NOVELTY - Electrochemical energy is extracted from hydrocarbon fluids by positioning spaced apart anode (16) and cathode (18) layers on porous, non-densified yttria-doped zirconia electrolyte substrate (14); flowing fuel-oxidant mixture (20) directed over the electrolyte; maintaining electrolyte temperature in excess of 575degreesC; and extracting electrochemical energy from anode and cathode. The fuel-oxidant mixture is flowed at 40-120 cm/s. The anode and cathode enjoy an open circuit voltage of 0.75 V.    USE - Extraction of electrochemical energy from hydrocarbon fluids used to convert potential electrochemical energy to electricity.    ADVANTAGE - The method makes use of single chamber solid oxide fuel cell design that incorporates porous, non-densified yttria-stabilized zirconia electrolyte material and porous catalytic electrodes along with an optimized linear flow rate of fuel-oxidant gas mixture over the electrolyte to maximize the diffusion rate of the fuel and oxidant through the cell to increase the fuel efficiency and open cell voltage output.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method of converting potential electrochemical energy in hydrocarbon fluids to electricity. The fuel is methane, butane, and propane. The oxidant is oxygen and air. The electrolyte layer is made of yttria stabilized zirconia. The anode layer is made of nickel-oxide-yttrium-zirconium dioxide. The cathode layer is made of (lanthanum, strontium) (cobalt, iron) oxide. The anode layer is nickel oxide and/or yttria-doped zirconia. The cathode layer is lanthanum-strontium-cobalt-iron-oxide (La0.8Sr0.2Co0.2Fe0.8O3). The anode layer is cobalt dioxide, nickel oxide, nickel oxide-yttria stabilized zirconia, cerium dioxide, or gadolinium-doped cerium oxide. The cathode layer includes acceptor doped lanthanum-manganese oxide.    DESCRIPTION OF DRAWING(S) - The drawing is a perspective view of a single chamber solid oxide fuel cell device.    Fuel cell system (10)    Fuel cell device (12)    Electrolyte substrate layer (14)    Anode layer (16)    Cathode layer (18)    Fuel/oxidant mixture (20)    Oxygen (24)