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.
This paper presents operating and performance characteristics of a nine-stack solid-oxide fuel cell combined-heat-and-power system. Integrated with a natural-gas fuel processor, air compressor, reactant-gas preheater, and diagnostics and control equipment, the system is designed for use in unconventional oil-and-gas processing. Termed a "Geothermic Fuel Cell" (GFC), the heat liberated by the fuel cell during electricity generation is harnessed to process oil shale into high-quality crude oil and natural gas. The 1.5-kW e SOFC stacks are packaged within three-stack GFC modules. Three GFC modules are mechanically and electrically coupled to a reactant-gas preheater and installed within the earth. During operation, significant heat is conducted from the Geothermic Fuel Cell to the surrounding geology.The complete system was continuously operated on hydrogen and natural-gas fuels for ∼ 600 hours. A quasi-steady operating point was established to favor heat generation (29.1 kW th ) over electricity production (4.4 kW e ). Thermodynamic analysis reveals a combinedheat-and-power efficiency of 55% at this condition. Heat flux to the geology averaged 3.2 kW m −1 across the 9-m length of the Geothermic Fuel Cell-preheater assembly. System performance is reviewed; some suggestions for improvement are proposed.
A one-dimensional model of a high-temperature solid-oxide fuel cell (SOFC) stack contained in a geothermic fuel cell (GFC) assembly is presented. The GFC concept, developed by IEP Technology Inc., involves the harnessing of heat generated during SOFC stack operation for the liberation of oil and gas from oil shale. The first GFC prototype, designed and built by Delphi Automotive, LLC., is comprised of three 1.5-kW SOFC stacks housed in a stainless-steel casing. Hot exhaust gases exiting the stacks are directed out of the stack-containment vessel, rejecting heat to the surroundings before being exhausted above ground. The primary aims of this work are to develop modeling tools to (1) predict the stack electrochemical performance and (2) elucidate the thermal characteristics of the stack assembly during operation through modeling and simulation. Aspen Plus process-simulation software and an embedded electrochemical model are utilized to predict the temperature dynamics and the electrical output of the GFC stack. The stack performance is decomposed with a temperature-dependent Area Specific Resistance (ASR) obtained from analysis of experimental data from a single stack that was operated over a wide temperature range. Independent full-scale stack testing has enabled performance validation of the electrochemical model. Experimental data from the three-stack GFC assembly has been used to calibrate the thermal-modeling approaches and the external heat-rejection predictions. Simulation results for steady-state conditions under hydrogen fuel are presented and compared to experimental data from thermocouples on the GFC prototype. The model will be used to explore the interaction of the geothermic fuel cell with the oil-shale formation in which it is installed.
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