Development of empirical models for estimation of global solar radiation exergy in India

Abstract

In this work, exergy of incoming solar radiation is estimated using empirical models. Long-term meteorological data (1986–2000) consisting of monthly mean diffuse and global solar radiation on a horizontal plane, ambient temperature and sunshine hours for 23 selected stations were available from Indian Meteorological Department (Pune), India. Exergy of direct and diffuse radiations was calculated using Petela model and summed to obtain exergy of global solar radiation. Beam and diffuse exergy efficiencies were in the range of 0.9286–0.9365 and 0.7189–0.7499 respectively. Estimated global exergy efficiencies were found in the range of 0.7700–0.8912. Empirical models were developed by correlating global solar exergy (in the form of global exergy efficiency and global exergy efficiency factor) in terms of clearness index and relative sunshine period. Four categories of single predictor models were defined with each consisting of eight models. Statistical analysis was used to compare and evaluate the accuracy of the models. Further, Global Performance Indicator was calculated and used to rank the models within the individual categories of models as well as the overall group of the 32 developed models. Overall assessment proved that power model with the clearness index is the best one for estimation of global exergy efficiency factor.