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Self-cleaning solar panels could find use in the dusty environs of Arizona, the Middle East or Mars

The views expressed are those of the author and are not necessarily those of Scientific American.


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solar cell,MongoliaThe best places to collect solar energy are also some of the dustiest on Earth and beyond, a quandary that leads to inefficiencies in how well the cells are able to convert strong sunlight into renewable electricity. The solution, according to new research, is to coat solar cells with material that enables them to chase away dirt particles on their own with the help of dust-repelling electrical charges.

A dust layer of 4 grams per square meter can decrease solar power conversion by 40 percent, says Malay Mazumder, a research professor in Boston University’s Department of Electrical and Computer Engineering. To put this in perspective, dust deposition in Arizona is about 17 grams per square meter per month, and the situation is worse in many other solar-friendly sites, including the Middle East, Australia and India. Mazumder, who led the study, presented the results Sunday at the 240th National Meeting of the American Chemical Society (ACS).

The electrodynamic transparent screen developed by Mazumder and his colleagues is made by depositing a transparent, electrically sensitive material—indium tin oxide (ITO)—on glass or a clear plastic sheet covering the solar panels. When energized, the electrodes produce a traveling wave of electrostatic and dielectrophoretic forces that lift dust particles from the surface and transport them to the screen’s edges. The researchers found that 90 percent of deposited dust can be removed by the transparent screen in fewer than 60 seconds.

This works in part because many solar panels are positioned at an angle—the raised dust would simply fall off. Whereas solar panels are generally placed in dry, open spaces, the researchers are hoping to make their technique and technology also work to keep raindrops and mud from adhering to solar panel surfaces as well.

Mazumder and his colleagues had been researching the problem in 2004 for the U.S. Department of Energy when NASA came calling. The Jet Propulsion Laboratory (JPL) was looking for an answer to at least part of the dust problem it had encountered on the moon and Mars, where robots and other machinery must contend with dirt and debris that coat their sensors and solar panels. The researchers are also looking at more terrestrial applications.

Future generations of dust-proof solar panels are likely to have electrodes embedded in their glass surfaces. These electrodes, like the original filters, would be powered by the solar cell itself, so they would have to operate using very little energy. Sensors would monitor dust levels on the surface of the panel and energize the surface when dust concentration reached a critical level.

This dust-busting technology may have applications outside the renewable energy market as well, Mazumder says. Helicopters taking off and landing in dry, dusty areas could benefit from self-cleaning windshields, as could delicate lenses used in laboratories and telescopes.

The Boston University research is just the latest attempt at self-cleaning technology. With inspiration from the sacred lotus (Nelumbo nucifera), which remains pristine despite growing in muddy waters, a "revolution in self-cleaning surfaces is under way," Peter Forbes wrote in the August 2008 issue of Scientific American.

Several other approaches rely on nanotechnology. U.K.-based glass manufacturer Pilkington has since 2001 sold its ActivGlass, which features a nanocoating of transparent titania. And Michael Rubner and Robert Cohen of the Massachusetts Institute of Technology (M.I.T.) are working with industrial partners to commercialize glass surfaces (mirrors and windshields, in particular) coated with nanoparticles that resist fogging.

Image of solar panel installation in rural Mongolia courtesy of Chinneeb, via Wikimedia Commons

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  1. 1. medwhiz 12:16 pm 08/22/2010

    Imagine your car with this!?!

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  2. 2. JamesDavis 8:38 pm 08/22/2010

    If you could make that work in removing snow, it would be great in the northern states.

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  3. 3. ITgreybeard 10:52 pm 08/22/2010

    Excellent and important idea, and may coalesce with a second idea of elevating the solar cells sufficiently off the ground and with support structure clearance such that crop-raising or grazing can occur underneath. The secondary use of the land might become feasible when a significant percentage of the solar energy is blocked from evaporating ground and plant moisture, or from burning what is below. In other words, the panels can provide shade for flora and fauna.

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  4. 4. sethdayal 12:16 am 08/23/2010

    Wonder how much that will cost?

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  5. 5. Johnay 2:58 am 08/24/2010

    I imagine it would have to cost less than the cost of cleaning them manually plus the value of the unrealized power generation between cleanings, over the lifetime of the panel.

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  6. 6. NOC on Solar 11:23 am 11/6/2010

    NOC on Solar, from Clarke Clean, http://www.clarkeclean.com, or http://tinyurl.com/2czd7je, out of San Jose CA has developed an ultra thin nanotechnology that creates an anti-static, hydrophobic surface on solar panels for a self cleaning solar panel effect. For pennies per square foot, this technology can be applied to panels, once every 3-5 years (depending on your specific environment). Because it is anti-static, it allows dust, pollen, dirt to rest on the highest surface of the solar panel glass so that when Mother Nature steps in with rain, snow, wind, the debris is easily removed. As an owner of panels, best practice is to have a monitoring system on your array. This will tell you when your panels need to be cleaned. If they are treates with NOC on Solar, cleanings will be fewer and far between and when you do need to clean, cleaning will be faster.

    Europe long ago embraced the fact that you have to clean solar panels. In the US we have been sold the “Emperor’s New Clothes (Hans Christian Andersen)”. We’ve been told that solar panels don’t need maintenance, when in fact they do. Would you park your $90,000 Porsche outside and expect it to remain clean? Of course not! The windshield would need to be washed so that you could see thru it. Solar Panel glass works the same way. It needs to be cleaned because it gets dirty and light transmittance is reduced just as visibility is reduced on a windshield. If light transmittance is reduced your panels aren’t working.

    The difference with NOC on Solar is that we are the thinnest hydrophobic technology on the market. A hydrophobic surface can be created with other products (wax, oils, polymers) but because of their chemical make up, they actually impede light transmittance. If you rubbed a layer of oil on your windshield you would have a hydrophobic windshield, one that is not long lasting, and one that does not provide high visibility. Treating your solar panel with a wax or oil has the same negative effect on light transmittance.

    In a nutshell, you want to treat your panels with the thinnest solution, a long-lasting solution, to create a high transmittance, hydrophobic solar panel. NOC on Solar is the only one on the market that does all this.

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  7. 7. NOC on Solar 11:25 am 11/6/2010

    And, we have a product that DOES work with cars as well, NOC on Glass Visual Enhancement System, for purchase here:
    http://www.clarkeclean.com/v2/index.php?option=com_rokquickcart&view=rokquickcart&Itemid=189

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  8. 8. anumakonda 8:44 am 12/24/2012

    Good article.Dust is a big problem in developing countries for wider use of solar PV. Water is scarce to clean it in desert regions like Rajasthan in India. Cleaning manually in hot summer is time consuming and costly.

    Why not Scientists develop non sticky dust glass ? A glass where the dust won’t stick to the surface but slides with a periodic jerk. In Rajasthan,India there is ambitious Solar PV Programme for large scale power. Dust storms in Rajasthan during summer are common which are carried to far way places.

    The Loo is a strong, hot and dry summer afternoon wind from the west which blows over the western Indo-Gangetic Plain region of North India and Pakistan. It is especially strong in the months of May and June. Due to its very high temperatures (45 °C–50 °C or 115°F-120°F), exposure to it often leads to fatal heat strokes.
    Dr.A.Jagadeesh Nellore(AP),India
    E-mail: anumakonda.jagadeesh@gmail.com

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