Solar Spectral Characterization of Three Different Locations at Alpine Latitudes Using Average Photon Energy
Abstract
The characteristic of the solar spectrum is one of the most important factors to be taken into account when evaluating the solar resource of a certain area, for photovoltaic applications. In fact, the spectral distribution of irradiance, coupled with the spectral responsivity of photovoltaic modules, is responsible for the effective performance of a photovoltaic system in real outdoor conditions. This paper investigates the variability of solar spectrum at three different locations at Alpine latitudes: Vienna (Austria), Kanzelhöhe (Austria) and Lugano (Switzerland). The Average Photon Energy (APE) index is used to quantify the spectral distribution. It is derived from outdoor measurements and computed for the range 350-900 nm. The diurnal and seasonal variability of APE is assessed under real conditions of cloudiness as well as under clear sky conditions. The results are interpreted considering the atmospheric properties of the investigated sites, and an example of assessment of how much the spectral variability influences the performance in generated current of photovoltaic modules is shown.
Keywords
Solar spectrum, Spectral effect, Average photon energy, Photovoltaic, Spectral responsivity, Spectral