Can Incandescent Bulbs Be Made Efficient?

[Erik Sine]

Can Incandescent Bulbs Be Made Efficient?

By Leora Broydo Vestel

May 29, 2009, 9:35 am

The race to find more efficient lighting technologies appears to have an unlikely dark horse: the incandescent light bulb.

While traditional incandescents will soon be phased out in the United States and abroad, researchers are plugging away to create more efficient versions that comply with looming new standards — while also providing an alternative for consumers who find compact fluorescents objectionable.

Scientists at the University of Rochester gave Green Inc. an advanced peek at their newly-developed method for nearly doubling the efficiency of an incandescent by blackening the tungsten filament with a short pulse laser. The results of their work will be published in an upcoming issue of the journal Physical Review Letters.

According to the Chunlei Guo, an associate professor of optics at the university, the laser process creates a unique array of tiny structures on the surface of the filament, making it more effective at radiating light. Regular incandescent bulbs convert only about 10 percent of the energy used into light, while the rest is emitted as heat.

“With the same electric power input the lamp is about twice as bright,” said Mr. Guo. And though the technology is still in the early stages of development, Mr. Guo believes it would not be difficult for bulb companies to add a tungsten blackening step to the manufacturing process. “The implementation should be fairly straightforward,” he said.

Meanwhile, researchers at Deposition Sciences in Santa Rosa, California have found a way to increase the efficacy of an incandescent to nearly 40 lumens per watt by using reflective coatings which allow waste heat to be converted to visible light. The light output of traditional incandescents, depending on the wattage, are between about 10 and 20 lumens per watt.

“If you can get up to the levels we’re talking about it really changes the game,” said Norm Boling, vice president of research and development for the company. “It means you can have the attributes of an incandescent and still have the efficiency. You can have your cake and eat it too.”

Lighting companies are already using earlier versions of Deposition Sciences’ coatings to manufacture more efficient incandescents, such as Philips Lighting’s Halogena line, which promises to be up to 38 percent more efficient, with light outputs of up to 23 lumens per watt and 3,000-hour lifespans.

In Europe, Philips recently introduced the EcoClassic range of incandescents which are touted as 50 percent more efficient than traditional bulbs.

Industry experts believe the price of advanced incandescents – Philips’ A-shaped Halogenas are about $5.00 a piece at Amazon.com and Home Depot – are expected to come down as more consumers are forced to seek out bulbs that meet new efficiency standards.

Utilities and government agencies are also considering offering financial incentives to make them more affordable.

“If they save energy and are cost effective we’ll bundle them into an incentive program,” said Gregg Ander, the chief architect for the utility Southern California Edison. (California will begin phasing out inefficient incandescents starting in 2011 – one year ahead of the rest of the nation.)

For all of this, light emitting diode (LED) and compact-fluorescent products already on the market have stated efficiency ratings ranging from 40 to more than 100 lumens per watt, making it difficult to predict how long incandescents will stay in the game.

Chris Calwell, a senior research fellow with Ecos Consulting, believes combining various research efforts – such as those occurring at the University of Rochester and Deposition Sciences – may be the key to the incandescent’s staying power.

“Based on the pace of the science we’ve seen thus far, I think we will be surprised at how good the next generations” of incandescents will be, Mr. Calwell said.

Michael Siminovitch, the director of the California Lighting Technology Center, described super efficient incandescents as the “holy grail” of lighting industry research right now.

“The stuff is happening, and will happen,” Mr. Siminovitch said. “We’re all going to be doing it because people hate fluorescents so much.”

The federal Energy Star program does not certify advanced incandescents. But that may change if the technology catches up to C.F.L.s, which are purported to use 75 percent less energy than incandescents and last seven to 10 times longer.

Alex Baker, the lighting program manager for Energy Star, told Green Inc. that if the performance of a halogen or other advanced incandescent source rivaled that of currently qualified C.F.L.s, the program might consider certifying them.