NOVELTY - A direct antifreeze concentration-control system comprises fuel cell(s) for generating electricity, a thermal management system for controlling the temperature within the fuel cell, a water-recovery device for recovering water from process exhaust stream and for distributing recovered water within the power plant, and a process exhaust by-pass line secured between plant exhaust line and vent.    USE - For controlling the concentration of direct anti-freeze within a direct anti-freeze solution cooling fluid passing through a fuel cell power plant.    ADVANTAGE - The inventive system effectively maintains the concentration of antifreeze within a proper antifreeze concentration range.    DETAILED DESCRIPTION - A direct antifreeze concentration-control system consists of fuel cell(s) (12), thermal management system, water-recovery device (64), and process exhaust by-pass line. The fuel cell generates electricity from reducing fluid and process oxidant reactant streams. The fuel cell includes an electrolyte (32) secured between anode and cathode catalysts (34, 36) and a porous water-transport plate (40) connected with the cathode catalyst. The management control system controls the temperature within the fuel cell. An organic anti-freeze solution that is non-volatile at fuel cell operating temperature passes through the porous water-transport plate. The water-recovery device is connected with a process exhaust stream for recovering water from the process exhaust stream. The process exhaust by-pass line is secured between the plant exhaust line and a plant exhaust vent (68). The plant exhaust vent includes a process exhaust by-pass control valve for selectively directing the process exhaust stream to by-pass the water-recovery device and to pass out of the plant through the plant exhaust vent.    DESCRIPTION OF DRAWING(S) - The figure shows the antifreeze concentration-control system.    Fuel cell (12)    Electrolyte (32)    Anode and cathode catalysts (34, 36)    Water-transport plate (40)    Water-recovery device (64)    Plant exhaust vent (68)