Your Second “Skin”?

Maybe you can take it with you, after all.

One day soon you may be able to wear solar like a patch of solidarity on your sleeve. It sounds like the setting of some utopian novel, an almost too-obvious sci-fi fantasy - flexible solar “skin” efficient enough to power everything from ubiquitous personal devices such as cell phones, laptops and mp3 players to larger hallmarks of technology such as hybrid cars and generators. A research team led by physicist Steven Novack at the Idaho National Laboratory has recently developed a technique that could allow for the practical application of small, flexible solar “stamps” comprised of infrared-converting nanoantennae no more than a few billionths of a meter in diameter.

What makes this technology so unique is that it utilizes a wavelength of light that up until recently had been considered too weak for solar technology. Most solar cells harness shorter wavelengths of electromagnetic radiation such as visible and ultraviolet light because these wavelengths are powerful enough to knock individual electrons loose from atoms, thereby generating direct electrical current. Too weak for this process, infrared light is, however, strong enough to induce electrons to vibrate. If these electrons are arranged in flexible arrays such as in crystalline lattices built from highly conductive metals, these vibrations would be powerful enough to create an alternating current (though a high-frequency rectifier - not yet developed - would be required for conversion to direct current). More significantly, by utilizing clever design principles, such nanoantennae have been shown to convert over 90% of available infrared, more than double the conversion efficiency of typical solar cells.

Referring to this breakthrough as a “solar” technology might be misleading, however, since it relies on collecting heat that rebounds off the earth’s surface rather than sunlight itself. Since the earth continually emits this radiation, this distinction gives the process yet another advantage over conventional solar in that it would be able to generate energy under conditions averse to conventional solar panels such as nightfall or cloud cover, even potentially recycling the waste heat from engine exhaust and other sources. This potential raises a possible secondary benefit of this technology: it could be used to keep computers and other electronic devices from overheating.


The tiny structures are comprised of miniature gold spirals embedded in polyethylene plastic, which can then be “stamped by the billion” onto plastic sheets and applied to virtually any surface. Novack even envisions the development of double-sided sheets tuned to convert radiation of differing wavelengths, simultaneously tapping multiple regions of the sun’s energy spectrum.

Sources: “Feeling the Heat”, The Economist; “Nanoantennas envisioned as possible replacement for solar cells”, TG Daily; “Flexible nanoantenna arrays capture abundant solar energy”, eScience news; “Solar Skin: A Sheet of Tiny Antennas”, Solar Feeds; “Sheets of Tiny Antennae Harvest Sunlight and Heat”, Discovery News;“Solar Nantenna Electromagnetic Collectors”, Novack, et al. (technical paper presented at 2nd International Conference on Energy Sustainability).


Posted on Monday, September 29th, 2008 at 9:52 am | Tagged in Energy, Photovoltaics, Renewables, Technology | posted by Bill

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