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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 factor is applied uniformly to all components after shading losses and before corrections.

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Inputs

NameSymbolUnitsDescription
Soiling LossSlossS_{loss}%Soiling loss percentage for the current timestep

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Outputs

NameSymbolUnitsDescription
Soiling FactorUsoilU_{soil}—Fraction of irradiance transmitted (0-1)

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Detailed Description

The soiling factor is calculated from the soiling loss percentage: Usoil=1−Sloss100U_{soil} = 1 - \frac{S_{loss}}{100} The source of SlossS_{loss} depends on the selected model:
  • None: Sloss=0S_{loss} = 0 (modules assumed perfectly clean, Usoil=1U_{soil} = 1)
  • Monthly: SlossS_{loss} is retrieved from user-specified monthly values (12 values, one per month)
  • Weather: SlossS_{loss} is read from the weather file for each timestep (e.g., from PVRADAR soiling data)

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Application to Irradiance

The soiling factor is applied uniformly to all plane-of-array irradiance components (beam, sky diffuse, and ground-reflected irradiance): Gbeam,soiled=Gbeam,shaded×UsoilG_{beam,soiled} = G_{beam,shaded} \times U_{soil} Gsky,soiled=Gsky,shaded×UsoilG_{sky,soiled} = G_{sky,shaded} \times U_{soil} Gground,soiled=Gground,shaded×UsoilG_{ground,soiled} = G_{ground,shaded} \times U_{soil} Soiling is applied after near-field shading and horizon shading, and before incidence angle modifier (IAM) corrections.