What is the Organic Rankine Cycle?
Organic rankine cycle systems convert thermal energy to electrical energy
The heat source to drive an ORC system can come from:
- Biomass boilers or gasifiers
- Waste heat sources, for example rejected heat from from power plants, or CHP systems fuelled by natural gas, landfill gas or bio oil.
The Organic Rankine Cycle (ORC) is based on the principle whereby a liquid is heated, causing it to evaporate, and the resulting gas is used to turn an engine, which is then connected to a generator, and thus creates power.
In a traditional power station, the working fluid is water, the evaporated gas steam, and the engine is a steam turbine. ORC technologies use working fluids which boil at much lower temperatures than water, allowing power generation from 'low grade' heat sources. The working fluid in an ORC system is contained in a closed loop, such that the working fluid is condensed after it has been through the engine, and then recirculated. The engines used in ORC packages vary in type, including small turbines and purpose designed 'expander' units.
Waste heat to power organic rankine cycle systems can come from power plants, CHP on natural gas, landfill gas or bio oil. Even waste heat coming from exothermic processes, steel mills and glass production or incinerators can be used to power an ORC unit.
Following the introduction of the Renewable Heat Incentive (RHI), systems which generate power and heat from biomass have become very economically attractive in the UK. The use of an ORC unit in combination with biomass boilers is an excellent solution to derive the optimum financial benefits from this incentive scheme.
ORC technology improves the overall efficiency of a system via waste heat recovery and produces no emissions.