Patent ID: 7595125

Claim:
A fuel cell stack comprising a plurality of unit cells stacked in a stacking direction, wherein each unit cell includes a first separator, a second separator, and an electrolyte electrode assembly that is sandwiched between the first and second separators, the electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between said electrodes, said electrodes have a substantially square shape having a side length in a range of 140 mm to 200 mm, and said first and second separators have a substantially square shape having a side length in a range of 200 mm to 300 mm, and at least one of said first separator and said second separator has: a reactant gas supply passage formed in a first side portion, a reactant gas discharge passage formed in a second side portion opposite the first side portion, a reactant gas flow passage formed on a first surface facing said electrodes, the reactant gas flow being formed along a substantial portion of the first surface in a direction from the first side portion to the second side portion, a coolant supply passage formed in a third side portion, a coolant discharge passage formed in a fourth side portion opposite the third side portion, and a coolant flow passage formed on a second surface opposite the first surface, the coolant flow passage being formed along a substantial portion of the second surface in a direction from the third side portion to the forth side portion and connected to the coolant supply passage and the coolant discharge passage, wherein the coolant flow passage is formed between one of said first separator or said second separator of a unit cell and one of said first separator or said second separator of an adjacent unit cell.