NOVELTY - An organic antifreeze solution is passed through a thermal management system (54) for cooling the fuel cell (12). A split oxidant passage (28) directs the process oxidant stream into and through a fuel cell, a reformer feed branch (124) to fuel processing components and a process exhaust stream through the plant exhaust passage (98).    USE - For fuel cell power plants of transportation vehicles, portable power plants, stationary power plants.    ADVANTAGE - Separate sealed thermal management system for operating in sub-freezing conditions is eliminated. The water exiting through oxidant and anode exhaust streams for processing hydrocarbon fuels is utilized by fuel cell. Uncatalyzed membrane barrier components of humidification system between antifreeze cooling fluid and fuel cell are eliminated. Freezing water level is minimized when the fuel cell is not operated. The mass and heat leaving the plant is directly transferred back to the plant by the mass transfer medium.    DETAILED DESCRIPTION - A fuel cell producing electrical energy from reducing fluid and process oxidant streams has an electrolyte provided between anode and cathode catalysts. The fuel processing component comprises a burner and reformer. The burner (122) receives an anode exhaust stream through an anode exhaust passage provided between the anode flow fluid (14) and burner. The reformer (126) in fluid connection with the fuel cell reforms the hydrocarbon fuel into reducing fluid. The thermal management system comprises porous water transport plates which are in fluid connection with the cathode catalyst. The organic direct antifreeze solution comprises glycerol, butanetriol, alkanetriol and pentanetriol, and is non-volatile in cell operating temperatures. The antifreeze solution oxidized by anode and cathode catalysts has a freezing point of -29 degrees C, a surface tension is greater than 60 dyne/cm at the operating temperature of the fuel cell, and a partial pressure of antifreeze above operating temperature of at most 0.005 mmHg. The pressure controller maintains a positive pressure differential between the reactant streams passing through the fuel cell and the direct antifreeze solution passing through the porous water transport plates so that the reactant streams are at a greater pressure than the antifreeze solution. The direct mass and heat transfer device (96) transfers mass and heat exiting the plant to the plant within the process oxidant stream and in fluid connection with oxidant inlet (26) and plant exhaust passage. The mass transfer medium sorbs and desorbs the polar fluid substance consisting polar molecules. The mass transfer medium supported by a separator housing (102) in relation with oxidant and exhaust streams, has direct antifreeze solution as the liquid transfer medium. The maximum system exhaust temperature for the operating system in water balance is calculated by the formula TEX = 1000/((2.855528-(2.855282-(4(-0.34911) x 6.1893-Log10(14.696 /(7.14/UO2+0.5)/MFW))))0.5)/(2x(-0.34911)))-460 where TEX is the maximum system exhaust temperature in degrees F, UO2 is the system air utilization, and MFW is the mole fraction of water for direct antifreeze solution. The fuel processing thermal exchange loop follows the heat exchanger (134) in relation with reformed fuel heated by an oxidizer (148) for removing heat from reformed fuel. The coolant-coolant heat exchanger (44) directs the cooling fluid with the antifreeze solution cooling fluid. The mass transfer medium has an enthalpy exchange barrier (108) comprising hydrophilic pores of pore size 0.1-100 microns for supporting a liquid transfer medium. The water treatment system (184) has a demineralizer (174) in fluid communication with a thermal management system. The degasifier (182) in mass transfer in relation with thermal management system and oxidant inlet directs the process oxidant into the fuel cell for removing dissolved contaminants in the direct antifreeze solution.    DESCRIPTION OF DRAWING(S) - The figure shows schematic view of the operating system of direct antifreeze cooled fuel cell power plant.    Fuel cell (12)    Anode flow fluid (14)    Oxidant inlet (26)    Split oxidant passage (28)    Coolant-coolant heat exchanger (44)    Thermal management system (54)    Heat transfer device (96)    Plant exhaust passage (98)    Separator housing (102)    Enthalpy exchange barrier (108)    Burner (122)    Reformer feed branch (124)    Reformer (126)    Demineralizer (174)    Degasifier (182)    Water treatment system (184)