Estimation of global solar radiation, sunshine hour distribution and clearness index in three Geopolitical Regions of Southern Nigeria

Abstract

The concept of solar energy and its applications in this present day world would come to be one of the solutions to the present problem of instability and epileptic power supply in Nigeria. In this research work, the baseline data for the mean monthly global solar radiation (H) and sunshine hours (S) for three geopolitical regions of Nigeria, namely Port-Harcourt (South-southern Nigeria) (5.000N, 6.950E), Enugu (South-eastern Nigeria) (6.70N, 7.60E) and Ikeja (South-western Nigeria) (6.580N, 3.320E), were obtained from the Nigeria Metrological Agency (NIMET) in Nigeria over the period from 1996 to 2010. The data for global solar radiation were measured using a Gunn-Bellani radiometer, and a linear regression correlation model was developed. The clearness index estimated for each station and other surrounding towns/villages with similar meteorological conditions was also developed. The results show that using the Angstrom-Prescott model, the Angstrom coefficients (a and b) for estimating the global solar radiation were: 0.07 and 0.12; 0.27 and 0.58; 0.25 and 0.63 for Port-Harcourt, Enugu and Ikeja respectively.The average sunshine hour for the period of the study was estimated to be four hours, five hours, forty minutes and five hours, 0 minutes and six seconds for the three meteorological stations in this study. The average global solar radiation for these stations was estimated to be 10.003 MJm-2day-1, 15.006 MJm-2day-1 and 14.440 MJm-2day-1respectively. The results show that the root-mean-squared-error, mean-bias-error and mean percentage error were generally less than 0.6, 0.2 and 3.84 respectively for all of the stations considered. The study concluded that the Angstrom- Prescott model plays a significant role in predicting and estimating solar energy potentials in these geopolitical zones.