JPH07211336A - Fuel cell power generation system - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a fuel cell power generation system capable of suppressing the wasteful power consumption of an air blower at the time of power load fluctuation, particularly at a partial load, and improving the overall power generation efficiency. [Constitution] In a fuel cell power generation system for supplying power to a hydrogen electrode 1a and an oxygen electrode 1b of a fuel cell 1 to generate power,
For the blower 4 that supplies the air taken in from the outside air to the oxygen electrode of the fuel cell, it was connected to the power supply circuit of the blower drive motor 4a as an air volume control means for generating an appropriate air volume corresponding to the power load fluctuation of the fuel cell. Inverter 7
And a load current detector 8 connected to the output circuit of the fuel cell
And an arithmetic unit 9 for calculating a proper rotation speed of the blower on the basis of the output signal of the load current detector and giving a control command to the inverter, so that an appropriate air flow rate corresponding to the fluctuation of the electric power load of the fuel cell can be obtained by the blower. It is generated and supplied to the oxygen electrode of the fuel cell.

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 system, and more particularly to a control system for an air (oxidant) supply system for a fuel cell.

[0002]

2. Description of the Related Art As is well known, power generation in a fuel cell is performed by supplying a reaction gas to its hydrogen electrode and oxygen electrode to generate electric power. The hydrogen electrode is reformed by a reformer using natural gas as a raw fuel. A reformed gas rich in hydrogen is supplied, and the air taken in from the outside air is supplied to the oxygen electrode through a blower in an amount necessary for the battery reaction.

Here, the air blower is an electric blower,
It uses a portion of the power generated by the fuel cell to operate it. Normally, the blower generated air volume, that is, the air air volume supplied to the oxygen electrode of the fuel cell (the oxygen utilization rate in the fuel cell is constant) is fixedly set according to the rated load (maximum load) of the fuel cell. The air blower drive motor is running at a constant rotation speed. In this case, the transmission end output 100
In the fuel cell power generation system of KW, the amount of air to be supplied to the oxygen electrode of the fuel cell at the rated load is 368 Nm ³ / h, and the power of the blower required for this, that is, the power consumption of the drive motor is 1.8 KW. Yes, about 2 of the power generated by the fuel cell
% Is consumed in operating the air blower.

[0004]

By the way, in the conventional method in which the air blower is operated at a constant speed regardless of the fluctuation of the electric power load as described above, excessive air is supplied when the electric load is operated at a partial load less than the rated value. As a result, the electric power generated by the fuel cell is consumed more than necessary by the blower, and the overall power generation efficiency of the fuel cell power generation system decreases.

The present invention has been made in view of the above points, and an object of the present invention is to solve the above-mentioned problems and suppress wasteful power consumption of an air blower due to power load fluctuation (partial load) to achieve a total power generation efficiency. Another object of the present invention is to provide a fuel cell power generation system capable of improving fuel efficiency.

[0006]

In order to achieve the above object, according to the present invention, the blower supplying the air taken in from the outside air to the oxygen electrode of the fuel cell is adapted to the fluctuation of the electric power load of the fuel cell. An air volume control means for generating the appropriate air volume is provided. The blower air volume control means controls the rotation speed of the blower drive motor in accordance with the power load based on the load current detector connected to the output circuit of the fuel cell and the output signal of the current detector. The controller comprises an inverter connected to the power supply circuit of the blower drive motor, and an arithmetic unit for calculating the proper rotation speed of the blower based on the output signal of the load current detector and giving a control command to the inverter. Can be implemented in combination.

[0007]

In the above, when the electric power load is reduced to the rated value or less while the generated electric power of the fuel cell is being supplied to the electric power system, the load fluctuation is detected by the current detector and based on the output signal thereof. The computing unit computes the proper rotation speed of the air blower corresponding to the generated air volume from the data of the air supply volume required for the partial load operation, and gives a control command to the inverter based on the computation result to supply the blower drive motor. The deceleration control is performed on the rotation speed of. As a result, the electric power consumed by the blower in the partial load operation can be minimized to suppress unnecessary electric power consumption, and the overall power generation efficiency of the fuel cell power generation system can be improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a system diagram of a fuel cell power generation system. Reference numeral 1 is a fuel cell, and a hydrogen electrode 1a of the fuel cell is rich in hydrogen through a reformer 2 and a CO shifter 3 using natural gas as a raw fuel. The reformed gas is supplied, and the oxygen electrode 1b is supplied with the air taken from the outside air through the air blower 4 to generate electric power by the electrochemical reaction in the presence of the electrolytic solution. The unreacted off-gas discharged from the hydrogen electrode of the fuel cell 1 is supplied to the burner 2a of the reformer 2 and burned to give a heat amount necessary for the reforming reaction. The power generated by the fuel cell 1 is supplied to the power system 6 via the DC / AC converter 5, and a part of the power generated is supplied to the drive motor 4a of the air blower 4, which is an auxiliary machine, to supply the air blower. I am driving 4

