Solar panel cleaning and system maintenance
What the exam tests
Solar panel cleaning and system maintenance tests practical care of operating arrays: soiling loss, safe cleaning methods, preventive maintenance, performance monitoring, and fault detection.
Core rules
- Soiling reduces irradiance reaching the cells; loss depends on dust, pollen, bird droppings, snow, and pollution. Cleaning frequency should follow manufacturer guidance, site conditions, and measured performance loss, not a fixed calendar.
- Use soft brushes, microfiber, or mild non-abrasive detergent with low-mineral water. Avoid high-pressure washers, abrasive pads, and harsh chemicals that can damage glass, frames, or edge seals.
- Clean early morning or late evening when modules are cool. Cold water on hot glass can cause thermal shock; working on wet, energized arrays increases shock and slip risk.
- Follow the manufacturer's instructions and warranty terms; some coatings and anti-reflective glass are sensitive to abrasion.
- Maintenance includes visual inspection for cracked glass, discolored cells, loose connectors, corrosion, and animal nests; torque checks; thermal imaging; IV-curve tracing; inverter filter and fan service; and monitoring alerts.
- Document commissioning and maintenance per IEC 62446-1 and use monitoring data to compare actual yield with expected yield.
Worked example
A 10 kW array produces 50 kWh on a clear day. Soiling is estimated at 5%, so the loss is 0.05 × 50 = 2.5 kWh/day. If energy is worth $0.15/kWh, the daily loss is about $0.38. If cleaning costs $100 and soiling remains at 5%, the simple payback is 100 ÷ 0.38 ≈ 267 days; if soiling is 15%, the payback is about 89 days. The decision should also consider water use, safety, and warranty.
Traps
- Cleaning hot glass with cold water or using abrasive tools.
- Assuming every soil type requires the same cleaning method or frequency.
- Ignoring electrical safety and fall protection while cleaning roof arrays.
- Treating a monitoring alarm as a cleaning problem when the real fault is a failed inverter or open connector.