Performance assessment of different day-of-the-year-based models for estimating global solar radiation - Case study: Egypt

• Published in: Journal of atmospheric and solar-terrestrial physics Vol. 149; pp. 69 - 80
• Main Authors: Hassan, Gasser E., Youssef, M. Elsayed, Ali, Mohamed A., Mohamed, Zahraa E., Shehata, Ali I.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-11-2016
• Subjects: Atmospheric models; Day of year; Egypt; Empirical models; Estimates; Estimating; Global solar radiation; Mathematical models; Performance evaluation; Polynomials; Solar energy; Solar radiation; Statistical indicators; Trigonometric functions; Egypt, Arab Rep; Day of year; Empirical models; Global solar radiation; Statistical indicators; Solar energy; Egypt
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2016.09.011

Different models are introduced to predict the daily global solar radiation in different locations but there is no specific model based on the day of the year is proposed for many locations around the world. In this study, more than 20 years of measured data for daily global solar radiation on a horizontal surface are used to develop and validate seven models to estimate the daily global solar radiation by day of the year for ten cities around Egypt as a case study. Moreover, the generalization capability for the best models is examined all over the country. The regression analysis is employed to calculate the coefficients of different suggested models. The statistical indicators namely, RMSE, MABE, MAPE, r and R2 are calculated to evaluate the performance of the developed models. Based on the validation with the available data, the results show that the hybrid sine and cosine wave model and 4th order polynomial model have the best performance among other suggested models. Consequently, these two models coupled with suitable coefficients can be used for estimating the daily global solar radiation on a horizontal surface for each city, and also for all the locations around the studied region. It is believed that the established models in this work are applicable and significant for quick estimation for the average daily global solar radiation on a horizontal surface with higher accuracy. The values of global solar radiation generated by this approach can be utilized in the design and estimation of the performance of different solar applications.
•7 models based on Day-of-the-year are used to estimate solar radiation over Egypt.•Models are developed, validated and evaluated using 20 years of measured data.•4th order polynomial model gives good predictions for the global solar radiation.•The hybrid sine-cosine model has the best performance among the suggested models.