Energy and Exergy Performance Comparative Analysis of a Solar-Driven Organic Rankine Cycle Using Different Organic Fluids

Abstract

In this study, the performance of parabolic trough collector (PTC) integrated with an organic Rankine cycle (ORC) is investigated to find the optimum operating scenarios and to assess the exergy destruction at different components of the system. A commercial PTC LS-2 model with Therminol VP-1 as heat transfer fluid was integrated with an ORC that was examined for its thermal and exergetic performance using different organic fluids. It was found that every fluid has an optimum pressure and temperature level at which it works better than other fluids. R134a (tetrafluoroethane, CH2FCF3) showed the best performance for the turbine inlet temperature range from 340 K to 440 K regarding the achieved energy and exergy efficiencies. At a temperature of 362.8 K and a pressure of 2750 kPa, R134a showed the highest energy efficiency of 8.55% and exergy efficiency of 21.84% with the lowest mass flowrate required in ORC. Energy efficiency of other fluids, namely, R245fa (pentafluoropropane, CF3CH2CHF2), n-pentane, and toluene, was less than 5%. On the other hand, toluene exhibited thermal efficiency of 23.5% at a turbine inlet temperature of 550 K and a pressure of 2500 kPa, while the exergy efficiency was 62.89% at solar irradiation of 1 kW/m2.