Application and Characterization of an Artificial Grime for Photovoltaic Soiling Studies

Effective evaluation and prediction of photovoltaic performance loss due to soiling require consistent test methods. Natural soil accumulation is time-consuming and location specific, and thus does not provide reproducible results across different geographic regions. Therefore, we have demonstrated a laboratory technique to artificially apply soil to a specimen and quantify the resulting effects of the film on the transmission of incident light. An artificial soil analogue was formulated with NIST-traceable components and applied to the specimen using an aerosol spray gun. This approach produced consistent soil coatings, which were directly correlated to electrical performance loss of multicrystalline Si cells in a laboratory setting. Two independent measurement techniques were used to quantify the influence of the layer of artificial soil on the spectral transmission of light. It was found that the performance loss due to deposited soil could be effectively predicted over a range of mass loadings. Furthermore, it was demonstrated that the composition of the blend, termed "standard grime," had a significant and repeatable influence on performance loss. The methods presented here provide the basis for further study of the influence of specific soil types on the performance loss of PV systems. It is envisioned that these laboratory studies could be coupled with field studies to better understand these effects.