An extremely interesting bit of technology here
http://www.gizmag.com/high-energy-density-supercapacitor/37075/$this->bbcode_second_pass_quote('', 'T')he hybrid supercapacitor is reportedly six times as energy-dense as a commercially available supercapacitor and packs nearly as much energy per unit volume as a lead-acid battery.
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Like other supercapacitors, their device charges and discharges very quickly and lasts more than 10,000 recharge cycles. But, according the scientists, their invention also stores six times more energy than a conventional supercapacitor, holding more than twice as much charge as a typical thin-film lithium battery in one fifth the thickness of a sheet of paper.
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Supercapacitors are usually stacked on top of each other and packaged into a single unit, but the researchers have been able to take advantage of the thinness of their device by integrating it inside a solar cell array. In this application, it was found that the supercapacitor could quickly store electrical charge generated by a solar cell during the day, hold the charge until evening, and then power an LED overnight.
This is just one of many potential uses for the technology.
But of course, the difficulty is getting from the lab to commercial production (see algae biofuels etc).
