Keywords: Earth', s surface, correlation models, diffuse solar radiation, ASHRAE model, India, modelling
Correlation model of hourly diffuse solar radiation based on ASHRAE model: a study case in India
Measurements of diffuse and global solar radiation carried out from January 2001 to December 2005 at Ahmedabad, Mumbai, Calcutta, Chennai and Pune cities of India, representing varying weather conditions of the entire country, have been used to develop the correlation model for the estimating hourly values of diffuse solar radiation on horizontal surface. The comparisons of the present estimated hourly diffuse solar radiation for different locations have been made with theoretical models of American Society of Heating Refrigeration and Air–conditioning Engineers (ASHRAE) (1999), Parishwad et al. (1997) and Erbs et al. (1982) along with the measured data. It is observed that in comparison to other models, new proposed model (modified ASHRAE model) estimates better hourly diffuse solar radiation for all Indian stations. For further validation and to observe the accuracy of present model over others, the root mean square error (RMSE), mean bias error (MBE) and t–static test have also been carried out.