Modelling the Earth’s Solar Irradiance Across Some Selected Stations in Sub-Sahara Region of Africa

Document Type : Original Article


1 Physics and Solar Energy Programme, College of Agriculture Engineering and Science, Bowen University, Iwo, Osun State, Nigeria

2 Statistics Programme, College of Agriculture, Engineering and Science, Bowen University, Iwo, Osun State, Nigeria


Solar radiation is an important parameter in the study of electricity and/or thermal system installation. Direct monthly irradiance data measurements of the earth’s horizontal surface irradiance for the year 1985 to 2019 for nine stations (Sokoto, Birnin Kebbi, Maiduguri, Ilorin, Calabar, Port-Harcourt, Enugu, Iwo, and Ikeja) were collected from the achieve of HelioClim satellite website. The stationarity of the series was determined using the time plot of the irradiance data between the periods under study but the formal test of stationarity was carried out using the Augmented Dickey-Fuller (ADF) test with a p-value less than 0.05 signifying stationarity.  Different autoregressive integrated moving average (ARIMA) models were fitted to the irradiance data for each of the selected stations.  The results revealed that Sokoto, Maiduguri, and Kebbi have their maximum solar irradiance at about  and their minimum at about , while Ilorin has its maximum solar irradiance at about  and its minimum solar irradiance at about . Ikeja, Iwo and Port-Harcourt, Calabar and Enugu have their maximum solar irradiance  and their minimum solar irradiance at about . It is therefore concluded that for Kebbi, Iwo and Maiduguri, the best model was ARIMA (3,0,3), for Calabar and Sokoto, it was ARIMA (2,0,2) while for other locations like Enugu, Ikeja, Ilorin and Port Harcourt, ARIMA (2,0,3) was the best model for forecasting irradiance in these study areas. The forecasted values of irradiance between January till December 2020 with its corresponding 95% confidence levels indicate good prediction of solar irradiance for future occurrence.


1.    Babar, B., & Boström, T., 2016, Estimating solar irradiation in the Arctic, Renewable Energy and Environmental Sustainability, 1(34): 1–5.
2.    Badescu, V., 2008, Modeling solar radiation at the earth’s surface, Modeling Solar Radiation at the Earth’s Surface: Recent Advances. Springer Berlin Heidelberg.
3.    Mohandes, M., Rehman, S., & Halawani, T. O., 1998, Estimation of global solar radiation using artificial neural networks, Renewable Energy, 14(1–4): 179–184.
4.    Trajković, S., Todorović, B., & Stanković, M., 2001, Estimation of FAO Penman c factor by RBF networks, FACTA UNIVERSITATIS Series: Architecture and Civil Engineering, 2(3): 185–191. Retrieved from
5.    Reddy, K. S., & Ranjan, M., 2003, Solar resource estimation using artificial neural networks and comparison with other correlation models, Energy Conversion and Management, 44(15): 2519–2530.
6.    Aweda, F. O., Akinpelu, J. A., Falaiye, O. A., & Adegboye, J. O., 2016, Temperature Performance Evaluation of Parabolic Dishes Covered with Different Materials in Iwo, Nigeria, Nigerian Journal of Basic and Applied Sciences, 24(1): 90-97.
7.    Aweda, F. O., Oyewole, J. A., Falaiye O. A., & Opatokun, I. O., 2018, Estimation of Evaporation rate  in Ilorin Using Penman Modified Equation,  Zimbabwe Journal of Science and Technology, 13: 20–25. Retrieved from
8.    A Holst, 2020, Encyclopedia Britannica. Clean Air Act.
9.    Baumgartner, J., Höltinger, S., & Schmidt, J., 2018, Evaluation of technical modelling approaches for data pre-processing in machine learning wind power generation models, In 20th EGU General Assembly, Proceedings from the conference held 4-13 April, 2018 in Vienna, Austria (Vol. 20, pp. 2018–14305). Retrieved from
10. Rahman, M. R., Hossain, M. S., Shehab Uddin, S., & M Ibrahim, A. S., 2019, Fabrication and Performance Analysis of a Higher Efficient Dual-Axis Automated Solar Tracker, Iranian (Iranica) Journal of Energy and Environment, 10(3): 171–177.
11. S. Jain, & U. Chandrawat, 2018, Photocatalytic Degradation of Sulfamethoxazole in Visible Irradiation Using Nanosized NiTiO3 Perovskite, Iranian (Iranica) Journal of Energy and Environment, 9(1): 31–40.
12.           Okundamiya, M. S., & Omorogiuwa, O., 2015, Viability of a Photovoltaic Diesel Battery Hybrid Power System in Nigeria, Iranian (Iranica) Journal of Energy and Environment, 6(1): 5–12.