Soiling and self-cleaning of PV modules under the weather conditions of two locations in Arizona and South-East India

During long-term operation of photovoltaic (PV) power plants soiling of PV module surface can cause significant energy yield losses. These are dependent on the site characteristics such as climatic conditions or surrounding environment, and also on the glazing characteristics of the PV module. This paper presents the results of an experimental study on annual soiling losses measured at two locations: a) Tempe (Arizona) with hot and dry climate, b) Chennai (India) with tropical climate. Soiling effects were studied by means of two mini-modules, of which one has been regularly cleaned whereas the other was exposed to natural soiling. For the first year of operation our results show 3.7% annual soiling losses for Tempe and 2.3% for Chennai. The contribution of angular losses caused by the change of the angular characteristic of the glass surface is approx. 22% for the Tempe test site. Comparative study of the soiling behavior of 3 types of PV glazing (standard glass, standard glass with antireflective coating, deeply textured glass) showed that AR coating is comparable to non-coated glass. For deeply textured glass we observed 7% higher annual soiling loss at Tempe test site.