Quantifying Year-to-Year Variations in Solar Panel Soiling from PV Energy-Production Data

We present a method for quantifying solar panel soiling loss from PV energy-production data and show how it can be used to quantify year-to-year variations in soiling loss. Cleaning events are automatically detected, eliminating the need for precipitation data or assumptions about cleaning. The method also calculates the reduction of energy yield due to soiling, not just a soiling rate. We apply the method annually and also to multi-year datasets. We find significant year-to-year variation in soiling loss, a result with important implications for site planning and financing. The method presented here can leverage existing datasets of daily energy yield to quantify annual and total soiling risk without the need for new hardware and serves as a supplement to standard plant planning practices.