Patent ID: 6586123
Filing Date: 2003-07-01
Classification: H01M,Y02E

Abstract:
A method of operating a PEM fuel cell system comprising a plurality of fuel cells, each having a cathode support plate, an anode support plate, a membrane electrode assembly disposed between said support plates, oxidant flow fields on the cathode side of said membrane electrode assembly, and fuel flow fields on the anode side of said membrane electrode assembly, said method comprising:flowing a hydrogen-containing gas through said fuel flow fields; flowing air at substantially atmospheric pressure through said oxidant flow fields; and controlling the flow rate of air in response to a load current to maintain an air stochiometry, S, of: S=[A+B(iâˆ’C)]Â±D, for i>C S=AÂ±D, for i&lE;C where A is a fixed stochiometry used with current densities greater than, equal to and below i, B is a slope of stochiometry as a function of current density, i is actual current density, C is a current density at which the schedule changes from being fixed to varying with current density, and D is a range of stochiometries between zero and about 20% of A.