LED evolution could replace light bulbs

But development is brisk, and the Department of Energy has estimated that LED lighting could cut national energy consumption for lighting by 29 percent by 2025.  The total savings on U.S. household electric bills until then would be $125 billion.

LEDs have other advantages that are propelling them into niche uses, despite their upfront cost.  Current white LEDs will last up to 50,000 hours, about 50 times as long as a 60-watt bulb.  That's almost six years if they're on constantly.

That makes them attractive for places where changing bulbs is difficult or expensive — like on the outside of buildings or in swimming pools.  Osram Sylvania, the lighting subsidiary of German manufacturer Siemens AG, makes 27-foot long strips of flexible, adhesive tape covered in LEDs for such applications.

Hotels are interested in using LEDs in bedside lamps to save them the trouble of replacing burned-out bulbs, said Jim Anderson of Lamina Ceramics, which showed off a 6-watt array of LEDs that produce light equivalent to a 20-watt halogen bulb.

LEDs are also durable. Being solid-state, they can resist the vibrations in aircraft and cars, according to Narendran, who has worked with Boeing Co. on designs for aircraft cabins.

General Electric Co. and smaller iLight Technologies of Evanston, Ill., make glowing LED signs that look like neon.  Neon lighting is a leading cause of fires at restaurants and the signs are vulnerable to vandalism. 

By contrast, LED signs made of Plexiglas are tough.  At the trade show, iLight exhibited an LED sign that still worked after taking a blast from a shotgun.  The limitation: iLight's signs can't be made economically on a one-off basis, as done at small neon-sign shops around the country.

The feature of LEDs likely to propel them into homes is aesthetic, not practical.  Arrays that mix red, green and blue LEDs can produce any color of the rainbow.  Instead of a dimmer, you might have three sliding knobs that let you mix color.

"On a very hot day you might want blue light to cool it down a bit, or on a winter day you may want to simulate sunlight," said Steve Landau of Lumileds Lighting, an LED-making joint venture of Agilent Technologies Inc. and Philips Lighting.

Qantas Airways Ltd., the Australian airline, recently outfitted its first-class cabin with LED lighting that shines a deep blue when it's time to sleep.

A system like that would be too expensive for most homes, but industry experts believe the price will come down in a few years as the technology develops.

"We are still in a very young research environment," said Norbert Hiller, vice president at Cree Inc. of Durham, N.C., which produces blue and green LEDs. "Our researchers keep surprising us."

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