A study of overcast, partly cloudy and clear skies by global illuminance and its variation features

9th Edition of the International SOLARIS Conference

Lou, Siwei^1 ; W Li, Danny H.^2 ; Chen, Wenqiang^2

School of Civil Engineering, Guangzhou University, 230 Guangzhou Higher Education Mega Centre, West Outer Ring Road, Panyu District, Guangzhou, China^1

Building Energy Research Group, Department of Architecture and Civil Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong^2

关键词: anisotropic sky;    Building energy saving;    Building envelopes;    Daylight illuminance;    Diffuse skylight;    Fourier transfers;    High frequency HF;    Luminance distributions;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/556/1/012015/pdf
DOI  :  10.1088/1757-899X/556/1/012015

来源: IOP

【 摘 要 】

The diffuse radiance and luminance distribution in the skydome can determine the solar energy on the building envelope in various orientations and under complex obstructions. The diffuse sky is anisotropic for clear and partly cloudy skies, while isotropic for overcast skies. Thus, identifying the sky conditions are essential to the sky radiance and luminance studies. Previously developed approaches using statistic data suffered from data shortage and inaccuracy. Sunlight under cloudy skies may frequently be blocked, causing the high-frequency illuminance fluctuations. The illuminance should variate smoothly under clear skies without clouds. In this work, we studied the horizontal irradiance time series, its variation frequency, and its relationship to the sky conditions determined by the luminance scan. The work contributes to identifying the sky conditions and skylight distributions using the horizontal global daylight illuminance that is measured by the fixed sensors.