LED lighting sources operates differently than incandescent and fluorescent sources. Unlike previous generations of luminaire technology, it does not use electrically excited gas to produce luminance. It uses diodes, or semiconductors, that illuminate when current passes through them.
LED lighting is the most energy efficient light source. These bulbs last far longer than incandescents and CFLs. They also, when they are properly engineered, are far more versatile than other sources of illumination. The only drawback that they currently offer is front-end cost. They are typically much more expensive than halogens, incandescents, and fluorescent lamps. However, their cost effectiveness comes in the form of savings produced by lower operating costs.
Originally LEDs were either red, green, amber, or blue. There never has been such a thing as a white LED. However, white illuminance can be produced in two different ways. One method mixes luminance together. The other uses a phosphor coating that changes the color of the illuminations to white. Phosphor coating on bulbs can be readily recognized by its yellow color.
Solid state technology prevents LED lighting from failing the way incandescent and fluorescents do. However, they can begin to fade through a process known as lumen depreciation. Direct flow of current heats up the diode. This heat has to be drawn away from the semiconductor by a heat sink. Thermal management is the most important aspect of diode based illumination. Keeping temperature down is the key to longer lamp life. Otherwise, the amount of luminance will decrease and the color will shift. Because of the color shift, LED product lifespan is based on the anticipated future depreciation of 30 percent of the bulbs suffering from lumen depreciation.
Solid state replacements are available for incandescent and CFLs. Larger bulbs look like traditional bulbs but do not emit luminance the same way. As directional luminaires, they shine luminance in a linear direction, so special bulb designs and reflectors are needed to disperse the luminance in the same manner that incandescent and fluorescent bulbs operate.
Standard, retail LED lighting products can replace incandescentlamps that are rated 5 to 60 watts. Newer products can replace even higher wattages. These products must, however, exhibit superior lumens output to qualify as legitimate retrofits. For instance, in the EU, lamps used to replace 60 watt incandescent bulbs must output 806 lumens. This is in Europe.
There are many new types of solid state fixtures emerging on the market. There are track lights, recessed luminaires, and standard bulbs. The US department of energy estimates that over the next 20 years LEDs will save the country 265 billion dollars and prevent the construction of 40 new power plants. Cost has decreased to 50 dollars or less.
Many decorative LED lighting products can now be used with dimmers. LEDs last approximately 30,000 hours if they can operate at normal or cooler than normal temperatures. Dimmers are one way to reduce temperature. Compare this to 1000 hours for incandescent bulbs and 8000 for fluorescent. This advance in engineering allows diode-based festoon lamps to be incorporated into general applications.
Because these bulbs are small, they can be used for a number of high-end designs. Examples include the decorative illumination of coves, cabinets, and kitchen counter tops.