LEDs offer numerous benefits due to their mode of operation:
LEDs are highly efficient. In traffic signal lights, a strong market for LEDs, a red traffic signal head that contains 196 LEDs draws 10W versus its incandescent counterpart that draws 150W. Various estimates of potential energy savings range from 82% to 93%. With the red signal operating about 50% of the day, the complete traffic signal unit is estimated to save 35-40%. It is estimated that replacing incandescent lamps in all of America’s some 260,000 traffic signals (red, green and yellow) could reduce energy consumption by nearly 2.5 billion kWh. At the end of 1997, more than 150,000 signals were retrofitted, almost all of them red.
In architectural applications, the greatest penetration of LEDs has been in exit signs, both new signs and retrofits. LED retrofit products, which come in various forms including light bars, panels and screw in LED lamps, typically draw 2-5W per sign, resulting in significant savings versus incandescent lamps with the bonus benefit of much longer life, which in turn reduces maintenance requirements. Some of these products are designed specifically for either on-face or two-face exit signs. Many new LED exit signs are also available, including edge-lit designs. LED products currently make up about 50% of the exit sign market. A study conducted by the Lighting Research Center in 1998 found that about 80% of new exit signs being sold in the U.S. utilize LEDs. Note that most retrofits are restricted to use in stencil-type signs versus panel-type signs.
Some LEDs are projected to produce a long service life of about 100,000 hours. For this reason LEDs are ideal for hard-to-reach/maintain fixtures such as exit sign lighting and, combined with its durability, pathway lighting. This service life can be affected by the application and environmental factors, including heat and if being overdriven by the power supply.
Range of Colors
LEDs are available in a range of colors (see above), including white light. White light can also be produced through color mixing of red, blue and green LEDs. In addition, through the innovative combination of various-colored LEDs, dramatic color-changing effects can be produced from a single fixture through dynamic activation of various sets of LEDs. Manufacturers such as Color Kinetics offer fixtures that employ this principle. Color Kinetics offers track, theatrical, underwater, outdoor and other fixtures utilizing variable-intensity LEDs that can provide more than 16.7 million colors, including white light. These fixtures can be individually controlled via a PC, DMX controller or proprietary controller to generate effects including fixed color, color washing, cross fading, random color changing, strobing and variable strobing.
Dr. Nadarajah Narendran of the Lighting Research Center is doing some exciting research on the use of colored LEDs in retail display lighting. Preliminary research suggests that using colored LED background lighting combined with spot lighting on merchandise may improve energy efficiency and reduce maintenance costs while catching the eye of the consumer in a fresh manner.
No UV Emissions/Little Infrared
LEDs produce no UV radiation and little heat, making them ideal for illuminating objects, such as works of art, that are sensitive to UV light.
LEDs are highly rugged. They feature no filament that can be damaged due to shock and vibrations. They are subject to heat, however, and being overdriven by the power supply.
Small Size/Design Flexibility
A single LED is very small and produces little light overall. However, this weakness is actually its strength. LEDs can be combined in any shape to produce desired lumen packages as the design goals and economics permit. In addition, LEDs can be considered miniature light fixtures; distribution of light can be controlled by the LEDs’ epoxy lens, simplifying the construction of architectural fixtures designed to utilize LEDs. A controller can be connected to an LED fixture to selectively dim individual LEDs, resulting in the dynamic control of distribution, light output and color. Finally, DC power enables the unit to be easily adaptable to different power supplies.
The other benefits of LEDs include:
- Lights instantly
- Can be easily dimmed
- Silent operation
- Low-voltage power supply (increased safety)
by Eric Strandberg,
Lighting Design Lab
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