An experimental investigation on a recuperative Organic Rankine Cycle (ORC) system for electric power generation with low-grade thermal energy

In this study, a small-scale recuperative Organic Rankine Cycle (ORC) system capable of generating electric power using low-grade thermal energy was setup and experimentally investigated at different operating conditions. The experimental setup consisted of typical recuperative ORC system components, such as a turboexpander with high speed electricity generator, plate recuperator, finned-tube air cooled condenser, ORC fluid pump and plate evaporator. R245fa was used as the working fluid in the recuperative ORC system due to its zero ozone depletion potential (ODP) and appropriate thermophysical properties for ORC system. The working fluid was evaporated in a plate evaporator by hot thermal oil flow which was circulated and heated by exhaust flue gases of an 80kWe microturbine CHP unit. The test rig was fully instrumented and extensive experiments were carried out to compare and examine the influences of various important parameters including heat source temperature and ORC pump speed etc. on the performances of ORC systems with and without recuperator integration. The test results are essential in understanding the system operations and can contribute significantly to optimal system design, component selections and controls.