4E analysis and multi-objective optimization of compression/ejection transcritical CO2 heat pump with latent thermal heat storage

To promote the goal of peak carbon dioxide emissions and carbon neutrality, low-energy consumption buildings require innovative technologies and efficient energy management. In this paper, the multi-objective optimization and the energy, exergy, economic and environmental (4E) analyses of the compression/ejection transcritical CO2 heat pump with latent thermal storage (TPE-LTES) system are conducted, and the influences of crucial parameters on the system performance are evaluated. The results show that the optimal comprehensive COP and annual hot water production (mDHW) of the TPE-LTES system are 3.59 and 3110 tons, respectively. Then, the comprehensive exergy efficiency of the TPE-LTES system owns 48.93 % higher than that of the heat pump unit. Furthermore, the optimal life-cycle cost (LCC) and life-cycle CO2 emissions (LCCE) of the TPE-LTES system are 708,073 CNY and 575,512.79 kg, respectively. Moreover, with constant discharge pressure, the evaporative superheat can be preferentially increased to reduce the system LCC and LCCE. Finally, the comprehensive COP and exergy efficiency of the system can be improved by increasing the inlet water temperature, while the increasing inlet water flow rate is the least desirable. This work is helpful to promote the research and application of latent heat storage unit integrated into air source heat pump.