The organic Rankine cycle is is similar to the Rankine steam cycle, but uses an organic fluid such as refrigerants and hydrocarbons instead of water as the working fluid. The ordinary Rankine cycle uses thermal power to convert water to steam, which expands through a turbine in order to generate electricity.

ORC systems can provide significant environmental benefit by capturing waste heat for electrical or mechanical power thus reducing fossil fuel dependency or improving overall energy efficiency.

An Organic Rankine Cycle (ORC) system is a closed thermodynamic cycle used for power production from low to medium-high temperature heat sources ranging from 80 to 400°C and for small-medium applications at any temperature level.

The technology was developed in the late 1950s by Lucien Bronicki and Harry Zvi Tabor. Naphtha engines, similar in principle to ORC but developed for other applications, were in use as early as the 1890s.