Life cycle techno-enviro-economic assessment of dual-temperature evaporation transcritical CO2 high-temperature heat pump systems for industrial waste heat recovery

• CO 2 dual-temperature evaporation HTHP systems are proposed to recover waste heat. • Energy efficiency can be improved with ejector and dual-temperature evaporator. • New proposed HTHP shows superior life cycle carbon emissions and cost performances. • Ej-Evap2-C system has the shortest payback period compared with coal-fired boiler. Replacing fuel-fired boilers by using efficient heat pump plants to recover industrial waste heat is an effective solution to achieve the “dual carbon” target. Three novel transcritical CO 2 high-temperature heat pump systems (Ej-Evap2-A, Ej-Evap2-B, and Ej-Evap2-C) are proposed in this study, by introducing the technique of dual-temperature evaporation realized with an ejector for cascade heat absorption from the heat source. Considering the application in the scenario of industry requirement of hot water heating, the life cycle performances of the new proposed heat pump systems and fuel-fired boilers are comprehensively studied from the perspectives of energetic, emissions, and economic. A sensitivity analysis about the new configuration heat pump system is also conducted considering the variation in electricity and coal price. The results demonstrate there exists an optimum discharge pressure that maximizes the coefficient of performance (COP). Ej-Evap2-C shows a maximum COP of 4.85, which is 14.40% higher than the baseline CO 2 heat pump system (Base), and the exergy efficiency of Ej-Evap2-C is 7.86%∼15.19% higher than that of Base. Among the eight heating methods including coal-fired boilers (CFB), gas-fired boilers (GFB), electric heating boiler (EHB) and five kinds of CO 2 heat pump systems, Ej-Evap2-C shows the least pollutant emissions and life cycle cost. Furthermore, Ej-Evap2-C has the shortest payback period of fewer than 7 years compared with the CFB. The dual-temperature evaporation CO 2 high-temperature heat pump is promising to substitute traditional fuel-fired boilers to generate high-temperature fluid in the future.