Let there be LEDs

Makers of the technology commonly associated with Christmas lights are aiming to take on the conventional light bulb.

It started innocently enough.

Marcel Jean Vos, an interior and commercial designer in London, bought some light-emitting diodes to create a small lighting system in the kitchen of his apartment.

Now, four years later, Vos has transformed a neighboring one-bedroom apartment into a space lighted entirely with LEDs, the solid-state technology more commonly associated with the tiny lights on electronic gadgets.

The apartment has 360 LED arrays and about 20 yards of plastic ribbons embedded with the glowing semiconductors. The lighting effects include a kitchen counter that changes color, an illuminated shower stall, a candle that has chips instead of a wick and a light sculpture.

"Everyone is looking for an excuse to ditch the incandescent light bulb," said Vos, the chief executive of Vos Solutions, his design consultancy. "And it is about time. We are using extra energy for nothing."

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But his project demonstrates both the advantages and the drawbacks of replacing incandescent light, a technology that has not changed substantially since Thomas Edison developed his first successful bulb in 1879.

Despite its enormous number of light fixtures, Vos' apartment uses no more electricity than four 100-watt incandescent bulbs would, he said. ("And what kind of fun can you have with just four light bulbs?" he asked.)

But offsetting the frugality is the staggering cost of the installation. Vos estimated that he spent $50,000 to create the apartment's lighting system.

"Right now, it's something that's only for the rich and famous," said Vos.

While Vos' apartment is unusual--he makes the unverifiable claim that it is the world's first residence entirely lighted by chips--he is not alone in his thinking that LEDs may help end the reign of the conventional light bulb. Major manufacturers like General Electric and Royal Philips Electronics, along with some much smaller newcomers, want to find a place in every home for LED illumination.

What began with Christmas tree lights and under-the-cabinet lights may eventually lead to inexpensive, solid-state lighting systems. Researchers are promising lights that will be more like wallpaper than bulbs.

The research into solid-state lighting is motivated by light bulb makers who want to create new and profitable products. But saving energy is a consideration, too. About 20 percent of all electricity in the United States is used for lighting. A shift from bulbs to LEDs and other more efficient kinds of lighting could cut that percentage in half, easing the strain on power systems and reducing the chances of a blackout like the one that affected the northeastern United States and Canada last August.

"What we're looking at here is really changing the way people think about their environments," said Mark Roush, a former lighting designer who is now a senior marketing executive at Philips Lighting. "And there's nothing that drives awareness of lighting more than not having it."

Hot and bothersome
In the incandescent bulb, it would seem that Roush and his counterparts at other companies have an easy target. "The standard by which we judge all light sources is the incandescent," he said. "But the incandescent has very poor color rendering."

The incandescent bulb, which works by heating a thin metal filament so that it emits light, is also inefficient. About 90 percent to 95 percent of the electricity that goes into most incandescent bulbs is converted to heat rather than light.

"It's absolutely the least efficient light bulb you can buy," said Anil R. Duggal, the manager of GE's light energy conservation program. And you don't have to be an engineer to know how little it takes to shatter an incandescent bulb or how frequently the filament burns out.

But one factor sweeps all those considerations aside when most household users go shopping: incandescent bulbs are very inexpensive. Standard bulbs commonly sell for as little as 50 cents each, and even brighter and longer-lasting halogen incandescent bulbs can be had for a few dollars. That makes more efficient alternatives like compact fluorescents, at $10 or more, seem extravagant, and leaves little or no room in the market for the even more expensive lights that use LEDs.

LEDs are tiny devices, made of semiconductor material, that allow an electric current to travel in only one direction and produce light as a byproduct of current flow. Like fluorescent lights, LEDs do not have filaments, so they run cooler and last longer. Their higher prices might be offset by longevity and lower operating costs, but few consumers do those calculations while pushing a shopping cart. "I know that when I go into a store, I mostly look at what's in my wallet," said Gert Bruning, a lighting researcher at Philips Research.

