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Severe Soiling — Field Documentation

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Soiling is one of the most common causes of underperformance in established solar systems. Bird droppings are particularly problematic — unlike dust and pollen, bird droppings concentrate on specific panels and create intense shading that can activate bypass diodes.

Soiling Types

Type Visual Impact Priority
Bird droppings White/gray deposits, concentrated High — partial shading of cells High
Bird colonies Large areas, heavy coating Very high Urgent
Pollen season Yellow/green uniform coating Moderate Seasonal
Dust/dirt Gray uniform coating Low to moderate Annual
Construction dust Heavy gray or brown Moderate to high Assess

Production Impact

Bird droppings create "hot spot" conditions:

  1. Droppings block light to specific cells
  2. Those cells stop producing but the rest of the panel continues
  3. The non-producing cells act as resistors — they absorb power from the working cells
  4. This generates heat — the "hot spot" visible in thermal imaging
  5. Bypass diodes activate to protect the affected cell group
  6. Panel production drops by 33–66% (one or two bypass diode groups bypassed)

Assessment Protocol

  1. Ground-level visual inspection of array surface
  2. Aerial observation from roof edge or drone if available
  3. Thermal imaging — soiling-related hot spots are distinctive
  4. Compare monitoring data — were there production dips? When?

Cleaning Standards

Not all soiling requires immediate cleaning:

  • Light uniform dust/pollen: Rain typically handles this. Manual cleaning if very heavy or extended dry period.
  • Bird droppings — isolated panels: Clean affected panels. Document quantity and location.
  • Bird colony evidence: Full array cleaning + critter deterrent assessment. Escalate to lead.

Cleaning method: - Deionized or low-mineral water preferred (avoids mineral deposits on panels) - Soft brush or squeegee — never abrasive materials - Never use pressure washer directly on cells or junction boxes - Work in morning or evening (cool panels) — thermal shock risk if cleaning hot panels with cold water

Documented Cases

Specific site cases to be added here.