Numerical evaluation of solar irradiation for buildings and solar energy applications

Determining the amount of solar energy received on a surface is important for solar energy modeling and assessment as well as for buildings energy modeling. This paper presents a comparison between analytical and experimental data for normal, diffuse, and global horizontal average hourly solar radiation per month in Beirut (33.89 N; 35.50 E). Optimal position for solar panels is also investigated in 3 configurations: constant optimal angle; monthly variable tilt angle; and solar sensors with a tracking system of the solar race. After validating the numerical model comparing it to a weather file data for normal, diffused, and global horizontal average hourly solar radiation per month, optimization was made to determine the optimal position of solar collectors according the Generalized Reduced Gradient (GRG2) Algorithm which is normally used for optimizing nonlinear problems. The results show a good accuracy between numerical model and available weather data. The optimum angle of inclination for the city of Beirut is close to 30° (27.9°). By varying this angle monthly (i.e. through an adjustable tilt chassis), a 6% increase of collected energy is obtained compared to a constant optimal angle. As for the system, it has great interest as it allows an increase of 37% of solar energy compared to a constant optimal angle.