Panel Soiling
The build-up of dust, sand, pollen, bird droppings and exhaust soot on the panel glass, preventing light from reaching the cells. The loss varies with the type and thickness of the soiling; a thin, uniform layer of dust lowers output proportionally, while dense marks such as bird droppings create a shading effect.
Soiling has two different damage mechanisms. The first is a uniform reduction in light transmission; this produces a roughly linear fall in output. The second is localised, opaque deposits: these behave like partial shade, limit the current of the series string and can bring the bypass diodes into play. This second type gives a far greater loss relative to the area it covers.
The rate of soiling is set by the site conditions. Farmland, desert climate, the surroundings of a construction site, a location close to heavy traffic and areas with a high bird population soil quickly. Rain does some washing, but it can turn the dust layer into mud and in some cases temporarily make things worse.
In large-scale solar plants this loss is a direct loss of revenue, so regular cleaning is an operating item. AXI's ROBEG ELS-03 solar panel cleaning robot has been developed for this job; with its 800 mm industrial brush it removes the layer of dust, sand and dirt without damaging the panel surface and runs on a grid-independent DC battery.
The context in which this term is used: Solar plant panel soiling and robotic cleaning