Design and eco-technoeconomic analyses of SOFC/GT hybrid systems accounting for long-term degradation effects

This study compares two SOFC/GT (solid oxide fuel cell with gas turbine) hybrid systems to that of two standalone SOFC systems via eco-technoeconomic analyses that account for long-term degradation effects. Four cases were examined: 1) standalone SOFC plant without a steam bottoming cycle; 2) standalone SOFC plant with a steam bottoming cycle; 3) SOFC/GT hybrid plant without a steam bottoming cycle; and 4) SOFC/GT with a steam bottoming cycle. This study employed a real-time 1D SOFC model with an empirical degradation calculation integrated with steady-state balance-of-plant models. Simulations used Matlab Simulink R2017a, Aspen Plus V10, and Python 3.7.4 with a pseudo steady-state approach. The results showed that, with some trade-offs, the SOFC/GT hybrid plant with the steam bottoming cycle is the best option, with an overall efficiency of 44.6% _LHV, an LCOE (levelized cost of electricity) of $US 77/MWh, and a CCA (cost of CO₂ avoided) of -$US 49.3/tonneCO₂e. The sensitivity analysis also indicated that SOFC/GT hybrid plants were less sensitive to SOFC price compared to standalone SOFC plants. The sensitivity analysis indicated that using a larger gas turbine and replacing the SOFC stack less frequently was the better design choice for the SOFC/GT hybrid plant.