Capacity investigation of air source heat pump heating and cooling system for ultra-low energy residential building in hot summer and cold winter area: A case study of Shanghai

In hot summer and cold winter regions, the adoption of air-source heat pump (ASHP) heating and cooling systems is key to improving building energy efficiency and promoting electrification. To decide the capacity of ASHPs, this study investigates the load characteristics of an ultra-low energy residential building in Shanghai using DeST software for intermittent operational simulations and WUFI-Plus software for coupled heat and moisture transfer analysis. The simulation results indicate that, compared with continuous operation, the heating and cooling loads of each room under intermittent operation increase by 100% to 200%, while the household-wide load only rises by 50% to 60%. Despite this, indoor heat consumption can be reduced by nearly 20%. Additionally, the coupled heat and moisture transfer of the envelope structure significantly affects its thermal performance in high humidity environments. Consequently, the total heating load of the building increases by approximately 10%, whereas the total cooling load rises by about 20%. Moreover, in hot summer and cold winter areas, ASHP units are prone to frequent defrosting during winter, leading to a significant decline in heating performance. Based on the load characteristics of buildings in these regions and the operational performance of heat pump units, a comprehensive method for selecting and matching heat pumps is presented. The results indicate that although the cooling load is dominant, the ASHP unit should still be selected according to the heating load and checked for cooling load, which provides a guidance for the design and selection of ASHPs for ultra-low energy residential buildings in hot summer and cold winter regions.