Despite plenty of technical advances, incandescent lightbulbs still rule when it comes to color and quality of light. The trouble is, they don’t always last so long, and they waste almost all of their energy, emitting it as heat.
But what if you could have the color of incandescents, with the efficiency of an LED? That’s the promise of new research out of MIT. The new bulb works by arraying nano-mirrors around a regular incandescent element, reflecting the wasted heat back into the element. This brings incandescents into the efficiency range of LED and fluorescent bulbs.
Incandescent bulbs look so good because they emit all colors of light, whereas LEDs and other more efficient light sources only manage a subset of all the colors of visible light. If you look at the color-range emitted by some energy-saving bulbs, chinks of the spectrum are missing. Our eye adjusts, but like digitized music compared to tape or vinyl, the brain may still subconsciously notice those gaps. This "full-spectrum" light also means incandescents are better than anything else at rendering colored objects faithfully. They’re like tiny little suns, only yellower (although the yellow tint has nothing to do with the "full-spectrum" aspect).
Published this week in Nature, the paper details the method. The bulb’s element is surrounded by a "cold-side nano-photonic interference system," essentially a mirror which lets visible light pass but reflects infrared heat. This heat is then reabsorbed by the element, causing it to emit more light. It’s a clever trick, and in principle very simple. To make the lamp, the tungsten element itself was modified too—the MIT bulb uses a ribbon instead of a strand, which is better for soaking up that reflected heat.
The experiment, carried out by physicists Ognjen Ilic, Marin Soljačić, and John Joannopoulos, managed to triple the efficiency of an incandescent bulb to 6.6%. The team thinks it could refine the setup to reach 40% efficiency, which is at the upper limit possible for any light source. An LED maxes out at 15% efficiency.
If the process of layering up the nano-mirrors can itself be made efficient enough for cheap manufacture, we could be back in business. You will be able to relax in your home, listening to your analog vinyl records and enjoying the prints made from your film camera in the full-spectrum, perfectly color-rendered light of an incandescent bulb, all without destroying the planet. It sounds like hipster heaven.