Sustainable By Design: Energy Efficient LEDs Show Promise
By Anne Cosgrove
Published in the April 2006 issue of Today's Facility Manager
Lighting is one of the first building systems many facility managers look at when striving to save energy consumption and costs. For most projects, the savings can begin from the time the new lighting system is in place. This across the board approach to improving efficiency works well for many facilities, and it appears lighting will continue to be a go-to item for facility managers looking for sustainable strategies.
Most facility managers have heard of LEDs (light emitting diodes), but much of the information available indicates this lighting technology has a way to go before being suitable for widespread use throughout a building. Relatively high costs and some operational issues are current challenges, but opportunities to reduce energy usage for specialized areas in and around buildings with LED lighting systems do exist for a variety of applications.
“Today, smaller space illumination is more feasible for LED lighting rather than complete overhead lighting,” says Brian Terao, senior product marketing manager, LED Products at OSRAM Opto Semiconductors in San Jose, CA. “Wall washing, small recessed down lights, cove lighting, MR type fixtures, and task lighting are where we currently see LED applications.”
Some hotels are using LEDs in bedside and bathroom lighting to reduce energy wasted when guests leave lights on when not in their rooms or as a night light. In a pilot project designed to track energy savings, The Sacramento Doubletree Hotel in California installed one-watt LED nightlights outfitted with occupancy sensors in its 400 guestrooms. Data loggers were used to track the lights’ energy consumption over a two-month period. The combination of occupancy sensor and LED technologies resulted in a 50% energy savings compared to the previous fixtures. The project was a partnership of Lawrence Berkeley National Laboratory, the California Energy Commission, the Sacramento Municipal Utility District, and WattStopper, Inc.
Exit signs are an area where LED technology has been embraced in many types of facilities. The U.S. Department of Energy (DOE) reports that LED exit signs with the Energy Star label consume 44kHw of energy annually with a service life of at least 10 years.
On the other side of the coin, facility managers tasked with lighting areas that require large swaths of light are also increasingly employing the technology. Architectural lighting, signage, and grounds illumination are rapidly becoming home to LED applications. The concentrated illumination, energy efficiency, and long life of LEDs make the lighting source a practical choice for these areas.
A primary advantage cited for LEDs is their higher lumens per watt emitted, compared to incandescent and fluorescent lighting. Lumens per watt is the measure of the light output (lumens) produced per unit of input electrical power (watts). While statistics vary (there are currently no industry standards), researchers at the DOE have improved the efficacy of white LEDs to approximately 50 lumens per watt.
This is compared to a fluorescent lamp, which emits about 85 lumens per watt and incandescents, which emit about 15 lumens per watt. LED proponents point out that while fluorescent lamps have a higher lumens per watt output than today’s LEDs, some of these lumens are lost in the fixture or luminaire in which it is housed. Also, LEDs are directional, which results in more of the lumens visible to the eye.
Long life expectancy is another sustainable aspect of LEDs. Some smaller units are cited as having 100,000 hours of life. DOE research has found the white LEDs suitable for larger scale applications have a useful life of around 35,000 hours; other figures are as high as 50,000 hours. (The average life of a fluorescent lamp is between 9,000 and 20,000 hours.) The “useful life” is defined by many manufacturers as the point at which light output reaches 70% of its initial output. LEDs do not burn out; they get dimmer.
Long life also reduces maintenance demands for these lighting systems, which has made LEDs an increasingly popular choice for building exteriors and other places that can be a challenge to access. Durability is also a factor here; since an LED is a solid-state device, it is quite resistant to vibrations.
An operational challenge is thermal management—conducting the heat generated away from the LED. Heat is not radiated as in conventional lighting technology but is retained in the LED package. Controlling this heat is key to successful LED luminaire design and involves a systemwide harmony of components. Therefore, projects that are wholesale replacement of the lighting system are most promising at present.
“A challenge is retrofit versus new fixtures,” says Terao. “To take the most advantage of the benefits LEDs can offer, new fixtures are a good start. While the ability to retrofit existing fixtures will enable more rapid adoption of LEDs, a direct fixture replacement of an LED for a bulb may not be optimal.”
The lack of industry standards is also an obstacle to widespread adoption of LED lighting. Until there is a common set of characteristics across the board, it is not surprising that facility managers will be hesitant to enter this realm of lighting for their buildings. As part of its R&D program, the DOE is working with Energy Star to create LED guidelines for consumers.
So when will LEDs be ready to fulfill the needs of all those lighting applications in between? That is difficult to say. But as research continues and breakthroughs surface, facility managers can be ready for the next step in the development of this technology.
Information for this article was provided through an interview with Terao and from the DOE and the California Energy Commission. For more on the DOE research program, visit www.netl.doe.gov/ssl/. To read more about the Sacramento Doubletree Hotel project, visit www.archenergy.com/lrp/advlight_luminaires/project_4_1_reports.htm; the project number is CEC-500-2005-141-A10.
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