Soiling

Soiling — the accumulation of dust, pollen, bird droppings, and other contaminants on module surfaces — is one of the most significant and underestimated sources of yield loss in operating PV systems. Losses of 1–5% are common in temperate climates; in arid and desert environments they can exceed 30% between cleaning events. Accurately quantifying soiling loss requires dedicated instrumentation and a clear methodology, distinct from the irradiance and temperature correction applied to standard performance analysis. This section covers soiling sensor technologies, monitoring system design, data interpretation, and the use of soiling measurements to optimise cleaning schedules and validate cleaning effectiveness.