Evaluation of the Temperature based Models for the Estimation of Global Solar Radiation in Pretoria, Gauteng province of South Africa

Abstract

The measurement of solar radiation is difficult to carry out due to the cost and techniques involved especially in developing countries like South Africa. A variety of solar models with different weather parameters as inputs have been used to estimate the global solar radiation around the world. Since air temperature records are readily available around the world, models based on air temperature for estimating solar radiation have been widely accepted. Estimation of global solar radiation (H) from the daily range of air temperature (ΔT) offers an important alternative in the absence of the measured H or sunshine duration.  In our present work, the estimation of the monthly average daily global solar radiation for Pretoria has been determined, based on two models:  Hargreaves -Samani and Clemence. The performance of the two models is validated by comparing the measured and the estimated global solar radiation for the three different stations under study. The statistical comparison between the estimated and measured value leads to the conclusion that the two temperature models have potential to estimate the global solar radiation in the area under study.