Conversion of solar radiation data from horizontal to tilted surface using analytical methods, experimental validation and photovoltaic application

Solar energy is known as one of the most productive and sustainable alternative energy sources. Solar energy is converted into electrical energy through photovoltaic cells. In this study, data obtained from the polycrystalline type solar panel with 36 cells and the system already established at coordinates of 40°42'52,2" N, 31°31'29,8" E by the Department of Mechanical Engineering have been used. Thorough the outdoor experimental test facility incorporating pyranometers, sensors and data loggers, the irradiance in inclined surface, the irradiance in horizontal surface, current, voltage and temperature values were collected at 1 minute intervals. The purpose of this study is the conversion of the solar irradiance from the horizontal surface to that on the inclined surface by using two different models and to compare the results to the measured solar irradiance on the inclined surface. The measured irradiance values on horizontal surface was converted into the inclined surface values through isotropic and anisotropic models, and the converted values were compared with the measured values on the inclined surface. The difference between the measured and calculated values were calculated by using three different statistical parameters, namely R2, RMSE and MBE thus the accuracy of the models was comparatively analyzed. Besides, the current-voltage and power-voltage characteristics were obtained for some selected days by using the analytical 4-parameter photovoltaic model. The current-voltage and power-voltage characteristics were then calculated on the inclined surface using the measured and calculated irradiance values and compared to each other. Furthermore, the power and energy values calculated both on the horizontal and inclined surfaces for different seasons were compared to show the seasonal effect of inclination.