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

April 6, 2004

General News
LRC studies human response to light, discovers evidence of mechanism leading to melatonin suppression
Experimental setup used to evaluate light exposure from blue LEDs and clear mercury white lamps

Scientists have long known that light plays an important role in regulating the human body’s daily biological rhythms—also known as circadian rhythms—including the sleep-wake cycle, alertness, and hormone production. At night and under conditions of darkness, the pineal gland produces melatonin, a hormone closely related to the body’s master clock. Using techniques from visual psychophysics, LRC researchers are gaining a better understanding of the mechanisms that convert light into neural signals in the human circadian system. A recently published LRC study is the first to show evidence of a “color” mechanism in the circadian system that controls melatonin suppression when humans are exposed to light.

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Expand your lighting knowledge through LRC courses
Logo for Live! From LRC

This spring, the LRC has packed its calendar with a number of lighting education short courses, including Live! from the LRC, a new Internet-based teleconference seminar program, and the ever-popular LED Lighting Institute.

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Field study proves success of fluorescent technology for streetlighting in a rural community
Prototype fluorescent streetlights installed along Clark Street in Easthampton, Massachusetts

Residents and town officials of the rural community of Easthampton, Mass., recently helped the LRC complete a field study regarding the application of fluorescent lamps in streetlights. The purpose of the project was to demonstrate how to use a newly developed photometry system for streetlighting and to combine a design for increased visibility with energy efficiency.

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Lighting quality and office work: A field simulation study
Photograph of simulated office space

This study, led by LRC lighting scientist Peter Boyce, Ph.D., addressed the question: "Can different forms of realistic office lighting affect the performance of office work or the health and well-being of employees?" LRC researchers furnished an office in Albany, N.Y., as a typical open plan workplace for nine workers, with perimeter windows allowing access to a view but with limited daylight penetration. They conducted two experiments involving a variety of lighting installations. These experiments were designed to test the effects of lighting systems on performance and well-being, as well as indications of the processes that might mediate these effects.

The Light Right Consortium funded this study. A 167-page report detailing the study and findings is available at

LRC expands graduate education program

In the coming academic year, the Lighting Research Center will expand its graduate education programs. In addition to the highly successful two-year Master of Science in lighting degree, which has become a leading degree program in the field of lighting, the LRC will offer two new graduate degrees: a one-year master's degree and a doctoral degree in architectural sciences with a concentration in lighting. The existing M.S. in lighting program remains the premier masters program in the field of lighting and will continue to be offered here at the LRC.

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LED study seeks to benchmark performance of high-power devices
LRC research specialist Yimin Gu examining one of the LED life test chambers

The evolution of light-emitting diode technology has brought to market LED products with greater light output, efficiency, and reliability than ever before. Improved performance, experts say, has propelled these devices into an increasing number of niche applications requiring colored light. These experts also agree that we may soon see white LEDs employed in some types of general lighting. Despite a basic understanding of current LED performance, specific data and life predictions have not been established, particularly for the long-term performance of these devices. For the past year, LRC solid-state lighting researchers have been conducting an ongoing, long-term study to better understand the changing characteristics of different LEDs over time and how a variety of operating conditions affect device performance.

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LRC, government and industry work to improve color problems with compact fluorescent lamps
Photo of a typical compact fluorescent lamp

“Expensive.” “Poor color.” “Poor fit.” “Unfriendly.” Consumers participating in a focus group study about compact fluorescent lamps made their views known. Now the LRC, the U.S. Environmental Protection Agency (EPA), and the U.S. Department of Energy (DOE) are seeking ways to improve CFL products and increase consumer acceptance of ENERGY STAR®-rated lamps. In February the LRC gathered Energy Star CFL manufacturing partners for a roundtable meeting, sponsored by the EPA, to present findings from the focus group study and LRC laboratory measurements, and to discuss issues of CFL color consistency.

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Field Test DELTA Snapshots: Staircase lighting
Field Test DELTA Snapshot: Staircase Lighting

Staircase lighting typically remains on at full output levels even when no one is in the stairway. A new DELTA publication examines a new type of lighting control for staircases. The publication shows energy and photometric conditions before and after retrofit with Occu-smart® luminaires, offered by LaMar Lighting Co., Inc. These luminaires use built-in occupancy sensors to automatically dim the fluorescent lamps to a low, standby level when the space is unoccupied.

Two New York City sites were evaluated—a high-rise residential complex and a commercial office building. Flexible settings and adherence to building code illuminance levels were among the reasons the Occu-smart luminaires were selected for the egress staircases at each location. Optional standby levels provide dimmed lighting from 5 percent to 33 percent of full output when unoccupied. The 33 percent option chosen at the residential complex resulted in energy savings of 53 percent, or 50,300 kWh annually. The design of the new luminaires also increased illuminances without sacrificing energy savings. The Occu-smart luminaire features a wrap-around diffuser that emits light at high angles, above 90° from vertical. For more information on this and other DELTA publications, go to

Lighting controls take center stage in commercial-lighting efficiency project
Screen capture of Reducing Barriers website

How can commercial businesses use lighting to control energy consumption? In the United States, businesses spend 20 percent to 30 percent of their total energy budget on lighting. Lighting controls and energy-efficient lighting systems have long been promoted as tools to control energy consumption, yet customer acceptance and implementation are still low. LRC researchers recently wrapped up a three-year project exploring the problems, questions and potential solutions associated with the use of lighting controls and systems designed to reduce energy demand.

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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.

2004 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.

Rennselear Polytechnic Institute