WASHINGTON – The government is pushing scientists and engineers to get rid of one of the world’s worst energy-wasters – the ordinary light bulb.

An incandescent bulb turns only 5 percent of the electricity it consumes into light. The rest is wasted as heat. A fluorescent lamp is more efficient, but it still puts out only 25 percent of its energy as light.

With the aid of academic and private industry researchers, the Department of Energy is seeking to replace those profligate bulbs with “solid state lighting” devices that attain 50 percent efficiency – 10 times better than ordinary bulbs, twice as good as fluorescents.

Solid state lighting systems consist of light emitting diodes (LEDs), such as those found in digital clocks and phones, car taillights and dashboard indicators, traffic signals, stage lights, stadium displays and many other niche applications.

An LED device is made of semiconductors, the silicon crystals used in computer chips. It produces little heat, uses no hazardous materials like the mercury in fluorescent tubes, and lasts for thousands of hours, even years.

By 2025, the Energy Department claims solid state technology could cut in half the electricity Americans use for lighting, significantly reducing energy demand and environmental pollution. It could save $30 billion a year in electric bills.

“Solid state lighting can provide tremendous energy savings,” said Jerry Simmons, deputy director for energy sciences at the Sandia National Laboratory in Albuquerque, N.M. “There is no reason we can’t do better than 50 percent efficiency.”

The incandescent bulb, first successfully marketed by Thomas Edison in 1879, is the “last technology that still uses vacuum tubes,” Simmons said. “We want to send the old vacuum tubes to the museum where they belong.”

To accomplish the goal, Congress last year authorized $50 million a year for a Next Generation Lighting Initiative. The latest round of five LED research contracts were awarded in June.

Widespread application of solid state lighting is years away, however.

“Replacing conventional lighting for general illumination will be hard,” Simmons said. “We need technology breakthroughs to lower the cost and to compete with conventional lighting.”

“Solid state lighting is still four to five times more expensive to install than traditional light sources,” said John Ekis, sales director of Lamina Ceramics in Westampton, N.J.

But the cost is dropping by 20 percent or more per year, Ekis said. He predicted that solid state lighting sales will double from $4 billion this year to $8 billion in 2010.

Solid state lighting also is far from being as efficient as it needs to be. An average LED produces 25 lumens (the standard unit of light) per watt. That’s not much more than the 20 lumens produced by a conventional incandescent bulb.

The goal is to reach 75 lumens per watt by the end of 2007, and 200 lumens by 2025, Simmons said.

Last month, a lighting company, Cree Inc., of Durham, N.C., claimed that it achieved a record of 131 lumens per watt in the laboratory.

It’s easy to produce red light with solid state devices, but blue and green are harder. White light – the kind needed for general illumination – is the most difficult of all and is just beginning to come into use.

The largest white light display in the world, containing 12.5 million LEDs, is in the Fremont Street mall in Las Vegas, according to Ghassan Jabbour, an engineering professor at Arizona State University in Tempe. Another 27,000 LEDs illuminate the words inscribed in the Thomas Jefferson Memorial in Washington.

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