A comparative study of various models for estimating global solar radiation in Hebron city, Palestine
A comparative study of various models for estimating global solar radiation in Hebron city, Palestine
Date
2015-04-28
Authors
Alsamamra, Husain
Journal Title
Journal ISSN
Volume Title
Publisher
Quality Scientifc Publishing
Abstract
Solar radiation is a primary driver for many physical, chemical, and biological processes on the
earth’s surface. Solar energy engineers, architects, agriculturists, hydrologists, etc. often require a
reasonably accurate knowledge of the availability of the solar resource for their relevant applications
at their local. In solar applications, one of the most important parameters needed is the long-term
average daily global irradiation. For regions where no actual measured values are available, a
common practice is to estimate average daily global solar radiation using appropriate empirical
correlations based on the measured relevant data at those locations. These correlations estimate the
values of global solar radiation for a region of interest from more readily available meteorological,
climatological, and geographical parameters. The present study aimed to calibrate existing models and
develop a new model for estimating global solar radiation data using available measured
meteorological records such as precipitation or temperature. Fifteen empirical global radiation models
based on meteorological variables were generated and validated using daily data in the period of
January 2007 to December 2011 at Hebron city meteorological station in Palestine. Validation criteria
included coefficient of determination, root mean square error, mean bias error, mean absolute bias
error, mean percentage error, and mean absolute percentage error. The best result was derived from
the model proposed, which uses extraterrestrial solar radiation, saturation vapor pressures,
transformed rainfall data and daily minimum relative humidity as predictors. The new multiple
regression relation giving accurate estimates of daily global solar radiation was suggested. It has a
high coefficient of determination R2 = 0.94. The results showed that the suggested model can estimate
the global solar radiation with acceptable values of RMSE, MBE and MABE (2.38, 0.08, 1.75 MJ m-2
day-1, respectively); and MPE and MAPE (-6.49%, 19.32%). Temperature based models provided less
accurate results, of which the best one is the Bristow and Campbell model (R2 = 0.89). The
Hargreaves and Samani model is simple and are recommended to estimate the daily global radiation
when only temperature data are available and when the coefficients cannot be determined. Based on
overall results it was concluded that the meteorological based method provides reasonably accurate
estimates of global solar radiation, for the site where coefficients of the model were developed.
Description
Keywords
Global Solar Radiation, Empirical Models, Model Comparison, Solar Radiation Models