The long-awaited sulfur lamp
Ever since October of 1994 when Rockville, MD-based manufacturer Fusion Lighting Inc. introduced the sulfur microwave lamp (with help from the U.S. DOE), those in the lighting industry have been watching the high-tech lamp carefully.
Fusion’s Solar 1000 sulfur lamp operates by bombarding a golf ball-sized bulb filled with sulfur and argon with microwaves from a device called a magnetron. The light emitted has a very high efficacy of 105 lumens per watt, a correlated color temperature of 6000K, a CRI of 79, and can be dimmed to 30% of output with less than 300 Kelvin color shift. Additionally, only 27% of the light emitted from the lamp is in the ultraviolet or infrared spectrum, compared to 50% for metal halide and 62% for cool white fluorescent. Recently, the company increased the lamp’s lumen maintenance to 100%, and although the bulb has an essentially limitless lifespan, the system’s life is limited by the magnetron’s 20,000 hour rating.
Over the last several years, the lamp has won awards from Popular Science and Discover for its innovative design, and has been installed — usually with accompanying light-distribution systems by companies like
3M — in a number of demonstration areas, including the National Air and Space Museum, an auto assembly plant in Michigan, a subway installation in Sweden, and, just recently, an Air Force base in Ogden, TX. "We’ve been doing many prototype demonstration installations, but we believe that in ‘98 we’ll be going to a production level," said Dan Estrada, a spokesman for the company. Although the price of the lamp varies depending on the delivery system, in a light pipe system the lamp’s cost is approximately $2,500 per unit, plus $60 per foot of light pipe. "It’s a competitive system when the life-cycle costs are considered," said Estrada.
"The jury is still out on the sulfur lamp," said Jo Anne Lindsley, principal of Lindsley Consultants Inc., a New York-based lighting design firm. "My initial opinion of the lamp after seeing it in a test demonstration in Washington was that the color was problematic — pale and slightly greenish. But the light can be filtered, and there are some experimental projects using fiber optics we might use it for."
A major problem with Fusion’s lamp has been the weight of the power supply for the magnetron system, which could weigh as much as 50 pounds. The recently introduced Light Drive 1000 system, however, includes a new lightweight electronic power supply that allows the entire lamp system to weigh in at approximately 20 pounds.
The lamp also lacks a wide variety of fixtures, a problem companies like Cooper Lighting and Moldcast Lighting are working to address. In fact, early last year Cooper Lighting installed two prototype freestanding kiosks in the Sacramento Municipal Utility District building in Sacramento, CA. The kiosks use the Fusion lamp to indirectly light a 2,000-square-foot room. Meanwhile, Fiberstars is working on a fiber optic system that efficiently distributes the lamp’s bright light.