Abstract: A PEM fuel cell power plant system (10) has a process air pump (26), which may be a fan, a blower or a compressor, with an adiabatic efficiency of between 40% and 70%. The process air at the inlet 27 of the cathode reactant gas flow field 16 is between 1.07 atmospheres and 1.85 atmospheres, and may be at an optimal pressure for maximum overall system efficiency P={0.45+2.6E?1.8E2} atms±0.2 atms where P is the air inlet pressure and E is the adiabatic efficiency of the process air pump.

Abstract: The outflow of coolers or water transport plates of a fuel cell stack (15) is fed to the inlet of a gas/liquid separator (12), the liquid output of which is connected through a primary pump (11a) to a liquid accumulator (21). A secondary pump (44) connected to the liquid output (20) of the liquid accumulator is fed to the principal inlet (31) of an eductor (32), the secondary inlet being connected to the gas output of the gas/liquid separator. The outlet (37) of the eductor is fed through a conduit (38) to a point below liquid level in the liquid accumulator. Thus, failure of the secondary pump (44) will not cause cavitation of the primary pump (11a) through the eductor so that coolant will continue to flow through the fuel cell stack. A demineralizer (26) is fed through a pressure reducing orifice (25) from the outlet of the secondary pump.

Abstract: The outflow of coolers or water transport plates of a fuel cell stack (15) is fed to the inlet of a gas/liquid separator (12), the liquid output of which is connected through a primary pump (11a) to a liquid accumulator (21). A secondary pump (44) connected to the liquid output (20) of the liquid accumulator is fed to the principal inlet (31) of an eductor (32), the secondary inlet being connected to the gas output of the gas/liquid separator. The outlet (37) of the eductor is fed through a conduit (38) to a point below liquid level in the liquid accumulator. Thus, failure of the secondary pump (44) will not cause cavitation of the primary pump (11a) through the eductor so that coolant will continue to flow through the fuel cell stack. A demineralizer (26) is fed through a pressure reducing orifice (25) from the outlet of the secondary pump.

Abstract: A PEM fuel cell power plant system (10) has a process air pump (26), which may be a fan, a blower or a compressor, with an adiabatic efficiency of between 40% and 70%. The process air at the inlet 27 of the cathode reactant gas flow field 16 is between 1.07 atmospheres and 1.

Abstract: A PEM fuel cell power plant system (10) has a process air pump (26), which may be a fan, a blower or a compressor, with an adiabatic efficiency of between 40% and 70%. The process air at the inlet 27 of the cathode reactant gas flow field 16 is between 1.07 atmospheres and 1.