Analysis Of Cooling And Heating Demand Moving Towards Near Zero Energy Civil Building In Severe Cold Region And Cold Region

With the rapid development of economy,the energy issue has become a difficult problem we have to face.Since the building energy consumption is an important part of the social terminal energy consumption,building energy conservation has been paid worldwide attention.Since the development of building energy conservation plan was put forward in 1986,China has successively achieved 30%,50%,65%energy saving goals for building energy efficiency.The Ministry of Housing and Urban-Rural Development has carried out“China passive low energy building demonstration project”in cooperation with the German Energy Agency in2009.In recent years,many provinces and cities successively put forward and develop green buildings,passive buildings,near zero energy buildings,and even zero energy buildings and productive energy buildings.Realizing the zero energybuildings is the target of building energy conservation development,and the near zero energy building is the route which must be passed.This paper utilizes DeST software to simulate and analyze the annual heating and cooling demand of near zero energy civil building in severe cold region and cold region,and put forwards strategies on fresh air heat recovery and sunshade of buildings in severe cold region and cold region.This paper presents HDD18 and CDD26 of main cities in the five secondary climate zones according to the climatic characteristics of the severe cold and cold region.Nine typical cities for each climate zone were seleted based on its distribution characteristics.Typical building models were established by analyzing the main influencing factors of building heating energy consumption and the specific value of each factor was determined by referring to common values or recommended values.Models of 12 typical residential buildings and four typical office buildings have been built in this paper.The thermal parameters and indoor parameters have been designed according to the relevant standards.The hourly heating and cooling demand of typical buildings were simulated by DeST software.The results show that the heating demand of civil buildings in cold region are lower than10kWh/(m~2·a).Except for the cities with sufficient solar radiation such as Lenghu,Songpan,etc,the heating demand of most cities in severe cold region are higher than 20kWh/(m~2·a).The cooling demand for residential buildings in severe cold and cold areas is less than15kWh/(m~2·a).The heating demand for office buildings is larger,especially in cold areas,which can reach up to more than 30kWh/(m~2·a).The orthogonal test approach is employed to analyze the significance of the factors affecting the building cooling and heating load.It is concluded that the most significant factor of building cooling load and heating load is the heat dissipation per unit area and the fresh air volume,respectively.Through further studies,the results indicate that 75%fresh air sensible heat recovery is recommended for the residential buildings during heating period in both severe cold region and cold region.Moreover,it is better to set 70%fresh air total heat recovery for cold region and no heat recovery for severe cold region during air conditioning period.For office buildings,the relative energy saving rate of any mode of fresh air heat recovery is higher than70%.Thus,the two fresh air modes can be applied for severe cold and cold region.We suggest that 70%fresh air total heat recovery should be employed for cold region,while the severe cold region is not suiable to apply heat recovery during air conditioning period.When setting internal sunshade in the buildings,the relative energy saving rate are all above 10%for office building in severe cold region and cold region.With both fresh air heat recovery and internal sunshade,the annual cooling load of office building in cold region are more than 25 kWh/(m~2·a)when the fresh air heat recovery and internal sunshade are both used in buildings.The main reason is that the building internal heat source in the office building is much larger.Moreover,the part of heat is difficult to release in time for the ultra low energy building with high air tightness.Futhermore,this paper analyzes the feasibility of zero energy consumption in typical urban buildings.The results show that the use of heat recovery is more energy saving.For residential buildings with smaller scale or lower layers,zero energy consumption can be achieved.It is difficult to achieve zero energy consumption for residential buildings with larger scale or high storeys and office buildings.Finally,this paper selected a near zero energy office building in Dalian to validate the model.The measured parameters such as the hourly temperature of each room and outdoor,hourly solar radiation and heat transfer coefficient of external wall were input into DeST software and the hourly heating load was simulated.The results show that the accuracy of the model built by DeST is vertified by hourly temperature indoor and hourly heating load of the whole building.