Evaluation of net radiation in Uyo, Calabar and Port Harcourt, Nigeria

Abstract

Knowledge of net radiation is essential in any location that requires a solar energy technology application. This work evaluates net radiation in three cities of close boundaries (Uyo, Calabar, and Port Harcourt) in southern Nigeria. The atmospheric data for the period of 20 years (2000-2020) were obtained from the Nigerian Meteorological Agency (NIMET). The mean values of the surface albedo, net shortwave and longwave radiation were computed using Mathematical tools and SPSS packages. The result obtained showed that the highest value (0.694, 0.687, and 0.685 for Uyo, Calabar and Port Harcourt respectively) of the albedo was in the rainy season with its peak in August while its lowest values of 0.489, 0.577 and 0.594 for Uyo, Calabar and Port Harcourt respectively were in the dry season within November to March. The net radiation Rn was observed to vary directly with the net shortwave and longwave radiation but indirectly with albedo. The highest net radiation values obtained were 6.512 MJm-²day-1, 4.52 MJm^-2day^-1 and 4.313 MJm^-2day^-1 for Uyo, Calabar and Port Harcourt correspondingly. The lowest were 2.717 MJm^-2day^-1, 2.144 MJm^-2day^-1 and 2.308 MJm^-2day^-1 for Uyo, Calabar and Port Harcourt respectively. Solar energy applications are encouraged in these cities since the albedo results are higher than the minimum standard of 0.3.