Building a Better Light Bulb
by Bill Chameides | January 14th, 2010
posted by Erica Rowell (Editor)
Might walls be the light bulb of the future? (Credits: http://www.flickr.com/photos/r00s/1438557021/ – http://creativecommons.org/licenses/by/2.0/)
The race is on to develop the modern light bulb, but it may be that the modern light bulb won’t be a bulb.
Incandescents — The Old Standard Bearer
Since the days of Thomas Edison, the incandescent light bulb has been the king of illumination. It works on a basic principle of physics: the hotter a body is, the more light it radiates.
In an incandescent light bulb electrons are forced through a filament to make it so hot that it glows. Because so much of the electrical current’s energy goes into heating the filament, incandescent bulbs tend to be very inefficient. And so, acting on today’s low-carbon imperative, many people are looking to replace the incandescent with something more efficient.
Others have not yet given up on the incandescent and are working to make that 19th century lighting technology as efficient as its rivals — the compact fluorescent light (CFL) and light-emitting diode (LED) (both described here).
CFLs — The (Relatively) New Kid on the Block
Seemingly poised to replace the incandescent, CFLs work on the basis of fluorescence instead of incandescence.
A beam of electrons is sent through a gas causing the electrons in that gas to be excited from their ground, low-energy state to a higher energy state. When the electrons relax back to their ground state, the extra energy is released as light via a photochemical reaction.
Because fluorescence does not depend on heating the gas, CFLs are more efficient than incandescents; typically CFLs use about 75 percent less energy to produce the same amount of light as an incandescent.
LEDs — Closing Fast
But there are people out there who don’t like CFLs — they don’t care for the light quality, the flicker, and the fact that they use mercury. Not to worry; there’s an up-and-coming alternative — commonly referred to by its three-letter moniker LED.
LEDs work on the same fluorescence principle as CFLs but with a twist. Instead of sending a current through a gas, LEDs make use of a crystal semiconductor with varying properties from one end to the other (hence the term diode). Electrons on one end of the diode tend to be in a high-energy state and at the other a low-energy state. When exposed to a current, electrons flow from the semiconductor’s high-energy end to its low-energy end, and the energy change shows up as light.
A typical LED is slightly more efficient than a CFL, and has the added advantages of a much longer life expectancy and no mercury. That’s why many experts believe that while CFLs may be a temporary replacement for the incandescent, the future of illumination will more likely belong to LEDs.
Not So Fast, Mr. LED
While LEDs may eventually win the illumination race, they are nowhere close to the finish line. They’re expensive, and the light they give off can be harsh (although advances may have already made some complaints in this area a thing of the past). But still, in terms of giving either incandescents or CFLs a run for the money, LEDs seem relegated so far to primarily flashlights, where long life and low power requirements are at a premium, and outdoor applications, where the harshness of the light is not an issue.
While we’re on the subject of LEDs, here’s something folks had not anticipated: LEDs don’t work in the snow.
Because incandescents generate heat, they can melt away any snow or ice that might land on them. But the small amount of heat from LEDs means that when they are outside in snowy conditions, they might well get buried. Is this a problem? Potentially yes, since LEDs are being deployed in traffic signals in no small number across the country.
Earlier this month, Joanna Bush of the Department of Transportation in Wisconsin, which has transitioned 90 percent of its state-owned signal lights to LEDs, admitted that “we certainly do see crashes and accidents [during snow storms] attributed to the fact that people can’t see the heads,” referring to the blocked colored lenses of a traffic signal.
In her view, though, the problem of snow accumulation on the traffic signals “isn’t enough to convince us to move over from LEDs.”
So while the world awaits a high-tech solution to the problem of snow-obscured LED traffic lights, Wisconsin’s DOT, not wanting to sweep the potentially serious problem under the rug, has its own quick fix: “dispatch workers with brooms to clear the lenses.” The 21st century meets Disney’s The Sorcerer’s Apprentice?
Feel the Glow
It could turn out that the next illumination king could be none of these three.
A Welsh company called Lomox is working on a technology based on organic LEDs that would cause walls that are coated with the product and charged with a low-voltage current to glow.
The company claims that its technology will be two and a half times more efficient than the best bulbs available today and will illuminate a dimmer-equipped room in much the way sunlight brightens a room.
Cool. Can’t you just see it: Ten years from now, you sit down with your e-reader in your dark room on a snowy winter night and command a robotic broom first to switch on the wall and then to go outside and sweep off the yard lights.filed under: energy efficiency, faculty
and: CFLs, compact fluorescent light bulbs, energy-efficient lighting, LEDs, light-emitting diodes, technology