Comparison of Seventeen Models to Estimate Diffused Radiation on a Tilted Surface
Abstract
Global and diffuse solar irradiances are, in general, measured on horizontal surfaces, but the flat plate collector and solar photovoltaic are mounted on inclined surfaces to maximize the amount of incident solar radiation. This study aims to evaluate 17 models transposing daily diffuse solar irradiance from horizontal to inclined surfaces. The collector surface is considered to be facing south and the calculations are based upon the daily measured global irradiance for the horizontal surface. The beam, diffused and reflected components of the radiations are calculated as the tilt angle is varied from 0-90°. The maximum mean annual radiations for Khuzdar with highest sky clearness index (KT) and Lahore with lowest KT among selected stations were found to be 326 W/m2 and 209 W/m2 corresponding to the daily optimum tilt angle that varies from 0-75° throughout the year. The average maximum total solar radiation for optimum annual tilt was reported as 190 W/m2 and 289 W/m2 for the Lahore and Khuzdar stations. It is found that maximum energy can be collected if the tilt angle is varied daily.