Skip to content

Air Pollution Casts Shadow over Solar Energy Production

July 1, 2017

By Paul Homewood


h/t Jo Nova



dirty solar panels with Michael Bergin

Duke engineering professor Michael Bergin (left) stands with Indian Institute of Technology-Gandhinagar colleague Chinmay Ghoroi (right) next to that university’s extremely dusty solar panel array.


Global solar energy production is taking a major hit due to air pollution and dust.

According to a new study, airborne particles and their accumulation on solar cells are cutting energy output by more than 25 percent in certain parts of the world. The regions hardest hit are also those investing the most in solar energy installations: China, India and the Arabian Peninsula.

The study appears online June 23 in Environmental Science & Technology Letters.

“My colleagues in India were showing off some of their rooftop solar installations, and I was blown away by how dirty the panels were,” said Michael Bergin, professor of civil and environmental engineering at Duke University and lead author of the study. “I thought the dirt had to affect their efficiencies, but there weren’t any studies out there estimating the losses. So we put together a comprehensive model to do just that.”

With colleagues at the Indian Institute of Technology-Gandhinagar and the University of Wisconsin at Madison, Bergin measured the decrease in solar energy gathered by the IITGN’s solar panels as they became dirtier over time. The data showed a 50-percent jump in efficiency each time the panels were cleaned after being left alone for several weeks.

The researchers also sampled the grime to analyze its composition, revealing that 92 percent was dust while the remaining fraction was composed of carbon and ion pollutants from human activity. While this may sound like a small amount, light is blocked more efficiently by smaller man-made particles than by natural dust. As a result, the human contributions to energy loss are much greater than those from dust, making the two sources roughly equal antagonists in this case.

“The manmade particles are also small and sticky, making them much more difficult to clean off,” said Bergin. “You might think you could just clean the solar panels more often, but the more you clean them, the higher your risk of damaging them.”

Having previously analyzed pollutants discoloring India’s Taj Mahal, Bergin already had a good idea of how these different particles react to sunlight. Using his earlier work as a base, he created an equation that accurately estimates the amount of sunlight blocked by different compositions of solar panel dust and pollution buildup.

But grimy buildup on solar panels isn’t the only thing blocking sunlight—the ambient particles in the air also have a screening effect.

For that half of the sun-blocking equation, Bergin turned to Drew Shindell, professor of climate sciences at Duke and an expert in using the NASA GISS Global Climate Model.

Because the climate model already accounts for the amount of the sun’s energy blocked by different types of airborne particles, it was not a stretch to estimate the particles’ effects on solar energy. The NASA model also estimates the amount of particulate matter deposited on surfaces worldwide, providing a basis for Bergin’s equation to calculate how much sunlight would be blocked by accumulated dust and pollution.

The resulting calculations estimate the total loss of solar energy production in every part of the world. While the United States has relatively little migratory dust, more arid regions such as the Arabian Peninsula, Northern India and Eastern China are looking at heavy losses — 17 to 25 percent or more, assuming monthly cleanings. If cleanings take place every two months, those numbers jump to 25 or 35 percent.

There are, of course, multiple variables that affect solar power production both on a local and regional level. For example, a large construction zone can cause a swift buildup of dust on a nearby solar array.

The Arabian Peninsula loses much more solar power to dust than it does manmade pollutants, Bergin said. But the reverse is true for regions of China, and regions of India are not far behind.

“China is already looking at tens of billions of dollars being lost each year, with more than 80 percent of that coming from losses due to pollution,” said Bergin. “With the explosion of renewables taking place in China and their recent commitment to expanding their solar power capacity, that number is only going to go up.”

“We always knew these pollutants were bad for human health and climate change, but now we’ve shown how bad they are for solar energy as well,” continued Bergin. “It’s yet another reason for policymakers worldwide to adopt emissions controls.”


It should be a no brainer, but the sunniest regions also tend to be the driest, and hence dustiest.

I hear that India is experimenting with robot cleaners, but either way, cleaning will add to the cost.

Jo Nova also makes the important point that cleaning solar panels also risks damaging them.

  1. Joe Public permalink
    July 1, 2017 10:47 am

    Surely the owners of the panels in that image would have been aware of declining generation? Particularly as they’re a university.

    It’s strange that the ‘white’ satellite dish in the background appears not to have been affected so badly!

  2. martinbrumby permalink
    July 1, 2017 10:50 am

    I’m shocked.
    Shocked, I tell you!

    Who would have imagined such a way-out, unforseeable thing?

    Dust reducing solar panel efficiency? Some mistake, surely?

    And as someone who has wandered some of the backstreets in Varanasi, hard to imagine dirt being a problem?!?

    I wonder how dead dogs, piles of litter & faeces affects panel output?

    Not for nothing is India a country with a space programme and with some of the brightest and best engineers in the world. But out of this elite’s little bubble, no-one could accuse the Indians of being as obsessive about cleanliness as the Swiss.

    I think that whoever develops the promised “robot cleaner” will clean up. In more ways than one.

    • dave permalink
      July 1, 2017 10:56 am

      “…robot cleaners…”

      Taking their place with the other Untouchables?

