Modelling photovoltaic soiling losses through optical characterization.

Area of Science:

• Solar Energy Research
• Materials Science
• Environmental Science

Background:

• Soiling on photovoltaic (PV) modules is a global issue impacting solar energy generation.
• Contaminants like dust, soot, and pollen reduce the light reaching solar cells.
• Understanding soiling effects is crucial for optimizing PV system performance.

Purpose of the Study:

• To compare naturally accumulated soiling on PV glass at diverse global locations.
• To analyze the spectral impact of soiling on light transmittance.
• To establish a correlation between soiling characteristics and optical consequences.

Main Methods:

• Spectral hemispherical transmittance measurements of soiled PV glass coupons.
• Analysis of soiling composition including particle size distribution.
• Comparison with the IEST-STD-CC 1246E cleanliness standard.

Main Results:

• Natural soiling significantly impacts the blue and ultraviolet (UV) spectrum more than visible and infrared (IR) light.
• Soiling transmittance spectra showed similar patterns across all seven worldwide sites.
• Particle size distribution aligned with the IEST-STD-CC 1246E standard.
• Fractional surface coverage by particles showed a linear correlation with transmittance reduction.

Conclusions:

• Soiling's optical impact is predictable and disproportionately affects shorter wavelengths.
• A modified Ångström turbidity equation effectively describes soiling transmittance spectra.
• Estimating soiling's optical effects is feasible using particle size distribution and cleanliness values.