4 July 2018

Cleaning solar panels in dry weather can offer significant benefits

Solar panels on the roof of a Utrecht University building. Photo credit: Wilfried van Sark

Most installation companies claim solar panels are maintenance-free. However, for long periods of dry weather cleaning may be beneficial. A lack of rainfall leaves panels covered in dust and less able to absorb sunlight. Utrecht University researcher and solar energy expert Wilfried van Sark was interviewed by NOS evening news about the implications of dirty solar panels.

Rainfall usually keeps solar panels clean, certainly in the Netherlands. Dry and hot weather causes dust and dirt to stick to the panels. So despite the recent sunny period, panels are not working as well as they could be. Dusty panels absorb around 10% less sunlight."10 percent less means five euro cents per panel, so with around ten million solar panels in the Netherlands, on a sunny day like this we are missing out on half a million euros", says van Sark.

Farmers and big businesses profit from cleaning

This reduction in sunlight absorption does not make a huge difference to individuals with ten solar panels on their roofs, “they only lose about 15 euros per month,” says van Sark. However, for large installations cleaning may be cost-effective. “Farmers and big businesses stand to save 600-700 euros per month if they clean their panels provided their installations are large enough,” he goes on to explain. This can be done using special 'cleaning robots'. They are operated remotely, for example from a hydraulic work platform.

Wilfried van Sark was interviewed by NRC as well. In these two articles he explains why consumers always need to keep track of their solar yield, and why they need to make sure solar panels aren’t overshadowed by growing trees or accumulated dirt and dust.