The Dirty Truth About Solar Power

Renewable energy faces many formidable challenges, including cost, technology, site permits and transmission access.

To that list you can now add one more: bird droppings.

“You don’t see solar arrays on the coast, and the reason is bird poop,” UC Santa Cruz engineering professor Michael Isaacson told the Santa Cruz Sentinel this week. “It covers the panels and makes them inefficient.”

Bird droppings—as well as leaves, dust and pollen—can cut the output of solar panels by 20 percent or more, making them far less efficient and economic. Monitors that show voltage and current from solar installations register a distinct notch in output when cells get dirty.

UC Santa Cruz’s Center for Sustainable Energy and Power Systems is working on new solar cell materials that will help overcome the problem. In the meantime, there are some low-tech solutions to this environmental nuisance.

At home, you can simply hose off your rooftop panels or wash them down with a sponge to keep them clean. A few tips: be careful not to fall off your ladder or roof, never walk on your panels, read the manual before using any cleaning products and check for cracks in the panel covers before you wash.

Be sure as well that any cleaning agent you use is environmentally friendly and has somewhere to drain without harming nearby trees and shrubs or staining the side of your building.

You can also invest in automated solar panel cleaning systems to eliminate much of the hassle—but your wallet had better be fat.

You can also shop for bird barriers and exclusion systems to keep them away from your roof as much as possible.

Keeping large commercial solar panels clean in dusty desert installations is a much bigger challenge—both to limit labor costs and the use of precious water. In some locations, solar output can fall 40 percent after winds kick up sand and dust to coat the cells with grime.

Technology first developed for NASA rover missions to Mars may come to the rescue. As described by a Boston University professor at a professional conference last summer, it involves applying electrostatic charges to the face of the panels to push dust toward the edges. The process takes just a couple of minutes. “With this new technology, solar panels can be automatically cleaned without water or labor,” he said.

But don’t expect it to work with bird poop.

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