power generation instead of supplying a reaction gas, the temperature is raised to the full operating temperature of the cell flow, so that power generation operation can be started. At the same time, the supply of fuel gas GF and air GA is started in a state where the temperature is about 130°C by the heating medium, and at the same time, the output current of the fuel cell is gradually increased by the current control device 7, and the output current of the fuel cell is gradually increased by the generated heat. By performing an operation to bring the battery temperature up to the operating temperature, a measure is taken to avoid high-temperature deterioration of the electrodes during this temperature raising process.

On the other hand, the temperature of the heat medium contained in the heating tank is set at approximately 170°C, which is an intermediate temperature between the standby temperature and the operating temperature.
A single liquid such as water is configured to serve as a heating medium during startup and as a cooling medium during operation without changing its set temperature.

However, it is difficult to maintain the standby temperature and the temperature increase rate at startup.
In the conventional method, which mainly controls the bypass flow rate to the side passage 17 using the control valve 16, it is often difficult to finely control the temperature because it is fixed with a flooded active mouth heat tank that exceeds the heat medium. There was a problem in that the standby temperature and operating temperature were prone to change.

The purpose of this invention is to
The aim is to completely improve and stabilize battery temperature control accuracy.

[Means to solve all problems]

In order to solve the above problems, the present invention provides a fuel cell in which liquid-cooled cooling plates are stacked for each unit cell in multiple layers, and a temperature maintained at an intermediate temperature between the operating temperature and the standby temperature of this fuel cell. A main circulation path including a heating tank containing a heated heat medium and a circulation pump that returns the heat medium to the heating tank through the entire cooling plate, wherein the main circulation path is located near the heating tank inlet of the main circulation path. a three-way switching valve disposed in the fuel cell, and a side passage communicating with the discharge side of one of the three-way switching valves and the suction side of the circulation pump; 1 When power generation is on standby.

and shall be configured to control the temperature during power generation operation.

[Effect]

In the configuration of this invention, by providing a side path in which the heat medium is diverted via the three-way valve near the heating tank in the main circulation path, the heating tank functions as a buffer tank, and the heating tank is controlled by the three-way valve to separate the heat medium from the heating tank. This makes it easy to control the supply amount of heat medium over a wide range. The heat medium that circulates to the cooling plate side via the side passage is cooled by heat dissipation in the circulation system, so it is easy to lower the heat medium temperature to, for example, the standby temperature of the fuel cell. In addition to heat supply from the pump, standby flow rate and rising speed can all be controlled smoothly.

〔Example〕

The following description will be made based on all the embodiments of this invention.

FIG. 1 is a system flow diagram showing a temperature control device for a fuel cell according to an embodiment of the present invention. In the figure, 170
The heat medium 12 heated to .degree. Cooling plate of fuel cell 1 5. The main circulation path 15 returning to the heating tank 11 via the heat exchanger 14 is provided with a proportional control type three-way switching valve 26 on the inlet side of the heating tank 11, and one of the discharge sides is connected to the side. It is connected via line 27 to the suction side of circulation pump 13 . Further, the temperature of the cooling plate 5 is detected by the temperature sensor 18, and the flow rate regulator 29 proportionally controls the three-way switching valve 26 according to a command signal issued by the temperature regulator 19 based on the difference between the detected temperature and the set temperature. Through this control, the amount of heat medium 12 that returns to heating tank 11 and the amount that flows back to side passage 27 are controlled.

In the system configured in this way, the heating tank 11 having an upper space functions as a buffer tank, and the 17 ml of water from the heating tank 11 that joins the suction side of the circulation pump 13 is
The ratio between the flow rate of the heat medium heated to 0° C. and the flow rate of the heat medium from the side path 27 can be freely controlled by the three-way switching valve. Therefore, the temperature of the fuel cell 1 is 130°C.
When maintaining the standby temperature at a temperature of about It is now possible to lower the temperature to nearly 130 degrees Celsius, and by supplementing with the high temperature heat medium from the full heating tank 11 when the heat medium temperature is too low, the fuel cell temperature can be accurately and stably maintained at the standby temperature. can do. Further, the same applies at the time of startup), by controlling the temperature of the circulating heat medium by the flow rate distribution of the one-way switching valve 26, a desired temperature increase rate can be obtained.

