Options for energy-efficient lighting continue to increase. Compact fluorescent bulbs may last longer than incandescent bulbs, but disposal issues because of the mercury they contain, plus general issues with light quality, have made some consumers look for alternatives. Light-emitting diodes, or LEDs, were at first not meant for general home use. However, technological advances have made them a viable competitor to other forms of lighting.
Identification
A light-emitting diode is a solid-state lighting system in which semiconductor material emits light. Solid state means that the apparatus emitting the light is solid and not a gas. Each diode is small, and bulbs meant for general lighting group the diodes together in an array. At first they were only available as colored diodes and not white light, but, in 1993, Japanese company Nichia found a way to change the light from a diode to make it white, by coating a blue chip with a substance called a phosphor.
Uses
Take a look at a string of small Christmas lights, and chances are you'll see that the traditional pointy bulb is now a flat-topped cylinder--an LED. LEDs have been used in penlights, alarm clocks and car lighting. Arrays of diodes combined with different diffuser lenses have allowed manufacturers to build LED bulbs for interior and exterior home lighting, including spotlighting and recessed lights. LED light strips also function as supplemental growing lights for plants. The different diode colors can provide the specific wavelengths that plants need to flower or increase foliage.
Significance
Light-emitting diodes do not contain mercury as compact fluorescent lights do. They also send any heat back into a heat sink behind the diodes, so the array does not emit heat--helpful on a hot day when you want to limit the amount of extra heat around you. LEDs do not emit ultraviolet radiation, either, according to ToolBase Services, and this means the lights do not attract bugs. LED lights are steady--not flickering like some fluorescents--and they don't create interference with electrical appliances such as radios. A quality LED array may last up to 50,000 hours given optimal conditions, and the Energy Star program, run by the Department of Energy and the EPA, reports that LED lighting uses only 25 percent of the energy an incandescent bulb would need.
Drawbacks
Although manufacturers are creating more fixtures that can handle LEDs and LED bulbs now come with bases that fit standard light sockets, LED efficiency and life span still depend on the quality of the fixture. LEDs are also very sensitive to heat, and constant, hot ambient temperatures can reduce the number of life hours of the diodes. Another drawback is cost; ToolBase Services notes that LEDs can cost nearly $25 to $60 for a small array meant for a small lamp or night light. Availability can be an issue as well, although Sari Kreiger of The Wall Street Journal reported in 2008 that the market for LEDs continues to grow.
Considerations
A variety of LED is the organic light-emitting diode, or OLED. The Energy Star program says these are sheets of "carbon-based compounds that glow when a current is applied through transparent electrodes." OLEDs may come in the form of a film or layer that attaches to the wall.
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