Impact of Non-Uniform Soiling on PV System Performance and Soiling Measurement

We present a case study from commercial-scale PV power plants in the US Southwest, demonstrating that accurate soiling measurement requires detection of PV module power loss in order to account for non-uniform soiling, such as along the edges of modules. Small amounts of non-uniform soiling may cause significant power losses that cannot be detected accurately through measurements of short-circuit current alone. Furthermore, based on aerial IR and visual inspection and I-V curve data acquired at a number of sites, we believe that the non-uniform soiling phenomenon is common in regions with higher rates of soiling and little rain, especially for low-tilt installations.