Incandescent light bulbs may put out a warmer-looking, more familiar type of light than LEDs or compact fluorescents, but they're far less efficient – the majority of the energy they use is wasted, mainly in the form of heat. Technology may save them yet, however. Scientists at MIT and Purdue University have developed an ultra-efficient new incandescent bulb that reuses the heat it gives off, converting that heat into more light.
With traditional incandescent bulbs, both visible and infrared light are created by heating a tungsten filament, causing it to glow. Both wavelengths flow unimpeded out into the room, with the infrared doing nothing other than dissipating as heat.
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In the case of the new two-stage incandescent, however, the filament is surrounded by structures known as photonic crystals.
Made from abundant elements and manufactured using conventional material-deposition technology, these crystals allow visible light to pass through, but reflect the infrared back onto the filament. This helps keep the filament heated, glowing and emitting more visible light, while using much less electricity than it would otherwise.
The bulb could conceivably score very high when it comes to luminous efficiency – this is a measure of how well a light source produces visible light. While regular incandescents have a luminous efficiency of 2-3 percent, with compact fluorescents coming in at 7-15 percent and LEDs at 5-15, the two-stage incandescent could reportedly manage up to 40 percent once developed further.
The current proof-of-concept model sits at around 6.6 percent, although even that figure is in line with some LEDs and fluorescents, and is three times better than conventional incandescents.
A paper on the research was recently published in the journal Nature Nanotechnology.