The organic Rankine cycle is is similar to the Rankine steam cycle, but uses an organic fluid such as refrigerants and hydrocarbons instead of water as the working fluid. The ordinary Rankine cycle uses thermal power to convert water to steam, which expands through a turbine in order to generate electricity.

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.

ORC: How it works Where heat pumps use electrical power to create thermal energy for various purposes, an ORC system uses heat energy to generate electricity. In a typical ORC design, a thermal energy source feeds an evaporator to drive an expander or “reverse compressor”, which in turn generates the electricity.

ORC WHR system consists of four major components: pump, evaporator, expander and condenser, as shown in Figure 1.