Study of Models for Predicting the Mean Hourly Global Radiation from Daily Summations

It is mandatory to predict the hourly solar radiation received during the average day of each month for different solar energy applications, particularly in design methods, Scientists have developed methods to achieve this using different input parameters. The objective of this study is to compare statistically existing models for estimating the mean hourly global radiation incident on a horizontal surface from mean daily global radiation and to recommend one that best fits measured data from five Indian locations chosen namely, Bangalore, Jodhpur, Mumbai, New Delhi and Srinagar. From our results it is observed that Collares-Pereira and Rabl model as modified by Gueymard (CPRG) yields the best performance for estimating mean hourly global radiation incident on a horizontal surface for Indian regions. In addition to CPRG model, Collares-Pereira and Rabl (CPR) and Whillier /Liu and Jordan (WLJ) models yield better performance than Newell, Baig and Garg models. Moreover each model gives an average amount of under-estimation in the calculated value.