A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are becoming more common place as awareness of their effectiveness spread. Introduced as a practical electric component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.
When a light-emitting diode is forward-biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. LEDs are often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern.
LEDs present many advantages over incandescent light sources including lower Energy Consumption, longer lifetimes, improved robustness, smaller size and faster switching. LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output. Solid state devices such as LEDs are subject to very limited wear and tear if operated at low currents and at low temperatures. Many of the LEDs made in the 1970s and 1980s are still in service today. Typical lifetimes quoted are 25,000 to 100,000 hours, but heat and current settings can extend or shorten this time significantly.
Efficient lighting is needed for sustainable architecture. A typical 6-watt LED lamp emitted 450 to 650 lumens which is equivalent to a standard 40-watt incandescent bulb. A standard 40-watt incandescent bulb has an expected lifespan of 1,000 hours, whereas an LED can continue to operate with reduced efficiency for more than 50,000 hours, 50 times longer than the incandescent bulb.
One kilowatt-hour of electricity will cause 1.34 pounds (610 g) of CO2 emission. Assuming the average light bulb is on for 10 hours a day, one 40-watt incandescent bulb will cause 196 pounds (89 kg) of CO2 emission per year. The 6-watt LED equivalent will only cause 30 pounds (14 kg) of CO2 over the same time span. A building’s carbon footprint from lighting can be reduced by 85% by exchanging all incandescent bulbs for new LEDs.
LED light bulbs could be a cost-effective option for lighting a home or office space because of their very long lifetimes. Consumer use of LEDs as a replacement for conventional lighting system is becoming increasingly popular. In general, all the LED products (all products utilized for consumer use) can be divided into two major parts: public lighting and indoor lighting.