ESTIMATION OF GLOBAL SOLAR RADIATION USING SUNSHINE-BASED MODEL IN MAIDUGURI, NORTH EAST, NIGERIA

The facilities used for measuring and recording of global solar radiation are not easily available due to the cost and techniques involved. The limited effort of the measurement indicates that there is a need to establish theoretical methods for estimating solar radiation based on the available meteorological data. In this work, the measured data of solar radiation on a horizontal surface and number of sunshine hours for Maiduguri for 15 years (1996-2010) were collected and analyzed, regression constants for the first order Angstrom-type correlations for Maiduguri were calculated using regression analysis. The monthly calculated clearness index and monthly sunshine duration were correlated and modeled using four existing sunshine-based models which are linear, quadratic, exponential and power equations. The results of the four models were compared. It was observed that the quadratic model performed better in terms of coefficient of determination than the other three models. A modified form of Ogelman model has therefore been recommended in estimating the monthly average daily global solar radiation for Maiduguri.