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

Friday, October 3, 2003

Load-shedding systems may reduce power outages
LRC is developing low-cost system to limit electric demand at peak times.
In light of the recent distressing power outages to northeastern United States, new methods of reducing strain on the nation's power grid are in greater demand than ever. Rather than sacrificing our precious air conditioning, new lighting methods allow office workers to keep their cool while offering energy-efficient, cost-effective means to reduce the likelihood of further system failures. Lighting could present businesses with an inexpensive "insurance policy" against such interruptions.

The Lighting Research Center at Rensselaer Polytechnic Institute, in conjunction with the US Department of Energy, New York State Energy Research and Development Authority, California Energy Commission, and Connecticut Light and Power, as well as leading lighting manufacturers, have been developing a simple, practical and low-cost system using the concept of load shedding-limiting the demand for electricity at particular times to make better use of existing electric capacity.

Over the last three years, LRC researchers have developed load-shed lighting systems to allow a utility, in cooperation with building managers, to shed electric load quickly and reliably by sending a signal to a building's lighting system. Andrew Bierman, LRC lighting system specialist, states, "The ballast works by reducing the current supplied to the lamps, thereby dimming them by 30 to 60%. This reduction in lamp current reduces electrical power demand." While a seemingly small power reduction when viewed as an individual light bulb, the lighting systems of commercial buildings contain thousands of lights—typically three for every 100 square feet. Nearly a megawatt of electrical load could be reduced for every 3 million square feet of occupied commercial real estate. Bierman adds, "This load could be shed at a moment's notice and would not disrupt the activities of the occupants."

Unlike other electrical loads, lighting can be operated at reduced power levels for short periods of time with little or no decrease in the productivity of business. This is because people are remarkably adaptive at working under a variety of lighting conditions. LRC studies indicate that temporary light level reductions of up to 50% are acceptable to the majority of occupants engaged in common office tasks. In fact, light level reductions of up to 15% are undetectable to most people if such reductions occur smoothly over a period greater than a few seconds. For larger reductions, smoothly reducing light levels over a period of a few seconds greatly reduces the perception that light levels have changed.

Lighting is an easy target for those interested in reducing and even preventing energy grid crises. Virtually all commercial buildings use lighting. Done properly, lighting is easy to control. Lighting load reduction is measurable, repeatable, and largely independent of other variables. By contrast, to effectively measure energy savings in HVAC systems, factors such as outside temperature, humidity, area size, number of occupants, and the activity of those occupants must be considered.

"Load management through lighting is a viable alternative to building new power stations and should be part of an integrated public policy strategy to prevent future outages," says Dr. Mark Rea, Director of the LRC.

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



© 2003 Rensselaer Polytechnic Institute, Troy, NY 12180 USA.

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