Session: 06-05 Fuel Cell Driven Cycles II

Paper Number: 129298

129298 - Techno-Economic Analysis of the Solid Oxide Semi-Closed CO2 Cycle for Different Plant Sizes 

As the pressing need of reducing global CO2 emissions into the atmosphere grows by the day, the development of new technological solutions for clean energy production has become a major focus of research in the past decade. Carbon capture and storage (CCS) is expected to play a key role in the path towards carbon mitigation, and in particular oxy-combustion has shown a vary good potential, as it allows to achieve near-zero emissions with limited costs. In this framework, the Allam cycle is one the oxy-turbine cycle most studied in literature, with the highest Technology Readiness Level and with the highest industrial interest. On the other hand, researchers from Politecnico di Milano developed and patented the Solid Oxide Semi-closed CO2 cycle (SOS-CO2), a hybrid oxy-combustion cycle that combines a Solid Oxide Fuel Cell (SOFC) with a regenerative-based semi-closed CO2 cycle. Detailed simulation results published in refs-[1], [2] indicate that utility size cycles (400 MWel) can achieve exceptionally high efficiency (ranging from 69 to 75%, depending on the configuration) and a competitive cost of electricity [2].
The purpose of this work is to perform a detailed techno-economic evaluation of the performance of the SOS-CO2 cycle for different plat sizes, ranging from large utility applications (400 MWel) to oil and gas/industrial (50 MWel). The analysis is based on a detailed cycle simulation model built in Aspen Plus [2] and specific design optimization models for the most critical cycle components, i.e., the regenerative heat exchanger and the turbine. The cost correlation will be taken from validated literature data, and all the costs related to the air separation unit (ASU) and CO2 treatment systems will be considered, including the CO2 purification and compression unit (CPU), transport and storage. 
In the analysis, the results found for the SOS-CO2 cycle will be compared with those found for the Allam cycle in a previous study under publication [3].
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 limits the negative effect of the turbomachine efficiency drop. In terms of costs, the SOS-CO2 cycle is competitive with the Allam cycle not only in terms of efficiency, but also in terms of cost of the produced electricity: for example, for 400 MW plants the SOS-CO2 has an efficiency of 68.7%, while the Allam of 53.1%. Given this difference, even though the investment cost of the SOS-CO2 is significantly higher (2500 €/kW vs. 2000€/kW), the Cost of Electricity (COE) for the SOS-CO2 and the Allam cycle results to be 111.5 €/MWh and 119.1 €/MWh, respectively. Both the studied cycles have specific emissions below 4 gCO2/kWh, thanks to the adoption of a high efficiency distillation-based CPU.
Although its lower technology readiness level compared to the Allam cycle, the promising results found in the study justify further research and development activities on the SOS-CO2 cycle.
References
[1]    R. Scaccabarozzi, M. Gatti, S. Campanari, and E. Martelli, “Solid oxide semi-closed CO2 cycle: A hybrid power cycle with 75% net efficiency and zero emissions,” Appl. Energy, vol. 290, p. 116711, May 2021, doi: 10.1016/J.APENERGY.2021.116711.
[2]    M. Martinelli, R. Scaccabarozzi, M. Gatti, S. Campanari, and E. Martelli, “Techno-Economic Analysis of the Solid Oxide Semi-Closed CO2 Cycle and Comparison with Other Power Generation Cycles with CO2 Capture,” J. Eng. Gas Turbines Power, pp. 1–31, Oct. 2023, doi: 10.1115/1.4063740.
[3]    M. Martinelli, P. Chiesa, and E. Martelli, “Techno-economic assessment of the Allam cycle for different plant sizes, oxygen purities and heat integration with external sources,” Submitted to Appl. Therm. Eng., 2023.

Presenting Author: Matteo Martinelli Politecnico di Milano

Presenting Author Biography: Matteo Martinelli is PhD student performing his thesis at Politecnico di Milano under the supervision of Prof. Emanuele Martelli. His research focuses on the development, modelling and optimization of oxy-turbine cycles with particular focus on the Allam cycle and the novel cycle called "SOS-CO2".

Authors:

Matteo Martinelli Politecnico di Milano
Stefano Campanari Politecnico di Milano
Emanuele Martelli Politecnico De Milano - Dept. of Energy