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Solar suffers in smoky skies

I read about Southern Oregon University’s new plans for using solar power. How efficient is it when we have smoky days like we did this summer? How does it do in the winter when the daylight hours are short and we could be having rain or fog? I don’t know what percentage of the time on average our winter days are rainy or foggy, but it seems like a lot of them are. I am all for solar power, but it probably does better in Phoenix, Arizona, than Phoenix, Oregon.

— Liz N.

Like the rest of us in Southern Oregon, our solar panels were also likely experiencing lower production levels during the long weeks of smoke, but there’s more to the story that makes it hard to quantify the actual impact, said Buz Thielemann, a seasoned veteran of the private energy industry.

Thielemann told us that smoke reduces solar efficiency, because the sunlight that comes through is more diffuse. Cloud cover has a similar effect.

“It isn’t so much the dirt as it is the smoke that’s causing diffuse light, and that has a bigger impact,” he said.

Others say the residue from ash and particulates from wildfires can have a noticeable impact on energy production.

Tom Gauntt, a spokesman for Pacific Power, said it’s important to have a maintenance plan in place when installing a solar array. If people need to clean off their panels, it’s important to use soft microfiber that won’t leave scratches.

Thielemann said the little bit of rain we got recently was enough to clean off his array, which is one of the largest residential setups in the Rogue Valley.

It can be difficult to quantify exactly how much solar efficiency was lost to the smoke, because panels are touchy and can be affected by other factors — a major one is temperature. Thielemann said that a smoky 70-degree day would see higher energy output than a 100-degree day.

“Solar likes cold and clear,” he said.

Send questions to “Since You Asked,” Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to youasked@rosebudmedia.com. We’re sorry, but the volume of questions received prevents us from answering all of them.