Quoted from:Ali A. Sabziparvar,A simple formula for estimating global solar radiation in central arid deserts of Iran[J],Renewable Energy,Volume 33, Issue 5,2008,Pages 1002-1010,ISSN 0960-1481,

https://doi.org/10.1016/j.renene.2007.06.015

Over the last two decades, using simple radiation models has been an interesting task to estimate daily solar radiation in arid and semi-arid deserts such as those in Iran, where the number of solar observation sites is poor. In Iran, most of the models used so far, have been validated for a few specific locations based on short-term solar observations. In this work, three different radiation models (Sabbagh, Paltridge, Daneshyar) have been revised to predict the climatology of monthly average daily solar radiation on horizontal surfaces in various cities in central arid deserts of Iran. The modifications are made by the inclusion of altitude, monthly total number of dusty days and seasonal variation of Sun–Earth distance. A new height-dependent formula is proposed based on MBE, MABE, MPE and RMSE statistical analysis. It is shown that the revised Sabbagh method can be a good estimator for the prediction of global solar radiation in arid and semi-arid deserts with an average error of less than 2%, that performs a more accurate prediction than those in the previous studies. The required data for the suggested method are usually available in most meteorological sites. For the locations, where some of the input data are not reported, an alternative approach is presented.

(1)In Daneshyar method, solar constant of 1353 (W/m ² ) has been used by the workers. Since the new suggested average value of solar constant is about 1367 (W/m ²), the total daily global radiation was multiplied by a factor.

(2)For each month, the monthly mean global radiation was modifified by the Sun–Earth distance correction factor.

(3) Height effect was also applied separately on beam and diffuse radiation. For calculation of the height correction factor in the new method, Tehran (where Daneshyar calibrated his suggested model) is taken as the reference.