Integration of sewage source heat pump and micro-cogeneration system based on domestic hot water demand characteristics: A feasibility study and economic analysis

The reduction of carbon emissions from building space heating and cooling technology has become a crucial approach in achieving global carbon neutrality. Among these technologies, heat pumps and cogeneration systems are effective methods for carbon reduction in buildings. However, in numerous studies of coupled system operation, few scholars have considered the energy use of domestic hot water. This research investigates the operational feasibility of a sewage source heat pump coupled with a micro-cogeneration system, using a large-scale hotel building as the basis for the study. An economic operation strategy, based on the load characteristics of domestic hot water, is proposed and validated through simulation using TRNSYS software. The results showed that the proposed system can reduce peak power usage by 37 % annually, leading to lower operating costs. The calculations indicate that the proposed system can decrease the annual operating cost by 402,300 CNY compared to a single sewage source heat pump system. The payback period for the proposed system is estimated to be 6 years at the current time-of-use electricity price. Under various energy policy conditions, 71 % of the proposed system’s payback period is less than 20 years. Moreover, the emissions of SO2, NOx, and CO2 are reduced by 73.5 %, 73 %, and 64.8 % respectively. The system offers substantial economic and environmental benefits, and this study can serve as a reference for energy supply systems in cold regions.