MIT makes incandescent light more energy efficient than LED

Researchers at MIT have devised a method in which heat radiation from a filament is reflected back to the filament using a nanomaterial and then emitted again as visible light. As a result, an incandescent lamp can be more economical than an LED lamp.

The system works with a ‘photonic nanocrystal’ developed by MIT, which works for a large number of wavelengths and angles. The photonic crystal is made up of stacked thin layers on a substrate. It transmits visible wavelengths while reflecting infrared wavelengths. That infrared radiation heats the filament again, converting more heat into light. Because the infrared radiation is always reflected back to the filament, a part is always converted into light.

The technique allows filament lamps to achieve efficiencies of up to 40 percent, according to the team, which would be a huge gain over the 2 to 3 percent of a conventional incandescent lamp. During the study itself, an efficiency of 6.6 percent was achieved. On the MIT site, one of the researchers makes a comparison with fluorescent light, which has an efficiency of between 7 and 15 percent. LED lighting currently achieves a light efficiency of between 5 and 15 percent.

The use of residual heat through reflection is not new and has been used for some time in various sensors in which, for example, light-sensitive cells have been processed, the researchers write in their paper in Nature Nanotechnology. The big difference with solar collectors is temperature; a filament becomes about 2700°C and making a material that can withstand that temperature is no easy task.

MIT’s efficient filament. The test set-up achieves an energy-to-light conversion of 6.6 percent, which should theoretically be stretched to 40 percent. Source: MIT