JPH0574477A - Load limiting device of fuel cell power plant - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the heat dissipation capacity of the cooling tower of the exhaust heat removal device decreases due to the rise in atmospheric temperature in midsummer, the temperature of each device such as the fuel cell is maintained within an appropriate range. Provided is an output limiting device capable of performing the above. [Structure] Temperature detector 6 provided at air inlet of cooling tower 4
Inputs an atmospheric temperature signal 7 to an output upper limit function generator 8. The output upper limit function generator 8 calculates the amount of heat at which the surplus heat generated at that time becomes equal to the maximum heat dissipation capacity of the cooling tower 4, and inputs this to the low value selector 10 as the output upper limit signal 9. .. An output set value signal 11, which is another signal, is given to the low value selector 10 from the output setter 12, selects the lower value from both, and inputs it to the fuel cell power plant 2 as the output command signal 13. is doing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation plant, and more particularly, to an output capable of maintaining power generation even if the exhaust heat removal device incorporated in the plant deteriorates in capacity due to an increase in atmospheric temperature. Regarding the restriction device.

[0002]

2. Description of the Related Art A fuel cell power plant is provided with an exhaust heat removing device for removing heat generated by an electrochemical reaction in a fuel cell and surplus heat generated by other devices from the device to maintain an appropriate temperature. Here, a heat exchanger that removes heat by the cooling medium circulating around these devices and discharges it outside the system, a cooling tower that always keeps the temperature of the cooling medium circulating through the system at an appropriate level, and a medium circulation pump And are provided. On the other hand, the control system is configured such that the output of the fuel cell power plant follows the output set value to obtain the actual output, and the output upper limit at this time is determined by the design maximum output value of the fuel cell unit. For this reason, the plant constituent equipment other than the fuel cell unit has the equipment capacity sufficient to satisfy the planned maximum output condition of the fuel cell unit. The above-mentioned exhaust heat removal device is also given the ability to satisfy the planned maximum output based on the same consideration.

[0003]

By the way, regarding the cooling tower, there is a problem in setting the condition of the atmospheric temperature as a cooling source in planning the plant. The higher the set temperature, the larger the heat transfer area and the larger the amount of air flow in order to bring the temperature of the cooling medium to an appropriate level, but there is a certain limit. In conventional fuel cell power plants, consideration is given to maintaining the capacity of the cooling tower throughout the year. Generally, a safety factor is assumed based on the maximum temperature in summer and the actual value, and the atmospheric temperature around 40 ° C should be included in the design conditions. I have to. However,
It is extremely rare in Japan that the maximum temperature exceeds 40 ° C throughout the year. For example, according to the statistics, in Tokyo after 1923, on August 21, 1953, 3
The highest temperature is 8.4 ° C. On the other hand, from 1950 to 1980
The average daily maximum temperature in August up to the year was 30.8 ° C,
Considering that the maximum temperature is a phenomenon of several days in the middle of summer and several hours in the daytime, it is necessary to reconsider setting the atmospheric temperature to around 40 ° C. as a design condition of the cooling tower. Nevertheless, it is difficult to completely ignore the temperature around 40 ° C as a practical problem. In fact, the daytime temperature in the middle of summer is close to this level, and if the amount of heat dissipated in the cooling tower falls below the surplus heat generated over hours, the fuel cells and other equipment The temperature rises, forcing the plant to shut down. On such a summer day, the demand for electricity is at its peak, which could lead to the worst result that it is useless when it is important.

Thus, when planning the cooling tower, the atmospheric temperature is set to 4
Setting the temperature around 0 ° C is becoming difficult to move, and the heat transfer area inevitably increases, which requires a large occupied area, while the air volume also increases significantly, resulting in enormous power costs. Must be accepted.

In particular, it is said that it is desirable that a fuel cell power plant, which has great expectations as an urban power generator, has a small occupying area and is small in size, and an enormous reduction in power cost and a positive solution to these problems are strongly desired. Is desired.

Therefore, an object of the present invention is to maintain the temperature of each device such as a fuel cell within an appropriate range even if the heat dissipation capacity of the cooling tower is lowered due to the rise in atmospheric temperature in the middle of summer. To provide the output limiting device.

[0007]

SUMMARY OF THE INVENTION An output limiting device according to the present invention includes a detector for detecting an inlet atmospheric temperature of a cooling tower and outputting a signal, and a constant value when the detected temperature is within a predetermined temperature range. , And when the temperature rises over the temperature range, a function generating means for calculating a value that gradually decreases and outputting a signal, a signal given from this function generating means, and a set actual output set value of the fuel cell power plant And a low value selecting unit that selects a low value from both signals and outputs it as an output command signal to the fuel cell power plant.

[0008]

The concept of output limitation of the present invention will be described with reference to the drawings.

