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 arenot easily available due to the cost and techniques involved. The limitedeffort of the measurement indicates that there is a need to establishtheoretical methods for estimating solar radiation based on the availablemeteorological data. In this work, the measured data of solar radiation on ahorizontal surface and number of sunshine hours for Maiduguri for 15 years(1996-2010) were collected and analyzed, regression constants for the firstorder Angstrom-type correlations for Maiduguri were calculated usingregression analysis. The monthly calculated clearness index and monthlysunshine duration were correlated and modeled using four existingsunshine-based models which are linear, quadratic, exponential and powerequations. The results of the four models were compared. It was observedthat the quadratic model performed better in terms of coefficient ofdetermination than the other three models. A modified form of Ogelmanmodel has therefore been recommended in estimating the monthly averagedaily global solar radiation for Maiduguri.