Patent ID: 7588844
Filing Date: 2009-09-15
Classification: H01M,Y02E

Abstract:
1. A method of starting a fuel cell at a freezing temperature of water or less, said fuel cell including an electrolyte electrode assembly, and separators sandwiching said electrolyte electrode assembly, said electrolyte electrode assembly including a pair of electrodes, and an electrolyte interposed between said electrodes, said method comprising the steps of: providing a freezing temperature operation control map, the freezing temperature operation control map including a first pressure control map for controlling pressures of a fuel gas and an oxygen-containing gas supplied to the fuel cell, and a first flow rate control map for controlling at least a flow rate of the oxygen-containing gas supplied to the fuel cell, the first pressure control map defining a relationship between the pressures of the fuel gas and the oxygen-containing gas and an output current of the fuel cell at the freezing temperature of water or less, the output current of the fuel cell increasing proportionally as the pressures of the fuel gas and the oxygen-containing gas increase in the first pressure control map, providing a normal operation control map, the normal operation control map including a second pressure control map for controlling pressures of the fuel gas and the oxygen-containing gas supplied to the fuel cell, and a second flow rate control map for controlling at least the flow rate of the oxygen-containing gas supplied to the fuel cell, the second pressure control map defining a relationship between the pressures of the fuel gas and the oxygen-containing gas and the output current of the fuel cell at a temperature higher than the freezing temperature of water, the output current of the fuel cell increasing proportionally as the pressures of the fuel gas and the oxygen-containing gas increase in the second pressure control map, wherein a first gas pressure according to the first pressure control map causes the fuel cell to generate a first level of the output current at the freezing temperature of water or less, and a second gas pressure according to the second pressure control map causes the fuel cell to generate a second level of the output current at the temperature higher than the freezing temperature of water, and the first gas pressure is greater than the second gas pressure when the first level of the output current equals the second level of the output current; selecting a first operation in which the fuel cell is controlled using the freezing temperature operation control map when it is detected that the temperature of said fuel cell is the freezing temperature of water or less, performing the first operation of said fuel cell using the pressures of the fuel gas and the oxygen-containing gas and the flow rate of the oxygen-containing gas determined from said freezing temperature operation control map to generate a required output current of the fuel cell, wherein the generated output current of the fuel cell is provided to an external circuit in the first operation; and switching from said first operation to a second operation in which the fuel cell is controlled using the normal operation control map when it is detected that temperature of said fuel cell exceeds said freezing temperature of water.