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'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.

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 quantity or the amount of available waste heat can be calculated using the equation shown below. (1) Q = V × ρ × C P × Δ T where, Q (J) is the heat content, V is the flowrate of the substance (m³/s), ρ is density of the flue gas (kg/m³), C_p is the specific heat of the substance (J/kg.