A Method to Estimate Direct and Diffuse Radiation in Hong Kong and its Accuracy

Hourly global (total of direct and diffuse horizontal) solar radiation data for Hong Kong can be obtained from the Royal Observatory of Hong Kong. However, data on intensities of direct and diffuse radiation, which are required in detailed calculation of energy transport across building envelopes, are not available. To address to this need, a correlation between diffuse and global solar radiation for Hong Kong has been established, on the basis of global and diffuse solar radiation intensities measured at the Hong Kong Polytechnic from October 1990 to July 1994. Further analysis has been carried out to accertain the accuracy of prediction of this correlation and to see if the accuracy will vary with seasonal changes and solar altitude angle. In this paper, the correlation and the results of the analysis are presented. Application of the correlation to estimate the direct and diffuse radiation intensities from known global intensities is described. Also, the correlation is compared with the measured data a...