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LEDs Replacing Light Bulbs

An article from the Boston Globe on the effort to replace light bulbs with LEDs:

Three local companies think it's about time to change Edison's light bulb. They say that light-emitting diodes, or LEDs, are the future of illumination. Most people are familiar with the glowing red LEDs used as indicators, to show that there are messages waiting on your answering machine, for example. But today's LEDs can be used to light up restaurants, Broadway stages, and even bridges.

They're essentially microchips that manipulate electrons to produce light. Unlike Edison's bulb, there's no filament to burn out, and they don't get especially hot when they're on. Other plusses: They can last 10 times times longer than an incandescent bulb, and they require much less electricity -- up to 80 percent less -- to produce the same amount of light. And here's a stunning projection: If the world switches over to LEDs rapidly enough, it could obviate the need to build more than 100 power plants between now and 2020.

The problem is cost. Like early computer chips, today's LEDs are still too expensive to spark mass adoption. "You could replace a 100-watt light bulb with a 60-watt LED, and get the same brightness," says John Fan, chairman and founder of Kopin Corp., a Taunton company that makes LEDs. "You'd save 40 percent on power, but it would cost about $100. We need to bring that price down." ...

No one knows how quickly the shift to LEDs will happen -- the technology has been around since 1962 -- but most experts consider it inevitable. And this is an overwhelmingly positive tech trend: By some estimates, LEDs could reduce global energy use for lighting by half by 2025.

Found on Slashdot.


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I love LEDs myself, but this is just silly.

Compact fluorescent bulbs are more efficient than incandescent bulbs and even LEDs. There are regional programs where the power company has given away CFL bulbs to local users just to put off building more powerplants. They're cheap, and they work.

The first problem with LEDs is scale. 1 regular light bulb runs just fine on 100V and consumes 100W (putting out some fraction as light). 1 regular LED wants to be fed something between 2.4-4.3V and typically consumes 20 mW (That's 500 times less power). So you need a couple hundred of these to get the same light as a normal bulb, and you need some electronics to mess with the power.

The second problem is color. The first LEDs were a nice pure red (good for photo-labs, but not around the home). They've since added orange, yellow, green, aqua, blue and purple; but as you get up in to the higher colors, the chemistry gets exotic and expensive, and they're not as efficient. (That's why red stop lights were replaced first, then yellow, and only recently green.) There's a thing called a "white" LED, but it isn't. Its a blue LED that uses some of the light to excite a yellow phosphor which fills out the other colors. So this "white" light takes the most difficult color to make and spends some of it on balancing out the spectrum; further reducing its efficiency.

So keep up the development of LED flashlights (which last 20-100 hours on one set of batteries and don't break when dropped), but stick with CFLs for house lighting.

John Woolverton

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