Patent ID: 8182951

Claim:
A fuel cell system comprising: a polymer electrolyte fuel cell having a membrane/electrode assembly, temperature controlling means for controlling temperature of the polymer electrolyte fuel cell, temperature detection means for detecting temperature of the polymer electrolyte fuel cell, controlling means for controlling the temperature controlling means for controlling a maximum temperature of the polymer electrolyte fuel cell within a range from 90 to 140° C., based on temperature information from the temperature detection means, and humidity controlling means for controlling humidity of oxidant gas supplied to the polymer electrolyte fuel cell, wherein the membrane/electrode assembly comprises an anode including a catalyst layer containing a proton conductive polymer, a cathode including a catalyst layer containing a proton conductive polymer and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton conductive polymer contained in the catalyst layer of at least one of the cathode and the anode is a polymer which has repeating units based on a perfluoromonomer having an alicyclic structure or a perfluoromonomer capable of forming an alicyclic structure by cyclic polymerization, and has ion exchange groups, and wherein the controlling means further controls the humidity controlling means based on the temperature information from the temperature detection means so that the relative humidity of the oxidant gas supplied to the polymer electrolyte fuel cell is at most 30% at the maximum temperature of the polymer electrolyte fuel cell.