Life cycle energy, economic, and environmental analysis for the direst-expansion photovoltaic-thermal heat pump system in China

The photovoltaic-thermal heat pump system, which integrates multiple energy technologies, can meet the building's diverse energy needs. This study evaluates the energy, economic, and environmental performance of a direct-expansion photovoltaic-thermal heat pump system for domestic hot water supply through a life cycle approach. The annual thermal and electrical outputs are estimated. On this basis, economic analysis is conducted with indicators of life cycle cost, levelized cost of heat, and investment payback time. Moreover, a detailed life cycle assessment is performed to evaluate the environmental impact, following three methods: cumulative energy demand, IPCC 2021 global warming potential, and ReCiPe 2016 Endpoint. Results show that the proposed system is highly effective, with a 9.67% increase in annual electricity output over traditional photovoltaic systems and a self-sufficient rate of 88.21%. The system also has a significantly lower environmental impact than conventional heating systems, with a life cycle environmental impact of only 3-5% compared to electric boilers. The environmental payback time ranges from 0.33 to 5.18 years, according to the three methods used in the study, which is shorter than the investment payback time of 2.49-5.21 years, suggesting the need for cost reduction for future promotion. Moreover, electricity consumption during the operation stage accounts for 32-52% of the total environmental impacts. Thus, decarbonization of the power grid and improvements in system efficiency can significantly reduce the system's environmental footprint. Overall, the photovoltaic-thermal heat pump system is an intriguing strategy for building energy conservation, offering high energy efficiency, acceptable costs, and low environmental impact.