Self-cleaning surfaces aren’t a particularly novel idea, and self-cleaning glass commercial products made by companies, such as Saint Gobain, have been around in various products for at least five years – but at a premium price. These technologies use a TiO2 coating to photocatalyze organic dust that is then washed away by humidity and rain. However, for some dusty (e.g., nonorganic) materials, even this self-cleaning system doesn’t work.
The cost and performance problems with these existing systems are unfortunate, especially when it comes to photovoltaic solar panels and mirrors, particularly when one considers that many utility-scale solar energy systems are being located in desert areas that are prone to large amounts of non-organic dust. In some of these regions, even dragging out a hose or water truck to rinse off PV panels and mirrors is not practical nor economically feasible.
The effects of the dust on these solar energy system are tangible. “A dust layer of one-seventh of an ounce per square yard decreases solar power conversion by 40 percent,” explains MIT visiting professor Malay K. Mazumder. “In Arizona, dust is deposited each month at about four times that amount. Deposition rates are even higher in the Middle East, Australia and India.”
Mazumder knows something about dust. He has worked with NASA on a similar but more difficult problem: Extraterrestrial dust. When the problem is dust on surfaces somewhere lacking Earth’s atmosphere and weather – say, Mars or the moon – terrestrial technology just won’t cut it. Lunar dust was nasty stuff for astronauts to deal with and is described as tiny pieces, sharp and interlocking pieces of glass or coral that is everywhere on the lunar surface.
According to NASA, Mars dust isn’t quite so bad, but still a big problem:
Dust is also ubiquitous on Mars, although Mars dust is probably not as sharp as moon dust. Weathering smooths the edges. Nevertheless, Martian dust storms whip these particles 50 m/s (100+ mph), scouring and wearing every exposed surface. As the rovers Spirit and Opportunity have revealed, Mars dust (like moon dust) is probably electrically charged. It clings to solar panels, blocks sunlight and reduces the amount of power that can be generated for a surface mission.
NASA knew that dust interference with solar panel function could be catastrophic for Mars missions. Working with the agency, Mazumder and other researchers developed a novel self-cleaning solar panel technology for use in lunar and Mars missions.
Now, Mazumder says the time has come to apply the same technology on earth. “Solar panels powering rovers and future manned and robotic [NASA] missions must not succumb to dust deposition. But neither should the solar panels here on Earth,” he says
Mazumder describes the technology he has in mind as having three parts. The first part is thin layer of transparent, electrically sensitive material on the glass or plastic covering of a solar panel. The second part is a sensor to monitor dust levels on the surface of the panel. The third part is a system to send a brief electric charges over the surface of the panel. Because, like the stuff on moon and Mars, most Earth dust carries an electrical charge, delivering alternating electric fields acting through the thin layer on the panel dislodges, carries and deposits dust particles off and away from surfaces.
According to a news release, Mazumder says a two-minute process removes about 90 percent of the dust deposited on a solar panel. Further, his approach requires only a small amount of electric power, which can easily be supplied by the panel.