Abstract: A bypass plate and an intermediate plate are interposed between a stack body and a negative electrode terminal of a fuel cell stack. An oxygen-containing gas passage extends through the bypass plate and the stack body. The intermediate plate has a small opening. The opening has a cross sectional area smaller than a cross sectional area of the oxygen-containing gas supply passage. The opening is formed by an extension extending into the oxygen-containing gas supply passage. The extension removes water in the oxygen-containing gas, and discharges the water into a bypass flow passage.

Abstract: A system and method for draining remaining water in a gas passage of a fuel cell, which has a simple structure and the remaining can be efficiently and reliably drained outside. Water which remains in a gas passage of the fuel cell is first drained by increasing the flow rate of the reaction gas while the operation of the fuel cell is stopped. The remaining water which has not been drained is then drained by increasing the pressure of the reaction gas and then decreasing the increased pressure. The increase and decrease operation of the pressure of the reaction gas is started after the increase of the flow rate of the reaction gas is started. Typically, the increase of the pressure of the reaction gas is started when a predetermined time has elapsed after the increase of the flow rate of the reaction gas is started.

Abstract: A fuel cell system comprises a fuel cell in which first reactant gas and second reactant gas are supplied to generate electricity, an evaporator for evaporating a raw fuel, which combusts exhaust gas discharged from said fuel cell and makes use of said exhaust gas to evaporate and volatize a raw material for said first reactant gas, a reformer which reforms the evaporated and volatilized raw fuel vapor by means of a reforming catalyst to produce the first reactant gas, and an air-introducing device, which introduces air used to be reformed into the evaporator or the reformed in a manner that the flow rate of the air is controlled depending upon the output from the fuel cell and upon the temperature of the raw fuel vapor.