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Nano-Crystal Concentrators Could Make Incandescent Bulbs More Efficient Than LEDs

ByTim De ChantNOVA NextNOVA Next

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A bit of nanotech could soon modernize Thomas Edison’s most famous invention. By crafting photonic crystals to sandwich the traditional tungsten filament, electrical engineers have boosted the light-emitting efficiency of the humble incandescent by 6.6%.

Notoriously inefficient incandescent bulbs may soon surpass the most miserly LEDs if engineers are able to goose the process further, the researchers said. While LEDs are up to 20% efficient, scientists think this process could spawn bulbs that are up to 40% efficient.

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A zig-zagging tungsten wire powers the new photonic crystal bulb.

Here’s Robert Service, reporting for Science:

“This is beautiful work,” says Shawn-Yu Lin, an electrical engineer and optics expert at the Rensselaer Polytechnic Institute in Troy, New York. He and others note that there is plenty of room for further improving the mirrors, which could ultimately push the efficiency of the bulbs well beyond what is possible with today’s lighting technologies. And because lighting consumes 11% of all electricity in the United States, any such improvement could dramatically lower energy use, and, by extension, the carbon dioxide emissions that contribute to climate change.

While the MIT engineers slightly modified the traditional tungsten wire by folding it back and forth instead of winding it in a coil, the photonic crystal they developed is the key advance. Visible light photons pass through the crystal, which reflects infrared radiation back at its source. The nanoscale material is made of successive layers of tantalum oxide and silicon dioxide deposited on thin layers of glass.

By sandwiching the tungsten wire between two plates of the material, the scientists were able to recycle a fraction of the excess heat to produce more light photons. Heat loss is the biggest sap on efficiency for traditional incandescent bulbs. The new bulbs still have a ways to go before catching up to LEDs, but scientists unaffiliated with the work think photonic crystal bulbs could not only be more efficient, but also relatively easy to mass produce.

Photo credit: Marin Soljačić/MIT