Brushes for Solar Farm Panel Cleaning: Robots, Trucks and Manual
Industry guide · 6 min read · updated 2026-10-24
Dust, pollen, bird droppings and industrial grime all cut the light reaching PV cells. How much that costs depends heavily on the site. A year-long study of six locations in Chile measured annual energy losses from soiling of up to 39% on the dry northern coast, against 3% or less at higher, rainier sites, and noted that losses reported elsewhere are typically 1 to 7% a year. On dusty, dry sites, cleaning is a real operating cost, and the brush is the part of the cleaning system that touches the glass.
Solar farms clean with three main kinds of equipment: rail or frame-mounted robots that travel along a row, truck or tractor-mounted rotating brushes, and manual poles. Each one uses a different brush format, but they all have to meet the same rule: remove soiling without scratching the glass or its anti-reflective coating.
1. Three cleaning methods and their brushes
Robot rollers are the most common replacement item because the robot runs every day or every few days across thousands of modules. Our solar panel cleaning rollers are spiral-wound in soft PA66 nylon in sizes such as 110 × 903 mm, 150 × 903 mm, 150 × 1200 mm and 170 × 900 mm.
| Method | Typical brush | Water use | Main brush concern |
|---|---|---|---|
| Row-mounted robot | Spiral or tufted roller spanning the module width | Often dry or low-water | Long continuous life; even contact along the full length |
| Truck or tractor machine | Large rotating cylinder or disc on a boom | Usually with water | Contact pressure control; fill must not trap grit |
| Manual pole | Soft flat or rotary brush head | Usually with water | Softness; operators press unevenly |
2. What module makers allow
Before choosing a brush, read the cleaning section of the module manufacturer's manual, because cleaning that breaks those rules can put the warranty at risk. As an example, LONGi's maintenance manual for its modules sets these limits:
- Tools: no blades, scouring wire, metal tools or abrasive materials. Soft brushes are allowed, and it names nylon thread of 0.06 to 0.1 mm diameter.
- Water pressure on the module surface: not more than 0.7 MPa.
- Water quality if not municipal water: pH 6 to 8, conductivity at most 3000 µS/cm, total dissolved solids at most 1000 mg/L, hardness 0 to 450 mg/L.
- Temperature: water and module should be within 10 °C of each other, and no cleaning when ambient is below 5 °C.
- No steam, abrasive powders, strong acids or alkalis. Automatic cleaning equipment is allowed if it does not damage the modules.
3. Filament choice: soft, consistent and UV-tolerant
Nylon is the normal choice for PV brushes because it recovers its shape well after bending; DuPont puts nylon's bend recovery at over 90%, ahead of polyester and polypropylene. That matters on a robot whose filaments flex millions of times. Fine, soft filament spreads the contact load and is what module makers ask for; our scratch-proof nylon-66 PV roller is built around that requirement.
Avoid abrasive-loaded filament and any wire on PV glass. Also avoid fills that are too dense for dry robots: very tightly packed fill can hold grit against the glass instead of flicking it off. Our guide to solar panel cleaning brush filament compares filament options in more detail.
Outdoor exposure is the other factor. Robots park in full sun, so ask for UV-stabilised filament and confirm the core material is suitable for your site's heat and cold.
4. Dry robots vs wet cleaning
Dry robots are popular on desert sites where water is scarce. Their brushes do all the work, so filament softness, density and roller speed all matter. Wet cleaning with trucks or poles lets water carry dirt away, which reduces the work done by the bristles and the risk of scratching, but adds water treatment and logistics.
Bird droppings, lichen and sticky pollution usually need water. LONGi's manual describes a sequence of sweeping, then removing attached debris, then washing with water and a brush, and allows alcohol on oily contamination only when water alone fails.
5. Inspection and replacement
- Check robot rollers for flattened or matted filament, especially at the ends where the roller meets the module edges.
- Look for broken tufts or bare sections in the spiral; a gap leaves a stripe of uncleaned glass on every pass.
- Check for grit packed into the fill. If sand stays trapped after a run, clean or replace the roller before it starts marking the glass.
- Inspect a few modules under low-angle light for fine scratches after a new brush type goes into service.
- Keep a stock of spare rollers matched to each robot model so swaps happen during routine maintenance.
6. What to send for a quote
If you are matching an existing robot, a sample roller is the fastest way to a correct quote. Send the details via Request a Quote.
- Roller outside diameter, length and spiral or tuft pattern (photos of the old roller help).
- Shaft or hub details: bore, key, hex, end caps or drive coupling.
- Robot or machine make and model and whether it runs dry or wet.
- Module type (glass/backsheet or glass/glass, framed or frameless) and any brush rule in the module manual.
- Site climate (dust type, temperature range) and quantity per year.
Frequently asked questions
- What kind of brush is safe for cleaning solar panels?
- A soft, non-abrasive brush, normally fine nylon. Module manuals forbid metal tools and abrasive materials; LONGi, for example, allows soft brushes with nylon filament 0.06 to 0.1 mm in diameter. Check your own module maker's manual before choosing.
- Can solar panels be cleaned dry with a brush?
- Yes, many robots on dry, dusty sites clean without water. Dry cleaning works best on loose dust; bird droppings and sticky deposits usually need water. Keep the brush clean so trapped grit is not dragged across the glass.
- How much power does dirt on solar panels cost?
- It depends on the site. A study across six sites in Chile measured annual soiling losses from 3% or less up to 39%, and the authors note typical losses elsewhere of 1 to 7% a year.
- What water pressure is safe for cleaning PV modules?
- Follow your module maker's limit. LONGi's maintenance manual caps water pressure on the module surface at 0.7 MPa and asks for water within 10 °C of the module temperature.
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