Zeitschrift für Grundlagen erneuerbarer Energien und Anwendungen
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Characterization of Sky Conditions at Benin City and Owerri in Nigeria

Njoku MC, Ofong I, Ogueke NV and Anyanwu EE

Characterization of sky conditions at Benin City and Owerri located in the south-south and south-east parts of Nigeria has been carried out using clearness index, diffuse ratio, diffuse coefficient and relative sunshine. An average yearly global solar radiation of 160.31 MJ/m² and 168.35 MJ/m² was calculated, with daily range of 17.44 MJ/m² to 12.50 MJ/m² and 16.15 to 12.94 MJ/m² estimated at Benin City and Owerri, respectively. For both study locations, the months of December and January recorded the highest variability of global solar radiation, while the month of August recorded the lowest level of solar radiation.

The monthly value of clearness index K_T calculated for each study location indicates cloudy sky conditions devoid of clear days, though it also indicate the possibility of harvesting more solar radiation in Benin City than Owerri. Five seasonal periods were identified for both locations, and their K_T curves followed the same line pattern for that of Ibadan, hence, the generalized K_T curves of Liu and Jordan may not be applicable to the locations.