Table of contents
Introduction
The century has passed since electroluminescence was demonstrate in the laboratory,and nearly 50 years have passed since then- general Electric's Nick Holonyak jr. Invented light - emitting diode LED. Holonyak successfully synthesized a gallium arsenide phosphid.cristal that emits a faint but 'tunable' red light when turned on initially customer applications for LEDs consisted only of portable calculators, music players and TV power indicator.
Discovery of other customers application has lagged behind. For example ten year passed before Holonyak's students discovered how to increase the light output ten times his. Today the energy efficiency,increase light output,long life and significantly faster switching times of LEDs are paving the way for application such as interior lighting, scrolling text displayed,video displayed, automatic lights,outdoor lighting and traffic lights. He was taken this white paper primarily evaluates the foreseeable prospect of LED lighting compared to existing alternative fluorescent lights.
Why LED Technology is Energy - Effecient
LED lighting is helping to transform the built environment in a more sustainable way primarily in team of reducing energy demand. LEDs belong to the class of semiconductors that have replaced transistors and inherently at very low power settings.
Early LEDs used in the first non-analog wristwatches and used to indicate the on state of desk and pocket calculators, portable radio and cassettes players operated just at 30 - 60 milliwatts. It wasn't untill the turn off the century ( 1999 ). That chip sizes become large enough to hold even 1 watt. This performance improvement also required an innovation in mountai mounting the LED chip on a metal block.
Brightness
The technology of LED lighting is maturing, and product on the market already exceed the luminosity - to - power ratio of incandescent bulbs and today's most popular replacement, standard fluorescent lighting.
An incandescent bulbs rated at 60 - 100 watts emits about 15 lumens per watts ( lm/w ), while a standard 40 watts fluorescent bulbs achieves a maximum of 100 ( lm/w ). In 2002 philips limileds lunched his 5 watts LED rated between 18 / 22 lm/w. from 2003 to 2010 manufacturers in the united states japan, south korea and taiwan raised the bar initially reaching 208 lm/w in refrigerator laboratory environment. In 2009, 100 lm/w was already available in commercial products.
Other Advantages
First, the range of available colors continues to expand. For example, in the 1990s gallium arsenide LED were developed by metal oxide chemical vapor deposition of ultra - thin layer of alloys on sapphire.this result is a device structure that reflects at least 90% of the light generator in the active layer.
Almost as soon as the device finally completed the primary color palette of LED lighting ( green ), the brightness double ( marktech optoelectronics 2010).it can now be used outdoors during the day such as that traffic lights. Additionally,LED lighting in team of waste disposal and UV radiation. The product class is so finally tuned that it emits no UV rays at all.
