Techno-economic-environmental analysis and fluid selection of transcritical organic Rankine cycle with zeotropic mixtures

Waste heat recovery is regarded as highly efficacious in ameliorating energy and environmental problems brought on by rapid economic and societal growth. The organic Rankine cycle (ORC), specifically transcritical ORC (tORC) garners significant attention for its potential in waste heat power generation. Researchers still seek to further improve performance for tORC, such as using zeotropic mixtures. Aimed at selecting the working fluid pairs that can bring better performance for tORC, this study provides a more comprehensive performance evaluation of tORC systems by developing a novel multi-attribute integrated assessment model that encompasses techno-economic-environmental aspects. To establish this model, the detailed mathematical models of the tORC are established first and used to obtain system performance indicators. Then, a refined analytic hierarchy process to assign weights to various performance indicators to complete the multi-attribute integrated assessment model. With the utilization of the proposed model, a thorough comparative analysis of the tORC system with ten groups of zeotropic mixtures is performed. Thus, the results of the working fluid selection can be obtained. Results show that R245fa/R600 and R600/R600a are more recommended than other working fluid pairs, with R600/R600a being the preferable choice when prioritizing environmental impact. While R245fa/R1234yf has the worst thermodynamic and environmental performance and R245fa/R227ea owns the worst economic performance. In conclusion, the findings show that employing a zeotropic mixture combines the benefits of the pure working fluids that comprise it. Compared to previous studies, this study provides a more comprehensive look at the selection of working fluids for tORC systems. It can offer valuable insights for selecting the appropriate working fluid more effectively for future applications.