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Choosing Lighting Fixtures –
Light-emitting Diode (LED) Technology and Applications

There have been great leaps in efficient lighting in recent decades, from the traditional incandescent to halogen to compact fluorescents. The next technology on the horizon is light-emitting diodes (LEDs).

LEDs were introduced in the 1960s, but high costs limited them to a few niche applications such as on/off indicators on home and office electronics. There have been great advances in recent years, and LEDs are being commonly used for traffic signals, vehicle brake lighting and exit signs.

There are many advantages to LED lighting, the greatest being efficiency. Many LEDs offer 90 percent efficiency, compared with 5 percent for traditional lighting sources. This represents significant cost advantages to consumers and reduced greenhouse gas emissions that contribute to climate change.

Other advantages include:

  • long life
  • low heat dissipation
  • improved visibility
  • resistance to shock and vibration
  • reduced maintenance costs
  • vivid colours
  • high luminous intensity
  • compatibility with integrated circuits
  • compact size and light weight

The many potential applications for LEDs are only just being explored. These include street lighting, seasonal lighting, commercial signage and indoor/outdoor residential lighting. LEDs will not only revolutionize how we light to see, but how we see lighting.

Technology Profile on LED

Light-emitting diodes (LEDs) life span and flexibility are just some of the features that set LEDs apart from other light sources.

How Do LEDs Work?

An LED is a semiconductor device (diode) that emits light when an electric current passes through it. The diode produces a monochromatic (one colour) light on a single wavelength ranging from red (˜700 nanometres) to blue-violet (˜400 nanometres). Because LEDs produce a pure colour of light, tinted lenses are not needed to filter the light to the desired colour. As a result, all of the visible light is projected from the LED.

LEDs consume very little power – they are up to 90 percent efficient, which means that only a small proportion of the input energy is consumed to produce heat. In comparison, traditional light sources (e.g., incandescent bulbs) are 5 to 10 percent efficient, with 90 percent or more of the input energy wasted in the form of heat.

Another type of LED currently under development is made up of semiconducting organic polymers. These organic LEDs (OLEDs) are only about 10 percent efficient but are expected to be less expensive to manufacture than regular LEDs.

A Little History

The first LED – a diode emitting yellow light – was developed by Henry Joseph Round in 1907. This early version was too dim to be useful, however, and it was not until 1968 that visible red light was emitted through a diode.

Over the years, diode technology was improved to create more colours and to increase the brightness of the light projected. Until the 1990s, however, high production costs limited the use of LEDs to a few niche applications, such as "on/off" indicators for home and office electronics.

Today, LEDs that produce red, green and amber light are a proven technology that can generate significant energy, operating and maintenance cost savings. As the purchase price of LED products continues to decline, their use is growing. LEDs are now used in many applications, including traffic lights, exit signs, flashlights, outdoor lighting, tunnel lights, seasonal and display lighting, automotive lights, roadway lighting, commercial signage and more.

Researchers are continuing to develop a cost-effective white light that will allow LED technology to compete with other light sources in the lucrative residential and commercial markets.

More than Energy Efficiency

LEDs offer substantial benefits beyond energy efficiency, they:

  • have no moving parts and are much more robust and resistant to vibration than other light bulbs available on the market.
  • have a much longer life span than regular bulbs. Some LEDs can operate for up to 100 000 hours, depending on the quality of the diode and the application. (The life span for LEDs can vary significantly and light output will diminish over time.)
  • produce a highly visible light and are compact in size, facilitating their use in a variety of capacities.
  • produce coloured light, eliminating the need for a tinted lens to produce the desired colour. In outdoors applications, this prevents a phenomenon known as "phantom light," which occurs when the sun (or other light) reflects off a tinted lens or traditional light source and makes a light appear to be on when it is off.
  • do not generally suffer catastrophic failure after initial energizing. If individual diodes do fail, the overall light output will not be noticeably affected, thus strengthening product reliability. This feature, along with LEDs' resistance to impact and vibration, can make a lighting product less prone to vandalism in some applications.
  • can deliver additional savings through reduced maintenance costs (i.e., they can avoid the material and labour costs involved with continually replacing conventional bulbs).

The voltage and current required to operate LED lights are so low that small batteries or solar panels can be used as a back-up power source, improving safety in traffic signal applications. In some cases, solar panels can act as the primary power source, avoiding the costly construction of power lines to remote locations.

Although the benefits are many, LED technology has some drawbacks. For example, the intensity of LED lights tends to decrease as the temperature around the lights increases. As well, light intensity diminishes over time. Research is continuing to resolve these issues.

LEDs: Light at the End of the Tunnel

Clearly a leader on the energy efficiency front, LED technology is poised to revolutionize how lighting systems are designed and installed across North America. The future looks brighter indeed with LEDs.