Techno-Economic Analysis of the Solid Oxide Semi-Closed CO2 Cycle and Comparison With Other Power Generation Cycles With CO2 Capture

Abstract

This work presents the techno-economic analysis of the solid oxide semi-closed CO2 cycle (SOS-CO2), a hybrid semi-closed cycle with solid oxide fuel cells (SOFC) recently developed by Politecnico di Milano for power generation from natural gas with near-zero CO2 emissions. According to previous studies, the cycle is able to achieve an outstanding net electric efficiency of 75.7%. while capturing more than 99% of the generated CO2. All the cycles components, including the fuel cell and the turbine, have been designed and sized with the aim of assessing the performance and the capital cost. The energy and economic key performance indicators are compared with those of two benchmark cycles with CO2 capture: the Allam cycle and a combined cycle with amines. Moreover, a sensitivity analysis is performed on the forecasted cost of the natural gas and the SOFC stacks. The results indicate that the specific total capital requirement of the SOS-CO2 cycle (2504 €/kWel) is considerably higher than the Allam cycle (1926 €/kWel) and combined cycle with amines (1981 €/kWel). On the other hand, the SOS-CO2 cycle benefits from its far higher efficiency (74.0% versus 53.9% of the Allam cycle and 52.8% of the combined cycle with amines) which makes the cycle less sensitive to the fuel cost and CO2 tax. In terms of cost of electricity, the SOS-CO2 cycle turns out to be the best technology for natural gas prices above 8 €/GJ, while the Allam cycle appears to be the preferred option at lower fuel prices. For a fuel cost of 12 €/GJ, the SOS-CO2 cycle features a cost of electricity of 106.2 €/MWh, lower than the Allam cycle (119.1 €/MWh) and the combined cycle with amines (126.9 €/MWh).