How many engineers does it take to permanently unscrew a light bulb? At San Jose's Lumileds Lighting, the answer is hundreds. Lumileds, a joint venture of Agilent and Philips Electronics...

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SAN JOSE, Calif. — How many engineers does it take to permanently unscrew a light bulb? At San Jose’s Lumileds Lighting, the answer is hundreds.

Lumileds, a joint venture of Agilent and Philips Electronics, makes semiconductor chips known as light-emitting diodes, or LEDs.

LEDs are found everywhere, from the tiny flashes on digital cameras to the blue lights that illuminate the Arc de Triomphe in Paris at night.

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And if all goes right, Lumileds will one day see its LEDs replace the common light bulb.

Federal studies estimate that replacing light bulbs with white LEDs could save $17 billion a year in energy costs, or the equivalent of 30 power plants.

LEDs consume less power, don’t use harmful pollutants such as mercury and last 10 times longer than conventional lights. They cost more at the outset, but over time they save money in electrical bills and maintenance.

In the laboratory, LEDs have been made that generate 100 lumens per watt, a measure of brightness. In about two years, commercial LEDs should hit about 50 lumens per watt, said Keith Scott, Lumileds market-development manager. “That could be a very important milestone for quality,” he said.

Still, acknowledged Lumileds Chief Technology Officer George Craford, “Eliminating the light bulb will take a long time.”

Craford, a pioneer in LED technology, has been working on the problem for 35 years.

LEDs have been around since General Electric introduced them in 1962. Hewlett-Packard, from which Agilent was spun off in 1999, started making LEDs in the 1960s. Craford’s team of hundreds of engineers has made steady progress with their colorful LEDs. Lumileds’ customers have designed LEDs into the automobile taillights, traffic signals and flat-panel TV sets.

About a decade ago, Craford and a few others began collaborating with Philips Electronics, a leader in light bulbs. After joint research, they formed a business in 1997 and began selling brighter LEDs in 1999.

They make their LEDs in $300 million factories like Lumileds’ San Jose plant.

Each decade, LED prices have fallen by a factor of 10 while performance has grown by a factor of 20. This phenomenon, known as Haitz’s Law after former Agilent scientist Roland Haitz, is the LED equivalent of Moore’s Law in the chip industry, which holds that chip performance doubles every 18 months.

Conventional light bulbs heat a filament to produce light. LEDs are more efficient because they don’t produce nearly so much heat. The big challenges are in making LEDs that match conventional light bulbs’ cost, brightness and ease of use.

Standard 60-watt light bulbs generate around 850 lumens. That’s about 14 lumens per watt of power. By comparison, Lumileds’ Luxeon III LEDs are brighter at 30 lumens per watt. But that’s not enough to beat fluorescent bulbs at about 80 lumens per watt. For now, it takes a number of Luxeons to match the brightness of a bulb.

One obstacle is creating white-light LEDs. Incandescent light bulbs start out as white lights. But LEDs come in blue, green yellow and red. To make a white LED light, Lumileds has to mix the colors. Since there is some inefficiency in doing that, the brightness isn’t as great and the costs are higher compared to colored LEDs.

Then there is cost. LEDs need to improve costs about 100-fold for LEDs to match the price of a light bulb. Based on historical progress, that will take about a decade, said Young Sohn, president of Agilent’s semiconductor products group, one of the biggest LED sellers.

“It may take five to 10 years, but one day we’ll go to a Wal-Mart and buy LEDs instead of light bulbs,” said Jagish Rebello, an analyst at market researcher iSuppli in El Segundo, Calif.

Little by little, LEDs are encroaching on light bulbs, especially for colored lights. Since the color mixture can be controlled, LEDs are good for mood lighting.

Mixing white light with red is more relaxing and romantic, while blue-tinged lights are the work horse of offices.

Where design takes priority over cost, LEDs can win. The Rabat jewelry store in Barcelona, Spain, uses nothing except Lumileds LEDs for illumination. More than 4,000 LEDs bathe the store in every color of the rainbow.

The high-brightness LED market is expected to grow from $2.7 billion in 2003 to $6 billion in 2008, according to market researcher Strategies Unlimited in Mountain View, Calif.

The winner of the race to replace the light bulb probably will be the company that can make LEDs’ advantages affordable.

“Nobody wants to pay $100 for a light bulb, no matter how much it saves them” in energy costs, Craford said.