Experimental investigation for the estimation of the intensity of solar irradiance on oblique surfaces by means of various models

Abstract In the literature several models have been derived by different authors in order to predict the solar irradiance intensity over inclined surfaces, however for the most models accuracy at various inclinations have not been verified. The study evaluated the estimation of solar irradiance at different tilt angles by means of different models based on the experimental measurements. For this purpose, two groups of models (isotropic and anisotropic) were carried out: the first group of models was used for estimating the diffuse solar irradiance component, and the second group was used for estimating the global solar irradiance. Five models have been selected and implemented for the estimation of the diffuse solar irradiance component, and five models have been selected for the estimation of global solar irradiance. The results of the analysis were compared with local experimental measurements for diffuse radiation and global irradiance. There are three tilt angles (0°, 30°, 60°) and a two-axis tracking system has been determent for comparison experiments with the model estimated results. The results showed all the selected models generated an error percentage in both the diffuse and global irradiance investigations.