Solar Energy Resource Assessment in Minna, Nigeria: Influence of Sunshine Duration and Extraterrestrial Radiation

Abstract

Accurate solar energy resource assessment is fundamental for the efficient planning, 
design, and deployment of photovoltaic (PV) systems, particularly in tropical regions 
where atmospheric conditions strongly influence solar irradiance. This study 
evaluated the influence of sunshine duration and extraterrestrial radiation on solar 
energy potential in Minna, Nigeria, using ten years (2015–2024) of meteorological 
data. The analysis focused on the relationships among global solar radiation, sunshine 
duration, extraterrestrial radiation, and clearness index to characterize the site's 
solar resource availability. The results indicate an annual mean global solar radiation 
(={H}) of approximately 18–19 MJ·m⁻²·day⁻¹ (equivalent to about 5.0–5.3 
kWh·m⁻²·day⁻¹), with maximum values occurring during the dry season (~21 
MJ·m⁻²·day⁻¹) and minimum values during the wet season (~14–15 MJ·m⁻²·day⁻¹). 
Despite these seasonal variations, the observed solar radiation consistently exceeded 
the minimum operational threshold required for efficient PV electricity generation 
throughout the year. Statistical analysis revealed a strong positive correlation 
between sunshine duration and the clearness index (R² = 0.89), demonstrating the 
significant influence of sunshine hours on atmospheric transmissivity. In contrast, the 
weak relationship between extraterrestrial radiation (={H}ₒ) and measured global 
solar radiation (={H}) (R² ≈ 0.04) indicates that atmospheric factors, including cloud 
cover, humidity, and dust aerosols, predominantly regulate surface solar radiation. 
The estimated annual PV electricity yield of 1,400–1,800 kWh/kWp further confirms 
Minna's high solar energy potential. These findings underscore the importance of 
climate-responsive PV system design, incorporating seasonal variability, hybrid energy 
integration, and effective dust mitigation strategies to maximize long-term energy 
efficiency, reliability, and sustainability.