Martha Krebs, head of DOE's Office of Energy Research, was in Sacramento for the public debut of a sulfur lamp lighting system (in background) designed by Berkeley Lab scientists.
Researchers at the Center's Lighting Research Group have developed the first high-efficiency lighting fixtures to capitalize on the extraordinary brightness and remarkable energy efficiency of the award-winning sulfur lamp. Through a partnership between Berkeley Lab and Cooper Lighting, a major U.S. lighting manufacturer, prototypes of these new fixtures have been installed in the headquarters lobby of the Sacramento Municipal Utility District, one of the largest municipal utilities in California.
"This system will make it practical for sulfur lamps to be integrated into common interior spaces, which should accelerate their market penetration," says Michael Siminovitch, a principal investigator in the Building Technologies Program's Lighting Group. Although these new fixtures were designed around the physical dimensions and photometric properties of a specific commercial sulfur lamp, the technology behind them can be applied to other 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. 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. The sulfur lamp (Spring 1995, p. 5) was unveiled two years ago. Consisting of a golf-ball-sized glass globe filled with argon and a tiny amount of sulfur, the 1,000-watt version of this microwave-powered lamp is six times more efficient and 75 times brighter than a conventional 100-W incandescent bulb.
The sulfur lamp was invented by Fusion Lighting Inc. of Rockville, Maryland, which is now selling a 1,000-W version called the Solar 1000. (DOE provided some of the financial support for this R&D.) A major impediment to the widespread adoption of the sulfur lamp has been the lack of high-efficiency fixture systems for delivering its light to the interiors of commercial spaces. To distribute the illumination, sulfur lamps on display at the Forrestal Building, DOE's headquarters in Washington, D.C., relied on a light guide, a hollow tube lined with a reflective material. Light from the source travels along the reflective material, diffusing out to illuminate the space.
"Illumination from a light guide can pose problems with glare and low efficiency when used to light interior spaces," according to Siminovitch. What has been needed is an indirect, low-glare system that takes advantage of not only the high energy efficiency and brightness of sulfur lamps, but also their high CRI (Color Rendering Index), which puts them on par with sunlight for quality of illumination.
Siminovitch, Carl Gould, and Erik Page, all with the Lighting Group, 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 applications from interior spaces of shopping malls to building 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," says Siminovitch. "By varying the distribution geometry and the relative spacing of the kiosks, they can deliver a large range of illuminances." A single kiosk could replace from 10 to as many as 30 conventional ceiling fixtures in an open-space office. In laboratory tests, the light fixtures scored an efficiency rating of 90 percent, which is significantly higher than the ratings for light guides and among the highest ratings for any white light source/fixture system. Working closely with a manufacturer of light fixtures was a critical asset to this research.
"Cooper Lighting brought insights and capabilities to the table as to how this technology could be manufactured," says Siminovitch. "It's a good example of how the products of science can lead to commercial opportunities through an industrial partnership."
--Lynn Yarris
Michael Siminovitch
Building Technologies Program
(510) 486-5863; (510) 486-6940 fax
Lynn Yarris is senior writer in Berkeley Lab's Public Information Department.
This research is supported by DOE's Office of Building Technologies, State and Community Programs, with cost-sharing from Cooper Lighting and SMUD