The working principle of the organic Rankine cycle is the same as that of the Rankine cycle: the working fluid is pumped to a boiler where it is evaporated, passed through an expansion device (turbine, screw, scroll, or other expander), and then through a condenser heat exchanger where it is finally re-condensed.

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.

The Organic Rankine Cycle's principle is based on a turbogenerator working as a conventional steam turbine to transform thermal energy into mechanical energy and finally into electric energy through an electrical generator.

The Rankine cycle is an idealized thermodynamic cycle of a heat engine that converts heat into mechanical work while undergoing phase change. The thermal efficiency equals 1 minus the ratio of the low-to-high pressures to the power of 1 minus the reciprocal of the heat capacity ratio.