Smoke, ash hindering solar energy in San Mateo County

“Last Wednesday, no production at all,” said Steve Pariani, owner of Burlingame-based Solar Pro Energy Systems. “A lot of my systems were producing zero power.”

It’s not that the sun needs to be visible for solar panels to produce power. On the Peninsula, which experiences its share of fog, solar panels do produce energy.

“Have you ever gotten a sunburn on a cloudy day?” Pariani asked. “When we have plain old fog, fog allows light to come through. There is no particulate in the air.”

The smoke and haze that has engulfed the Bay Area and triggered more than 30 straight Spare the Air” days, however, is a different matter. Pariani said while sunlight refracts off moisture droplets that comprise fog, the ash and soot produced by the fire does not allow sunlight to pass through. “While it may look very similar, the smoke and ash pose a different problem,” Pariani said. “You have a lot of particulate matter. You have ash and embers … and that completely blots out the sun.”

Not only does the ash prevent the sun from shining through, it also hampers panel production. When everyone’s cars are covered in ash, that same matter is also building up on roof panels, thereby further reducing panel efficiency.

Phil Green, owner of Solar-Klean, a San Carlos-based business that cleans residential, commercial and utility solar systems, said dirty panels can cut efficiency by more than 30%. “We [cleaned] a system Friday and the homeowner gained 35% efficiency after we cleaned their panels,” Green said. “I’ve seen some gains higher than that. … The ash was unforgiving.”

Green said he’s seen a definite uptick in work orders. Deemed an “essential” business, Green and Solar-Klean have stayed working, for the most part, through the pandemic.

“The ash is reducing the efficiency, enormously, for residential and commercial projects,” Green said. “Ash, compounded with regular soiling, is increasing the soiling rate.”

Green said simply hosing off the panels from the ground can get rid of some of the soiling, but if the panels have never been cleaned, the system will need more than a rinse to really get off the dirt and grime buildup. There is also a safety element involved because to get at some panels, homeowners may find it necessary to climb on the roof to better rinse the system.

“Some folks are just not comfortable getting on the roof, so I always recommend a professional,” Green said. “If you hose them off, that’s fine. But it’s not going to remove the caked on soil. It will only remove some soiling, which in some instances, is fine.”

Green said his company uses long-handled scrubbers in which the water is sprayed up the shaft and directly into the scrubber head. In addition, Green uses a four-stage water filtration system, which he designed himself, that eliminates more than 99% of total dissolved solids (TDS) found in tap water.

“You’re definitely going to need to get more aggressive (to really clean the panels). … The only way to remove soiling effectively would be to scrub them off with a brush. … (Our system) scrubs and rinses at the same time,” Green said. “I stay away from soaps and detergents because it could, potentially, damage the panel.” Green recommends, even in the best of times, to clean your panels at least twice a year — once late in spring to best take advantage of the longer summer days, and again in late summer-early fall to be sure they’re operating at maximum efficiency for the shorter winter days.

“It depends on where you are. Different people are getting different amounts of smoke and ash,” Pariani said. “Once the sun comes back out fully, maybe the ash is blocking 20% to 40% of power production.”

Pariani also said the amount of ash buildup depends on how the panel is angled on the roof. Those solar panels that sit flat will accumulate more soiling than those mounted at an angle.

But if you’ve waited this long to clean your solar system, you might just want to wait a few more days.

“Should I wash my panels now? … Don’t go up on your roof if it’s just going to be worse tomorrow,” Pariani said.