Soiling loss
Energy lost to dust, dirt, and deposits on the module glass.
Soiling loss is the reduction in PV output caused by dust and dirt on the module surface. It is quantified as a soiling ratio (actual ÷ clean-condition output) and typically costs 1–6% of annual yield depending on climate. Unlike hardware faults it recovers with rain or cleaning, which is exactly what makes cleaning an optimisation problem.
Symptoms
- Whole-plant performance ratio drifting down between rain events.
- A sawtooth yield pattern: gradual decline, sharp recovery after rain/cleaning.
- Stronger losses in dry, dusty, or agricultural-dust seasons.
SCADA signatures
- Soiling ratio (measured vs. clear-sky-expected) declining at a steady daily rate.
- Step recovery in the ratio aligned with rainfall above a wash-off threshold.
- Loss roughly uniform across strings — distinguishes soiling from hardware faults.
Root cause
Airborne dust, pollen, agricultural and industrial particulates, and bird droppings accumulate on the glass and block irradiance. The accumulation rate is climate- and site-specific; rain partially or fully cleans depending on intensity.
Financial impact
In dusty climates soiling can exceed 5%/year if uncleaned. But cleaning has a cost and a water footprint, so the real question is economic: clean only when the recovered energy beats the cleaning cost. NuraVolt’s optimiser answers that per site.
How NuraVolt detects it
NuraVolt estimates the soiling ratio through a five-layer stack — from a DustIQ sensor (when present) down to a physics-based loss disaggregation — and forecasts accumulation with a rain-aware model, then runs a cleaning-schedule optimiser over 1,000+ scenarios to find the ROI-maximising cleaning dates.
Frequently asked questions
See also
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