Measurement of Solar Irradiance for Determining the Optimal Tilt Angle for Photovoltaic Panels

The challenge of solar panel installers in determining the tilt angle needed to obtain optimal performance from the photovoltaic panels was the focus of this paper. The performances of two 150 W panels under varied conditions of temperature and solar irradiance on a plane at two different heights (1 m and 11.5 m) from the ground surface were determined to find the effects of tilt angle and altitude on their performances. Measurements of solar irradiance, temperature, open-circuit voltage, and short circuit current were made at various tilt angles and compared to one another based on the measured irradiance. The optimal tilt angle at the experimental site was found to be 15°SW (165°). At this angle, the irradiance was 818.05 Wm–2 compared to 792.26 Wm–2 at 15°NE (15°), 780.44 Wm–2 45°NE (45°) and 767.63 Wm–2 at 45°SW(135°) at 1 m from ground surface, while at 11.5 m the irradiance at 15°SW was 861.99 Wm–2 compared to 685.98 Wm–2 at 15°NE, 624.33 Wm–2 at 45°NE and 676.49 Wm–2 at 45°SW. Hence the performance of a photovoltaic panel solely depends on the tilt angles relative to the height at which the panel is mounted. Keywords: Solar, Irradiance, Photovoltaic, Panels, Tilt angle