Numerical Simulation of SOFC System Performance at 90% Fuel Utilization with or without Anode Off-Gas Recycle for Enhancing Efficiency

To investigate possibility to enhance electrical efficiency, performance of methane-fueled 10 kW SOFC systems was numerically simulated with calculated voltage-current-density curves at 750ºC of a single cell with a bipolar plate, which approximated a stack performance. Operation at 90% fuel utilization (U_f) with anode off-gas recycle (AGR) and with steam reforming (no recycle) led to 75-67%-LHV and 72-66%-LHV DC electrical efficiency at 0.05-0.40 A/cm², respectively. System simulations considering heat loss from a cell stack clarified that 750ºC stack temperature can be maintained at 0.12-0.40 A/cm² and 64-58% and 63-59% net AC electrical efficiency will be attainable at U_f = 90% with and without AGR, respectively. Furthermore, enhancement of net AC efficiencies was found to be 11-10 percentage points at those current densities against ones of a Ene-farm-like conventional system using steam reforming at U_f = 73%.