Empirical models for predicting global solar radiation using meteorological parameters for Sokoto, Nigeria

Davidson O Akpootu,Bello I Tijjani,Usman M Gana

doi:10.14419/ijpr.v7i2.29160

Abstract

The performances of sunshine, temperature and multivariate models for the estimation of global solar radiation for Sokoto (Latitude 13.020N, Longitude 05.250E and 350.8 m asl) located in the Sahelian region in Nigeria were evaluated using measured monthly average daily global solar radiation, maximum and minimum temperatures, sunshine hours, rainfall, wind speed, cloud cover and relative humidity meteorological data during the period of thirty one years (1980-2010). The comparison assessment of the models was carried out using statistical indices of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t â€“ test, Nash â€“ Sutcliffe Equation (NSE) and Index of Agreement (IA). For the sunshine based models, a total of ten (10) models were developed, nine (9) existing and one authorâ€™s sunshine based model. For the temperature based models, a total of four (4) models were developed, three (3) existing and one authorâ€™s temperature based model. The results of the existing and newly developed authorâ€™s sunshine and temperature based models were compared and the best empirical model was identified and recommended. The results indicated that the authorâ€™s quadratic sunshine based model involving the latitude and the exponent temperature based models are found more suitable for global solar radiation estimation in Sokoto. The evaluated existing â„«ngstrÃ¶m type sunshine based model for the location was compared with those available in literature from other studies and was found more suitable for estimating global solar radiation. Comparing the most suitable sunshine and temperature based models revealed that the temperature based models is more appropriate in the location. The developed multivariate regression models are found suitable as evaluation depends on the available combination of the meteorological parameters based on two to six variable correlations. The recommended models are found suitable for estimating global solar radiation in Sokoto and regions with similar climatic information with higher accuracy and climatic variability.Â Â Â

Highlights

Solar radiation is the energy transferred from the sun in the form of radiant to the earth’s surface or it is the electromagnetic radiation emitted from the Sun
Muhammad and Darma [10] employed the monthly mean minimum/maximum temperature and relative humidity data obtained from Nigerian Meteorological Agency (NIMET), Abuja-Nigeria during the period of 6 years (2005 – 2010) to estimate the monthly average daily global solar radiation on a horizontal surface for Kano, Nigeria using modified Ångström models from which models were developed with regression coefficients a and b of (1.2577 – 1.0167) and (0.8317 – 0.0043) based on temperature ratio and relative humidity
A wide-ranging study was carried out to help in the selection of the most fitting and accurate models based on the statistical test indicators of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), t – test, Nash – Sutcliffe Equation (NSE) and Index of Agreement (IA) using meteorological parameters of measured monthly average daily global solar radiation, maximum and minimum temperatures, sunshine hours, rainfall, wind speed, cloud cover and relative humidity meteorological data during the period of thirty one years (1980-2010) for Sokoto located in the Sahelian region in Nigeria

Summary

Introduction

Solar radiation is the energy transferred from the sun in the form of radiant to the earth’s surface or it is the electromagnetic radiation emitted from the Sun. Muhammad and Darma [10] employed the monthly mean minimum/maximum temperature and relative humidity data obtained from Nigerian Meteorological Agency (NIMET), Abuja-Nigeria during the period of 6 years (2005 – 2010) to estimate the monthly average daily global solar radiation on a horizontal surface for Kano, Nigeria using modified Ångström models from which models were developed with regression coefficients a and b of (1.2577 – 1.0167) and (0.8317 – 0.0043) based on temperature ratio and relative humidity. Olatona and Adeleke [11] developed some simple empirical models for the prediction of monthly mean daily solar radiation on a horizontal surface for Ibadan from sunshine hours and minimum and maximum temperatures data obtained from International Institute of Tropical Agriculture (IITA) Meteorological station at Ibadan, the data obtained covered a period of twenty years (1992 – 2011). Multivariate based models were developed for the study area

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