Here, according to the present invention, a speed control inverter 7 is connected to a power supply circuit for the drive motor 4a of the air blower, and a load current detector (CT) arranged in the output circuit of the fuel cell 1 is connected. 8 and the calculator 9 constitute an air volume control means for the air blower 4. That is, based on the output signal of the load current detector 8, the calculator 9 corresponds to the electric power load at that time, and the air flow rate to be supplied to the oxygen electrode 1b of the fuel cell 1 (the electric power load and the fuel cell need to be supplied. The rotation speed of the air blower 4 required to obtain an amount of generated air corresponding to the air flow rate is predetermined), and the control command obtained from the calculation result is given to the inverter 4a to drive the motor 4a. Control the rotation.

[0010] Here, the numerical values will be specifically described.
For the fuel cell 1 having a transmission end output of 100 KW, the required air amount to be supplied to the oxygen electrode 1b is 368 Nm ³ / h at 100% load (rated load), whereas at 75% load (partial load) 262 Nm ³ / h, 1 at 50% load
68 Nm ³ / h. Therefore, when the rotation speed of the drive motor 4a is controlled so that the air blower 4 obtains the generated air amount of the above-mentioned value based on the output signal of the load current detector 7 against the fluctuation of the electric power load, the partial load operation is particularly achieved. The power consumption of the drive motor 4a at that time is reduced. Specifically, the electric energy consumed to operate the air blower 4 at 100% load is 1.8 kW, whereas the 75% load, 50%
The power consumption in the load is reduced to 1.4KW and 1.1KW, respectively. As can be seen from this, by appropriately controlling the generated air volume of the air blower in response to changes in the power load,
At 50% load, the power consumption of the air blower 4 can be reduced by about 40% compared to 100% load, which improves the overall efficiency of the fuel cell power generation system especially at partial load.

[0011]

As described above, according to the present invention, the blower for supplying the air taken in from the outside air to the oxygen electrode of the fuel cell is provided with the air volume control means, and is suitable for the power load fluctuation of the fuel cell. By generating a large amount of air flow with the blower, compared to the conventional method of operating the blower at a constant speed regardless of load fluctuations, the power consumption of the blower is reduced especially at partial load, and the fuel cell It is possible to significantly improve the overall power generation efficiency of the power generation system.

[Brief description of drawings]

FIG. 1 is a system diagram of a fuel cell power generation system according to an embodiment of the present invention.

[Explanation of symbols]

 1 Fuel Cell 1a Hydrogen Electrode 1b Oxygen Electrode 2 Reformer 4 Air Blower 4a Drive Motor 5 DC / AC Converter 6 Power System 7 Inverter 8 Load Current Detector 9 Computing Unit

Claims (3)

[Claims] 1. A fuel cell power generation system for supplying reaction gas to a hydrogen electrode and an oxygen electrode of a fuel cell to generate electric power, wherein air taken from the outside air is supplied to the oxygen electrode of the fuel cell through a blower. A fuel cell power generation system, comprising: an air volume control means for generating an appropriate air volume corresponding to a change in electric power load of the fuel cell with respect to the blower. 2. The fuel cell power generation system according to claim 1, wherein the blower air volume control means has a load current detector connected to an output circuit of the fuel cell, and a blower drive motor based on an output signal of the current detector. A fuel cell power generation system comprising: a controller for controlling the number of revolutions of the fuel cell according to the power load. 3. The fuel cell power generation system according to claim 2, wherein the controller calculates an appropriate rotation speed of the blower based on the output signal of the inverter connected to the power supply circuit of the blower drive motor and the load current detector. A fuel cell power generation system comprising: an arithmetic unit that gives a control command to the inverter.