The goal of these experiments is to detect early glass aging, determine required cleaning cycles and develop protective measures, depending on the weathering. One of the test conditions is atmospheric weathering of installed photovoltaic modules. Additionally in the AiF research project "Cleaning of semi-finished glass products and products made of glass" we used glass panes with different compositions for these ageing experiments. This information is important for the glass which covers PV modules. Changes in the glass surface can lead to transmission decrease and lower the efficiency of the modules. The pollution of the glass surfaces by foreign substances such as aerosols, dust and pollen can initiate long-term changes that cannot be removed by cleaning. Various cleaning methods and cleaning agents were used. The glass surfaces were examined in relation to the exposed different atmospheric conditions. The evaluation of suitable measurement methods to assess different characteristics of the glass surfaces was necessary. In addition, a long term changing of the efficiency was observed after cleaning the PV modules. The energy yields were evaluated and analysed.
