Soiling test methods and their use in predicting performance of photovoltaic modules in soiling environments

Photovoltaic modules installed in most outdoor locations accumulate soil which reduces power output. To better understand and model this problem, and to evaluate surface treatments that might help to alleviate the problem, we developed soiling test methods to mimic specific environments. Many factors that affect accurate measurements and the extrapolation of laboratory measurements to outdoor performance are discussed. Examples of various materials, including some that have anti-soiling properties, are included to illustrate the importance of accurate testing and the care that must be exercised when using laboratory data to predict real-world performance.