Modelling Photovoltaic Soiling Losses through Optical Characterization: Article No. 58

Leonardo Micheli, Greg Smestad, Thomas Germer, Hameed Alrashidi, Eduardo Fernandez, Sumon Dey, Honey Brahma, Nabin Sarmah, Aritra Ghosh, Nazmi Sellami, Ibrahim Hassan, Mai Desouky, Amal Kasry, Bala Pesala, Senthilarasu Sundaram, Florencia Almonacid, K.S. Reddy, Tapas Mallick

Research output: Contribution to journalArticlepeer-review

88 Scopus Citations


The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Angstrom turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value.
Original languageAmerican English
Number of pages13
JournalScientific Reports
StatePublished - 2020

NREL Publication Number

  • NREL/JA-5K00-74546


  • cleanliness value
  • particle size distribution
  • soiling


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