Techno-Economic Analysis of the Solid Oxide Semiclosed CO2 Cycle for Different Plant Sizes

Abstract

This work presents a detailed techno-economic evaluation of the solid oxide semiclosed CO2 (SOS-CO2) cycle, a hybrid semiclosed cycle with solid oxide fuel cells (SOFC) developed by Politecnico di Milano. for different plant sizes, ranging from large utility plants (400 MWel) to industrial applications (50 MWel). The analysis includes the design and sizing of all the cycle components, including specific design optimization models for the most critical cycle components such as the regenerative heat exchanger and the turbine. Results are compared with the performance of the Allam cycle, an oxy-combustion cycle with higher technology readiness level (TRL). The results show that the SOS-CO2 cycle maintains high efficiency over the whole size range thanks to the modularity of the fuel cell and the regenerator, which counterbalances the decrease in turbomachine efficiency at small sizes. For the utility scale plant, despite its higher specific investment cost (3761 €/kW versus 2490€/kW), the SOS-CO2 cycle appears to be competitive with the Allam cycle in terms of cost of electricity (COE) (128.4 €/MWh and 127.8 €/MWh of the Allam cycle) thanks to its higher efficiency (68.9% versus 53.1%). At smaller sizes, the higher efficiency and the lower dependance on the economies of scale make the SOS-CO2 more economically advantageous: for the 50 MWel plant, the cost of electricity of the SOS-CO2 is 175.8 €/MWh versus 205.8 €/MWh of the Allam cycle.