Fuel cell system, and method of stopping fuel cell system

摘要

For implementing a stop control which extracts a current from a fuel cell and consumes a cathode side oxygen at a system stop, the current extraction from the fuel cell is ended in a state that a certain quantity of oxygen smaller than when the current extraction is started remains on a cathode side of the fuel cell. With this, the hydrogen movement to the cathode side after the system stop can be effectively suppressed and thereby a cathode internal hydrogen concentration at the system start can be kept low, thus making it possible to properly process the cathode side hydrogen at the system start.

主权项

1. A fuel cell system for implementing, at a system stop, a stop control which extracts a current from a fuel cell and consumes a cathode side oxygen when a supply of a fuel gas to an anode side of the fuel cell is continued and a supply of an oxidant gas to a cathode side of the fuel cell is stopped, the fuel cell system comprising:
a controller programmed for ending the stop control when a remaining quantity of cathode side oxygen is reduced to a certain quantity; and a hydrogen processor configured to process hydrogen by lowering a hydrogen concentration on the cathode side to less than or equal to a combustible concentration when the fuel cell system starts, wherein the certain quantity is set to a value such that a maximum hydrogen concentration on the cathode side in a left-uncontrolled period after the system stop is an internal maximum hydrogen concentration that is less than or equal to a hydrogen processing capability limit of the hydrogen processor at system start.