On the calibration and applicability of global solar radiation models based on temperature extremities in India

In the present work, global solar radiation models based on the difference of monthly-average daily ambient temperature extremes are calibrated for country-wide application in India. Solar radiation measurements obtained from the Indian Meteorological Department for 22 locations of India for a duration of 15 years (1986-2000) were used. Solar radiation models based on temperature extremes were reviewed and 33 forms were considered for analysis. The models were derived using all the collected data by fitting a model form and extracting the coefficients with the help of DataFit (R) software. The calibrated models were analyzed and compared using statistical tools and ranked using Global Performance Indicator (GPI) where a higher value represented a model's better performance. Then, the models were arranged using GPI and it was found that model form 33 (fourth order polynomial) resulted in best estimation capability with a GPI of 0.0763. Further, Model 23, Model 28, Model 24, and Model 26 were also among the top models with GPI values of 0.0655, 0.0587, 0.0478, and 0.0426, respectively. Best ranking models were also used to obtain estimates for representative sites in regions with different climate characteristics within India and it was found that the models performed reasonably well.