Modelling and Estimation of The Optimum Tilt Angle of Photovoltaic Systems, Case Study: Libya

The most important parameter for designing solar photovoltaic (PV) systems is the tilt angle of PV panels with horizontal surface. It determines the amount of radiation incident on PV panels surfaces, thus it is required for an economic evaluation of solar PV systems. For this reason, this study aims to estimate the optimum tilt angle of solar PV panels to exploit the maximum daily solar radiation on the inclined surface. The analysis was achieved based on measured data recorded in four cities of Libya. The optimum tilt angle was determined by changing the angle of surface from 0° up to 90° with the 1° resolution and searching for the maximum value of the corresponding daily total solar radiation. In addition, Six empirical models were established to estimate the optimum tilt angle of PV panels. Their empirical coefficients were determined using non-linear regression technique. The models accuracies were evaluated using statistical criteria such as mean bias error, MBE, root mean square error, RMSE, and correlation coefficient, R. A combined statistical indicator, CSI, has been developed to assess and rank the performance of models. The presented results showed that the optimum tilt angle in the four studied sites varied from 0° to 59° throughout the year, it increased during the winter and decreased during the summer. The results also showed that both third-order polynomial and Fourier model presented the best efficiency in estimating optimum tilt angle with R = 0.9943.