Thermo-economic analyses of solid oxide fuel cell-gas turbine hybrids considering thermal cell gradients
Fabian Rosner, Ashok Rao, Scott Samuelsen
Abstract
The thermodynamic performance of a solid oxide fuel cell (SOFC)-gas turbine (GT) hybrid system has been investigated at steady state operating conditions considering overall cell temperature differences and local thermal gradients inside the SOFC. The obtained simulation results served as input for the thermo-economic evaluation of the SOFC-GT hybrid. The system has been studied at two different operating voltages, various operating pressures, and fuel utilization factors. The results show that operating the system at higher fuel utilization factors and higher pressure ratios results in a substantially increased air flow requirement to maintain acceptable temperature differences and thermal gradients. The highest efficiency is obtained at the higher operating voltage of the two studied scenarios, a moderate pressure ratio of 5 bar and a moderate fuel utilization of 87.6%. However, the lowest cost of electricity is obtained at the lower operating voltage, the same pressure ratio and a lower fuel utilization compared to the highest efficiency case.