Cleaning Solar Panels Often Not Worth the
Cost
Don't hire someone to wash your dirty solar panels. That's the
conclusion of a study recently conducted.
Researchers found panels that hadn't been cleaned, or rained on,
for 145 days during a summer drought in California
Overall, for a typical residential
solar system of 5 kilowatts, washing panels halfway through the summer would
translate into a mere $20 gain in electricity production. For larger commercial rooftop systems, the financial losses are
bigger but still rarely enough to warrant the cost of washing the panels. On
average, panels lost a little less than 0.05 percent of their overall
efficiency per day. The study is focused on smaller systems, for very large
installations, economies of scale may mean that washing panels is worth it.
Dust on PV panels does make a difference but it's not a big enough
factor in Wisconsin
Researchers also found that solar panels mounted at an angle of
less than five degrees caused bigger losses in efficiency. That's because dirt
slips off panels that are installed at a steeper angle. Here in SE Wisconsin we angle solar arrays at slightly less than
45 degrees.
But solar panels heavily soiled with bird droppings should be
cleaned. That's because the droppings essentially block all sunlight and will
not be washed away when it rains. Engineers also found that photovoltaic panels
were dirty enough to warrant cleaning due to very specific and localized
circumstances. For example, being directly next to and downwind of a highway,
factory or agricultural field may generate enough dirt to warrant cleaning.
Next steps in the study would be looking more closely at the sites
that did warrant cleaning and determine what caused the panels to get so dirty.
Finally, researchers could add collectors at specific sites to determine what
kind of dirt accumulates on the solar panels; whether special materials could
keep dirt from accumulating; and whether special, less costly washing systems
would do a better job at removing dirt from the panels.
