Estimating Global Horizontal Irradiance in Nigeria: An Empirical Modelling Perspective

Accurate Global Horizontal Irradiance (GHI) data is key to designing optimal solar PV systems. Limited by the availability and high cost of traditional pyranometers in developing countries like Nigeria, this study proposes a cost-effective alternative using the Ångström-Prescott model and readily available sunshine data from the Nigerian Meteorological Agency. Empirical models for GHI estimation were developed for 37 selected locations across Nigeria. The country was divided into three regions, and estimates were then compared with NASA data using statistical metrics like R², MBE, and RMSE to evaluate model performance. The results indicate that Sokoto, Ibi, and Abakaliki have the highest GHI values of 5.86 kWh/m²/day, 4.90 kWh/m²/day, and 4.76 kWh/m2/day, respectively. Conversely, the lowest GHI values were observed in Jos, Ilorin, and Benin City, with values of 4.84 kWh/m²/day, 4.71 kWh/m²/day, and 4.37 kWh/m2/day for regions 1, 2, and 3, respectively. Statistical tests revealed underestimation in the Gusau and Abuja models, slight overestimation in Sokoto, and the lowest accuracy in Jos. R² values ranged from 0.706 to 0.985, indicating strong correlations and high accuracy in most regions. By leveraging readily available sunshine data, this cost-effective method allows accurate GHI estimation, driving improved solar PV systems in Nigeria and similar contexts.