Quoted from:M. A. Al-Salihi, M. M. Kadam, and J. A. Mohammed, “Estimation of global solar radiation on horizontal surface using routine meteorological measurements for difffferent cities in Iraq,” Asian Journal of Scientific Research, vol. 3, pp. 240–248, 2010.

http://docsdrive.com/pdfs/ansinet/ajsr/2010/240-248.pdf

INTRODUCTION

In this study, global solar radiation received on horizontal surfaces, maximum temperatures, sun shine duration and relative humidity for Baghdad, Mosul and Rutba are presented, analyzed, tabulated and plotted on graphs and discussed for three selected locations which represents different weather condition of Iraq. Mosul in the North, Baghdad in the middle, Rutba in the West of Iraq. A correlation between the measurements of global solar radiation and meteorological parameters were given for the considered location. The correlation and regression coefficients, standard errors of estimation, mean bias error, root mean square error and t-statics are calculated. The values of correlation coefficients vary from 89% for Rutba station to 97% for Baghdad station and the error of estimation are between 0.035 and 0.063, t-statics varied between 1.2 and 2.06 for Baghdad and Rutba, respectively. It can be concluded that the presented models reasonably predict the global solar radiation received on horizontal surfaces and the expected solar radiation behavior.

Several empirical models were development by many researchers to predict the solarradiation for various location of the world, among these models (Kenisarian andTkachenkova, 1990).Also, Dincer et al.(1995) presented the most simple model, the data inthese models were correlated with their respective ambient temperature for estimating themonthly average of daily global solar radiation. Kenisarian and Tkachenkova (1990) noticedthat the global solar radiation and ambient temperature changes have periodical character,although the amplitude of these changes in each location can differ from each othersignificantly. They proposed relation using Fourier series for estimating global solar radiationdepending on the ambient air temperature. Empirical models are classified in three categories:sunshine based models,temperature based models, cloud based models (Firoz and Intikhab,2004;Myers,2005;Yang et al.,2006;Muneer et al.,2007;Ridha and Ammar，2008).Recently,some rescarches on modeling solar radiation have done in developing countries(Bashahu and Nkundabatware,1994; Museruka and Mutbazi, 2007),but yet comparativeresearches on techniques and approaches used and results are still needed.

In this study, multi linear correlation have been developed for estimation global solarradiation on horizontal surface in different cities in Iraq from a long term records of monthlymean daily maximum temperatures,sun shine duration and relative humidity for Baghdad,Mosul and Rutba.

Al-Salihi et al. also developed multi linear regression equations for Baghdad, Mosul, and Rutba, Iraq, to predict the relationship between the ratio of global to extraterrestrial solar radiations with the combinations of the following weather parameters: maximum temperatures(Tmax), sunshine duration (S/S0), and relative humidity (RH) as follows:

\( 𝐻/𝐻_0 = 10.78 + 0.071 S/S_0+ 0.0026 Tmax− 0.00078 (RH) \)  for Baghdad

\( 𝐻/H_0= 8.86 + 0.301 S/S_0+ 0.0035Tmax+ 0.00157 (RH) \)   for Mosul

\( H/H_0= 15.07 + 0.104 S/S_0+ 0.00139Tmax− 0.00112 (RH) \)  for Rutba