Application of Direct Oxidation of Liquid Hydrocarbon Fuels in Solid Oxide Fuel Cells to Automotive Auxiliary Power Units

To meet the increasing electrical power demands for advanced internal combustion engine (ICE) vehicles, auxiliary power units (APUs) are of growing interest. Fuel cell based APUs offer the potential for high chemical-to-electrical conversion efficiency with low noise and low emissions. It has recently been shown that solid oxide fuel cells (SOFCs) can be used to directly convert the chemical energy of liquid hydrocarbon fuels to electricity. Because the combustion reaction takes place by direct oxidation of vaporized fuel at the fuel cell anode, the expectation exists for development of compact, reformerless APUs that can operate on the same fuel that the ICE uses for vehicle propulsion. Critical issues for the transportation SOFC-APU applications are fast start-up and the need to survive extensive thermal cycling. Since many present high-volume automotive applications of ceramics survive in harsh thermal cycling and vibration environments (as in spark plugs, catalysts and exhaust sensors), it is suggested by analogy that fast-heat-up, long-life, high-value automotive SOFCs can be designed and manufactured. This paper will review recent direct oxidation laboratory results and mechanical and thermal property data about the ceramic constituents of SOFCs to help to prioritize needed research and development.