Solar panel bird proofing, and why the array is cleaned first
Bird proofing closes the 100 to 150 mm gap between panel and roof with a mesh skirt clipped to the panel frame. Clean and inspect the array before the mesh goes on, because the space underneath becomes very difficult to reach once it is closed.
Why the gap under a panel attracts birds
A rooftop array creates a sheltered cavity roughly 100 to 150 mm deep, dry, warm at night, and closed on top. Pigeons and starlings nest in it because it beats every other site on the roof. Once a colony establishes, the nesting material blocks airflow under the panels and the droppings accumulate on the panels above and below.
Two costs follow. The array runs hotter because convective cooling underneath stops, and every percentage point of panel temperature above the rating costs output. The droppings do something worse.
What droppings do that dust does not
Dust dims a cell. A dropping blocks it completely. A fully shaded cell in a series string stops carrying current, and the bypass diode across its substring switches in to carry the current around it. The array loses that entire substring rather than the area of the dropping.
On a typical 60-cell panel with three bypass diodes, one well-placed dropping removes a third of the panel’s output. That is the reason an array under a bird colony needs cleaning on a schedule of its own rather than the dust interval in how often to clean solar panels.
Hot spots follow. The shaded cell is reverse-biased by the cells still generating around it, and dissipates that power as heat instead of producing it. Repeated hot-spot cycling degrades the laminate permanently.
Mesh specification
| Component | Specification | Reason |
|---|---|---|
| Mesh material | PVC-coated galvanised steel | Bare galvanising corrodes at the coast; plastic mesh fails in UV |
| Aperture | Under 20 mm | Excludes pigeons and starlings while passing air |
| Height | Full gap plus 20 mm | A short skirt leaves a gap birds find within days |
| Fixing | Stainless clips onto the panel frame | Drilling the frame voids the panel warranty and breaches the roof |
| Clip spacing | 200 to 300 mm | Wider spacing lets wind lift the mesh edge |
| Access panel | One removable section per array | Inspection and cleaning under the panels stays possible |
The access panel is the item most installations leave out, and the one that matters most three years later.
The order of work
- Remove nesting material and droppings from under the array.
- Inspect the DC cabling for chew damage, which nesting birds cause routinely.
- Clean the panel glass, including any baked-on droppings.
- Check for hot-spot damage on cells that sat shaded for a long period.
- Fit the mesh skirt with stainless clips, leaving one removable access section.
- Return to the normal cleaning interval, now driven by dust rather than droppings.
Reversing steps three and five is the common error. Mesh fitted over a soiled array traps the soiling underneath, where no pole-fed brush reaches.
Removing droppings that have already dried
Dried droppings bond to glass and resist a normal wash. Soaking is the answer that protects the coating: wet the deposit, leave it 10 minutes, wet it again, then lift it with a soft brush. Scraping removes the deposit and the anti-reflective coating together. Method and brush choice are covered in how to clean solar panels.
Questions
Do bird droppings damage solar panels?
Yes, in two ways. A dropping fully shades the cell beneath it, which forces the bypass diode to carry the substring and reverse-biases the shaded cell into a hot spot. Repeated hot-spot cycling degrades the laminate permanently.
Can mesh be fitted without drilling the panel frame?
Yes, and it is the only correct method. Stainless clips grip the frame lip, so neither the frame nor the roof sheet is penetrated. Drilling a panel frame voids the manufacturer warranty.
Should an array be cleaned before bird proofing?
Yes. Mesh closes the space under the panels, so anything left underneath stays there. Cleaning and cable inspection both become far harder afterwards.