LED Lighting Technology
By Tom Burden
Light Emitting Diodes, more commonly known as LEDs, operate at lower temperatures, use less energy, tolerate vibration better and last far longer than conventional incandescent bulbs. They also do not contain small amounts of toxic mercury, an environmental disposal hazard associated with fluorescent and compact fluorescent lamp (CFL) lights. LEDs cost a bit more, but are worth their premium price in the long run. Here’s why:
Incandescent Bulbs Waste Energy
The light bulb, that marvel of technology created by Thomas Edison, operates by cramming a large volume of electrical current through a resistor encapsulated in a vacuum. This resistor, the tungsten filament, gets so hot that it glows white, and only the absence of oxygen prevents it from burning up in an instant. About 5% of the energy is released as light. The rest is mostly turned into heat, as we all know from burning our fingertips when we try to change a 60-watt bulb.
After more than a century, we’re still depending on Edison’s technology, but there are now cooler, more energy-efficient, and more “elegant” alternatives. In the very near future we’ll be seeing a lot more of them, mainly because they will reduce energy use and the production of greenhouse gasses. The Energy Independence and Security Act of 2007 requires roughly 25 percent greater efficiency for light bulbs, phased in from 2012 through 2014, beginning with the 100W bulb. This will effectively ban the sale of most current incandescent light bulbs. As of January 1st, 2011, standard 100W incandescent light bulbs have already been phased out of California stores. By 2020, bulbs must be 70 percent more efficient than they are today.
Light Emitting Diodes
LEDs, are becoming increasingly common on both land and water. They first gained wide use as indicator lights, such as automobile and trailer taillights, stoplights at intersections, and “ON” indictors on switches and electrical panels. LEDs for illumination, for lighting rooms, streets and boat cabins, for example, have not been as practical of an alternative until recently, because the light output (in lumens per watt of electricity) has not approached that of fluorescent lights or incandescents. That situation has now changed.
Early LEDs measured about .25mm across, and were low in light output. More recent designs are four times that size, and much brighter. High-output LED lights are now emitting enough light to illuminate larger and larger areas.
Clusters of LEDs connected together in combination with reflectors, diffusers and lenses, have surpassed the output of incandescent bulbs by a factor of ten times (over 150 lumens per watt, compared to 15 lumens per watt ).
LEDs operate on a totally different principle than traditional incandescent style lights. Instead of using a brittle metal filament that is susceptible to shock and vibration, LEDs are solid-state devices with no moving parts to break. The LED utilizes a semiconductor which produces light when current is passed through it. For the most part the semiconductor material is not consumed; it merely changes states making the LED efficient and long lasting.
How they work
LEDs are diodes, semiconductors that allow current to flow in only one direction. Two materials are placed very close together in what is called a “P-N junction”. Run a current through the junction, and light energy is released.
LEDs’ light color emission is determined by the chemistry of the device. There are two primary varieties of LEDs. The first, blue, white, green and ultraviolet LEDs use indium gallium nitride (InGaN).
The second type, red, yellow and orange LEDs, are built from aluminum gallium indium phosphide. Until recently it was difficult to produce a pure white LED, requiring the mixing of red, green and blue LEDs (RGB LEDs), blending the colors so the combined light was white (similar to how your television creates white light with red, green and blue dots). A more recent alternative (and a big step forward) uses a blue LED with a phosphor coating, which “yellows” the light so the blended color frequency is white.
Watt: the measure of energy used by a light, not a brightness rating.
Lux: a measurement of light at a single point. It does not measure the total light output of a fixture. Lux can be measured using an inexpensive light meter and is routinely used in photography.
Fixture Lumen: light output measurement of a fixture usually measured in an integrating sphere. While theoretical conversion of Lux into Lumens is possible, (having taking thousands of measurements) the accurate measurements of “Lumens” require the ability to measure light volume. This can only be accomplished using an Integrating Sphere and specialized calibration equipment.
Efficiency: LEDs are very energy efficient and consume less power, with up to 90% lower amperage draw than incandescent bulbs. Replacement of a few incandescent bulbs with LEDs reduces the load on your electrical system including your battery, alternator, and power converter.
Color: LEDs emit light in whatever color desired, without any color filters, as needed by traditional light sources.
Instant ON/OFF: LEDs activate instantly, so they provide immediate bright light. For brake lights on your boat trailer, LEDs provide an extra fraction of a second for that tailgating driver you can’t see in the blind spot behind your vessel.
Cool operation: LED lights are cool to the touch and can be left on for hours without incident, since they generate no waste heat.
Longevity: LEDs are rated for service lives of 50-100,000 hours compared to 3,000 hours for incandescent bulbs. Most incandescent bulbs need to be replaced within one year, but an LED light could last over 11 years before needing replacement. They don’t suddenly burn out like incandescent bulbs either, but gradually become dimmer.
Reduced wire gauge: Due to the low energy draw of LEDs, the gauge of wire used can be reduced. Caution: Typical incandescent fusing requirements are too robust for LEDs, so fusing must be sized for the low LED circuit draw. Incorrect fuse sizing can cause damage to your electrical system.