In the heart of Brazil, where the sun scorches the earth with unprecedented intensity, a groundbreaking study led by Juan Córdoba from the Faculty of Engineering, Department of Mechanical Engineering, Universidad del Atlántico, Barranquilla, Colombia, is paving the way for a more sustainable energy future. Published in ‘Resources’, the research delves into the intricate dance of energy, exergy, and exergo-sustainability in a supercritical CO2 Brayton cycle coupled with a Kalina cycle, all powered by the relentless sun.
The study, conducted in Araçuaí, Minas Gerais, a city that recently set a record for the highest temperature in Brazilian history, explores the potential of concentrated solar power (CSP) systems to generate renewable energy efficiently and sustainably under extreme solar conditions. Córdoba and his team found that at 900 °C, the system achieved a thermal efficiency of 56.67% and a net power output of 186.55 kW, but this also increased the exergy destroyed. However, the exergy efficiency peaked at 24.92% at a more moderate 700 °C, suggesting a sweet spot for optimal performance.
“The solar field presented the highest rate of irreversibilities (~62.2%),” Córdoba noted, highlighting the need for further optimization. This finding underscores the importance of improving solar receiver design and materials to enhance energy absorption and reduce thermal losses.
The study also revealed that a turbine inlet pressure of 18 MPa and a compressor efficiency of 95% significantly boosted both thermal and exergy efficiencies, reaching 54.98% and 24.62%, respectively. These findings are crucial for the energy sector, as they demonstrate the potential for high-efficiency, low-emission power generation using renewable sources.
The research also introduced exergo-sustainability indicators, such as the process exergy waste rate (EWR), the environmental effect factor (EEF), and the exergy sustainability index (ESI), to quantify the degree of sustainability of the proposed configurations. These indicators identified 700 °C as the outstanding operating temperature, balancing cycle efficiencies, exergy destruction, and power production.
The implications of this research are vast. As the world grapples with climate change and the urgent need to reduce greenhouse gas emissions, the findings from Araçuaí offer a promising pathway for the energy sector. By optimizing CSP systems and integrating them with advanced power generation technologies like the Brayton S-CO2/Kalina cycle, countries can move closer to a more sustainable energy future.
The study also opens avenues for further research, particularly in optimizing solar receiver design, improving materials for better solar energy absorption, and developing operation and maintenance strategies to maximize the lifespan of CSP components. As Córdoba aptly put it, “Future studies could address the relationship between operating conditions and capital, operating, and maintenance costs to maximize the economic viability of the Brayton and S-CO2/Kalina cycle in CSP systems.”
This research not only highlights the technical feasibility of operating Brayton S-CO2 combined cycles with CSP systems in regions of high solar irradiation but also underscores the potential for these systems to generate renewable energy efficiently and sustainably. As the world continues to seek cleaner and more sustainable energy alternatives, the insights from Araçuaí could shape future developments in the field, driving innovation and paving the way for a greener energy landscape.
