Correlation models for the estimation of diffuse fraction of global illuminance from satellite data

Information on amount of diffuse solar illuminance is very important for designing a daylight-integrated building. In this work, models for estimating diffuse fraction of global illuminance from satellite data were proposed. Global and diffuse illuminance measured at 4 sites in Thailand were used to calculate diffuse fraction of global illuminance. Earth-atmospheric reflectivity over these sites was also derived from MTSAT-1R satellite. Then, diffuse fraction of global illuminance and earth-atmospheric reflectivity were correlated to obtain the correlation models. The models were tested against an independent data set. It was found that the predicted diffuse illuminance and the measured diffuse illuminance were in reasonable agreement, with the root mean square different in the range of 11.3%-15.1%.