Very-short term forecast of global horizontal irradiance based on ground-based sky imager and lifted condensation level calculation

This pa per presents a novel very-short term GHI prediction approach which combines ground-based sky images derived cloud map forecast and cloud base altitude estimated using lifted condensation level calculation. To achieve accurate cloud map forecast, a transformation of original sky images is proceeded to eliminate spherical and coordinate distortion. The cloud base height calculation i s adopted to derive real sizes and locations of clouds, and finally obtain very-short term forecast of the local global horizontal irradiance. The validation of the proposed method is carried out by comparing predicted and measured irradiance of a test site. The results show that the method has high prediction accuracy, and has ability to predict the radiation fluctuation caused by the cloud sheltering process.