For now, that has made LED lighting mostly of interest to the commercial world, where energy use and maintenance costs are carefully watched. The vast video screens and animated signs that cover buildings in Times Square are the most dramatic commercial use of the technology. But the most common applications tend to be prosaic. Many traffic signals, Walk/Don't Walk signs and indicator lights on trucks and buses use LEDs.

GELcore, an LED lighting maker owned by GE and Emcore, a semiconductor company, recently unveiled an LED technology for illuminated street signs. Similarly, what appear to be neon tubes on new buildings are often plastic ribbons embedded with LEDs.

The major barrier to creating inexpensive LED lights for homes is not the semiconductors themselves. The real obstacle is the cost of overcoming several basic limitations of the chips.

The first is the nature of their light. Incandescent or fluorescent bulbs diffuse their glow over a wide area. LEDs, in contrast, are very bright only at a single point. That's handy for showing that a cell phone is charged or for making up one subpixel in a huge video billboard, but it's a drawback for filling rooms with light. "LEDs are very good at lighting effects," Roush said. "Now, they are coming across the threshold to effective lighting - delivering the light where you want it."

Most of the bulbs in Vos' apartment, which are the kind used for signs, achieve that result by combining several LEDs under a plastic lens.

Color coordination
Light color is also a problem. Currently, no LED produces light of a color suitable for everyday household use. The best produce a white light that has a pronounced and very unflattering blue tinge.

At the moment, there are two ways around the color problem. Many LED bulbs create white light by blending the output of separate red, green and blue diodes.

Scott Hearn, the president and chief executive of GELcore, said his researchers were developing an alternative in which the LEDs generate invisible ultraviolet light. That light, in turn, causes phosphors on the chip to glow. As with fluorescent lights, producing a specific color becomes a matter of adjusting the phosphors' chemical recipe.

GELcore began selling a $25 under-cabinet accent light this fall that uses a variation of the concept. The light has a series of blue LEDs that have been coated with yellow phosphors to improve their light color.

Most people in the LED-lighting industry have already conceded the business of replacing standard incandescent bulbs to efficient and compact fluorescent lamps. They're hoping to use the technology to introduce entirely new kinds of household fixtures.

"Having these flat things is a totally different way of looking at lighting," Roush said. "All of a sudden, I have dynamic color--color that can change. Inside spaces can be illuminated to match the whiteness of daylight outside, while buildings can change their colors outside."

The most successful LED lighting product for consumers so far emerged from a desire to overcome a common seasonal annoyance. Frustrated by the need to climb a ladder to replace burned-out Christmas lights on his house in Yardley, Pa., David Allen began looking into alternatives.

At first, Allen looked at developing fiber-optic systems. But along the way, he discovered that, contrary to industry assumptions, it was possible to assemble strings of LEDs that could be plugged in to wall outlets without a power converter. The lights are rated for up to 200,000 hours of usage.

This holiday season was the second that his Forever Bright lights were widely distributed in North America. While Allen declined to give sales figures, he said that sales of the lights increased by 500 percent over 2002, partly because of promotions by some electrical utility companies.

But even if more houses start to resemble Vos' futuristic apartment, the glory days of LEDs may be cut short by their younger sibling, organic light-emitting diodes, or OLEDs. Because they are based on plastics, OLEDs do not have to be manufactured in semiconductor factories. Nor are they limited to relatively small sizes. "Organic LEDs can potentially be made with a low-cost printing line, much like you print a newspaper," Duggal of GE said.

More important, they could be created on flexible materials, leading to new forms of lighting. Rolls of OLEDs could be produced as a kind of luminous wallpaper. Table lamps could exchange their bulbs for shades that provide both light and decoration. But OLEDs are in their infancy and so far have few applications. Philips uses them in an electric razor, and they are found in some small displays in car dashboards. They are not very energy-efficient, and the light output tends to decrease over time.

Duggal said that much work remained to be done to improve the technology. "How this gets adopted is going to be interesting," he said. "But making all this work is still a big challenge. It's not a done deal."

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