Organic Rankine Cycle (ORC)
The Organic Rankine Cycle is a thermodynamic power cycle that uses an organic working fluid with a low boiling point instead of water, so it can generate electricity from low- and medium-temperature heat. It is widely used to convert industrial waste heat and geothermal or biomass heat into power.
A conventional steam Rankine cycle needs high-temperature heat to boil water efficiently. The ORC swaps water for an organic fluid that vaporises at a much lower temperature, allowing the same boil–expand–condense–pump cycle to run on heat sources that would otherwise be too cool to use for power generation.
This makes the ORC a key technology for waste-heat recovery: exhaust from engines, kilns, furnaces and turbines, or hot process streams, can drive an ORC turbine to produce electricity on site. It is also used with geothermal, biomass and solar-thermal sources.
For industrial decarbonisation, ORC systems turn rejected heat into useful power, cutting fuel use and emissions and improving overall plant efficiency. Economics depend on the temperature and steadiness of the heat source and on the value of the electricity displaced.
Related reading
Related terms
Waste Heat Recovery · CHP / Cogeneration · Heat Exchanger · Industrial Decarbonization · Green Hydrogen · Psychrometrics