Some of the wasted heat may be recovered using the Rankine cycle, where an intermediate heat transfer loop is added that contains a working fluid whose properties allow it to pass through an expander to capture some of the exergy of the waste heat sources.

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 low speed ORC process has an electricity output of 400–1100 kW and electricity to heat ratio of 0.18–0.22. The ORC-concept has two circuits, one for thermal oil and another for organic fluid.

”Waste heat recovery” is the process of “heat integration”, that is, reusing heat energy that would otherwise be disposed of or simply released into the atmosphere. By recovering waste heat, plants can reduce energy costs and CO₂ emissions, while simultaneously increasing energy efficiency.