PNNL researchers see the light

December 14, 2012 

Jeff McCullough of Pacific Northwest National Laboratory opens the door to a styrofoam-insulated chamber, and inside 202 light bulbs are screwed into sockets on its top, every one of them burning brightly since May 2010.

The bulbs could change the way America lights its homes and businesses.

The improved light-emitting diode, or LED, bulbs last so long that you could put them in your will and your heirs could continue to use them, joked Marc Ledbetter, emerging technologies program manager for PNNL, during a tour Friday of its Lumen Maintenance Test Facility in Richland.

To date, the bulbs have burned for 21,500 hours and still have plenty of life left. They could last for 25,000 to 35,000 hours, or 25 to 35 years of typical use, according to PNNL.

More importantly, they use less energy than traditional incandescent light bulbs or compact fluorescent bulbs, researchers said. If every conventional 60-watt incandescent bulb in the United States were replaced with one, the nation would save $3.9 billion, according to the Department of Energy.

They use about one-sixth the watts of an incandescent bulb to produce the same output of light.

Soon they are expected to be on display at the Smithsonian, along with Thomas Edison's original incandescent bulbs, Ledbetter said.

"It really is that groundbreaking," he said.

PNNL, a Department of Energy national laboratory, was picked by DOE to conduct the light bulb testing for its Bright Tomorrow Lighting Prize, or L Prize, competition.

It's a contest developed in response to the Energy Independence and Security Act of 2007 to speed the development of more efficient lighting. Lighting accounts for 20 percent of the nation's energy use, Ledbetter said.

In the first phase of the

contest, manufacturers competed to develop a bulb to replace the typical 60-watt incandescent bulb, which has had the same basic design since Edison improved them in 1878.

The $10 million prize was won by Phillips last year for an LED bulb that met specifications developed by PNNL for meeting stress tests, requiring low power, being long lasting and providing a good quality light. The contest is credited with advancing Phillips' development of the bulb by three to five years in an already fast-changing field, Ledbetter said.

"The technology is on basically a rocket regarding performance," he said.

Although that part of the contest to find the best replacement for a 60-watt incandescent bulb is over, PNNL continues to test the performance of the winning LED lights.

"They are the most tested light bulb in history," said McCullough, PNNL senior research engineer.

In one of two PNNL test chambers, built at a combined cost of $1.3 million, a computerized robot tests the light given off by each bulb. The sphere-shaped robot moves along a track, taking about an hour to surround each bulb one by one and collect readings on light output and light quality.

Unlike incandescent bulbs that go dark suddenly when the filament inside breaks, LED bulbs slowly dim over time. But after 21,500 hours, these LED bulbs have yet to start dimming. Based on their performance to date, Ledbetter estimates they still will be at 98 percent brightness at 25,000 hours.

By contrast, incandescent bulbs typically burn for 750 to 1,000 hours before burning out, and compact fluorescent bulbs may last for 6,000 to 10,000 hours, although switching them on and off will shorten that.

The LED bulbs also have a light quality that many people prefer to fluorescent bulbs. Their light has the warm quality of incandescent lights, and they have a high color quality, rendering colors as true, the researchers said.

The Phillips L-Prize bulbs were sold in cooperation with certain utilities in some areas of the nation for about $50 initially, before dropping to the $30 to $35 range, Ledbetter said.

Some lighting experts project the price of high-quality LED bulbs will drop to less than $10, not a bad price for a bulb that lasts 25 times as long as incandescents, he said.

Now DOE is searching for the best replacement to the 90-watt halogen reflector lamp, or flood light, a bulb used for track lighting, outdoor security lights, retail spot lights and down lights.

PNNL has set up its second chamber in its Lumen Maintenance Test Facility in Richland to be ready for those bulbs.

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