Patent ID: 7887966

Claim:
A method for operating a PEM fuel cell power plant having a plurality of fuel cell assemblies, wherein each of said fuel cell assemblies comprises: a membrane electrode assembly (MEA); a pressurized cathode reactant flow field which includes a plate adjacent to one side of said MEA, said cathode reactant flow field plate being substantially impermeable to liquids; a pressurized anode reactant flow field which includes a plate adjacent to an opposite side of said MEA, said anode reactant flow field plate being permeable to liquids so that coolant can move through said anode reactant flow field plate; and coolant passages disposed adjacent to said anode reactant flow field plate, said coolant passages containing a pressurized coolant which is fed into said anode reactant flow field plate and said coolant is operative to evaporatively cool said fuel cell assemblies during operation thereof, said method comprising the step of: (a) maintaining a pressure in said anode reactant flow field which is greater than said coolant pressure in said coolant passages so as to ensure that said coolant will not flood the fuel cell assemblies; and (b) maintaining a cathode reactant flow field pressure which is less than the pressure in said coolant.