Energy, Exergy, and Exergo-Sustainability Analysis of a Brayton S-CO 2 /Kalina Operating in Araçuaí, Brazil, Using Solar Energy as a Thermal Source

Climate change and increasing energy demand drive the search for sustainable alternatives for power generation. In this study, an energy, exergy, and exergy-sustainability analysis was performed on a supercritical CO 2 Brayton cycle with intercooling and reheating, coupled to a Kalina cycle for waste heat recovery, using solar energy as a thermal source in Araçuaí, Minas Gerais, Brazil, a city that holds the historical record for the highest temperature recorded in Brazilian territory. The results show that at 900 °C the maximum values of thermal efficiency (56.67%), net power (186.55 kW), and destroyed exergy (621.62 kW) were reached, while the maximum exergy efficiency, 24.92%, was achieved at 700 °C. At a turbine inlet pressure of 18 MPa, the maximum thermal (54.48%) and exergy (24.50%) efficiencies were obtained. Likewise, working with a compressor efficiency of 95%, a thermal efficiency of 54.98%, a net power of 165.84 kW, and an exergy efficiency of 24.62% was achieved, reducing the exergy destroyed to 504.95 kW. The solar field presented the highest rate of irreversibilities (~62.2%). Finally, the exergy-sustainability analysis identified 700 °C as the outstanding operating temperature. This research highlights the technical feasibility of operating Brayton S-CO 2 combined cycles with concentrated solar power (CSP) systems in regions of high solar irradiation, evidencing the potential of CSP systems to generate renewable energy efficiently and sustainably under extreme solar conditions.