Abstract:In this paper, a method for the determination of the optimal tilt angle for yearly fixed flat-plate photovoltaic (PV) module at any given location is presented. The method is based on yearly global radiation incident on a horizontal plane as downloaded from NASA website. Futrthermore, PVSyst software that uses transposition model is used to generate the yearly global radiation incident on a tilted plane for various tilt angles, from 0° to 46°. The study is conducted for a health facility in Uyo, Akwa Ibom state, Nigeria with longitude of 7.860761, latitude of 5.011474 and elevation of 67.506 m. The optimal tilt angle is obtained from the quadratic trendline equation fitted to the graph of the transposition factor versus tilt angle. The result is that the optimal tilt angle for the yearly fixed flat-plate PV module at the selected Flocation is 9.71° which gives average yearly transposition factor 1.0105. Essential, the results indicate that about additional 1.05% of solar radiation will be captured per year by tilting the PV module at optimal tilt angle of 9.71°. At any other tilt angle less solar radiation will be captured per year.

Determination of optimal tilt angle for seasonally adjusted flat-plate photovoltaic (PV) modules based on Perez transposition model is presented. Particularly, two seasons are considered, namely winter and summer. As such, two optimal tilt angles are obtained which requires that the tilt angle the of flat plate PV module will be adjusted twice in a year. The method is based on yearly global radiation incident on a horizontal plane as downloaded from NASA website. Furthermore, PVSyst software that uses transposition model is used to generate the yearly global radiation incident on a tilted plane for various tilt angles, from 0° to 46°. The location used in the study is at longitude of 7.860761, latitude of 5.011474 and elevation of 67.506 m. The results show that the winter season optimal tilt angle is 25.46° the summer season optimal tilt angle is 0° and the yearly fixed optimal tilt angle is 7.16°. The annual transposition factor for the seasonally adjusted tilt angle is 1.05 whereas annual transposition factor for the year fixed tilt angle 1.01. The result amounts to 3.6% improvement is solar radiation capture due to the seasonal adjustment of the tilt angle when compare to the yearly fixed tilt angle.