METHODS FOR IMPROVING THE COLD STARTING CAPABILITY OF AN ELECTROCHEMICAL FUEL CELL

摘要

Temperature dependent methods can be used to improve the cold start capabili ty of fuel cell electric power generation systems. A method of ceasing operation of an electric power generation syste m improves the cold start capability and freeze tolerance of a fuel cell stack by reducing the amount of water remaining within the passages of the stack. The method involves purging one or more of the fuel cell stack oxidant and fuel passages at shutdown prior to allowing the fuel cell stack to drop to temperatures below the freezing point of water. Preferably purging at shutdown is conducted at a temperature below the stack operating temperature. Another method, used at start-up, involves directing a coolant fluid stream to the fuel cell stack only after a predetermined temperature above the freezing temperature of water is exceeded. Preferably, after freezing the fuel cell stack is heated to a temperature above its normal operating temperature before operation is commenced.