Is LED lighting
|
 |
| Issue #110 • March/April, 2008 |
We were one of the first publications to advise how incandescent light bulbs were going to be outlawed in several states and many countries due to their very poor energy efficiency. I have received many e-mails from irate readers saying this would never happen in their state or their country. Sorry to be the one to tell you, but the 2007 Federal Energy Legislation just signed into law in December by the President includes legislation to totally phase out the manufacturing of most incandescent light bulbs by 2012. California has already passed legislation to ban incandescent light bulbs by 2010.
In past articles I have also described how the more energy-efficient compact fluorescent lamps being promoted to replace these incandescent light bulbs are all imported from China, and are burning out years earlier than their advertised eight-year life. In addition, compact fluorescent lamps contain a small amount of highly poisonous mercury, which is a hazardous waste and a banned landfill substance. So if incandescent light bulbs are being banned, and if the more-expensive compact-fluorescent lamps have manufacturing quality and disposal concerns, what type of lighting will be in our future?
LED history
Although not really new, the LED lamp appears to be the most likely lighting technology for our future. For years we all have been buying stereos, televisions, and electronic games that had a red dot of light to indicate when the power was on. These tiny lights are LEDs, and most are red in color, although other colors are readily available.
An LED offers numerous advantages over almost every other form of lighting. Technically, an LED is actually an electronic diode, or light-emitting diode (LED), to be more specific, and contains the same materials and construction as any other electronic semiconductor component, except for being enclosed in clear see-through acrylic, not an opaque black block.
LED construction
Since an LED is an electronic device, it requires several wiring requirements that must be met. All LEDs are polarized just like a battery, and include a positive and negative terminal. In addition, an LED is very sensitive to high current flow, and most LED circuits include a tiny resistor or other electronic device to limit the current and voltage being supplied. LEDs are actually sized based on their current rating, not their voltage.
So how is something that requires additional wiring protection and produces only a tiny dot of light going to meet all our future lighting needs? The answer is very simple. An LED is almost indestructible, and its power requirements are so small it’s measured in milli-amps (0.001 amp) with most drawing less than 25 milli-amps when illuminated. If you increase the current supplied to any LED, it will get brighter, but its life will be significantly reduced. As long as the correct voltage and current levels are maintained, manufacturers have yet to determine the theoretical life of their LED products, which is estimated to be in excess of one-hundred thousand hours.
So what’s the catch? Why waste our time with incandescent light bulbs and fluorescent lamps if an LED is so great? Although recent LED innovation has produced a true white LED with much brighter output than those initial tiny red LED “dots,” they are still just a single point of light and require a focusing acrylic lens covering the glowing semiconductor junction. This means most LED “light bulbs” must contain anywhere from 36 to 72 separate LEDs, mounted in different positions to provide a reasonable distribution of light. These LED light bulbs currently cost over $40.00, and still have poor area illumination.
|
Although efforts are being made to improve this LED light distribution, most of the LED products being sold today are PAR reflector-type designs typically used for desk lamps, recessed lights, and task lighting that focuses on a limited area. This single point-of-light illumination makes it very difficult to design an LED “light bulb” that can illuminate a room in all directions from the bulb.
How LEDs work
When current is passed through the semiconductor junction inside a light-emitting diode (LED), the electrons in the diode junction energize this special material and produce light. By adjusting the chemical composition of these materials, different colors can be produced. Until recently, a white color was achieved by combining the separate light output from individual blue and yellow LEDs. Adding a very thin coating of a material over a blue LED that fluoresces white light when illuminated has resulted in a much brighter white LED.
Like many other semiconductor devices, electricity can only flow in one direction through an LED, which is why its terminals are polarized positive and negative. The actual color of a white LED is very close to natural sunlight, and room objects will appear more natural under LED illumination than fluorescent lighting. Since all incandescent light bulbs have a slightly warm-yellow color, the blue-white light from an LED lamp may appear “less normal” to many of us when accustomed to older incandescent bulbs. Most white LEDs fall between a 4,500 and 6,000 degree Kelvin color temperature, with the lower value more yellow, and the higher value more blue in color.
LED use today
There are many applications where LED technology is already starting to take over certain lighting applications. This includes recreational vehicles, boats, solar-powered walk lights, and off-grid solar homes where there is a need to minimize battery drain. LEDs are also replacing most commercial and institutional light bulbs in hard to access areas due to their very long life. In less than three years, LED technology has already replaced the incandescent reflector bulbs in most stoplights at intersections. The next time you are stopped at a traffic light, notice how each light now consists of groups of individual glowing green, red, and yellow LEDs.
Gone are the bucket trucks making the rounds each day and blocking traffic as they replace the incandescent bulbs that constantly burn out. You will also start to see roadside billboards and commercial signage having animated text and graphics, thanks to thousands of tiny computer-controlled LEDs in a variety of bright colors. By increasing the number of LEDs used, a roadside-size billboard can now provide television-quality graphics as large as a house. An LED does not have a filament like an incandescent light bulb that can burn out. An LED does not contain any gases or hazardous mercury like a compact fluorescent lamp, and an LED does not have a fragile glass envelope that can shatter. An LED does not get hot like most other lights. This makes an LED lamp a good choice when there is a high potential for damage from vibration or moisture, including instrument panel lighting in vehicles, boats, and aircraft.
Last Christmas was the first time LED Christmas tree lights were commercially available. Although not all brands are as bright as standard Christmas tree lights, these LEDs should eliminate the age-old problem of trying to find which bulb is causing the entire string not to light.
I recently purchased two identical-sized Christmas tree lighting strings having 50 lights each, which were both made by the same manufacturer. Both contained the same number of lights, and the same length and size of wire. Since all holiday lighting is available in different physical bulb sizes, I made sure both strings contained the same #C-5 size lamps. However, the string containing standard incandescent bulbs had a 20 watt electrical load, while the string of LED bulbs only required 2 watts. This is a 90% energy reduction for the same light output, not to mention finally ending the yearly struggle to get the darn things to light in the first place. You can achieve this same dramatic energy-reduction by replacing your other incandescent lights with LED lamps having an equal lumen output, while almost ending future bulb replacements.
As mentioned earlier, the electronic semiconductor producing the light is encapsulated inside a clear acrylic-type material. As long as the tiny power wires can be properly protected, an LED is waterproof, shockproof, does not get hot, and is almost indestructible unless smashed with a hammer, making these excellent light sources for more demanding military and mobile applications.
|
The photo above shows a small surface-mounted 12-volt DC fixture containing three white LED lamps. This size fixture will adequately illuminate a small room in a boat or RV, and can provide under-counter or task lighting in your home. The clear lens on this fixture helps to more evenly distribute the highly directional lighting from the LEDs.
Getting started
In Issue #97, Jan/Feb 2006, I presented the results of testing multiple flashlights and described how the LED models had burned continuously for over a week using the smallest AAA size batteries, which easily outlasted every other flashlight tested. If you want to see your lighting future, I suggest purchasing one of the LED flashlights highlighted in that article; you will be amazed with their very long battery life. Many readers will probably find the energy savings and extremely long life of an LED replacement bulb still do not justify the high cost, but anyone living off grid or planning to live off grid will find this lighting technology to be their Holy Grail. The reduced drain on a battery-based power system is dramatic, and well worth the higher cost.