Influence of Technological Changes on the Energy Yield of PV Modules: An Outdoor Study

To further increase the efficiency of PV modules, a variety of technical approaches targeting losses on cell and module level are pursued. Module efficiency is usually stated at standard test conditions (STC) whereas conditions during operation in the field are most of the time very different. From a customer perspective the specific energy yield is the far more important parameter, as it has immediate effect on the levelized costs of electricity(LCOE), which describes the costs of a kWh produced. The specific energy yield is strongly dependent on module characteristics at different operating points. Some of these properties such as low light characteristic, thermal behaviour or incident angle dependency can be influenced by technological changes resulting in a change of specific energy yield. To predict the quantitative effect of technological changes on annual energy production, module characteristics can be determined by outdoor measurements and fed into a simulation tool to quantify the gain or loss in annual energy yield of the changes applied. In this paper, two technological changes on cell and module level are investigated. First, the effect of anti-reflective coated glass is evaluated. The second investigation is related to a PERC cell structure. Therefore measured outdoor data from a photovoltaic test site are analysed to evaluate changes in module design with respect to their effect on outdoor performance. The results are compared to long term measurements of system installations to confirm the differences in energy yield. It is shown that technological changes can be applied on module and cell level that not only increase power under standard test conditions, but also lead to an additional improvement of the energy harvest per kWp and thus lower the LCOE.