Patent ID: 6635370
Filing Date: 2003-10-21
Classification: H01M,Y02E

Abstract:
A procedure for shutting down an operating fuel cell system, the system including at least one fuel cell, wherein during normal operation of the fuel cell system a continuous flow of air is fed into and through a cathode flow field in contact with a cathode electrode disposed on one side of an electrolyte within each fuel cell, and a continuous flow of fresh hydrogen containing fuel is fed into and through an anode flow field in contact with an anode electrode disposed on the other side of the electrolyte, and a electric current is generated by the fuel cell within a external circuit, wherein the current is operating a primary load connected to the external circuit, the shut-down procedure comprising:disconnecting the primary load from the external circuit; shutting off the fresh air flow to the cathode flow field; after shutting off the fresh air flow, reducing the concentration of oxygen remaining within the cathode flow field and increasing the concentration of hydrogen within the fuel cells by reacting hydrogen with oxygen within the fuel cells until no oxygen remains within the anode and cathode flow fields and the gas composition within the anode and cathode flow fields come to an equilibrium gas composition of at least 0.0001% hydrogen, balance fuel cell inert gases; and, upon reaching said equilibrium gas composition, maintaining a gas composition of at least 0.0001% hydrogen, balance fuel cell inert gases, all the while the system is shut-down.