Saturday, January 16, 2016

Return of incandescent light bulbs as MIT makes them more efficient than LEDs

An incandescent light bulb

Researchers at MIT have shown that by surrounding the filament with a special crystal structure in the glass they can bounce back the energy which is usually lost in heat, while still allowing the light through.
They refer to the technique as ‘recycling light’ because the energy which would usually escape into the air is redirected back to the filament where it can create new light.
"It recycles the energy that would otherwise be wasted," said Professor Marin Soljacic.
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Usually traditional light bulbs are only about five per cent efficient, with 95 per cent of the energy being lost to the atmosphere. In comparison LED or florescent bulbs manage around 14 per cent efficiency. But the scientists believe that the new bulb could reach efficiency levels of 40 per cent.
And it shows colours far more naturally than modern energy-efficient bulbs. Traditional incandescent bulbs have a ‘colour rendering index’ rating of 100, because they match the hue of objects seen in natural daylight. However even ‘warm’ finish LED or florescent bulbs can only manage an index rating of 80 and most are far less.
"This experimental device is a proof-of-concept, at the low end of performance that could be ultimately achieved by this approach," said principal research scientist Ivan Celanovic.
"An important feature is that our demonstrated device achieves near-ideal rendering of colours.
“That is precisely the reason why incandescent lights remained dominant for so long: their warm light has remained preferable to drab fluorescent lighting for decades.”
Thomas Edison patented the first commercially viable incandescent light bulb more than 130 years ago so that "none but the extravagant" would ever "burn tallow candles.”
It works 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 in a scene.

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