Study On Radiative Sky Cooling Performance Influencing Factors And Resource Distribution In China

With the concept of the carbon peak and carbon neutrality,the transformation of the energy structure has once again been highly valued by society and enterprises.Annual building energy consumption accounts for more than 20%of the total energy consumption in China.To a large extent,building energy saving depends on air conditioning energy saving.Radiative sky cooling has the advantages of low energy consumption and no pollution which has great application prospects in energy saving in air conditioning.Therefore,based on theoretical and experimental methods,this article explores and analyzes the influence pattern of the radiative sky cooling performance,and calculates the application potential of radiative sky cooling technology across China,which provides a theoretical basis for guiding the application of radiative cooling technology.The main contents of this work are as follows:Firstly,this paper proposes a fast and direct calculation method of atmospheric spectral emissivity and establishes a mathematical model of radiative sky cooling.The proposed model is compared with existing empirical models by the observed atmospheric radiation data from meteorological stations,and preliminarily verified the universality and accuracy.The radiative sky cooling performance experimental platform is designed and established.The experimeantal results further verify the proposed radiative sky cooling model during day time and night time.This model can calculate the real-time radiative cooling power performance effectively which is not affected by the application cases and weather conditions.Then,the influence factors on radiative sky cooling performance are investigated.The results under four typical weather conditions of sunny,cloudy,cloudy and rainy weather show that radiative sky cooling has the best cooling performance under clear night sky.Furthermore,the relationship between the environmental parameters and the cooling performance(including net radiative cooling power and available temperature drop)under different conditions are studied.The experimental results show that the radiative cooling performance is positively correlated with the ambient temperature,and negatively correlated with the precipitable water vapor,wind speed,solar irradiation and cloud cover.In addition,the non-radiative heat transfer process in the radiative sky cooling is studied.The results show that convection shield can effectively reduce the cooling loss caused by air flow,and the air spacing formed has a certain thermal insulation effect.Moreover,a new method with stability and accuracy of measuring the non-radiative heat transfer coefficient on radiative sky cooling is put forward and verified under different scenerios which can provide comparison between the reported cooling effects of different radiative materials.Finally,the radiative cooling potential in 271 cities across China is calculated based on the proposed model.Meanwhile,the radiative cooling resource distribution maps are illustrated.China has abundant radiative sky cooling potential for ideal broadband surface which posesses the annual average radiative cooling power is 70～100 W/m~2.The overall distribution of radiative cooling resources presents the spatial characteristics of"low in the southeast-high in the northwest"and temporal characteristics of"high in winter-low in summer".In addition,the time variation characteristics of the radiative cooling in typical cities of different building climate demarcations is discussed,which shows the main influencing factors of the radiative sky cooling effect are different for southern and northern cities with large climate differences.This work is significant for guiding the application of local radiative sky cooling technology.