Materials

Ultra-thin coating makes for self-cleaning solar panels

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Scientists in Germany have developed a new coating for solar panels that can make them self-cleaning
Scientists in Germany have developed a new coating for solar panels that can make them self-cleaning
A sample of the new self-cleaning glass coating, showing its water-repelling phase (top) and water-attracting phase (bottom)
Fraunhofer FEP

Solar panels can’t operate efficiently if they’re caked in dirt, but cleaning them regularly can become a time-consuming process. Engineers in Germany have now developed an ultra-thin coating that can make solar panels and other surfaces self-cleaning.

Solar is the biggest source of renewable energy, and it’s growing quickly. But as you could imagine, it’s not feasible to send someone out with a squeegee to clean millions of solar panels in each park. Having them clean themselves would be ideal – and now researchers at the Fraunhofer Institute in Germany have made strides towards that concept.

The team created a coating that changes its response to water based on the time of day, allowing it to shed any buildup of dust and dirt fairly quickly. The key ingredient is titanium oxide, which in its normal state repels water, forming drops that easily roll off. When the titanium oxide is exposed to UV light, however, it changes state to become highly water-attracting, which keeps the surface wet with a thin layer of water.

In effect, this makes for a self-cleaning coating. Dust or dirt that accumulates during the day can’t stick to the surface because the thin layer of water keeps it off, then at night the water beads up into droplets that easily roll off, taking the dirt with it. As a bonus, when the titanium oxide is activated with UV light it destroys organic molecules, effectively sterilizing the surface.

A sample of the new self-cleaning glass coating, showing its water-repelling phase (top) and water-attracting phase (bottom)
Fraunhofer FEP

The general idea has been implemented in self-cleaning glass previously, but it usually involves either a water-repelling or water-attracting mechanism, not both. Better yet, the Fraunhofer team’s new coating is designed to be mass produced roll-to-roll, and could be applied to existing solar cells, windows and other surfaces.

In tests, the team used a pilot plant to produce rolls of thin glass 30 cm (11.8 in) wide, 20 m (65.6 ft) long and only 100 micrometers thick, with the titanium oxide coating up to 150 nanometers thick.

There are of course hurdles still to overcome. The team says the thin glass is still very fragile, and vulnerable to heat. Future work will focus on improving this, investigating the possibility of using polymer films instead.

The research will be presented at the BAU trade fair in Munich in April.

Source: Fraunhofer Institute

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7 comments
pmshah
A few years ago one German glass panel manufacturer studied the Lotus leaves that naturally just do not get dirty. They studied the surface texture and replicated that exact texture for outer side of glass panels used in high rise buildings. The result was the window cleaners were made redundant. May be same technique could be used on glass panels covering the solar cells and avoid using any other chemical at all !
Primecordial
What happens during sub-zero temperatures? Something that sheds snow/ice would be more useful for those installations where it is below freezing for 5 months of the year.
P51d007
Giant windshield wipers?
GregVoevodsky
Does this work on Mars? It's sad that NASA can't figure out a way to clean solar panels – built in obsolesce for a new rover. They should do it right and extend it's life. I like this idea, along with compressed air or solar panel wipers.
deepdiamond
They make a treatment for auto glass to keep the water flowing off. It is available at most automotive part stores.
Karmudjun
Michael - nice article, and another incremental improvement in traditional PV technology. Keeping the solar absorption surface clean is essential for optimizing the PV cells solar absorption - but keeping the panels in the optimal temperature currently has the best effect on optimizing the PV output. Of course, it could be a "chicken and the egg' situation. Amazing research in prototypes of PV cells bonded above a solar thermal collector in university solar competitions - when the hydrothermal system is regulated to maintain the photovoltaic collector at the optimal temperature, your efficiency of the collected energy improves. Is this system scalable - I keep reading New Atlas waiting to see production models of dual function solar collection systems but haven't seen anything yet. Keep the incremental improvement papers coming Michael - one day we will be thrilled with the results!
TpPa
it should would be a major factor in making more money & saving money at the same time.