Self-cleaning solar panel coating optimizes energy collection, reduces costs

Jan 30, 2014 by Katie Elyce Jones
Solar power reflectors collect dust and sand, reducing their energy efficiency—a challenge ORNL researchers are tackling by developing a low-cost, anti-soiling coating.

Soiling—the accumulation of dust and sand—on solar power reflectors and photovoltaic cells is one of the main efficiency drags for solar power plants, capable of reducing reflectivity up to 50 percent in 14 days. Though plants can perform manual cleaning and brushing with deionized water and detergent, this labor-intensive routine significantly raises operating and maintenance costs (O&M), which is reflected in the cost of solar energy for consumers.

Under the sponsorship of the Department of Energy's Energy Efficiency and Renewable Energy SunShot Concentrating Solar Power Program, Oak Ridge National Laboratory is developing a low-cost, transparent, anti-soiling (or self-cleaning) coating for solar reflectors to optimize energy efficiency while lowering O&M costs and avoiding negative environmental impacts.

The coating—which is being designed by members of the Energy and Transportation Science Division, including Scott Hunter, Bart Smith, George Polyzos, and Daniel Schaeffer—is based on a superhydrophobic coating technology developed at ORNL that has been shown to effectively repel water, viscous liquids, and most solid particles. Unlike other superhydrophobic approaches that employ high-cost vacuum deposition and chemical etching to nano-engineer desired surfaces, ORNL's coatings are deposited by conventional painting and spraying methods using a mixture of organics and particles. In addition to being low-cost, these methods can be deployed easily in the field during repairs and retro-fitting.

There are, however, challenges to the successful development of such a transparent, anti-soiling coating. First, the coating must be very superhydrophobic to minimize the need for occasional cleaning, and it must have minimal (or even zero) effect on the transmission and scattering of solar radiation between the wavelengths of 250 to 3,000 nm. To meet these requirements, the coating must be no more than a few hundred nanometers thick, and the embedded particles must be considerably smaller. The extremely thin coating must also be durable under environmental exposure, including UV radiation and sand erosion, and be compliant according to the US Environmental Protection Agency Clean Air Act emission standards—which limits the selection and combination of particles and organics that can be used effectively.

During the first year of this project, researchers experimented with a variety of Clean Air Act–compliant organics and silica particles of different sizes. They arrived at a particular formulation combining organic compounds with silica particles, which are dispersed in two sizes to enhance area coverage of particles within the coating.

The anti-soiling coating exhibited excellent superhydrophobic properties, losing less than 0.3% of transparency over the entire solar radiation wavelength range. When exposed to several hundred hours of accelerated UV radiation and one hundred hours of salt fog exposure, the coating exhibited no degradation in superhydrophobic or optical transmission properties. Also, when glass slides with the anti-soiling coating were exposed to sand and in a custom-made wind tunnel, the did not adhere to the coated surface of the slides—showing great potential for its use in harsh environmental conditions.

In addition to anti-soiling coating for solar applications, ORNL researchers are using their superhydrophobicity expertise to develop anti-soiling cool roof coatings, as well as anti-icing and anti-condensation coatings for air conditioning and evaporative cooling applications, respectively. Going into 2014, the project has been funded for another year and will optimize the coating and perform accelerated exposure tests, as well as begin development on a scalable technique and perform small-scale field testing.

Explore further: One step closer to low cost solar cells

Related Stories

A new anti-frost and anti-fog coating for glass

Feb 27, 2013

In an advance toward glass that remains clear under the harshest of conditions, scientists are reporting development of a new water-repellant coating that resists both fogging and frosting. Their research ...

One step closer to low cost solar cells

Jan 27, 2014

The dwindling resources for conventional energy sources make renewable energy an exciting and increasingly important avenue of research. However, even seemingly new and green forms of energy production, like ...

Solar cells utilize thermal radiation

Nov 04, 2013

Thermal radiation from the sun is largely lost on most silicon solar cells. Up-converters transform the infrared radiation into usable light, however. Researchers have now for the first time successfully ...

Recommended for you

Obama launches measures to support solar energy in US

Apr 17, 2014

The White House Thursday announced a series of measures aimed at increasing solar energy production in the United States, particularly by encouraging the installation of solar panels in public spaces.

Tailored approach key to cookstove uptake

Apr 17, 2014

Worldwide, programs aiming to give safe, efficient cooking stoves to people in developing countries haven't had complete success—and local research has looked into why.

User comments : 0

More news stories

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

A homemade solar lamp for developing countries

(Phys.org) —The solar lamp developed by the start-up LEDsafari is a more effective, safer, and less expensive form of illumination than the traditional oil lamp currently used by more than one billion people ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...