In FIG. 2, the maximum amount of heat dissipated in the cooling tower is represented by a curve a as a function of atmospheric temperature, and the surplus amount of heat in the fuel cell power plant is represented by a curve b as a function of power generation output. When the fuel cell power plant is operated at the rated output, that is, when it is stable at the rated output point Pd, the surplus heat amount Qd is generated, and at this time, the atmospheric temperature is the set temperature Td at the rated output. Further, at this time, the amount of heat to be processed by heat dissipation in the cooling tower is the set temperature Td.
Is the amount of heat dissipated, which is equal to the surplus heat amount Qd. The present invention, which focuses on reducing the amount of heat dissipated,
Assuming that the temperature Td is set to 30 ° C., for example,
The amount of heat dissipated Q1 when the temperature rises to a temperature T1 higher than 30 ° C during a certain period of midsummer is the surplus heat amount Q described above.
Limit the amount of heat dissipated in the cooling tower so that it is always less than d. However, at this time, if the generated surplus heat of the fuel cell power generation plant remains the surplus heat amount Qd, it is impossible to process all of the surplus heat. Therefore, generation of surplus heat is suppressed so as to match the amount of heat radiated Q1 at the temperature T1. That is, under the assumption that the atmospheric temperature exceeds the design condition at the rated output, the output is suppressed in this temperature range so that a large amount of excess heat is not generated. The curve c indicating the output upper limit value shown in the figure is based on such an idea, and the output P1 at the temperature T1 is smaller than the rated output point Pd, and the surplus heat generated at this time is processed by the cooling tower. It becomes equal to the amount of heat radiated Q1 that should be performed, and it becomes commensurate with the capacity.

Thus, in response to a significant increase in atmospheric temperature expected during a limited time zone in midsummer, generation of excess heat is limited by suppressing the power generation output, thereby continuing the operation commensurate with the capacity of the cooling tower. However, the temperature of each device such as the fuel cell can be maintained within an appropriate range.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, an exhaust heat removal apparatus 1 that constitutes a cooling cycle includes a fuel cell power generation plant 2 including a device to be cooled,
It has a heat exchanger 3 that connects a cooling medium circulation system to the fuel cell power generation plant 2, a cooling tower 4 and a medium circulation pump 5 that are sequentially provided in the cooling medium system.

On the other hand, reference numeral 6 is a temperature detector, which detects the inlet atmospheric temperature of the cooling tower 4 and inputs it to the output upper limit function generator 8 as an atmospheric temperature signal 7. The output upper limit function generator 8 calculates the amount of heat at which the surplus heat generated at that time becomes equal to the maximum heat dissipation capacity of the cooling tower 4, and inputs this to the low value selector 10 as the output upper limit signal 9. This low value selector 10 has another signal, the output set value signal 11
Is supplied from the output setter 12, a low value is selected from both signals, and is input to the fuel cell power generation plant 2 as the output command signal 13.

During the plant operation, the output upper limit value is calculated by the output limit value function generator 8 based on the atmospheric temperature signal 7 provided from the temperature detector 6 provided in the cooling tower 4. At the rated output, the output upper limit signal 9 is always larger than the output set value signal 11 when the atmospheric temperature is lower than the design condition, and the output set value signal 1 is output as the output signal of the low value selector 11.
1 is selected. At this time, the fuel cell power generation plant 2 produces an actual output according to the output command signal 13 having a constant value. That is, the fuel cell power generation plant 2 is maintained in operation while maintaining the rated output. Since all of the generated excess heat at the rated output is dissipated in the cooling tower 4, the temperature rise of each device such as the fuel cell is limited and the proper temperature can be maintained.

On the other hand, when the atmospheric temperature becomes higher than the design condition, the output upper limit value calculated by the output upper limit value function generator 8 based on the atmospheric temperature signal 7 becomes smaller, and the low value selector 1
At 1, the output upper limit signal 9 is selected. At this time, the fuel cell power generation plant 2 produces an actual output according to the output command signal 13 having the small value. That is, the fuel cell power generation plant 2 is continuously operated under an output that is always smaller than the rated output. The surplus heat generated at the time of output suppression is smaller than the surplus heat generated at the rated output, and since all the surplus heat is dissipated in the cooling tower 4, the temperature rise of each device is restricted in the entire plant. Therefore, the proper temperature can be maintained. In this operation with output control, even if the cooling tower 4 has a small capacity, the heat transfer area can be reduced throughout the year if the operation at the maximum output is planned only during the limited summer time. Therefore, the cooling tower 4 can be downsized. On the other hand, it is possible to reduce the power cost by reducing the air volume because the capacity becomes smaller.

[0015]

As described above, the present invention is provided with the function generating means for outputting the signal for limiting the power generation output so as to correspond to the amount of heat radiated from the cooling tower. Even when the temperature rises, the temperature of each device such as the fuel cell can be maintained within an appropriate range.

Therefore, according to the present invention, the air-cooling type cooling tower can be constructed in a compact size corresponding to the low temperature design condition, and the excellent area of the fuel cell power plant is reduced. ..

[Brief description of drawings]

FIG. 1 is a block diagram showing an output limiting device of a fuel cell power plant according to the present invention.

FIG. 2 is a diagram for explaining the concept of output limitation according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Exhaust heat removal device 2 ... Fuel cell power plant 3 ... Heat exchanger 4 ... Cooling tower 5 ... Medium circulation pump 8 ... Output upper limit function generator 10 ... Low value selector

Claims (1)

[Claims] 1. A detection unit for detecting an inlet atmospheric temperature of a cooling tower and outputting a signal, and when the detected temperature is within a predetermined temperature range, a constant value is raised, and the temperature is raised beyond the temperature range. At this time, a low value is selected from both the function generating means for calculating the gradually decreasing value and outputting the signal, and both the signal given from the function generating means and the determined actual output set value signal of the fuel cell power plant. An output limiting device for a fuel cell power plant, comprising: a low value selection unit that outputs the output command signal to the fuel cell power plant.