Determining optimum tilt angles of solar surfaces in Sakarya, Turkey

This paper proposes the best tilting case for Sakarya city, Turkey. The main contribution of this work is the correlation of the tilt angle and the output of a photovoltaic (PV) module mathematically. For this purpose, new diffuse solar radiation equations are developed using existing equations in three groups: (i) group 1: the diffuse fraction (Kd) calculated by the clearness index (Kt); (ii) group 2: the diffuse fraction calculated by the sunshine fraction (Kn); and (iii) group 3: the diffuse fraction calculated by both the clearness index and the sunshine fraction. The most suitable equation of new and existing equations is selected for the city on the basis of different statistical indicators. This equation is used to predict the monthly average daily diffuse, beam, and total solar radiation for the city. Using the predicted data, optimum tilt angles of solar surfaces for different time periods are established. Finally, a PV module is modelled in Matlab and output of the module tilted at optimum tilt angles is evaluated.