Design and dynamic simulation of a solar-driven organic Rankine cycle with zeotropic mixture

• Solar-driven organic Rankine cycle with zeotropic mixture working fluid. • Dynamic investigation with the zeotropic mixture R601/R600 is conducted. • Zeotropic mixture increases the yearly yield by 3.7% and 1.5% compared to pure fluids. • Higher performance enhancement was found during the summer with the mixture fluid. • A lower payback period was found with the mixture fluid compared to the pure fluids. The present analysis concerns the design and dynamic simulation of a solar-driven ORC system using the zeotropic mixture R601/R600. The plant comprises evacuated flat plate collectors (EFPC) for effective solar energy capture and a thermal storage tank. A parametric analysis was carried out to determine the optimal design for maximizing electricity generation and ensuring economic viability for three working fluid scenarios: R601/R600 [0.3/0.7] mixture, R601, and R600. The annual electricity production of the system using the mixture reached 12 MWh, exhibiting an increase of 3.70% compared to R600 and 1.46% compared to R601. A closer analysis of the daily operation during winter, spring, and summer days revealed that while the mixture-based ORC exhibited fluctuations during operation, it still outperformed pure fluids in electricity generation across all examined days. Additionally, monthly trends showed that the performance improvement was more pronounced during the summer months, with a monthly electricity enhancement of 1.79% compared to R601 and 3.31% compared to R600. Overall, this investigation highlights the benefits of zeotropic mixtures in solar-driven ORC systems, demonstrating better energy performance at daily, monthly, and annual scales, and positioning them as a promising option for improving ORC efficiency.