Patent ID: 8067123

Claim:
A shutdown method of a fuel cell system, the fuel cell system comprising: a fuel cell comprising: a fuel electrode; an oxidant electrode; and an electrolyte membrane, the fuel electrode and the oxidant electrode being opposed to each other with the electrolyte membrane interposed therebetween; a fuel supply system which supplies a fuel gas to the fuel electrode, the fuel gas containing hydrogen; an oxidant supply system which supplies an oxidant gas to the oxidant electrode, the oxidant gas containing oxygen; a pair of fresh-air control valves which are individually provided for inlet and outlet sides of the fuel cell in the oxidant supply system and prevent ingress of the oxidant gas into the oxidant electrode; and a current extraction device which extracts current from the fuel cell during a system shutdown process, the method comprising: continuing the supply of the fuel gas to the fuel electrode through the fuel supply system, and stopping the supply of the oxidant gas to the oxidant electrode through the oxidant supply system; after stopping the supply of the oxidant gas, extracting current from the fuel cell; after extracting current, increasing pressure of the fuel gas in the fuel electrode to not less than atmospheric pressure and not less than pressure of the oxidant gas in the oxidant electrode; and after increasing the pressure of the fuel gas. airtightly closing the fresh air control valves to prevent the ingress of the oxidant gas into the oxidant electrode.