METHOD FOR OPERATING FUEL CELL SYSTEM

Conventional fuel cell systems had the problem of impurity gases flowing back from a buffer tank and a reduction in the voltages of unit cells when the supply pressure of an anode gas is caused to pulsate at startup. Provided is an operating method of a fuel cell system of a non anode-gas circulation type including a fuel cell stack (FS) formed by stacking multiple unit cells (FC), and being configured such that an impurity gas inside the fuel cell stack (FS) is pumped to the buffer tank (42) by causing pulsation of the supply pressure of the anode gas. The operating method include setting any one of the amplitude and cycle of the pulsation of the supply pressure of the anode gas to the fuel cell stack in accordance with the permeability of a nitrogen gas from a cathode side to an anode side. The method makes it possible to suppress unnecessary pulsation of the supply pressure of the anode gas at startup, and thus to maintain the concentration of a hydrogen gas in the fuel cell stack at an optimum level while preventing degradation in the mechanical strength of a membrane electrode structure that constitutes each unit cell.