Energy, exergy, and environmental (3E) analysis of a compound ejector-heat pump with low GWP refrigerants for simultaneous data center cooling and district heating

Abstract

This work presents an energy, exergy, and environmental evaluation of a novel compound PV/T (photovoltaic thermal) waste heat driven ejector-heat pump system for simultaneous data center cooling and waste heat recovery for district heating networks. The system uses PV/T waste heat with an evaporative-condenser as a driving force for an ejector while exploiting the generated electric power to operate the heat pump compressor and pumps. The vapor compression system assessed several environmentally friendly strategies. The study compares eleven lower global warming potential (GWP) refrigerants from different ASHRAE safety groups (R450A, R513A, R515A, R515B, R516A, R152a, R444A, R1234ze(E), R1234yf, R290, and R1243zf) with the hydrofluorocarbon (HFC) R134a. The results prove that the system presents a remarkable overall performance enhancement for all investigated refrigerants in both modes. Regarding the energy analysis, the cooling coefficient of performance (COPC) enhancement ranges from 15% to 54% compared with a traditional R134a heat pump. The most pronounced COPC enhancement is caused by R515B (a 54% COPC enhancement and 49% heating COP enhancement), followed by R515A and R1234ze(E). Concerning the exergy analysis, R515B shows the lowest exergy destruction, with the highest exergy efficiency than all investigated refrigerants.