Organic rankine cycles

Organic rankine cycle provide a good method to capture heat from low and medium temperature sources and convert them to to electricity. Two types are available, the first uses lower temperature sources, using water as a medium offering efficiencies of between 5 & 10%. The second type needs somewhat higher temperatures using thermal oil as the heat transfer medium and offer gross efficiencies as high as 22% (drops to ~18% when the pump and cooling fan losses are taken into account).