Study on the year-round demand flexibility in residential buildings: Control strategies and quantification methods

The transition to a renewable energy-centric system necessitates enhanced demand flexibility in buildings. The load characteristics of electrical appliances in residential buildings are influenced by various factors, including seasonal variations and user habits. However, there is a notable lack of comparative research on flexible load control across multiple seasons and day types throughout the year, as well as a scarcity of indexes and their grading applications that can comprehensively describe the multi-dimensional building flexibility characteristics. Therefore, this study focuses on typical residential buildings in Cold region and explores the flexible control effects of various strategies in diverse seasonal and day type scenarios. An innovation "digitized-graded" index system is established, grading index values based on flexibility strength, duration, and maximum reduction, thereby providing a comprehensive understanding of demand flexibility from both quantitative and qualitative perspectives. The findings reveal that different control strategies excel in different seasons and distinct evaluation dimensions. Specifically, the strategy of changing the air conditioning temperature set point performs best in summer, while the intermittent start-stop cycles strategy is more suitable for winter. Furthermore, these strategies dominate in Flexibility Strength Index (FSI) and Flexibility Duration Index (FDI), achieving maximum values of 39.3 % and 14 h, respectively, signifying "extremely strong flexibility" and "extremely long-term flexibility". Adjusting the lighting intensity is optimal in the transition season, followed by summer, and is least effective in winter. Additionally, shiftable loads using time transfer strategy exhibit a Maximum Reduction Index (MRI) of up to 13.9, indicating "extremely heavy reduction flexibility".