Energy flexibility of low-energy residential apartment in hot summer and cold winter regions: A comparative study on cooling season performance

Improving the building energy flexibility is an inevitable requirement for the large-scale use of renewable energy. To investigate the energy flexibility of low-energy residential apartments (LERA) in regions with hot summers and cold winters, the energy performance of LERA and regular residential apartments (RRA) during the cooling season was compared under different energy flexibility strategies, including reference conditions, upward flexibility events (UFE), and downward flexibility events (DFE). The results demonstrate that the LERA consistently outperformed RRA in terms of energy consumption and flexibility. Under the reference conditions, the energy consumption of the LERA was found to decrease by 63.3 % on sunny days and by 54.4 % on rainy days compared to that of the RRA. During UFEs, the LERA exhibits superior energy efficiency and stability. In the DFEs, the LERA effectively aligned the cooling demand with solar power availability, achieving a renewable energy self-sufficiency rate of 79.8 % compared with 37.2 % for the RRA. Furthermore, the electricity costs for LERA were significantly lower (up to 81 % lower) during peak tariff periods, demonstrating substantial cost-effectiveness. The findings revealed that LERA provide significant advantages in terms of energy flexibility, renewable energy utilization, and economic performance, contributing to reduced grid dependency and improved energy efficiency.