Investigation on the Possibility of Using Available Sunshine Duration Data of a Relatively Close Region to Estimate Global Solar Radiation for a Different Region

Abstract

Estimation of global solar radiation using existing models becomes necessary in areas where measurements are not carried outdue to lack of technical knowledge, unavailability of measuring instrument and cost of getting such measurements if available.In this study, the possibility of estimating the global solar radiation for a particular location using another location's sunshine duration data is explored due to the closeness in the latitude of the two locations and to what extent is the estimation true.  Ibadan's (latitude 7.37750N) sunshine duration data is used as Iwo's (latitude 7.62920N) sunshine duration data and employed in the Angstrom - Prescott's sunshine based model, while retaining the latitude of Iwo in the model, mean sunset/rise hour angle and extraterrestrial radiation. The sunshine duration data for Ibadan (2008 - 2012) was gotten from International Institute of Tropical Agriculture, Ibadan while the measured global solar radiation data for Iwo (2014 - 2015) was measured at Bowen University Iwo, Osun state in Nigeria. The estimated global solar radiation for Iwo is validated with measured global solar radiation at Iwo by carrying out some statistical analysis like mean bias error (-0.03), root mean square error (0.81), mean percentage error (-0.23), Nash-Sutcliffe error (r2) or coefficient of determination (0.88), coefficient of correlation (0.94). The estimated values when validated against the measured values performed excellently well. Hence it is possible to use the available sunshine duration data of another location as the sunshine duration data when estimating the global solar radiation available at the location of interest.