A Comparative Study of some Meteorological Parameters for Predicting Global Solar Radiation in Kano, Nigeria Based on Three Variable Correlations

Abstract

In this present study, twenty empirical regression equations based on three variable correlations were developed and used to estimate the monthly average daily global solar radiation on a horizontal surface using measured monthly average daily global solar radiation, sunshine duration, wind speed, maximum and minimum temperatures, rainfall, cloud cover and relative humidity parameters during the period of thirty one years (1980 – 2010) for Kano, Nigeria (Latitude 12.03⁰N, Longitude 08.12⁰E and altitude 472.5 m above sea level). The comparative performance of the developed models has been evaluated on the basis of statistical parameters using Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t – test and Nash – Sutcliffe Equation (NSE). The values of the correlation coefficient (R) and coefficient of determination (R²) were also obtained for each of the developed models. The MPE values for all the developed models lie within the acceptable range . The t – test produces perfect model performance at 95% and 99% confidence level for all the developed models. Three equations were recommended from this study, firstly, the model (Eqn. 20) with the highest value of R and R², secondly, the model (Eqn. 24) with the least value of RMSE and the highest value of NSE and thirdly, the model (Eqn. 31) with the least values of MPE and t – test. These developed models can be used for estimating monthly average daily global solar radiation for Kano, North – Western, Nigeria and other locations with similar weather conditions where the solar radiation data is unavailable.

Keywords: global solar radiation, Kano, variable correlation, Mean Bias Error (MBE) and coefficient of determination.