Thermodynamic and Exergoeconomic Assessment of Environmentally-Benign Zeotropic Mixtures in Organic Rankine Cycle for Sustainable Power Generation

Abstract

In the context of the sustainable energy transition, the organic Rankine cycle (ORC) is explored for energy conversion from renewable energy sources. The majority of ORC systems are explored with synthetic chemicals-based zeotropic mixtures as working fluids, which are detrimental to the environment. However, the choice of working fluids needs a holistic approach that considers not only maximizing the performance but also the cost-effectiveness, minimal environmental impact, and appropriate system sizing. This study aims to address this knowledge gap by performing a comprehensive energy, exergy, and exergoeconomic analysis of environmentally benign zeotropic mixtures with an emphasis on CO2 utilization and the influence of heat source temperatures. The application of the eco-friendly zeotropic mixture (DME-CO2) yielded significantly higher power (up to 50%), lower exergy destruction, and system compactness comparable to synthetic zeotropic mixtures for the conditions studied. The exergoeconomic analysis illustrated that maximization of power generation in conjunction with system compactness offers a cost-effective solution for harnessing renewable energy sources. The holistic approach employed in this study showcased that eco-friendly zeotropic mixtures can achieve cost parity with synthetic zeotropic mixtures while delivering comparable technical performance. The results also demonstrate that CO2 concentration is intricately linked to system performance, compactness, and cost and warrants further exploration of the optimal CO2 concentration.