The Cryo-Force Power-Cell System, an integrated, closed-loop liquid oxygen (LOX) and liquid hydrogen (LH2) proton exchange membrane (PEM) fuel cell system, has been designed to help unmanned underwater vehicles (UUVs) transition away from large-battery and fossil fuel technologies. Originally developed for the military to boost force efficiency, the system has been further developed for other markets by Sierra Lobo Inc., Milan, Ohio, the Department of the Navy, Office of Naval Research (ONR), Arlington, Va., and the Naval Undersea Warfare Center, Newport, R.I.
The cryogenic liquid reactants (oxygen and hydrogen) are stored in separate dewars and are then vaporized using the electrical power produced by the fuel cell to maintain each tank pressure at approximately 50 psia. Now gaseous, the reactants are further heated to 50 to 60 C using waste heat within the fuel cell and then humidified using water produced within the stack. The humidified oxygen and hydrogen reactants then enter the fuel cell to provide propulsive power. By-product water is removed with mechanical compressors.
The significant technological advancement is the integration of cryogenic pure reactants with a fuel cell system while meeting U.S. Navy specifications of storing 50 kg of oxygen and delivering 0.1 to 100 g/min of oxygen to support a 10 kW fuel cell system.