Germany grabbed the headlines in May when it was announced that its renewable energy sources had supplied close to 90% of its energy needs. Encouraging as it may be, the event also demonstrated that the grail of zero carbon electricity is still some way off, since fluctuations in wind and solar power force Germany to keep its coal plants running at all time to compensate for the downturns.
Countries in the Arabian Peninsula are blessed with steadier irradiance. But while desert expanses serve as an exemplary environment for solar farms, they face a dilemma of their own. Based on observations made at the King Abdullah University of Science and Technology (KAUST), on a given clear day, solar panels stand to lose anywhere between 0.4 and 1.1 percent of their output due to dust accumulation, explains Georg Eitelhuber, the creator of NOMADD, a NO-water Mechanical Automated Dusting Device. During a storm, they can lose as much as 60 percent within a couple of hours. Moreover, when moisture combines with dust, it creates a hardened layer that is significantly harder to take off.
On a sunny late summer day six years ago, German born Eitelhuber watched as servicemen shuttled buckets of water around newly installed solar panels. KAUST had just finished installing a test system; management and staff had gathered for the ceremonial cutting of the ribbon when they noticed that the grimy panels were unbefitting of a photo op and called upon servicemen to wash them. “This is crazy,” Eitelhuber thought to himself, as the men emptied gallons of water in the scorching heat.
Eitelhuber, now 38, got the call to join KAUST when it was being put together back in 2009. An engineering graduate with a masters’ degree in renewable energy, he taught physics at the university and got involved in its research for solar power. There wasn’t much concern for developing an alternate method for washing solar panels given the circumstances back then: labor was cheap, and no one had imagined that the demand for clean power would mushroom as it did in the following years.
As solar projects budded in the Middle East, Eitelhuber identified a set of constraints for a suitable system that would save on water and labor: It would have to be waterless, ideally automatic, simple yet robust enough to survive the harsh climate, easy to maintain and scalable. After two years of prototyping and testing at small scale, NOMADD crystallized as a waterless, brush-based system. In early 2012, it received $200,000 in seed funding to build the full-scale prototype.
The NOMADD attaches itself and moves along the metal structure that holds the panels. This is meant to keep the system from accidentally scratching or damaging the panel. This also means that each row of panels, which are typically connected to one structure, would have a dedicated NOMADD. A NOMADD is capable of sweeping a 200-meter row in 20 minutes.
The NOMADD also uses a direct drive motor to move along the rig, which, compared to motors that use a gearbox, has a much lower point of failure.
Finally, NOMADD uses a patented proprietary mechanical brush motion system. The brush, which sweeps horizontally over the board, is tilted diagonally. This inclination allows the dust to fall down as the brush runs over the surface: the dirt brushed at the leading end falls before the trailing end gets there; consequently, less brushing needed explains Eitelhuber.
The brush also hangs at a gravity-induced angle. “Having a free angle allows any orientation of the brush and thus many effective vertical lengths of the brush. Whatever vertical length is present, the system will accommodate (…) if the track separation changes, or things are installed out of tight tolerance, or if there is sag. We avoid this problem,” concludes Eitelhuber.
How does it compare to water?
TUV Rheinland, a global provider of certification services headquartered in Germany, has been testing NOMADD’s efficiency compared to washing with water. Eitelhuber claims that over a two months testing period, the NOMADD came within half a percentage point of the results from water washing. The tests compared output involving one wash per day versus one swipe a day. While the results are virtually the same, Eitelhuber is keen to highlight that using NOMADD does away with the costs of deionization and desalination of water. The added up savings he says mean that NOMADD pays for itself within two to three years. It should be noted that the NOMADD has an expected 25-year life span.
Eitelhuber is also keen on partnering with a panel manufacturer. Doing so ensures that the company is able to fine-tune its system based on the types of panels on offer. There are 5 different manufacturers in current testing, with more under discussion.
“With our partners, we are rolling out integrated NOMADD array demonstrations at larger scale for [the last quarter of] this year.”
It isn’t very hard imagining how the NOMADD could be adapted to different industries in the future. Next time you walk around your city, take a minute to count the glass facades around you.
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