Solar Builder

SEP-OCT 2017

Solar Builder focuses on the installation/construction of solar PV systems. We cover the latest PV technology (modules, mounting, inverters, storage, BOS) and equip installers/contractors with tips and tools to make informed purchasing decisions.

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Page 21 of 55

22 S E P T E M B E R / O C TO B E R 2 0 1 7 SILICON SUCCESSORS NREL is at the forefront of renewable research and pushing innovation, and scientists there have developed a new perovskite ink with a long processing window that allows the scalable production of perovskite thin films for high-efficiency solar cells. Keller was excited about it and pointed to a chart that showed a severe uptick in efficiency compared to today's cells. The catch is perovskite solar cells have yet to move beyond the laboratory. The crystalline structure of perovskites must be carefully grown upon a substrate, which is normally done by laboratory-scale spin coating — a technology that can't be scaled to large-scale man- ufacturing at this time. "It's years out from production, but you can see the increase in efficiency is a very steep slope, and then combine that with new technologies like inks and spray ons," Keller says. Over at Penn State, researchers are testing a proto- type of a new concentrating photovoltaic (CPV ) sys- tem with embedded microtracking that can produce over 50 percent more energy per day than standard sili- con solar cells. CPV focuses sunlight onto smaller but much more efficient solar cells, like those used on satel- lites, to enable overall efficiencies of 35 to 40 percent. Current CPV systems are large — the size of billboards — and have to rotate to track the sun during the day. These systems work well in open fields with abundant space and lots of direct sun. "What we're trying to do is create a high-efficiency CPV system in the form factor of a traditional silicon solar panel," says Chris Giebink, a Charles K. Etner assis- tant professor of Electrical Engineering at Penn State. To do this, the researchers embed tiny multi-junction solar cells, roughly half a millimeter square, into a sheet of glass that slides between a pair of plastic lenslet arrays. The whole arrangement is about 2 centimeters thick and tracking is done by sliding the sheet of solar cells laterally between the lenslet array while the panel remains fixed on the roof. An entire day's worth of MODULES & TECHNOLOGY By Chris Crowell

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