Energy and exergy analysis of Organic Rankine Cycles for six low-GWP refrigerants

Worldwide rapid industrialization has led to substantial low-temperature waste heat generation, posing both environmental challenges and opportunities for energy recovery. Organic Rankine Cycle (ORC) systems have emerged as a promising technology for converting such low-grade waste heat into useful power due to their ability to operate with organic working fluids at relatively low temperatures. This study presents a comprehensive energetic and exergetic analysis of three ORC configurations: Basic, Reheat, and Regenerative ORC using environmentally sustainable refrigerants with a low Global Warming Potential (GWP < 10). A numerical simulation is performed by Python programming to solve the mass, energy, entropy, and exergy balance equations of the ORC configurations to evaluate the performance of six low-GWP refrigerants: R-1243zf, R-1234yf, R-1234ze(E), R-1224yd(Z), R-1233zd(E), and R-1336mzz(Z). The investigation specifically assessed the impact of turbine inlet pressure (1.0 – 2.5 MPa) and pump inlet pressure (0.8 – 2.0 MPa) on key performance parameters: net power output, thermal efficiency, exergy efficiency, and total exergy destruction. The analysis reveals that R-1243zf consistently outperforms among other refrigerants across all configurations followed by R-1234yf, R-1234ze(E), R-1224yd(Z), R-1233zd(E), and R-1336mzz(Z). For all refrigerants, the optimal performance was achieved at the higher turbine inlet pressure of 2.5 MPa and the lower pump inlet pressure of 0.8 MPa. At the optimum pressures, R-1243zf exhibited strong performance across configurations: the Reheat ORC maximized net power output (33.8 kW), the Regenerative ORC maximized thermal efficiency (10.6%), and the Basic ORC achieved the highest exergy efficiency (36.0%). Under these optimal pressure conditions, R-1243zf demonstrated superior performance in the Basic ORC configuration, yielding the highest exergy (36.0%) efficiency and an effective balance of thermal efficiency (10.0%) and net power output (32.6 kW). The novelty of this study lies in the quantitative screening of low-GWP refrigerants (GWP < 10) across three ORC configurations, establishing a clear performance hierarchy and identifying the optimal fluid-architecture pairing (R-1243zf in a Basic ORC) for practical implementation under specified pressure conditions. • Energy and exergy analysis of Basic, Reheat, and Regenerative ORCs • R-1243zf shows highest power output and efficiency among six low-GWP fluids • Optimal performance achieved at 2.5 MPa turbine and 0.8 MPa pump inlet pressure • Reheat ORC maximizes power, while Regenerative ORC improves efficiency