An organic Rankine⁵ cycle turbine is a small turbine that is identical in design to a steam turbine but which uses a low boiling point organic fluid as its working fluid instead of water and steam. The turbine is packaged into a closed cycle system with a condenser and heat exchanger.

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 electrical efficiency is around 17% of the total energy input – about 3% higher than traditional steam turbines. The advantages of the ORC system are that it performs well under partial load and, because of the low working pressures and temperatures, it is not subject to the regulations of steam equipment.

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.