Exergy Analysis and Off-Design Modeling of a Solar-Driven Supercritical CO 2 Recompression Brayton Cycle

Felipe G. Battisti (), Carlos F. Klein, Rodrigo A. Escobar and José M. Cardemil ()
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Felipe G. Battisti: Department of Mechanical and Metallurgical Engineering, Pontifical Catholic University of Chile, Santiago 7820436, Chile
Carlos F. Klein: Department of Mechanical Engineering, Universidad de Chile, Santiago 8370456, Chile
Rodrigo A. Escobar: Department of Mechanical and Metallurgical Engineering, Pontifical Catholic University of Chile, Santiago 7820436, Chile
José M. Cardemil: Department of Mechanical and Metallurgical Engineering, Pontifical Catholic University of Chile, Santiago 7820436, Chile

Energies, 2023, vol. 16, issue 12, 1-26

Abstract: The latest generation of concentrated solar power (CSP) systems uses supercritical carbon dioxide (s-CO 2 ) as the working fluid in a high-performance recompression Brayton cycle (RcBC), whose off-design performance under different environmental conditions has yet to be fully explored. This study presents a model developed using the Engineering Equation Solver (EES) and System Advisor Model (SAM) to evaluate the operation of two solar-driven s-CO 2 RcBCs over a year, considering meteorological conditions in northern Chile. Under design conditions, the power plant outputs a net power of 25 M W with a first-law efficiency of 48.3%. An exergy analysis reveals that the high-temperature recuperator contributes the most to the exergy destruction under nominal conditions. However, the yearly simulation shows that the gas cooler’s exergy destruction increases at high ambient temperatures, as does the turbine’s during off-design operation. The proposed cycle widens the operational range, offering a higher flexibility and synergistic turndown strategy by throttling the mass flow. The proposed cycle’s seasonal first-law efficiency of 39% outweighs the literature cycle’s 29%. When coupled to a thermal energy storage system, the proposed cycle’s capacity factor could reach 93.45%, compared to the value 76.45% reported for the cycle configuration taken from the literature.

Keywords: solar-driven recompression Brayton cycle; part-load; supercritical CO 2; exergy analysis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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