The empirical models for estimating solar insolation in Serbia by using meteorological data on cloudiness

The paper presents empirical models for estimating solar insolation at a location in Serbia by using meteorological data on cloudiness. The models have been developed on the basis of the meteorological data on cloudiness and horizontal irradiation measurements at the locations of the city of Belgrade and the rural region of Bavanište in Serbia. In order to improve estimates of solar irradiation on clear days, the coefficients of annual variation of optical depth and the diffuse constant from the ASHRAE Clear Day model have been adjusted to the atmospheric conditions in Serbia. Furthermore, the ASHRAE Clear Day model has been enhanced by taking into account the daily optical depth and diffuse constant variations. The aim was to include real conditions on both clear and cloudy days throughout the year. Hence, a model that considers the influence of cloudiness on irradiation has been formulated. The developed models are simple and applicable in practice, as once they are established, only the basic meteorological data on cloudiness from the nearby measurement station are necessary for estimating the solar potential at a certain location.