Physical Science International Journal

Solar radiation data at horizontal level, tilted surfaces and in the atmosphere is an important feature in solar energy applications such as photovoltaic systems for electricity generation, solar collectors for heating and passive solar devices. This study presents an investigation of the dependence of global solar radiation incident on a tilted surface on some meteorological parameters for different tilt angles based on measured meteorological data of sunshine hours, relative humidity and temperature at Makerere University. Empirical models relating global solar radiation on tilted surfaces and meteorological data were formulated using data of six months. The empirical model for the estimation of daily global solar radiation on the tilted surfaces of 15⁰, 22.5⁰ and 30⁰, whose assessment is based on the statistical analysis with the Mean Bias and Root Mean Square difference that is in good agreement with the measured data on a tilted surface is equation 12. The model yielded a RMSE of 4.2654, with a low correlation coefficient of 0.3743 at a 95% confidence interval and MBE of 1.5801. Analysis of data for global solar radiation data attained over a period of 3 years, towards the verification of Akoba’s model [15] at a tilt angle of 22.5⁰ recommends a new model given in equation 13 that capitulated a RMSE of 2.5985, with a correlation coefficient of 0.8863 at a 95% confidence interval and MBE of 2.3391.