NOVELTY - Freeze tolerant fuel cell power plant for generating an electrical current from hydrogen containing reducing fluid fuel and oxygen containing oxidant reactant streams, includes a two-component mixed coolant of water immiscible fluid component and water component.    USE - For generating an electrical current from hydrogen containing reducing fluid fuel and oxygen containing oxidant reactant streams.    ADVANTAGE - The freeze tolerant fuel cell power plant is efficiently operated in sub-freezing conditions with effective water management and a minimal volume of water.    DETAILED DESCRIPTION - Freeze tolerant fuel cell power plant (10) for generating an electrical current from hydrogen containing reducing fluid fuel and oxygen containing oxidant reactant streams, comprises fuel cell (12) having a proton exchange membrane electrolyte (19). A coolant loop (42) including a porous water transport plate (44) is secured in heat and mass exchange relationship within the fuel cell. A coolant circulating mechanism (46) is secured to a coolant passage (68) in fluid communication with the porous water transport plate for circulating a coolant through the plate and for transferring water into or out of the plate with the coolant. A coolant heat exchanger (52) is secured to the coolant passage for removing heat from the coolant. An accumulator (66) is secured in fluid communication with the coolant passage for storing the coolant and water. The coolant is a two-component mixed coolant circulating through the coolant loop. The two-component mixed coolant contains a water immiscible fluid component and a water component. An INDEPENDENT CLAIM is also included for a method of operating a freeze tolerant fuel cell power plant, comprising securing an accumulator in fluid communication with the coolant passage for storing the coolant and water, and circulating a two-component mixed coolant through the coolant loop. The two-component mixed coolant contains a water immiscible fluid component and water component. The two-component mixed coolant is separated into the water immiscible fluid component and water component within the accumulator. Excess fuel cell product water from the water component of the accumulator is directed out of the accumulator.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a freeze tolerant fuel cell power plant with a two-component mixed coolant.    Freeze tolerant fuel cell power plant (10)    Fuel cell (12)    Proton exchange membrane electrolyte (19)    Coolant loop (42)    Porous water transport plate (44)    Coolant circulating mechanism (46)    Coolant heat exchanger (52)    Antifreeze coolant loop (54)    Antifreeze coolant passage (56)    Antifreeze coolant pump (58)    Antifreeze coolant radiator (60)    Accumulator (66)    Coolant passage (68)    Mixing system (69)    Coolant diversion valve (70)    Water immiscible fluid feed valve (72)    Mixing system by-pass valve (73)    Suction generating mechanism (74)    Mixer (76)    By-pass valve (88)    By-pass line (90)