The incandescent light bulb, maligned as an epic waster of energy, could be revived with a change in design that boosts their efficiency, university researchers said.
In a news release, the Massachusetts Institute of Technology said researchers at MIT and Purdue University collaborated on a new design that could prove to be more efficient than either fluorescent lamps or LEDs.
The new bulb uses a metal filament, just like a conventional light bulb. But instead of allowing radiant energy to escape, as it does in a conventional bulb, it’s reflected back to the filament where it’s re-absorbed and re-emitted as visible light. MIT described these “secondary structures” surrounding the filament as a type of photonic crystal composed of abundant materials and made with conventional material-deposition technology.
Conventional bulbs are being phased out under energy-efficiency regulations because as much as 95% of the energy they consume is wasted, mostly in the form of heat. Fluorescents and LEDs are rapidly taking their place, even as some consumers grouse about their cost or the quality of light they produce.
MIT said one characteristic of a lighting source is luminous efficiency, a metric which takes the reaction of the human eye to light into account. The luminous efficiency of a conventional incandescent light is between 2% and 3%, with fluorescents measuring between 7% and 15% and most commercial LEDs between 5% and 20%. These new bulbs have efficiencies as high as 40%.
Results of the research were reported in Nature Nanotechology, (the report is behind a pay wall).
Still in the lab
Don’t run out to the store quite yet. The first “proof-of-concept” bulbs produced by researchers don’t approach the 40% efficiency they believe the redesigned bulbs are capable of. Yet the measured 6.6% luminous efficiency is still three times as high as a conventional incandescent bulb, and as good as some fluorescents and LEDs.
There’s no mention in the MIT report of when the technology might become commercially available, or how the cost of the new bulbs would compare to the other alternatives.
But the research is very promising. The team succeeded in designing a crystal that works for a variety of light wavelengths and angles. The stack of layers can be assembled so that the desired wavelengths pass through and out of the bulb, while the infrared wavelengths are reflected.
One of the researchers said the technology might be applied to a number of other products.
“LEDs are great things, and people should be buying them,” said Marin Soljačić of MIT, one of the researchers. “But understanding these basic properties” about the way light, heat, and matter interact and how the light’s energy can be more efficiently harnessed “is very important to a wide variety of things.”
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Standard incandescent light bulbs are famous energy hogs, but a change in design can make them even more efficient than fluorescents and LEDs. University researchers have successfully developed a "proof-of-concept" bulb using the new technology.
