Patent ID: 8173316

Claim:
A method for operating a fuel cell system including a fuel cell that has a fuel gas flow path and an oxidant gas flow path and generates electricity if a fuel gas is supplied to the fuel gas flow path and an oxidant gas to the oxidant gas flow path, and when the fuel cell system is started, an atmosphere inside the fuel gas flow path is exchanged for the fuel gas by opening a discharge valve, while supplying the fuel gas flow path, the method comprising steps of: determining whether or not to conduct a cold start of the system; and when the cold start is determined, increasing a fuel gas concentration in the fuel gas flow path by increasing a total discharge amount of a gas to be discharged by opening the discharge valve detecting a shutdown time of electric power generation of the fuel cell, wherein the total discharge amount of the gas to be discharged by opening the discharge valve is increased as the detected shutdown time of electric power generation becomes longer.