Help CenterPerformance & Lifetime
Shading and soiling losses
Two environmental losses reduce real production versus the theoretical calculation: shading (trees, buildings, chimneys) and soiling (dust, sand, bird droppings, pollen).
On a series string, partial shading of a single cell can reduce the whole string's output far beyond the shaded surface area — cells in a panel are wired in series and limited by the weakest one.
| Shaded panel surface | Estimated production loss | Note |
|---|---|---|
| 5% | 10–20% | A single partially shaded cell is enough |
| 15% | 30–50% | With functioning bypass diodes limiting the damage |
| > 30% | 50–80% | Near-total loss possible without good bypass diodes |
Soiling is a distinct, more gradual phenomenon. In the Sahelian dry season (Harmattan), dust can reduce production by 1–3% per month without cleaning, up to 15–20% after several months with no rain or maintenance.
| Context | Typical soiling loss | Recommended cleaning frequency |
|---|---|---|
| Temperate urban area, regular rain | 2–5% annually | Natural rain cleaning usually sufficient |
| Sahelian zone, dry season (Harmattan) | 10–20% by end of dry season | Every 4–8 weeks during dry season |
| Near unpaved road / quarry | 15–25% | Every 2–4 weeks |
A slightly tilted panel (> 10°) self-cleans better with rain than a near-horizontal panel, where dust and stagnant water accumulate.
Common mistakes
- Ignoring brief morning or evening partial shading as "not significant"
- Planning no margin for soiling in a dusty Sahelian zone
- Cleaning panels with cold water in full heat (thermal shock, micro-cracks)