Patent ID: 7297424

Claim:
A fuel cell stack comprising a plurality of fuel cell units each including an anode electrode, and a cathode electrode, and a solid polymer ion exchange membrane interposed between said anode electrode and said cathode electrode, said plurality of fuel cell units being stacked with separators intervening therebetween, wherein each of said fuel cell units has a rectangular shape having a horizontal length longer than a vertical length; and a fuel gas supply port and an oxygen-containing gas supply port are formed at an upper portion of end edges on short sides of said fuel cell units, respectively, and a fuel gas discharge port and an oxygen-containing gas discharge port are formed at a lower portion of end edges on short sides of said fuel cell units, respectively, such that said fuel gas supply port and said oxygen-containing gas supply port are provided at diagonal positions with respect to said fuel gas discharge port and said oxygen-containing gas discharge port, respectively, a plurality of fuel gas flow passages connecting said fuel gas supply port and said fuel gas discharge port for supplying a fuel gas to said anode electrode, said fuel gas flow passages being serpentine passages each having two turns; and a plurality of oxygen-containing gas flow passages connecting said oxygen-containing gas supply port and said oxygen-containing gas discharge port for supplying an oxygen-containing gas to said cathode electrode, said oxygen-containing gas flow passages being serpentine passages each having two turns, wherein said serpentine passages include a plurality of first grooves and a plurality of second grooves, wherein a selected number of said plurality of first grooves merge into a selected number of said plurality of second grooves.