Fuel cell system

The fuel cell system according to claim 21, further comprising:

• an off-gas passage through which off-gas discharged from the fuel cell via the gas discharge passage flows;
• and
• an off-gas flow volume adjustment device, disposed in the off-gas passage, that adjusts a flow volume of the off-gas,
• wherein the controller controls the off-gas flow volume adjustment device to adjust the flow volume in accordance with the hydrogen concentration detected by the hydrogen concentration sensor.

A fuel cell system comprising:

• a fuel cell that comprises
• a plurality of unit cells stacked on each other;
• first and second end plates between which the plurality of unit cells are interposed;
• a gas supply passage, extending in a stacking direction of the plurality of unit cells, that supplies gas to the plurality of unit cells, and has an inlet on the first end plate side;
• and
• a gas discharge passage through which gas discharged from the plurality of unit cells flows and has an outlet on the first end plate side;
• a hydrogen supply device that supplies hydrogen gas to the plurality of unit cells in the fuel cell through the gas supply passage;
• a hydrogen concentration sensor, disposed in the gas discharge passage, that detects a hydrogen concentration in gas discharged from the plurality of unit cells;
• and
• an electricity generation controller that controls an electricity generation process in the fuel cell based on the hydrogen concentration detected by the hydrogen concentration sensor, when the hydrogen supply device supplies the hydrogen gas.

A fuel cell system comprising:

• a fuel cell that comprises
• a plurality of unit cells stacked on each other;
• first and second end plates between which the plurality of unit cells are interposed;
• a gas supply passage, extending in a stacking direction of the plurality of unit cells, that supplies gas to each of the plurality of unit cells, and has an inlet on the first end plate side;
• and
• a gas discharge passage through which gas discharged from the plurality of unit cells flows and has an outlet on the first end plate side;
• a hydrogen supply device that supplies hydrogen gas to the plurality of unit cells in the fuel cell through the gas supply passage;
• a first hydrogen concentration detector that detects a hydrogen concentration in gas which is discharged from a first unit cell in the plurality of unit cells and flows in the gas discharge passage;
• a second hydrogen concentration detector that detects a hydrogen concentration in gas flowing in the gas supply passage that is supplied to a second unit cell in the plurality of unit cells;
• and
• an electricity generation controller that controls an electricity generation process of the fuel cell in accordance with a time interval between a first time point and a second time point, wherein the first time point is when the first hydrogen concentration detector detects hydrogen, and the second time point is when the second hydrogen concentration detector detects hydrogen.