Advancing the effective use of light for society and the environment.

Tuesday, July 12, 2005

Study Explores Life, Dimming Capabilities of Fluorescent Lamps
By Jennifer Taylor
Dimming fluorescent lamp life test
Conan O'Rourke checks on dimming fluorescent lamps undergoing long-term life testing.

In June, the Lighting Research Center initiated one of the largest independent studies of fluorescent dimming systems to date. Over the next three to five years, the LRC will run a life-test study to investigate the performance of linear fluorescent lamps on a wide range of dimming ballasts, testing more than 850 systems in all. The results of this study will offer insights into critical design criteria for the compatibility and reliability of fluorescent dimming systems. In turn, these insights will provide a foundation for industry standards and a starting point for the development of improved products for controlling lighting and electrical loads.

The impetus for such a large-scale study is the growing interest in using advanced lighting control strategies to reduce energy consumption in buildings, says Conan O’Rourke, principal investigator for the life test. These strategies include dimming electric lights when enough daylight is available, or when it is necessary to reduce electricity consumption during times of high demand.

Fluorescent lamps originally were designed to work in a steady state-either fully on or fully off-not dimmed, says O'Rourke. Although fluorescent dimming systems have been manufactured and installed successfully in commercial buildings for 30 years, the impact of dimming on lamp life is not completely understood. Fluorescent dimming standards also have not been developed. These factors, combined with high initial costs, have limited widespread implementation of dimming control systems in commercial buildings.

O'Rourke says the study's aim is to explore the operational parameters of dimmed fluorescent lamps in order to minimize any performance problems that may appear and to provide a scientific basis for the development of standards. "Problems with just a small percentage of fluorescent dimming systems can be damaging to the industry as a whole," he says.

In 2003, the LRC conducted an initial study that looked at the interaction between dimming ballasts and fluorescent lamps, including failure mechanisms, electrode characteristics, ballast operation, and the effects of starting on lamp life (see Reducing Barriers to the Use of High-Efficiency Lighting Systems). The new life test, funded by the U.S. Department of Energy (DOE) and the National Electrical Manufacturers Association (NEMA), will build upon this prior research and provide a greater understanding of the measures that ensure lamp/ballast compatibility and reliable operation of dimming systems for controllable lighting applications.

Phase one of the project wrapped up last month with measurements to characterize all 864 systems and the official “switch on” of the lamps and ballasts. Prior to beginning the life test, the LRC worked with DOE, NEMA and the lighting industry to design the experiment. O’Rourke says from this point forward, the LRC will be monitoring each system for failure and will investigate the reason for failure. After completing the life test, the LRC will work with the DOE, NEMA and the lighting industry to draft standards for the dimming operation of fluorescent lamps. The LRC also will provide testing results to the lighting industry. O’Rourke says, “In the end, we hope that this work will lead to better performance and lower costs of dimming systems, which will spark demand and get more energy-saving lighting technologies into buildings.”

About the LRC

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment.


Rennselear Polytechnic Institute