WHY LED?

LED FOR MEDIUM AND LOW-LUMINANCE

LED Strip LightingLight Emitting Diode (LED) technology uses a fraction of energy compared to conventional incandescent or even CFLs. And they last a long time before needing replacement — up to and exceeding 50,000 hours, compared to 6,000 for a CFL or 1,000 for standard incandescent bulbs.
Incandescent lights work by using electricity to heat a filament until it glows. They also give off a lot of excess heat — you know that if you’ve ever touched a light bulb after it’s been on for even a short while. Fluorescent lights work by passing electrical current through a gas-filled tube, which causes it to emit light. LEDs work by channeling electric current through a semi-conductor material.

LEDs have already eclipsed incandescent sources, and when fixture performance is considered, they are powering past CFL and fluorescent in real world applications today. With their long service life, compact size, and far greater directional control, LED technology produces a unique opportunity to re-think many of the old paradigms of lighting system design. As the performance of LEDs continues its rapid expansion, and the cost of light delivered continues to drop, the obvious choice in general illumination will inevitably point toward solid-state lighting sources.
Energy savings from solid-state lighting does not come with the liability of mercury that fluorescent lamps possess, or any other hazardous materials. Reduction in energy use overall means a reduction in greenhouse gas emissions, reduced mercury and phosphor emissions from coal burning, a slower depletion of fossil fuel sources, reduced contribution to land fills from coal cinder, and a lower demand to build bigger, more expensive power-generating plants.

IN SUMMARY LED LIGHTS HAVE

Directional Light Emission – directing light where it is needed.

Traditional light sources emit light in all directions. For many applications, this results in some portion of the light generated by the lamp being wasted. Special optics and reflectors can be used to make directional light sources, but they cause light losses. Because LEDs are mounted on a flat surface, they emit light hemispherically, rather than spherically. For task lighting and other directional applications, this reduces wasted light. However, in applications where omnidirectional light is needed, advanced optics take advantage of LED’s efficiency, and spread plenty of light out evenly.

Size Advantage – can be very compact and low-profile.

The small size and directional light emission of LEDs offer the potential for innovative, low-profile, compact lighting design. However, achieving a low profile requires careful design. This works best in low-to-medium illuminance levels, where heat sinks don’t need to be as large. In office settings, slim LED panels offer aesthetically pleasing light, while virtually blending into the ceiling. In home applications, under, over, and in-cabinet LED lighting can be extremely low-profile, creating light where it is needed and being completely unobtrusive.

Breakage Resistance – no breakable glass or filaments.

LEDs are largely impervious to vibration because they usually do not have filaments or glass enclosures. Standard incandescent and discharge lamps may be affected by vibration when operated in vehicular and industrial applications, and specialized vibration-resistant lamps are needed in applications with excessive vibration. LED’s inherent vibration resistance may be beneficial in applications such as transportation (planes, trains, automobiles), lighting on and near industrial equipment, elevators and escalators, and ceiling fan light kits. LED durability may provide added value in applications where broken lamps present a hazard to occupants, such as children’s rooms, assisted living facilities, or food preparation industries.

Cold Temperature Operation – performance improves in the cold.

Cold temperatures present a challenge for fluorescent lamps. At low temperatures, higher voltage is required to start fluorescent lamps, and luminous flux is decreased. A non-amalgam CFL, for example, will drop to 50% of full light output at 0°C. The use of amalgam (an alloy of mercury and other metals, used to stabilize and control mercury pressure in the lamp) in CFLs largely addresses this problem, allowing the CFL to maintain light output over a wide temperature range (-17°C to 65°C). The trade-off is that amalgam lamps have a noticeably longer “run-up” time to full brightness, compared to non-amalgam lamps. In contrast, LED performance inherently increases as operating temperatures drop. This makes LEDs a natural fit for grocery store refrigerated and freezer cases, cold storage facilities, and outdoor applications. In fact, DOE testing of an LED refrigerated case light measured 5% higher efficacy at -5°C, compared to operation at 25°C.

Instant On – requires no “warm up” time.

This characteristic of LEDs is notable in vehicle brake lights, where they come on 170 to 200 milliseconds faster than standard incandescent lamps, providing an estimated 19 feet of additional stopping distance at highway speeds (65 mph). In general illumination applications, instant on can be desirable for safety and convenience.

Rapid Cycling Capability – lifetime not affected by frequent switching.

Traditional light sources will burn out sooner if switched on and off frequently. In incandescent lamps, the tungsten filament degrades with each hour of operation, with the final break (causing the lamp to “burn out”) usually occurring as the lamp is switched on and the electric current rushes through the weakened filament. In fluorescent and HID lamps, the high starting voltage erodes the emitter material coating the electrodes. In fact, linear fluorescent lamps are rated for different expected lifetimes, depending on the on-off frequency, achieving longer total operating hours on 12-hour starts (i.e., turned on and left on for 12 hours) compared to shorter cycles. HID lamps also have long warm up times and are unable to re-start until cooled off, so rapid cycling is not an option. LED life and lumen maintenance is unaffected by rapid cycling. In addition to flashing light displays, this rapid cycling capability makes LEDs well suited to use with occupancy sensors or daylight sensors.

Controllability – compatible with electronic controls to change light levels and color characteristics

Traditional, efficient light sources (fluorescent and HID) present a number of challenges with regard to lighting controls. Dimming of commercial-grade fluorescent systems is readily available and effective, although at a substantial price premium. For CFLs used in residential applications, dimming is more problematic. Unlike incandescent lamps, which are universally dimmable with inexpensive controls, only CFLs with a dimming ballast may be operated on a dimming circuit. Further, CFLs usually do not have a continuous (1% to 100% light output) dimming range like incandescents. Often CFLs will dim down to about 30% of full light output. LEDs may offer potential benefits in terms of controlling light levels (dimming) and color appearance.

  • LED lighting uses 80% less energy and produces 5x more light per watt than incandescent and halogen lighting.
  • LED lights do not produce as much heat. This saves on energy and maintenance costs.
  • LED lights last 50,000 hours or longer, about 25 times more than incandescent lights. This saves on maintenance and disposal.
  • LED lights do not contain mercury common in fluorescents.
  • The US Department of Energy estimates that LED lighting could reduce U.S. energy consumption by 29% by 2025.

APL also has many of these characteristics, but is far better in medium-to-high illuminance applications. Click here to learn more.