ABSTRACT
When estimating energy yields of planned solar technical systems, size-specific effects have to be considered. During operation, shading effects can lead to considerable losses of solar irradiation, which in turn would lead to significant discrepancies between the energy yields predicted by the sales company of the solar system and the energy yields actually obtained. In this paper a precise but yet cheap and fast method to evaluate shading effects on the energetic use of solar radiation is presented. An essential part of this procedure is the Skiameter (skia, greek = shadow), a device for opto-electronic surveying of the obstructed horizon. The practical application and results realised by using the Skiameter are discussed by analysing actual photovoltaic systems. Additionally, a validation of the whole procedure was done by comparing the data to measurements from the german 1000-roof-program. Losses of solar irradiation onto PV systems due to shading effects were calculated from Skiameter measurements with an average deviation of 3.3% compared to direct measurement.
