First Sulfur Lamp Lighting Fixtures Debut

November 22, 1996

By Lynn Yarris, [email protected]

Berkeley Lab scientists have developed the first lighting fixtures to capitalize on the extraordinary brightness and remarkable energy efficiency of the award-winning sulfur lamp. Prototypes of these new fixtures were installed in the lobby of the headquarters of the Sacramento Municipal Utility District (SMUD) and unveiled to the public last week.

"This system will make it practical for sulfur lamps to be integrated into common interior spaces, which should accelerate their market potential," says Michael Siminovitch of the Energy and Environment Division. Siminovitch was one of the principal investigators behind the concept and design of the new fixtures.

The research was carried out under a partnership between Berkeley Lab and Cooper Lighting, a major U.S. manufacturer. Although the new fixtures were designed around the physical dimensions and photometric properties of a specific commercial sulfur lamp, the technology can be applied to other highly bright, energy-efficient electrode-less lamps now under development.

Indoor lighting accounts for about 25 percent of the electrical energy consumed in the United States each year. It has been estimated that this consumption, which costs about $30 billion, could be cut in half if existing lighting systems were to be replaced with advanced energy-efficient alternatives. Two years ago, a new type of lighting technology--called a sulfur lamp--was unveiled and widely touted as the lamp for the 21st century. (It won several awards, including a 1995 Discover magazine award for technological innovation.) Consisting of a golf-ball sized glass globe filled with argon gas and a tiny amount of non-toxic sulfur, this microwave-powered lamp was four times more energy efficient and 75 times brighter than a conventional 100 watt incandescent bulb. It also outperformed the best fluorescent lamps.

The sulfur lamp was invented by Fusion Lighting Inc., a small company in Rockville, Md., which is now field testing a 1,000-watt version called the Solar 1000. A major impediment to the wide-spread adoption of the sulfur lamp has been the lack of high-efficiency fixture systems for delivering its light to the interiors of commercial spaces. Sulfur lamps on display at the headquarters of the U.S. Department of Energy, which helped fund the development of the prototype, relied on a "light guide" to distribute the illumination.

"Light guides are hollow tubes lined with a reflective material," says Siminovitch. "Light from the source travels along the reflective material and bleeds out to illuminate a space."

Illumination from a light guide can pose problems with glare and low efficiency when used to light interior spaces, Siminovitch says. What has been needed, he says, is an indirect low-glare system that could take advantage not only of the high energy efficiency and brightness of sulfur lamps, but also of their high CRI (Color Rendering Index), which puts them on a par with sunlight for quality of illumination.

Siminovitch and two colleagues in E&E's Lighting Research Group--Carl Gould and Erik Page--have developed a fixture that can be fitted with different reflectors to provide a variety of light distribution patterns. The fixture can also be mounted in various ways--on a free-standing kiosk, or on a wall or ceiling--to provide a high degree of flexibility and suitability across a broad range of interior lighting applications, from shopping malls to interior complexes and offices.

The free-standing kiosks are especially adaptable. "A series of detailed studies have been completed on developing optimized reflectors (for the kiosks) to accommodate different ceiling heights," Siminovitch says. "By varying the distribution geometry and the relative spacing of the kiosks, a large range of illuminance can be easily delivered."

Siminovitch claims that a single kiosk could be used to replace from 10 to as many as 30 conventional ceiling fixtures in an open-space office. In laboratory tests, their light fixtures scored an efficiency rating of 85 to 88 percent, which is as much as 25 percent better than the ratings for light guides, and among the highest ratings ever scored for any white light source/fixture system. Working closely with a manufacturer of light fixtures was a critical asset to this research, Siminovitch says.

"Cooper Lighting brought insights and capabilities to the table as to how this technology could be manufactured," he says. "It is a good example of how a piece of science can become an actual commercial opportunity through an industrial partnership."

Two of the new fixtures, outfitted with the Solar 1000 sulfur lamp, were switched on during an official "lighting ceremony" in the spacious lobby of SMUD headquarters on Nov.14. The fixtures are about eight feet tall and resemble flashlights standing on end with their beams directed skyward. About 20 seconds after the lamps were activated in the ceremony, their spinning sulfur light bulbs reached full speed and filled the lobby with easy-on-the-eyes illumination.

Speaking at the lighting ceremony along with representatives from SMUD, Cooper Lighting, and Fusion Lighting, were Berkeley Lab Director Charles Shank and Martha Krebs, head of DOE's Office of Energy Research. Although funding for this project came from DOE's Office of Energy Efficiency and Renewable Energy, Krebs has been one of the champions for Berkeley Lab's lighting program since her days here as an associate laboratory director.

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