Electrochemical- and Thermal-Performance Model of a High-Temperature SOFC System for Geothermic Fuel Cell Application

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.