Coupled Modelling Of Building Space Conditioning Demand And Urban Climate

The combined effects of global warming and urban heat island effects have led to an increase in summer extreme heat events in more and more cities.This not only results in higher requirements for creating a comfortable urban thermal environment,but also affects the building heating/cooling energy requirements,the energy consumption required for air conditioning,and the corresponding waste heat discharged into the urban environment.There is a close relationship between urban microclimate and building energy consumption:from the perspective of the city as a whole,there is spatial heterogeneity in the urban thermal environment,which acts directly as boundary conditions for calculating building energy consumption prediction of air conditioning and ventilation.On the other hand,the heat exchange between the outdoor thermal environments will in turn be released as waste heat into the urban environment.Therefore,it is of great significance to study the coupling relationship and methods between building energy consumption/heat release and urban microclimate.In the past,urban climate research focused on urban macro scales,and it was difficult to be applied to urban renewal and new urban planning practices.This paper first discusses the non-uniform distribution of the thermal environment in urban space through outdoor traverse observation.Next,it describes how to use GIS spatial information to extract and integrate the key information needed for building energy consumption and urban microclimate simulation,and use this information to perform urban urban energy and water balance simulation(SUEWS)at urban scale.Based on the Building Thermal Network Equivalent Circuit(RC)model,a building thermal process and a building heat relsease model(BEW)for urban-scale building energy consumption and heat release analysis were established.A longwave and shortwave radiation exchange sub-model(BEERS)is applied between the building envelope structure and the surrounding environment in urban buildings.And using the building GIS spatial information data of the city centers of Beijing,Shanghai,Chongqing and Chengdu as samples,the dynamic solar radiation and shadow characteristics of the urban canopy,the sky view factor were analyzed parametrically and the relevant empirical formulas for the estimation of the shadow fraction and sky view factors on the building envelope with time and space parameters were obtained.Then a dynamic coupling model between urban surface energy model(SUEWS)and building energy and waste heat model(BEW)is establihed to comprehensively simulate the feedback effect between urban meteorological parameters and space heating/cooling requirements.Taking the central area of Chongqing,which is loacated in the hot summer and cold winter zone as an example,the overall building cooling and heating load,anthropogenic heat flux,and 2m height air temperature were carried out for one year,with a time step of 5 min.The anthropogenic heat emission flux(Qf)calculated from bottom-up(BEW-SUEWS dynamic coupling)and top-down(SUEWS default CDD model)are also comparedThe results show that in Chongqing,within the hot summer and cold winter zone,the grid-averaged heating degree day(HDD 18)calculated using the weather data of surface weather stations is 22.7%smaller than that resulted from the SUMESS-BEW coupling model,while the number of cooling degree day(CDD26)is 9.4%larger than that of SUEWS-BEW.The average annual cooling demand of the grid calculated by the SUEWS-BEW coupling model is 6.2%lower than that of the standalone building model(without considering the influence of surrounding urban environment on temperature and long-and short-wave radiation),but 4.2%higher than considering radiation exchange with surrounding environment alone.Therefore,for buildings located in urban environments,the demand for cooling and heating is affected by the combination of long-term and short-wave radiation exchanges between surrounding buildings as well as elevated surface air temperatures in urban centersFinally,several examples are given to showcase the capability of the coupled framework.From the perspective of future climate change,the changes in cooling and heating demand caused by future climate change(2050)are estimated.The annual cooling demand will increase by 32.3%,the annual heating demand will decrease by 52.9%.Another case shows when pavement reflectance increases from 0.12 to 0.32,CDD26 decreases by 1.4%and HDD 18 increases by 0.3%,but the annual cooling demand increases by 4.8%and annual heating demand decreases by 2.8%This paper proposes a comprehensive framework for dynamic calculation with urban building energy consumption and microclimate coupled,and provides a systematic method and tool for promoting quantitative research on urban spatial planning.