With nations, including the U.S., sounding the death knell for energy inefficient incandescent light bulbs, folks are actively expressing concerns over the heir apparent, compact fluorescents. Among the problems: toxic mercury in the fixtures that can spread when they break, and which may require special treatment when it's time to dispose of burned-out fixtures.
(Photo: Three LED puck lights, each using a dozen independent LED units.)
Fortunately, the next lighting advance is already in place, and it doesn't have any mercury.
It's LED lighting, the acronym for light-emitting diodes.
These are the low-wattage lights that glimmer on the fronts of your computer to indicate its status, on your video camera to tell you it's operating and on your phone that tells you you have a message.
They work very differently from incandescents and fluorescents. Here's how the U.S. Department of Energy describes an LED's mechanics:
“It consists of a chip of semiconducting material treated to create a structure called a p-n (positive-negative) junction. When connected to a power source, current flows from the p-side or anode to the n-side, or cathode, but not in the reverse direction. Charge-carriers (electrons and electron holes) flow into the junction from electrodes. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon (light).”
LEDs, which have been in flashlights for a while now, are being fine-tuned to act as area lights as well.
Among the key issues with LEDs is getting a nice white natural light out of them—white is not a natural color for this technology.
“Red LEDs are based on aluminum gallium arsenide (AlGaAs). Blue LEDs are made from indium gallium nitride (InGaN) and green from aluminum gallium phosphide (AlGaP). "White" light is created by combining the light from red, green, and blue (RGB) LEDs or by coating a blue LED with yellow phosphor,” says the Department of Energy's Energy Efficiency and Renewable Energy office website.
A second challenge is getting them bright enough, but there's been plenty of research into that, and it's resulting in dramatic advances. It used to be that LED flashlights were kind of a joke. Today, you can actually make your way with them, and they're easily bright enough to read by.
Energy savings are already impressive, and they're growing. Lighting efficiency is mentioned in lumens per watt (amount of light divided by amount of energy required). Your grandmother's incandescent lightbulb gets 10 to 18 lumens per watt. Compact fluorescents get 35 to 60. As of late in 2006, LED lights were rated as anywhere from 22 to 59 lumens per watt, but it's estimated that with further technological advances, those numbers could nearly triple.
The Department of Energy figures the national energy savings in lighting from LEDs could run into the high tens of billions of dollars.
Also, they can handle vibration and rough treatment. And they don't burn out with nearly the frequency of other lights. (They can last 25 times longer than incandescents and 5 times longer than compact fluorescents, according to the energy department.)
The bad news: They are expensive, although energy savings, long life and lack of pollution problems could balance that.
Too, they do produce heat, and that heat needs to be dissipated to prevent changes in color, and reduced life of the fixture.
A key researcher in making LEDs brighter, Faiz Rahman of the University of Glasgow, said the future looks...well, you know.
“LEDs not only use less power than current energy efficient light-bulbs but they are much smaller and can last years without needing to be replaced. This means the days of the humble light-bulb could soon be over,” Rahman said.
© 2007 Jan W. TenBruggencate