Quoted from:Falayi E O ,  Adepitan J O ,  Rabiu A B . Empirical Models for the Correlation of Global Solar Radiation with Meteorological Data for Iseyin, Nigeria[J]. International Journal of Physical Sciences, 2008, 3(9):89–93.

https://academicjournals.org/article/article1380372857_Falayi%20et%20al.pdf

A number of multilinear regression equations were developed to predict the relationship between global solar radiations with one or more combinations of the following weather parameters: clearness index, mean of daily temperature, ratio of maximum and minimum daily temperature, relative humidity and relative sunshine duration for Iseyin Nigeria for five years (1995 - 1999). Using the Angstrom model as the base, other regression equations were developed by modifying Angstrom equation. The value of correlation coefficient (r) and value of Root Mean Square Error (RMSE), Mean Bias Error (MBE) and Mean Percentage Error (MPE) were determined for each equation. The equation with the highest value of r and least value of RMSE, MPE and MBE is given as: where H/Ho is the cleanness index, RH is the relative humidity, S/Smax is the relative sunshine duration, theta; is ratio of minimum and maximum daily temperature, T is the monthly average daily temperature. The developed model can be used for estimating global solar radiation on horizontal surfaces.

INTRODUCTION

Global solar radiation is of economic importance as a renewable energy alternative, recently global solar radiation has being studied due to its importance in providing energy for Earth’s climate system. The solar radiation reaching the Earth’s surface depends upon climatic conditions of a location, which is essential to the prediction, and design of a solar energy system by Burari and Sambo (2001). Several researchers have determined the applicability of the Angstrom type regression model for estimating global solar irradiance (Akpabio et al., 2004; Ahmad and Ulfat, 2004; Sambo, 1985; Sayigh, 1993; Fagbenle, 1990; Akinbode, 1992; Udo, 2002; Awachie and Okeke, 1990; El –Sebaii and Trabea; 2005, Falayi and Rabiu, 2005; Serm and Korntip, 2004; Jin et al., 2004; Skeiker, 2006). Of recent, Akpabio and Etuk (2002) have developed a multiple linear regression model with ten variables to estimate the monthly average daily globa solar radiation for Onne, Nigeria, Okogbue and Adedokun (2002) developed modified models for estimating global solar radiation with metrological data from 24 stations in Nigeria and also Chandel et al. (2005) developed a new correlation incorporating the latitude and altitude of a site to estimate the monthly average global solar radiation on horizontal surface using the sunshine hour and temperature data at six Indian stations with different geographical locations. Accurate modeling depends on the quality and quantity of the measured data used and is a better tool for estimating the global solar radiation of location where measurements are not available. The objective of the present study is to develop an equation that correlates monthly daily global solar radiation on horizontal surface for Iseyin, southwest, Nigeria.

Falayi et al. developed a number of multi linear regression equations to predict the relationship between global solar radiations with one or more combinations of the following weather parameters: clearness index (H/H0), mean of daily temperature (T), ratio of maximum and minimum daily temperature, relative humidity (RH), and relative sunshine duration (S/S0) for Iseyin Nigeria for five years(1995–1999), using the Angstrom model as base:

\( 𝐻/𝐻_0= 0.1874 + 0.8592 S/S_0 − 1.567 (𝜃) + 0.0033 (RH) − 0.00806 (𝑇) \)