Analysis of Low-Heat Upgrading Technologies for Organic Rankine Cycle Power Generation

Abstract

Heat below 70 ??C is a common by-product in current industries that is discarded as waste because of the difficulties involved in its exploitation. In this work is proposed an ORC power generation system capable of recovering this industrial waste heat by applying three heat boosting technologies: (i) Electrical heat pump system (EHPs), (ii) Gas engine-driven heat pump system (GEHPs), and (iii) Absorption heat transformer system (AHTs). The systems were mathematically modeled considering a thermal capacity of 250 kW for all three systems, with R365mfc as working fluid for EHPs and GEHPs, while the AHTs uses H₂O-LiBr. For each combination a 20 kW_e ORC power generator with R245fa as working fluid is considered. The systems were simulated using a heat source above 60 ??C. The results shown that from the proposed technologies, EHPs was the most suitable due to its compactness, simple installation and operation, while being also easily maintainable. In terms of the economic analysis, when the heat source is around 63 ??C, EHP-ORC also achieves the lowest Levelized Cost Of Electricity (LCOE) of 0.065 USD/kWh, while AHT-ORC and GEHP-ORC, 0.066 and 0.086 USD/kWh, respectively. In terms of the environmental impact analysis, the AHT-ORC can reduce CO₂ emissions by 86.4 Ton CO₂ eq./Year due to the low energy consumption of the system, while EHP-ORC and GEHP-ORC can reduce 63.0, and 37.8 Ton CO₂ eq./Year, respectively.