    • StewGreen permalink
      July 1, 2017 2:40 pm

      Varanasi is filled with burning ghats
      Where bodies are burnt on huge log piles.

  3. gallopingcamel permalink
    July 1, 2017 12:56 pm

    Even though it rains frequently here in Florida it is a major chore keeping our CSP and PV installations clean. That is the main reason for labor costs being high for solar power:

    Labor cost, $/MWh vs. generating technology:
    Gas powered steamer……..$0.63
    Combined cycle………………$1.50 (X 2.4)
    Nuclear………………………….$14.95 (X 23.7)
    Solar……………………………..$24.55 (X 39.0)

    So if you want to create (useless) jobs “Go Nuclear” or “Go Solar”. Here is a link that explains:

  4. July 1, 2017 2:01 pm

    Solar panel efficiency decreases above about 25C, which is relevant to India and Arabian regions as well as many other parts of the world.

    • Robert Christopher permalink
      July 1, 2017 10:03 pm

      ‘Solar panel efficiency decreases above about 25C, which is relevant to’ anywhere there is a lot of sunshine – which is where we think solar will do well! 🙂

  5. July 1, 2017 3:09 pm

    Er… snow? leaves? Film of water?

  6. tom0mason permalink
    July 1, 2017 4:12 pm

    “My colleagues in India were showing off some of their rooftop solar installations, and I was blown away by how dirty the panels were,” said Michael Bergin, professor of civil and environmental engineering at Duke University and lead author of the study. “I thought the dirt had to affect their efficiencies, but there weren’t any studies out there estimating the losses. So we put together a comprehensive model to do just that.”

    Yet again new age science and technology walks into a place and are upset that the local conditions do not meet expectations.
    When will these foolish people do some preliminary work to find out before they go ahead installing their equipment. New age waste of money because these ‘scientist and technologists’, as is normal these days, assume to much and do too little research in the field.

    • dave permalink
      July 2, 2017 8:15 am

      “…these ‘scientists and technologists’…”

      Remind ME of the Scotty in James Thurber’s fable. For those who do not know it…

      The Scotty Who Knew Too Much

      Several summers ago there was a Scotty who went to the country for a visit. He decided that all the farm dogs were cowards, because they were afraid of a certain animal who had a white stripe down its back, ‘You are a pussy-cat and I can lick you’ said the Scotty to the farm dog who lived in the house where the Scotty was visiting. ‘I can lick the little animal with the white stripe, too. Show him to me.’ ‘Don’t you want to ask any questions about him?’ said the farm dog. ‘Naw,’ said the Scotty,’YOU ask the questions.’

      So the farm dog took the Scotty into the woods and showed him the white-striped animal and the Scotty closed in on him, growling and slashing. It was all over in a moment and the Scotty lay on his back. When he came to, the farm dog said, ‘What happened?’ ‘He threw vitriol,’ said the Scotty, ‘but he never laid a glove on me.’

      A few days later the farm dog told the Scotty there was another animal all the farm dogs were afraid of, ‘Lead me to him,’ said the Scotty. ‘I can lick anything that doesn’t wear horseshoes.’ ‘Don’t you want to ask any questions about him?’ said the farm dog. ‘Naw,’ said the Scotty. ‘Just show me where he hangs out.’ So the farm dog led him to a place in the woods and pointed out the little animal when he came along. ‘A clown,’ said the Scotty, ‘A push-over,’ and he closed in, leading with his left and exhibiting some mighty fancy footwork. In less than a second the Scotty was on his back, and when he woke up the farm dog was pulling quills out of him. ‘What happened,’ said the farm dog. ‘He pulled a knife on me,’ said the Scotty, but at least I have learned how you fight out here in the country, and now I am going to beat YOU up.’ So he closed in on the farm dog, holding his nose with one front paw to ward off the vitriol and covering his eyes with the other front paw to keep out the knives. The Scotty couldn’t see his opponent and he couldn’t smell his opponent and he was so badly beaten that he had to be taken back to the city and put in a nursing home.


  7. Broadlands permalink
    July 1, 2017 5:48 pm

    And, according to the US EPA, it’s all that CO2 that is the REAL pollutant? Maybe that’s why those solar panels on the Martian rovers aren’t covered in dust?

  8. July 1, 2017 6:39 pm

    Instead of building robots, why not just employ people as panel cleaners – there are quite a lot of people in India. We should go from the Tiffin-Wallah to the Solar-Wallah.

  9. July 1, 2017 10:51 pm

    Reblogged this on Climate Collections.

  10. John F. Hultquist permalink
    July 2, 2017 2:02 am

    “… cleaning solar panels also risks damaging them …”

    For eyeglasses we pay extra for a treatment called Scratch-Resistant Lenses.
    These come with directions on how to keep from damaging them.
    Note they are “resistant to”, not scratch proof.

    Also, try cleaning these:
    clean these and break your neck

  11. Ken permalink
    July 2, 2017 2:03 am

    It’s worse than we thought.

  12. July 2, 2017 2:54 am

    They make some very good propane powered water pressure cleaners for solar panels.

Comments are closed.

%d bloggers like this: