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 is a technology that convert low-temperature heat sources into a mechanical energy, and it can be used to produce electrical energy in a closed system. The heat sources can be received from renewable energy such as geothermal, solar, and biomass.

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.

It is shown that by utilizing the full potential of screw expanders instead of turbines, it is possible to produce Organic Rankine Cycle (ORC) systems at these outputs, which can be installed for a cost in the range of $1500 to $2000 /kWe of net output.