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Soiling of solar energy systems, or the accumulation of particulate matter on their surface, can cause significant losses in energy conversion efficiency. However, predicting these losses is still not done, as no methods exist. Field measurements of mass accumulation and airborne PM 10 were conducted for more than one year at two sites in the Front Range of Colorado with the objective of developing soiling prediction models. For this study, only dry deposition was examined. The two sites, despite having different PM 10 concentrations, have indistinguishable average effective deposition velocities of 2 cm/s, although a large spread in the data was noted. These results are similar to results found in other deposition studies. The observed effective deposition velocities indicate that coarse particles are a dominant player in mass accumulation, and sampled airborne size distributions support this hypothesis. Using a model to calculate dry deposition yielded better agreement with deposition than a simple average deposition velocity data fit. This model combined with other research and models can be used for estimating average soiling rates and is most useful over long time scales especially months to years or longer.

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