| China is facing a large-scale urban expansion.The urban area has a relatively-large area of impermeable layers,which causes a heat island effect and affects the local climate negatively.Therefore,it is significant to study measures to mitigate the urban heat island effect.In this regard,this study uses the weather research and forecasting model?WRF?to simulate the cooling roof and solar roof of five major climatic zones in different climatic zones to mitigate the urban heat island in summer.Meanwhile,it explores the impact of solar roof on energy budgets and potential economic benefits in different climatic zones.The results are as follows:?1?All three roofs have different cooling capacity in urban areas in different climate zones.For the tropical monsoon region,the cooling capacity of metamaterial roofs is also the best,followed by high-reflectivity roofs and solar roofs.All roofs can cool the city at most1.2?,0.8?and 0.4?.For subtropical monsoon regions,the cooling capacity of metamaterial roofs is better than that of high-reflectivity roofs,and the cooling capacity of solar roofs is the weakest.The metamaterial roofs of the Yangtze River Delta,Chengdu-Chongqing City Belt,and the middle reaches of the Yangtze River bring the maximum temperature drop of 1.4?,0.6?,and 1.2?,respectively.The high-reflectivity roof reduces the maximum temperature by 1.0?,0.5?,and 1.2?,respectively.The solar roof reduces the maximum temperature by 0.8?,0.2?and 1.0?.The temperate monsoon region still has the best cooling capacity for metamaterial roofs.Meanwhile,high-reflectivity and solar roofs perform nearly.The diurnal variations of sensible and latent heat near the grounds show that cooling roofs have a significant impact on energy distribution near the ground,especially the sensible heat flux.The greater the decrease in near-surface temperature,the lower the corresponding average sensible heat flux level.However,all roofs have few influences on latent heat flux.?2?Both the metamaterial roof and the high-reflectivity roof can reduce the temperature in the boundary layer of the urban area by 0.1?0.8?and reduce the height of the boundary layer by 120?200 m.The performance of the solar roof is the weakest.?3?The metamaterial roof reduces ICHB in all areas and improves the human comfort index.The high-reflectivity roof can reduce the ICHB in all urban areas during the day,but can increase the human comfort index in the middle reaches of the Yangtze River at night.The solar roof can reduce the ICHB in the Chengdu-Chongqing and Beijing-Tianjin-Hebei regions all day,but can increase the ICHB in the Pearl River Delta,Yangtze River Delta and the middle reaches of the Yangtze River at night.?4?The installation of three roofs can change the regional precipitation center and precipitation.Metamaterial roofs have the strongest weakening of precipitation,followed by high-reflectivity roofs.The solar roof has fewer impacts on precipitation and often increases precipitation in some urban areas.?5?The amount of electricity generated by solar roofs is positively related to the density of the city.As the city density increases,the peak power generation in different urban areas is6.60?8.62 W·m-2,16.07?20.69 W·m-2,21.0?26.90 W·m-2,respectively.The power generation efficiency of solar panels is inversely related to urban density.With the increase of solar radiation during the day,the power generation efficiency of solar panels continues to decrease.?6?In the study area,the power generation of the solar roof in low-and high-density residential areas can meet the cooling consumption of air conditioners.However,the power generation of commercial areas can merely cover 52%?58%of air-conditioning energy consumption.The hourly power generation of the solar roof and the economic benefits in different cities are as follows.The Pearl River Delta is 2.53×109 k W·h;the Yangtze River Delta region is 4.06×109 k W·h;Chengdu-Chongqing is 0.84×109 k W·h;the middle reaches of the Yangtze River is 1.10×109 k W·h;Beijing-Tianjin-Hebei is 2.04×109k W·h. |
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