Abstract: A method for shutting down a fuel cell system includes: determining whether an outside air temperature is below a first predetermined reference temperature when a shutdown of a fuel cell system is detected; warming up the fuel cell stack by operating balance of plant components of the fuel cell system and a stack load using the power of the fuel cell stack, while the supply of hydrogen to the fuel cell stack is normally maintained, when the outside air temperature is below the first reference temperature; removing water in the fuel cell stack by passing air supplied by an air supply system through the stack load to supply heated air to a cathode of the fuel cell stack; and shutting down the fuel cell system by cutting off the supply of air after the removal of water. The method can eliminate or reduce cold start failure.

Abstract: The present invention provides a fuel cell system, which reduces the temperature of exhaust gas discharged from a fuel cell stack to a humidifier to increase the humidity thereof when the fuel cell stack operates at high temperature and high power, and thus improves the humidification performance for air as an oxidant in the humidifier and improves the performance of the fuel cell stack. For this purpose, the present invention provides a fuel cell system in which an intercooler is installed in an exhaust gas pipe, which connects a cathode outlet of the fuel cell stack and the humidifier, to cool the exhaust gas as a water supply source of the humidifier such that the intercooler reduces the temperature of the exhaust gas and, at the same time, increase the humidity thereof, thus improving humidification performance for air as an oxidant in the humidifier.

Abstract: The present invention provides a method for cold starting a fuel cell vehicle, the method preferably including supplying reactant gases for generating electricity to a fuel cell stack, and simultaneously performing a motoring process for operating the fuel cell vehicle by applying a portion of stack current generated in the fuel cell stack to a drive motor and a heating process for warming up the fuel cell stack by applying the remaining available stack current to a heater for heating coolant. Accordingly, the present invention preferably provides a more rapid and efficient cold start to the fuel cell vehicle.

Abstract: The present invention provides a novel integrated valve system for a fuel cell stack, in which an air shut-off valve for preventing the inflow of air when a fuel cell shuts down and a dry gas purge valve for improving cold startability are coaxially coupled to each other so that the air shut-off valve and the dry gas purge valve simultaneously open or close.