Comparative investigation on the performances of organic rankine cycles (orcs) for the exploitation of low temperature heat sources

Abstract

The present work aims at investigating the energetic performances of Organic Rankine Cycles (ORCs) for the exploitation of low temperature heat sources in small-scale applications. Specifically, a thermodynamic model has been developed and a parametric energy analysis has been carried out considering several organic fluids. Different system configurations have been investigated in order to define the proper ORC arrangements and the influence of the operating conditions on the system performances. Subcritical and transcritical cycles, with saturated and superheated conditions at the expander inlet, have been analysed and the impact of internal regeneration on ORC behaviour has been studied. The analysis shows the large influence of the operating conditions and the significant effect of the internal regeneration on the system performances. Specifically, the comparison between the different ORCs highlights that the transcritical cycle with internal heat exchange offers the maximum electric efficiency. Furthermore, results reveal that the proper selection of the organic working fluid is fundamental to maximise the system performances.