The Organic Rankine Cycle: Review

Abstract

Abstract

The extensive dependence on conventional fossil-fuel-based energy systems has been widely recognized as a major driver of anthropogenic climate change, primarily through the continuous release of greenhouse gas emissions. In this context, Organic Rankine Cycle (ORC) technology has emerged as a promising and technically viable solution for mitigating environmental impacts by enabling the efficient conversion of low- and medium-grade thermal energy, including industrial waste heat and renewable heat sources, into useful power. This review presents a comprehensive and updated assessment of Organic Rankine Cycle systems, with particular emphasis on recent developments in cycle configurations, working-fluid selection, and performance enhancement strategies. Unlike earlier reviews that predominantly focused on conventional ORC architectures operating under subcritical or supercritical conditions, the present study extends the discussion to advanced configurations, including recuperative, regenerative, reheated, two-stage, hybrid, and polygeneration ORC systems. The reviewed literature indicates that recuperative and regenerative configurations generally provide superior thermodynamic performance compared with simple and reheated single-stage cycles, mainly due to their enhanced internal heat recovery capability. Furthermore, two-stage ORC arrangements have demonstrated considerable potential for improving thermal efficiency and net power output, with reported enhancements reaching approximately 20% and 44%, respectively, relative to conventional single-stage systems. Hybrid ORC-based configurations, particularly those integrated with Brayton cycles or other complementary thermodynamic systems, exhibit even higher performance potential; however, their practical implementation is often constrained by the requirement for high operating temperatures. Overall, most experimentally and commercially investigated ORC systems operate within the small-scale power range, typically from about 1 kW to several tens of kilowatts, and commonly employ microturbines and plate heat exchangers as key system components.