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Summary

The soiling model accounts for irradiance losses due to dust, dirt, pollen, and other particulate matter accumulated on module surfaces. PlantPredict implements three soiling approaches: None (no soiling loss), Monthly (user-specified monthly loss values), and Weather (time-series loss values from weather data). The soiling transmission factor is applied uniformly to all plane-of-array irradiance components after shading losses and before incidence angle modifier corrections.

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Inputs

NameSymbolUnitsDescription
Soiling Model Type——Selection: None, Monthly, or Weather
Monthly Soiling LossSloss,monS_{loss,mon}—User-specified monthly loss (0-1, Monthly model only)
Weather Soiling LossSloss,weaS_{loss,wea}—Time-series loss from weather file (0-1, Weather model only)

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Outputs

NameSymbolUnitsDescription
Soiling Transmission Factorudirtu_{dirt}—Fraction of irradiance transmitted (0-1)
Soiling LossLsoilL_{soil}%Percentage loss due to soiling (0-100%)

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Detailed Description

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Model 1: None

When soiling is disabled, modules are assumed perfectly clean: udirt=1.0u_{dirt} = 1.0 Lsoil=0%L_{soil} = 0\%

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Model 2: Monthly

Users provide 12 monthly soiling loss values. For each timestep, the model retrieves the soiling loss for the current month: udirt=1−Sloss,monu_{dirt} = 1 - S_{loss,mon} Lsoil=(1−udirt)×100L_{soil} = (1 - u_{dirt}) \times 100 where Sloss,monS_{loss,mon} is the soiling loss fraction for the current month (0 to 1).

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Model 3: Weather

The weather-based model uses soiling loss values from the weather file for each timestep: udirt=1−Sloss,weau_{dirt} = 1 - S_{loss,wea} Lsoil=(1−udirt)×100L_{soil} = (1 - u_{dirt}) \times 100 where Sloss,weaS_{loss,wea} is the soiling loss fraction at the current timestep from weather data (0 to 1).

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Application to Irradiance

The soiling transmission factor is applied uniformly to all plane-of-array irradiance components: IPOA,soiled=IPOA,shaded×udirtI_{POA,soiled} = I_{POA,shaded} \times u_{dirt} This applies to beam, sky diffuse, and ground-reflected irradiance: Ibeam,soiled=Ibeam,shaded×udirtI_{beam,soiled} = I_{beam,shaded} \times u_{dirt} Idiffuse,soiled=Idiffuse,shaded×udirtI_{diffuse,soiled} = I_{diffuse,shaded} \times u_{dirt} Iground,soiled=Iground,shaded×udirtI_{ground,soiled} = I_{ground,shaded} \times u_{dirt} Soiling is applied after near-field shading and horizon shading, and before incidence angle modifier (IAM) corrections.

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References

  • Ilse, K., et al. (2019). Techno-economic assessment of soiling losses and mitigation strategies for solar power generation. Joule, 3(10), 2303–2321.
  • Micheli, L., & Muller, M. (2017). An investigation of the key parameters for predicting PV soiling losses. Progress in Photovoltaics: Research and Applications, 25(4), 291–307.
  • Coello, J., & Boyle, L. (2019). Simple model for predicting time series soiling of photovoltaic panels. IEEE Journal of Photovoltaics, 9(5), 1382–1387.