Energetic, environmental and economic comparative analyses of modified transcritical CO2 heat pump system to replace R134a system for home heating

Due to low efficiency of a basic CO2 transcritical cycle, the feasible system scheme of CO2 is studied to replace R134a for heat pump heating. Three modified CO2 systems are discussed for home heating, in which a transcritical CO2 cycle system combining technologies of two-stage compression, vapor injection and inter-stage cooling (CO2 HPTSC, VI, ISC) is proposed based on the other two modified CO2 systems. Meanwhile, they are evaluated with two basic systems of CO2 and R134a in energy, environment and economy. All modified CO2 systems in terms of energy efficiency are better than R134a base heat pump system (R134a HPbase). In particular, CO2 HPTSC, VI, ISC is the optimal system. By combining typical meteorological parameters of different regions in China, the seasonal performance factor (SPF), gases emissions and costs are studied. The annual gas emissions of modified CO2 heat pump systems are all lower than those of R134a HPbase. If the compressor cost could be decreased by 67.66%, the life cycle cost (LCC) of CO2 HPTSC, VI, ISC will rival that of R134a HPbase in Beijing area. It can be predicted that the modified CO2 heat pump systems will be more competitive in the future. (C) 2021 Published by Elsevier Ltd.

Automated summary

The study focused on feasible system schemes of CO2 to replace R134a for heat pump heating, proposing a transcritical CO2 cycle system that outperforms traditional systems in terms of energy efficiency, environmental impact, and economics, demonstrating strong competitiveness in the future.