Experiments and thermal modeling on hybrid energy supply system of gas engine heat pumps and organic Rankine cycle

This paper presents a hybrid energy supply system, which is composed of two subsystems (gas engine-driven heat pump system (GEHP) and organic Rankine cycle system (ORC)) and three major thermodynamic cycles (the vapor compression refrigeration cycle, the internal combustion gas engine cycle and ORC). In order to convert the low-grade gas engine waste heat into high-grade electricity, the ORC system is built up using R245fa, R152a and R123 as working fluids, and the ORC thermal model is also developed. Meanwhile, experiments of GHEPs in cooling mode are conducted, and several factors which influence the cooling performance are also discussed. The results indicate that the cooling capacity, gas engine energy consumption, gas engine waste heat increase with increasing of gas engine speed and decrease with decreasing of evaporator water inlet temperature. The waste heat recovered from gas engine is more than 55% of gas engine energy consumption. F6urthermore, R123 in ORC system yields the highest thermal and exergy efficiency of 11.84% and 54.24%, respectively. Although, thermal and exergy efficiency of R245fa is 11.42% and 52.25% lower than that of R123, its environmental performance exhibits favorable utilization for ORC using gas engine waste heat as low-grade heat source.