Statistical analysis of different global solar radiation sunshine models in Al-Aqiq, KSA

In this paper, solar irradiance data at Al-Aqiq, a governorate in the KSA, have been collected, investigated, and analyzed. The measured average of global solar radiation data for a month has been used for developing the linear and nonlinear correlations between the average worldwide radiation and sunshine hours for Al-Aqiq by using regression techniques. Several types of correlations are tested against experimental results to develop some statistical relations to estimate the daily, monthly, and yearly mean global solar radiation. The comparative analysis has been carried out based on different parameters like errors, coefficient of determination (R-2), and t-statistic (t-stat). The errors include mean absolute error, mean absolute relative error, root mean squared error, etc. The stated errors have been measured using the monthly mean of the measured and estimated values of the total solar radiation for Albaha University location, Al-Aqiq in Saudi Arabia. Therefore, the global performance indicators (GPI) have been calculated to determine the best model for this location. Al-Aqiq, KSA is located in a well geographical location for solar energy potential. The average solar radiation is 2.215 MWh/m(2)/year (6.07 kWh/m(2)/day). The results show that the presented correlations can predict the monthly mean of daily global radiation in the range of less than 0.0377 GPI. The average mean absolute error resulted in predicting the global radiation under 5%.