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In the effort to make the next generation of energy-efficient lighting, green just isn't pulling its weight.

It's not as efficient or bright as other colors, like red and blue, that are used in the next generation of energy-efficient lighting based on LEDs, or light emitting diodes.

LEDs - like those used in most modern traffic lights - are promising as a longer-lasting, more energy efficient and environmentally friendly lighting technology than compact fluorescent bulbs, researchers at Sandia National Laboratories say.

But in the effort to make better LED lights, green just hasn't been a team player, said Jerry Simmons, a scientist at Sandia who is trying to solve the green problem.

"If we could get green LEDs to be brighter, it would mean the amount of power you use to get solid state (LED) lighting would be much less than it is now," Simmons said.

Efforts at Sandia could help save energy and create a new economic sector for Albuquerque - especially if the state government decides to partner with the labs on an energy-efficient lighting initiative, Simmons said.

"We've spoken with some people in the Governor's Office about that," Simmons said. "There's some interest, and we think we could help them bring some businesses to Albuquerque. We're trying to write a proposal."

But getting green to behave so it can be used to spur that sort of economic growth will take time, Simmons said.

LEDs of other colors convert about 50 percent of the power they receive into visible light.

"Green, on the other hand, tends to be below 10 percent - down as low as 2-3 percent," Simmons said.

Nobody knows exactly why it's so hard to get green LEDs to perform, but it likely has something to do with how they're made - using a mixture of three chemicals grown on a silicon wafer, Simmons said.

"Green is considered by many to be the most important challenge in solid state lighting," Simmons said. "We think in 10 years, especially if we can solve this problem, LED lights will be more than twice as efficient as compact fluorescents."

Changing the chemical mixture, analyzing the structure of the LEDs on an atomic-sized scale and seeing how different temperatures influence the growth are all ways Sandia hopes to solve the problem, he said.

If it's solved, newer, more powerful LEDs will create a lighting revolution, said Jeffrey Tsao, another Sandia scientist working on the green problem.

LED-based light bulbs are already about 20 percent more energy efficient than compact fluorescent bulbs, and they last two to five times longer, Tsao said.

"And even though compact fluorescents and fluorescents save a lot of energy, you also have to worry about mercury and the environment with them," Tsao said. "LEDs are definitely free of mercury, and there's nothing else we're aware of right now that would cause environmental problems."

LED lighting could also be better for people who suffer from migraines, Tsao said.

It's thought that the flicker of fluorescent bulbs and the color of the light that they produce can trigger migraines in some people, he said.

"LEDs have no flicker, and the next generation has good quality color," Tsao said.

Some of the newer LED light designs also let people adjust the color of their white light, which could be beneficial for people who suffer from light-related problems, he said.

"There's a number of different whites, there are warm whites and cool whites," Tsao said. "Human circadian rhythms can be triggered by the type of white light we see."

Outside, people see a light that is more blue in the morning and more red in the late afternoon, Tsao said.

"The redder kind of light is sort of a trigger for the human system to start to wind down," Tsao said.

Tunable LED lights are very expensive right now, and can cost several times the amount of a traditional bulb, in part because of the green problem, he said.

But if Sandia and other labs can solve the green problem, those bulbs could become as inexpensive as compact fluorescents or other bulbs, he said.

"It's a very exciting time, overall, in solid state lighting," Tsao said.