1. Why LED lighting?

  A Light Emitting Diode (LED) is an electronic device that produces light when an electrical current is passed through it. The color of light that is emitted is dependent on materials from which the LED is made. LEDs are available in red, blue, amber, green and near-UV colors, with lumen outputs ranging from 10 - 200 lumens. The LEDs used predominantly in general illumination applications are “phosphor converted blue” LEDs, which are blue LEDs that have a layer of yellow phosphor placed over the chip. The phosphor absorbs some of the blue light and emits yellow light. When the unabsorbed blue light mixes with the yellow light, it creates “white” light.
There are several advantages as well as limitations in LEDs for general illumination purposes as seen in the IESNA table below.

 LED-based lighting fixtures can achieve efficacies ranging from 25 LPW to over 80 LPW, compared to an incandescent efficacy of 5-10 LPW. LEDs convert electrical energy to light at an efficiency of ~30%, compared to <5% for an incandescent, resulting in dramatically lower heat produced. LEDs can also achieve useful lifetimes ranging from 25,000 hours to >100,000 hours, compared to ~1000 hours for an incandescent. In addition, LEDs do not contain hazardous materials such as mercury vapor found in siCFLs. One of the limitation of LEDs are higher costs as high brightness LEDs, necessary for general illumination, are expensive. They also require electronic drivers to convert conventional AC voltage to discrete DC voltages for the LED arrays. These factors, combined with special thermal design considerations, make LED-based fixtures considerably more expensive. Another is limited applications due to the constraints of operating temperature environments, relative young technology and a slower uptake. LED-based lighting fixtures are not always available for every application or aesthetic requirement. Lastly, the wide range of LED-based lighting product types available means not all LED lamps are dimmable, and the ones that are can be limited in dimming performance and system compatibility.