ASK THE EXPERTS: Cleaning PV Arrays

A nice, soft brush with water and mild soap is the best way to clean dirty PV modules.

What is the most effective and safe method for cleaning a PV array? The company we bought our modules from suggested using only water to clean the modules to avoid scratching them.

We live in a desert mountain region of Mexico. A lot of dust and grime has accumulated on the array, and using water alone does not seem to be effective. Can a soft-bristle brush (like one used for washing cars) be used? What kind of detergent, if any, can be used, and how much?

Lamar Strickland • via email

I use a soft-bristle brush and plain water to clean my PV array. I do it early in the day, before the sun has a chance to heat the PV modules, which will evaporate the water and cause smearing.

I spray the array two or three times, letting the water soak into the grime and bird droppings for a bit, scrub (if necessary), and then rinse off the dirty water left after the scrubbing. Yes, a car-washing soft brush is good. If you want to use detergent, use a mild dish detergent.

If it rains regularly, PV arrays usually don’t need washing (and even some visible grime won’t affect output much). However, in arid areas and some agricultural areas, where farm machinery generates lots of dust, dirty PV modules can definitely reduce a system’s overall performance.

Michael Welch • Home Power Senior Editor

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