Monday, April 30, 2007

Low-Energy LED Lighting for Streets and Buildings

The 1,500 foot long LED display on the Fremont Street Experience is currently the largest in the world.
Enlarge picture

A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light through a form


of electroluminescence. LEDs are small extended sources with extra optics added to the chip, which emit a complex intensity spatial distribution. The color of the emitted light depends on the composition and condition of the semiconducting material used and can be infrared, visible or near-ultraviolet.

The Department of Trade and Industry-led Technology Programme in UK has funded a £175,000 ($350,000) grant to researchers at The University of Manchester to develop powerful low-cost LED lighting modules that can be used in buildings and on roads. Dialight Lumidrives - a company founded by a former student - is contributing another £175,000 to the scheme.

The main goal is to investigate how tightly packed groups of LEDs can be made to work safely and reliably, and with less energy consumption and lower sosts. LEDs lighting solutions have the potential to reduce energy consumption by between 25 and 50 per cent, depending on the applications.

Illumination applications using LEDs are already being used in advertising panels in the streets and for traffic lights, but their use in street and building lighting has yet to overcome some obstacles.

The technical ones involve thermal and electrical issues at the desired lighting levels (of 12,000 lumens and above, when a typical 60w household light bulb produces about 800 lumens), like the amount of heat generated by LEDs packed closely together.

Since the project aims to develop LED modules to be used outside, environmental factors will also be a concern, such as glare, pollution and even the possibility of a bird nesting over a vital heatsink.

Dr Roger Shuttleworth from the Power Conversion Group at The University of Manchester, said: "LED technology first came to prominence in instrument displays back in the 1970s, but we are increasingly seeing it used in things like traffic signals and car lights. Towards the end of the twentieth century, the old fashioned sodium street lights that made everything look orange were gradually replaced by high-pressure sodium lamps. While these are brighter and more aesthetically pleasing, and can help tackle street crime and anti-social behaviour, they are also less energy efficient. With the environment at the top of the public and political agenda, energy saving has become a very important issue. When you consider how many street lights there are in the UK alone, it's clear there are some big opportunities for energy and cost savings."

The many benefits of LEDs will include cutting energy consumption and overall running costs, reducing light pollution and the glow that radiates from big cities, and their longer lifespan which means they would need to be replaced less often, potentially cutting down on traffic disruption and local council repair bills.
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