Dust: it’s enemy number one for solar photovoltaic panels (PV) in the sunny, warm areas with the most potential for solar power. That’sbecause it takes less than a tablespoon of dust per square meter toreduce the electrical output of a typical PV panel by 40 percent.
“In Arizona,” says Professor Malay Mazumder of Boston University,“dust is deposited each month at about four times that amount.Deposition rates are even higher in the Middle East, Australia andIndia.”
Few home owners in the Southwest want to climb up on their roofseveral times a month to hose off the light-blocking dust. Utility-sized PV installations are hand-washed or use mechanical sprayers — buteither way is costly. In the desert there’s the additional problem ofincreasing water use in an arid land — one that is likely to grow drieras the climate changes.
The solution to this problem (or at least a solution) comes from the U.S. space program — which is fitting, giventhat PV panels were pioneered by NASA in the 1960s and ’70s to powersatellites and, most recently, rovers on Mars.
At the 240th National Meeting of the American Chemical Society (ACS) last weekend, Dr. Mazumder reported on advances in bringing thesame technology used to clean dust from the Mars rovers down to Earth.
The trick to cleaning PV panels without water is to incorporate anElectrodynamic Screen (EDS) like the one on the Mars rovers. An EDS is a thin, electrically sensitive layer on the surface of the panel. Whenenough dust accumulates on the EDS, a sensor triggers a small electricpulse which repels the dust.
NASA first developed the idea for an “electric curtain” in 1967. In 2003, NASA’s Electrostatics and Surface Physics Laboratory (ESPL) worked with researchers at the University of Arkansas at LittleRock (where Dr. Mazumder then taught) to design and build an EDS for the Mars rovers. (The ESPL website has a short video showing test modules working under space conditions.)
Mazumder reports that the EDS developed by his lab can remove 90percent of dust particles from a square meter of PV paneling in twominutes using just 10 watts.
Mazunder said the Earth-version of the EDS should be commercially available within a year.
Not all PV panels may require EDS technology, says Alan Bernheimer, a spokesman for First Solar, the world’s largest manufacturer of thin-film PV.
“Theoretically it would be possible to apply this technology to thinfilm solar modules,” Bernheimer wrote in an Email. “First Solar’sadvanced thin film technology, however, is productive in diffuse andlower light conditions, such as those caused by dust.”
While even thin-film panels eventually need to be cleaned, Bernheimer said First Solar has no plans to adopt the EDS technology.
For traditional silicon-based PV manufacturers, however, thedevelopment of waterless cleaning technologies is likely to be seen as a milestone on the road to renewable, sustainable, energy.
You can read a 2008 paper about EDS technology co-written by Prof. Mazumder here (PDF).