The Incandescent Light Bulb Strikes Back…

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Following the EU ban on traditional incandescent light bulbs, we all thought the future was based around LED lighting. But it seems that the clever people from MIT in America have given the incandescent light bulb a reprieve thanks to a technological breakthrough.

Incandescent lighting and its warm, familiar glow is well over a century old yet survives virtually unchanged in homes around the world. It is a simple design that everyone loves. But that has been changing fast, as regulations aimed at improving energy efficiency have been phasing out the old bulbs in favour of more efficient compact fluorescent bulbs (CFLs) and newer light-emitting diode bulbs (LEDs).

Incandescent bulbs, commercially developed by Thomas Edison, work by heating a thin tungsten wire to temperatures of around 2,700 degrees Celsius. That hot wire emits what is known as black body radiation, a very broad spectrum of light that provides a warm look and a faithful rendering of all colours to the human eye.

But these bulbs have always suffered from one major problem: More than 95 percent of the energy that goes into them is wasted, most of it as heat. That’s why country after country has banned or is phasing out the inefficient technology. Now, researchers at MIT and Purdue University have found a way to change all that.

Three MIT professors have made major breakthrough with what they call – light recycling. The key is to create a two-stage process, the researchers report.

The first stage involves a conventional heated metal filament, with all its attendant losses. But instead of allowing the waste heat to dissipate in the form of infrared radiation, secondary structures surrounding the filament capture this radiation and reflect it back to the filament to be re-absorbed and re-emitted as visible light. These structures, a form of photonic crystal, are made of Earth-abundant elements and can be made using conventional material-deposition technology.

That second step makes a dramatic difference in how efficiently the system converts electricity into light. One quantity that characterizes a lighting source is the so-called luminous efficiency, which takes into account the response of the human eye. Whereas the luminous efficiency of conventional incandescent lights is between 2 and 3 percent, that of fluorescents (including CFLs) is between 7 and 15 percent, and that of most compact LEDs between 5 and 15 percent, the new two-stage incandescent could reach efficiencies as high as 40 percent, the team says.

The first proof-of-concept units made by the team do not yet reach that level, achieving about 6.6 percent efficiency. But even that preliminary result matches the efficiency of some of today’s CFLs and LEDs, they point out. And it is already a threefold improvement over the efficiency of today’s incandescent light bulbs.

The team refers to their approach as “light recycling,” since their material takes in the unwanted, useless wavelengths of energy and converts them into the visible light wavelengths that are desired.  Put simply “It recycles the energy that would otherwise be wasted,”

Here at Easy-Lightbulbs.com we think this is a brilliant step forward. The majority of people still love the light from incandescent bulbs and the ease with which it works with all dimmers. If incandescent light bulbs are suddenly as efficient as LED’s then we will be able to bring them back into the UK and Europe for our customers.

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  • Damian Riney