Analysis of the Impact of Fresh Air on the Cooling and Heating Demand of Near-Zero Energy Residential Buildings

In China's energy consumption, building operation energy consumption accounts for more than 20% of the total energy consumption, and the prerequisite for reducing building energy consumption and lowering carbon emissions is to reduce energy demand. Near-zero-energy buildings can greatly reduce building energy demand with their better envelope and high airtightness, and have become a trend and hotspot for building development. Compared with general buildings, near-zero-energy buildings have the characteristics of low load demand and large proportion of fresh air load. Different ways of utilizing fresh air have a greater impact on the cooling and heating demand of near-zero energy buildings. In order to improve the efficiency of building HVAC systems and guide the development of special equipment, it is necessary to study the impact of fresh air utilization on the cooling and heating demand of buildings. Scholars at home and abroad have carried out a great deal of work in the study of cooling and heating demand of near-zero-energy buildings and the analysis of system energy efficiency. Zhao Anqi simulated and compared the fresh air loads of residential buildings in cold and frigid regions, and the results showed that fresh air sensible heat recovery is preferred in winter in cold and frigid regions, and full heat recovery is preferred in summer in cold regions. Chen et al. compared the characteristics of fresh air load in typical cities in four climate zones, and pointed out that compared with the envelope load, the fresh air load in each climate zone is relatively considerable.Liu et al. pointed out that passive heat recovery technology has the characteristics of high efficiency and low cost, and has a wide application prospect in zero energy buildings. Peng et al. simulated the heat load of near-zero-energy buildings in frigid and cold regions and the cold load in cold regions are positively correlated with the fresh air load, and Zhang et al. simulated the fresh air load of ultra-low-energy buildings in Shenyang, and the results showed that the better the performance of the envelope structure is, the greater the proportion of fresh air heat load to the total heat load is. Han Wusong et al. analyzed the HVAC system of an ultra-low-energy kindergarten in Beijing, and pointed out that the linkage between the exhaust air system and the fresh air system should be considered.Liang et al. concluded that high-efficiency fresh air heat recovery is crucial for reducing the operational energy consumption in near-zero-energy buildings in the northeast of the United Kingdom by monitoring the operational energy consumption of near-zero-energy buildings and conventional buildings. In recent years, the research on near-zero energy buildings has made significant progress in the direction of residential buildings. Qu Yan et al. analyzed a typical residential building case in Shanghai and proposed a technical index for near-zero energy residential buildings applicable to Shanghai. Li et al. utilized the clustering algorithm, combined with the building thermal design zoning, to give the reference range of annual cold consumption for cooling in different climate zones. Wang Lifeng et al. proposed a calculation method for the annual energy savings of using fresh air heat recovery devices in near-zero energy residential buildings, and analyzed the annual energy savings of using heat recovery devices in near-zero energy residential buildings. The above studies provide a solid foundation for the analysis of cooling and heating demand in near-zero energy buildings, but these studies mainly focus on case studies of buildings in severe cold and frigid regions, and the analyses about other climate zones are more limited. In addition, existing studies rely on theoretical calculations when proposing energy-saving methods for near-zero energy buildings, without considering the impact of building thermal inertia, etc. There is a lack of research on the impact of utilizing fresh air heat recovery systems and fresh air as a natural cooling source on building cooling demand based on building hourly loads. Therefore, this paper establishes a dynamic simulation model of a typical near-zero-energy residential building, simulates and analyzes its annual cold/heat consumption characteristics in different climatic zones and different fresh air utilization scenarios, and discusses the impact of fresh air heat recovery and the use of fresh air as a natural cooling source on the building's cold and heat demand, so as to provide a reference for the use of the fresh air heat recovery system and free cooling in different climatic zones, and provide guidance for the research and development of energy and environmental products dedicated to near-zero-energy buildings. This will provide a reference for the use of fresh air heat recovery systems and free cooling in different climate zones, and provide guidance for the research and development of energy and environmental products for near-zero energy buildings.