Prediction of Regional Global Horizontal Irradiance Combining Ground-Based Cloud Observation and Numerical Weather Prediction

This paper presents a novel very-short term GHI prediction approach which combines ground-based sky images derived cloud map forecast and cloud base height estimated using numerical weather prediction output. To achieve accurate cloud map forecast, a transformation of original sky images is proceeded to eliminate spherical and coordinate distortion. A WRF based numerical weather prediction model is set up to forecast the local meteorological parameters and estimate cloud base heights information. The cloud base height estimation is adopted to derive real locations and sizes of clouds, and eventually 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.