Comparative assessment of thermo-economic-environmental performance of various eco-friendly fluids in a solar-three-stage ORC operating under warm, non-temperate environment

This study compares the thermo-economic and environmental performance of nine eco-friendly fluids in a solar-driven three-stage series ORC (TSORC) operating in a warm, non-temperate environment. A computational model developed using Engineering Equation Solver (EES) software was employed to assess the impact of seven key operating parameters and environmental fluctuations on TSORC performance with different fluids. Detailed simulations were carried out under reference conditions, maintaining the temperature of the hot source at 400 °C. Subsequently, a multi-objective optimization integrating energy, exergy, economic, and environmental (4E) aspects was performed using an approach combining the traditional weighted sum method and a genetic algorithm integrated into the EES software, with the aim of obtaining an initial assessment of the potential for improvement of the TSORC system using the working fluid chosen. Performance indicators included net power output, energy utilization factor (EUF), total exergy destruction rate, exergy efficiency (EE), net present value (NPV), and annual CO 2 emissions reduction. Benzene was found to be the best-performing working fluid, followed by toluene, m-xylene, p-xylene, and ethylbenzene, respectively. However, in small-scale experiments, these latter fluids may be used as alternatives to benzene owing to its high toxicity. Optimization with benzene achieved substantial improvements: +35.5 kW net power output, +0.95 % EUF, +1.32 % EE, +225 k$ NPV gain, and a 791-tonne CO 2 emission reduction, with a 90 kW decrease in total exergy destruction. The analysis of hourly environmental fluctuations emphasizes the necessity of integrating an additional energy source into the TSORC to extend daily operation and mitigate solar intermittency effects.