Wednesday, December 2, 2009

LED lights, big prize, big promise

Those fragile spirals of light, compact fluorescents, are likely to have been just a transition in the world of illumination...

That's the transition between incandescent lights and light-emitting diodes, better known as LEDs.

(Image: three LED puck lights.)

It won't be long before the traditional incandescent will be thoroughly a dinosaur, a hugely inefficient device whose heat production costs you as much as the light it emits. Compact fluorescents (CFLs) are attractive because they fit into the same puka as an incandescent and use a quarter the power—but there are some pollution issues, notably toxic mercury in the tubes.

At some point, someone noticed that there might be illumination potential in those little red and green lights that tell you whether your television or computer is on or off.

But they are so tiny, and their initial applications were for cutesy flashlights that could burn for weeks on a flashlight battery, but provided so little light you could barely read by them.

That's changing. The first step was to develop arrays of little lights, so you could get enough LEDs in one place to provide useful illumination. It turns out the LED produces light at a fifth or less of the power of an incandescent, and a half to a third of compact fluorescents.

But it was still quirky, and expensive to make and to buy. Incandescents cost a few dimes. CFLs cost a few dollars. But LEDs of similar illumination cost a few tens of dollars.

Scary expensive... Or is it?

The computer guru Kim Komando makes a case for looking at energy use over the entire life of an LED. (Komando sells the things, so there's a caveat, but she seems to have her facts right.)

There's a big range in prices, so shopping can save lots. Here are some other online bulb sources: here and here and here.

One of the early arguments for CFLs, when they were more expensive than they are now, was to use them in places where the light burned a lot. Like maybe a front door light that you leave on most of the evening.

Same thing applies to LEDs. They use less power, plus, the darn things just don't seem to burn out. And because the thing will outlast dozens of incandescents and a handful of CFLs, screwing in lightbulbs might become a lost art.

But the important numbers are in energy use. And let's assume a 100 watt bulb, with the same light as a 12-watt LED. Let's assume it burns six hours a day, 365 days a year, for 2190 hours.

The incandescent uses 219 kilowatt-hours; the LED uses 26. If we're paying, say, 25 cents a kilowatt-hour, then that incandescent is costing you $54.75 while the LED adds $6.50 to the power bill.

Can that be right? It seems to be. Even at scary high cost, in high-use applications, the darn thing pays for itself in the first year. Even if the LED you buy gets half the efficiency of the one in our example, it remains far more efficient than incandescents.

Still, from a total cost standpoint, right now it still might make more sense to use CFLs. They rival LEDs in efficiency, plus they're considerably cheaper except in really long-burning applications.

A German company, OSRAM Opto Semiconductors, did some research comparing the three kinds of lights.

The research was released last month. It looked at the entire life cycle of the lights. What kind of toxicity was involved, how much it cost to build them, how much electricity they used in transport and in use, and what was involved in eventually disposing of them.

“Today, LEDs are already five times more efficient than incandescent lamps. In the future, however, it is expected that LEDs will become more than ten times more efficient compared to incandescent bulbs,” the report says. Some LED manufacturers already claim efficiency rates eight times those of incandescents—the rate we used in our example above.

The upshot of the study is that the LED uses only about 2 percent of its lifetime energy use in its manufacture, and that at this point in its development, it is many times more efficient than incandescents and about even with the more mature CFL in energy efficiency. But the study says there's still room for improvement in LED technology, and it will eventually be the most efficient lighting technology.

The New York Times this week talked about the issue.

The U.S. Department of Energy wants this technology to improve, because of its obvious benefits, and has offered a massive prize to a company that produces a 60-watt LED light that fits in standard sockets. It's the L-Prize, and it could be worth $10 million to the winner.

The L-Prize, it says, is “the first government-sponsored technology competition designed to spur development of ultra-efficient solid-state lighting products to replace the common light bulb.”

So far, only the electronics firm Philips has entered, with an LED replacement for an incandescent 60-watt bulb. The 60-watter is the key, because half of all incandescent light bulbs are sold at this level of illumination.

© Jan TenBruggencate 2009


Dave Smith said...

Another informative article, especially to us off-gridders. Any power that can be saved ....

zzzzzz said...

Actually, very bright, efficient LEDs have been around for quite awhile. About 20 years ago, LEDs were being used as tail, brake, and signal lights in cars, and shortly afterward, LEDS began showing up in traffic signals.

The problem wasn't a lack of brightness, it was the incomplete color spectrum. The breakthrough was the development of new materials that facilitated blue LEDs, which could be combined with red and green to give white.

Gil said...