Furthermore, during operation, the heat exchanger 14 is operated to recover the generated heat, and the heating tank 11 contains 170
The operating temperature can be maintained by cooling the fuel cell using the difference between the heating medium heated to ℃ and the operating temperature, and the heating medium cooled by the heat exchanger 14 passes through the side passage 27 to the cooling plate. By refluxing the water, efficient cooling becomes possible.

FIG. 2 is a diagram showing a modification of the embodiment;
This embodiment differs from the previous embodiment in that an off-control type three-way switching valve is used, and the same functions as the previous embodiment can be obtained, as well as the advantage that the control system can be simplified.

FIG. 3 is a diagram showing a further modified version of the embodiment,
The three-way switching valve 46 is composed of two operation valves 47 and 48, and the heating tank 11. The same function as described above can be obtained by controlling the flow rate of the heat medium diverted to the side path 27 by turning on and off the two operation valves alternately at a predetermined timing.

FIG. 4 is a configuration diagram of main parts showing another embodiment, in which the heating tank is a storage tank 51 for the heat medium 12 heated to 170°C,
This differs from the previous embodiment in that it is divided into a heat exchanger 52 that heats the heat medium 12 and connected via a circulation pump 53. For example, the heat exchanger 52 is placed close to the heat source. When exhaust heat is utilized, there are advantages such as being able to rationalize the layout of the equipment.

〔Effect of the invention〕

As described above, this invention provides a side passage between the three-way switching valve placed on the heating tank inlet side of the main circulation passage and the circulation pump suction side, so that the heat medium from the heating tank and the heat medium from the side passage are The configuration was such that they merged on the suction side of the circulation pump. As a result, compared to the conventional method in which the heat medium is heated to an intermediate temperature between the standby temperature and the operating temperature, the cooling plate of the fuel cell is Since the temperature of the heat medium passing through can be changed freely, for example, by bringing the heat medium temperature close to the standby temperature, the standby temperature can be maintained with high accuracy, and the temperature increase rate at startup can be easily adjusted. I can do it. Furthermore, since the standby operation and start-up operation described above can be performed without changing the temperature of the heat medium in the heating tank, it is easy to switch to control of the operating temperature using the heat medium at this temperature as the cooling medium. Moreover, by circulating the heat medium cooled by the heat exchanger to the cooling plate side through the side passage, an advantage is obtained that the operating temperature under heavy load can be maintained with high accuracy.

Furthermore, by maintaining the standby temperature and temperature increase rate with high accuracy, it is possible to obtain a device #U that reliably prevents high temperature deterioration of the electrodes, contributing to maintaining the power generation performance of the fuel cell stably for a long period of time. At the same time, since the device does not need to be complicated at all, there is an advantage that it can contribute to cost reduction of the fuel cell power generation device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a system 70 of a temperature control device for a fuel cell according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing mutually different modifications of the embodiment, and FIG. FIG. 5 is a system flow diagram showing a conventional temperature control device, and FIG. 6 is a characteristic diagram showing the relationship between fuel cell temperature and deterioration rate of an electrode catalyst.

Claims (1)

[Claims] 1) a fuel cell in which liquid-cooled cooling plates are stacked for each unit cell in multiple layers; a heating tank containing a heat medium maintained at an intermediate temperature between the operating temperature and standby temperature of the fuel cell;
A main circulation path including a circulation pump that returns the heat medium to the heating tank via the cooling plate, the three-way switching valve disposed near the heating tank inlet of the main circulation path; A side passage communicating with the discharge side of one of the switching valves and the suction side of the circulation pump, and by operating the three-way switching valve, the temperature of the fuel cell is controlled during startup, standby for power generation, and power generation operation. 1. A temperature control device for a fuel cell, characterized in that it is configured to.