For organizations in California with solar PV systems, “soiling” can be a constant battle.  Solar panels only work at peak efficiency when their surface area is clean and free of build-up, allowing full absorption of solar irradiance. Soiling buildup reduces the amount of power generated and thus substantially reduces the financial performance of these systems. In addition to dirt, pollen, agricultural dust, and bird droppings, forest fire ash adds to the list of harmful debris that can impact the productivity of solar panels.

Wildfire ash has been an increasing challenge in recent years.  In 2020 alone, Cal Fire reports that there have been over 8,000 wildfires that have burned over 3.7 million acres in California.  Since August 15th, when fire activity increased across the Western U.S., active fires have been an all too normal occurrence.

Analysis from an active solar PV system in Sonoma County showed a 58% drop in solar energy production when comparing the week of September 8 – 12 with the period of September 1-5 the week prior.  This substantial drop in energy production can be seen in the graphs below.

Graph showing lower solar production due to wildfire ash

Graph showing normal solar production

Wildfires are dangerous for several reasons.  In addition to the obvious issues of loss of life along and property, these fires release greenhouse gasses, soot and other particles into the atmosphere.  The wildfire produced particles do not reflect light, rather, they absorb light and often produce hazy conditions that create an “orange sky” effect, as recently seen in Northern California.  Particles in the atmosphere reduce the intensity of the sunlight and thus reduce the power generation of solar panels.

Ash particles in the atmosphere are different from normal cloud conditions.  In partly cloudy conditions, solar PV system production can drop by 10% to 25% depending on how long a system remains under cloud coverage.

This Sonoma County example is a school facility where, like most schools in the State, budgets are tight due to the impacts of COVID-19. During the first two weeks of September 2020, this school has experienced a loss in solar production of over 66% primarily due to wildfire ash debris and the related environmental haze.  This loss in solar production equates to the loss of valuable projected savings that will not be realized during this month.

To achieve, peak financial performance, most solar PV systems should be washed at least once or twice annually. Organizations impacted by wildfires or those in heavy agricultural areas will likely see additional benefit from their panels being washed immediately after heavy fire ash periods or after dust producing agricultural harvest periods.

Responsibility for cleaning of panel arrays falls to the system owner. If your organization owns your solar system, we encourage you to evaluate the cost-benefit of washing your panels; and establish the proper protocols to ensure that your systems are providing peak financial benefits.  Organizations with solar PPAs or leases should not attempt to clean soiled panels themselves, as this may risk violating the terms of the solar agreement. Solar PPA and lease customers should not assume that their providers are equally incentivized to conduct panel washings. Solar customers are sometimes surprised to find out that their solar systems have gone years without a single wash.

The buildup of ash/soiling on your solar panels could cause long term damage and void your warranty. Reach out to us to find out the impact to your solar panels and get a performance comparison assessment with similar solar PV systems in your area. If you are interested in comprehensive asset management for your owned or PPA managed solar PV system, please contact Phil Villagomez of TerraVerde Energy at phil@terraverde.energy .

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