The ORC turbogenerator uses medium-to-high-temperature thermal oil to preheat and vaporize a suitable organic working fluid in the evaporator (4>5). The organic fluid vapor rotates the turbine (5>6), which is directly coupled to the electric generator, resulting in clean, reliable electric power.

The exergy efficiency of the ORC system is defined as the ratio of the net power output to the exergy of waste heat before entering evaporation and is written as [37](8) η ex = W net m h [ ( h 9 - h 0 ) - T 0 ( s 9 - s 0 ) ] , where T₀ is the environment temperature; h₀ and s₀ are the specific enthalpy and specific ...

An organic Rankine cycle (ORC), is fundamentally the same as a steam Rankine cycle; however, it uses a lower boiling point organic fluid to better match its operation to lower temperature heat sources. ORC systems can achieve better efficiencies than steam turbines for smaller systems (less than a few MW_e).

The ORC technology is particularly suitable for the exploitation of medium-to-low enthalpy sources. It is a cost-effective solution with power outputs reaching up to 40 MWe per single generator for sources with water temperature from 100°C to 200°C or higher.