Experimental Testing of a Novel Kilowatt-Scale Multistack Solid-Oxide Fuel Cell Assembly for Combined Heat and Power

This paper describes experimental testing of a “geothermic fuel cell (GFC),” a novel application of solid-oxide fuel cells for combined heat and power. The geothermic fuel cell (GFC) is designed for in situ oil-shale processing. When implemented, the GFC is placed underground within an oil-shale formation; the heat released by the fuel cells while generating electricity is transferred to the oil shale, converting it into high-quality crude oil and natural gas. The GFC module presented here is comprised of three 1.5-kWe solid-oxide fuel cell (SOFC) stack-and-combustor assemblies packaged within a stainless-steel housing for the ease of installation within a bore hole drilled within the earth. The results from above-ground, laboratory testing of the geothermic fuel cell module are presented, with a number of operating conditions explored. Operation is demonstrated under hydrogen and natural-gas reformate fuels. The combined heat-and-power efficiency ranges from 56.2% to 74.2% at operating conditions that generally favor heat generation over electricity production. Testing of the geothermic fuel cell module over a wide operating range in a controlled, laboratory setting provides a valuable data set for developing more-detailed electrochemical and heat transfer models of module operation.