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How do Solar Panels Work?
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Solar panels are made of photovoltaic cells which convert sunlight into energy by grabbing photons from the sun to knock loose electrons. Photovoltaic cells are usually made of a sandwich of silicon wafers: one is positively charged, and the other negative, which creates an electric current. Phosphorus and boron are added to the top and bottom wafers to get the electrons moving. The tech behind solar cells isn't new: the first one was patented in 1888 and around 90 years later RCA Laboratories come out with the silicon version, although, it was based on the same basic concept. The solar cells in the 1970s were only capable of converting around one percent of solar power into usable electricity. Solar panels used today aren't significantly more efficient: most solar panels are only able to convert 20 percent of the solar energy they capture. By comparison, fossil fuel-generated electricity is about 40-percent efficient.
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Over a decade ago, the Defense Advanced Research Projects Agency (DARPA) started an initiative to create 50-percent efficiency in solar panels, and we're getting pretty close. In 2007, researchers from the University of Delaware announced the creation of a cell with 42.8-percent efficiency by separating sunlight into three different energy bins of high, medium and low, and directing them onto cells of various light-sensitive materials to cover the solar spectrum. And in 2014, Australian researchers announced they had created a 40-percent efficient panel in a paper published in the journal Progress in Photovoltaics. It boosted efficiency by including a filter that captured light bandwidths usually wasted by other models. The future of solar panels may not be with silicon-based panels. Research into a different material called perovskite has taken off over the past few years. Perovskite is a mineral with a crystalline structure made out of calcium and titanium that's easily synthesized in a lab. Perovskite's structure makes it especially good for solar applications, and research seems to be moving much faster compared to silicon. In the six years since it was first used, its efficiency has jumped from 3.8 percent to a certified 20.1 percent, putting it on par with conventional silicon panels. While perovskite panels aren't on the market yet, some start-ups promise to make them commercially available by 2017, so it's definitely something to keep an eye on.
UNSW researchers convert sunlight to electricity with over 40 percent efficiency (Eurekalert)
"UNSW Australia's solar researchers have converted over 40% of the sunlight hitting a solar system into electricity, the highest efficiency ever reported. The record efficiency was achieved in outdoor tests in Sydney, before being independently confirmed by the National Renewable Energy Laboratory (NREL) at their outdoor test facility in the United States."
DARPA pushes for 50% efficient photovoltaics to power soldiers' small tools (Spie)
"Photovoltaic solar cells already provide the armed forces with portable power supplies. But with their present low efficiency, a 60W laptop recharger would require more than 0.37m2 of solar cells."