Performance and thermo-sustainability analysis of non-hybrid organic Rankine cycles (ORCs) at varying heat source and evaporator conditions

Abstract

The performance and thermo-sustainability indicators (TSI) of non-hybrid organic Rankine cycles (ORCs) are considered at varying evaporator pressure (EVP) and heat source temperature (HST). The ORCs structures include the ORC-basic, ORC-internal heat exchanger (ORC-IHE), ORC-turbine bleeding and ORC-turbine bleeding/regeneration. The TSI considered exergy efficiency, waste exergy ratio (WER), exergetic sustainability index (ESI) and environmental effect factor (EEF). The calculated overall exergy efficiency varies from 35.35 to 47.23 for evaporator pressure between 2 and 3 MPa and 49.02 to 52.71 for HST between 500 and 650 K. Additionally, WER, ESI and EEF were found to vary from 0.253 to 0.278, 1.15 to 1.87 and 0.547 to 0.82, respectively while ESI decreases for all variants of HST. The results indicate high ESI and low WER in ORC-IHE and the ORC-turbine bleeding /regeneration for all variations in EVP and HST.