An Old Tradition Showcases the Newest Lighting
Technology
Source: US Department of Energy, Federal Energy
Management Program
Publication date: March 7, 2007
To the casual observer there was not anything particularly unusual
about the Capitol Christmas tree this year. The 65-foot Pacific
Silver Fir was as beautiful as any tree that has graced the Capitol
lawn since the tradition began in 1964. But for federal employees in
the know, this year's tree was a shining example of cutting-edge
technology. In addition to its 3,000 handmade ornaments, the tree
featured 10,000 light-emitting diode (LED) lights-lights that are up
to 90 percent more efficient than their incandescent counterparts
and cost just a fraction of the price to use. In fact, this year's
tree cost a mere $1 per day in energy.
Use of the LED lights signaled a federal commitment to conserving
energy, according to Architect of the Capitol (AOC) Alan Hantman,
who served as master of ceremonies at the tree lighting ceremony.
The Congress and the Office of the AOC are committed to implementing
energy-saving measures across the Capitol Hill complex and already
plan to use LEDs on future trees.
In 2005, approximately one-third of the lights on the Capitol tree
were LEDs, as a transition to all LEDs this year. The move to LEDs
was based on the clear efficiency advantage of LEDs and the fact
that LED bulbs last substantially longer before needing to be
replaced. While not as bright in appearance as traditional
incandescent bulbs, the intensity of the color of LEDs is greater,
making this year's rich red and blue bulbs a memorable image. The
strings of LED lights also proved easier to mount on the tree.
Eventual widespread use of LEDs by consumers will contribute
significantly to energy conservation. The conversion of electricity
into useful light is one of the least efficient energy conversion
processes in buildings today. Consumers and businesses spend
approximately $58 billion each year to light their homes, offices,
streets, and factories. Energy consumption for all lighting in the
United States is estimated to be 8.2 quads, or about 22 percent of
the total electricity generated in the U.S.
The Department of Energy's (DOE) Building Technologies Program has
the mission of reducing the amount of electricity used to illuminate
buildings by 50 percent by 2025. The Program is working in close
collaboration with research and industry partners to develop and
demonstrate energy-efficient, high-quality, long-lasting lighting
technologies, including white-light LEDs.
Colored LEDs have been around since the 1960s and are commonly used
in home electronics, automobile taillights, and even some traffic
signals and exit signs. White LEDs, however, are just now reaching
the point where they have enough luminous output and power to be
viable for building applications and consumer use. For most general
illumination applications, current LEDs cannot yet compete with
traditional sources on performance and cost.
In terms of performance, many of the white-light LED products
currently marketed as "energy efficient" have very low light output
compared with conventional light sources. This makes them less
desirable than their incandescent or fluorescent counterparts for
reading lamps and other applications requiring bright light. They
may be perfect, however, for applications where light is
specifically directed, such as lighting outdoor steps or pathways.
This is because LEDs emit light in a less diffuse pattern than
conventional bulbs, which emit light in all directions.
LEDs are the clear winners when it comes to durability and
efficiency. Being a solid-state device makes LEDs highly resistant
to damage caused by vibration, and the best white LEDs have been
found to have a useful life of about 35,000 hours, or four years of
continuous operation. Researchers have also improved the efficiency
of white-light LEDs to approximately 50 lumens per watt, almost four
times more efficient than incandescent sources.
There is widespread variation among current white LEDs primarily
because there are no consensus test procedures or performance
standards for LEDs. DOE is working to change that through its Solid
State Lighting Partnership with the Next Generation Industry
Alliance, an industry group including lighting giants General
Electric, Philips, Sylvania, and others. Working through this
partnership and others, DOE is involved in the testing of LED
fixtures, the creation of ENERGY STAR® criteria, and technology
procurement programs to help bring better-quality LEDs to market.
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