FUEL CELL SYSTEM

PROBLEM TO BE SOLVED: To improve fuel consumption while restraining power consumption of accessaries and preventing deterioration of power generation efficiency by inactive substance concentration increase, in a hydrogen circulation type fuel cell system. SOLUTION: This fuel cell system is provided, in a hydrogen circulation passage 10 for re-circulating an off-gas discharged from a hydrogen electrode of a fuel cell 1 to the fuel cell 1, with a hydrogen sensor part 17 detecting hydrogen concentration in the off-gas, and inactive substance discharge means 12 and 30 discharging an inactive substance in the off-gas to the outside. The inactive substance discharge means 12 and 30 have a buffer chamber 18b arranged oppositely to the hydrogen circulation passage 10 by interposing an electrolyte membrane 18a therebetween, and a discharge part 19 controlling a communication state between the hydrogen circulation passage 10 and the outside, and execute an inactive substance discharge process of selectively moving hydrogen in the off-gas to the buffer chamber 18b by carrying a current to the electrolyte membrane 18a when the hydrogen concentration falls below a predetermined value, and thereafter discharging the inactive substance to the outside by operating the discharge part 19 to make the hydrogen circulation passage 10 communicate with the outside. COPYRIGHT: (C)2008,JPO&INPIT