Fuel cell system and fuel cell control method

Abstract

A fuel cell system allows suppression of the deterioration of a fuel cell even if a part of a membrane configuring the fuel cell is unavailable for power production. The fuel cell is configured with a membrane, and an anode and a cathode provided so as to sandwich the membrane, and produces electric power from reaction of reactive gases via the membrane when the reactive gases are supplied to the anode and the cathode. The fuel cell system is configured with the fuel cell, an MEA power production effective area calculating means for calculating an area of the membrane surface available for power production, an upper limit power producing current calculating means for controlling the total power production of the fuel cell based on the power production effective area calculated by the MEA power production effective area calculating means, and a current controller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 2 is a cross-sectional view of a cell configuring a fuel cell;

FIG. 3 is a block diagram of a control unit used by the fuel cell system;

FIG. 4 is a graph illustrating a relationship between variations in the moisture content of a membrane which configures the fuel cell and states of the fuel cell system;

FIG. 5 is a graph illustrating a relationship between the default power production effective area and the moisture contents in the membrane;

FIG. 6 is a graph illustrating a relationship between power production effective area of the membrane and temperature of the fuel cell;

FIG. 7 is a graph illustrating a relationship between the upper limit power producing current and the power production effective area of the membrane; and

FIG. 8 is a flowchart of the fuel cell system.

Claims

1. A fuel cell system, comprising: a fuel cell including an anode, a cathode and a membrane sandwiched therebetween, and which produces electric power when reactive gases are supplied to the anode and the cathode;a power production effective area calculating means for calculating an area of the membrane surface available for power production as a power production effective area; anda total power production control means for controlling the total power production of the fuel cell based on the power production effective area calculated by the power production effective area calculating means.

2. The fuel cell system of claim 1, further comprising: a temperature detecting means for detecting a temperature within the fuel cell, whereinthe power production effective area calculating means calculates the power production effective area of the membrane when the temperature detected by the temperature detecting means is below freezing.

3. The fuel cell system of claim 2, further comprising: a moisture content estimating means for estimating a moisture content of the membrane, whereinthe power production effective area calculating means calculates the power production effective area of the membrane based on the temperature detected by the temperature detecting means and the moisture content of the membrane estimated by the moisture content estimating means.

4. The fuel cell system of claim 3, further comprising: a timer for measuring a stopping time of the fuel cell, whereinthe moisture content estimating means estimates the moisture content of the membrane based on at least the elapsed stopping time, when the fuel cell is stopped.

5. The fuel cell system of claim 3, further comprising: a current integrating means for calculating a current integrated value when the fuel cell is producing electric power, whereinthe moisture content estimating means estimates the moisture content of the membrane based on at least the current integrated value during the period when the fuel cell is producing electric power.

6. A control method for a fuel cell, which includes an anode, a cathode and a membrane sandwiched therebetween, and which produces electric power when reactive gases are supplied to the anode and the cathode, comprising the steps of: calculating an area of the membrane surface available for power production as a power production effective area; andcontrolling the total power production of the fuel cell based on the calculated power production effective area.

7. The control method for a fuel cell of claim 6, further comprising the steps of: detecting a temperature within the fuel cell and further, during when the temperature is below freezing, calculating the power production effective area based upon the detected temperature.

8. The control method for a fuel cell of claim 7, further comprising the steps of: estimating a moisture content of the membrane, and then calculating the power production effective area based on the detected temperature and the moisture content of the membrane.

9. The control method for a fuel cell of claim 8, further comprising the steps of: measuring a elapsed stopping time of the fuel cell, and then estimating the moisture content of the membrane based on at least the measured elapsed stopping time when the fuel cell is stopped.

10. The control method for a fuel cell of claim 8, further comprising the steps of: calculating a current integrated value when the fuel cell is producing electric power, and then estimating the moisture content of the membrane based on at least the current integrated value when the fuel cell is producing electric power.