Techno-economic feasibility of CO2 utilization in sustainable energy harvesting: Energy-Exergy-Economic-Environmental (4E) analysis

In the context of the green 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, exergoeconomics, and environmental (4E) analysis of eco-friendly zeotropic mixtures with an emphasis on CO2 utilization. The application of the eco-friendly zeotropic mixture (DME-CO2) yielded significantly higher power (up to 50 %), lowest exergy destruction, highest power-to-environmental impact ratio, and compactness comparable to synthetic zeotropic mixtures. The exergoeconomic analysis illustrated that maximization of power generation is not necessarily 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.