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.

Organic Rankine cycle (ORC) machines are used to convert low-temperature heat resources into power. Examples include systems making use of waste heat in a cogeneration system, low temperature geothermal electricity generation, solar ponds, and potentially OTEC.

The Rankine cycle operates in the following steps: 1-2-3 Isobaric Heat Transfer. High pressure liquid enters the boiler from the feed pump (1) and is heated to the saturation temperature (2). Further addition of energy causes evaporation of the liquid until it is fully converted to saturated steam (3).