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Wow that was hugely informative post Karl; I think the work is on to widen the wave length of the LED. the reaction times for the automotive use is one of the reasons many auto manufactures are tending to make the brake lights in LED and in several different configurations even turn signals are used as well. The other thing like Karl mentioned it the ability of the LED to pierce the when activated.
Thanks for the compliment. I'd like to add something to demonstrate the long life of LEDs. I bought a clock radio in March of 1982 (nearly 25 years ago). The clock radio has an LED display for the time. I still use it. The display has been on continuously for nearly the entire 25 years and it still works as well as it did when I took it out of the box in 1982. I've never had any parts replaced. That means that the LEDs in that display have been on continuously for nearly a quarter of a million hours and are still going strong. I don't think that even the Energizer Bunny can last that long.
I am now on my 6th week with the new energy saving lights. I've noticed one minor difference. The energy saving lights will be dimmer initially, but after about 30 seconds, they are just as bright as a regular incandescent, perhaps even more so.
I've noticed a couple of really neat things about them. If you turn them off in a dark room, they have a very faint glow for about a minute. Another thing I noticed is that they will glow for a second if there is any static discharge nearby. The reason for both phenomena is that the inside of the tube is coated with a phosphor that glows in the presence of an electrical field.
One other thing. Since the energy saving light bulbs are actually fluorescent light bulbs, they contain a small amount of mercury. You aren't supposed to dispose of them in the trash.
The reason that both energy saving lights and LEDs are so energy efficient is that they use more of their energy than incandescents to create light instead of heat. In the case of LEDs, nearly 100% the energy is used to create light. Energy saving lights use an electrically charged gas to stimulate a phosphor that glows in the presence of an electrical field. LEDs give off light using quantum effects. An energy saving light uses about 14 watts to give off the same light as a 60 watt light bulb. An LED light uses about 5 or 6 watts to do the same. Because LEDs generate light using quantum effects, they can only radiate a single wavelength. That is why LEDs come in single colors. White LEDs do not actually radiate white light, they emit ultraviolet light, but their enclosures are coated with a phosphor that radiates white light in the presence of ultraviolet light.
Major cities that have switched to LED lighting for traffic signals have reported cost savings of over 1 million dollars a year because LED traffic signals use so little electricity. In addition, LEDs have very long service lives. LED lighting can have a service life of about 100,000 hours (that's about 11 years of continuous use).
I've noticed that LEDs seem to give off a great deal of light in one axis (straight ahead), but as you move away from that central axis, the intensity of the light diminishes. That is why LEDs are so good in signal lights and displays. In those applications, the viewer is usually on, or near, the central axis. However, LEDs are not as well suited for general lighting for precisely the same reason. Many LED lights simply consist of a flat array of LEDs. So they give off an intense light directly in front of them, but the light quickly becomes fainter as you move away from that central axis. I think the problem is how the LEDs are distributed in LED light bulbs. If someone could invent a way to arrange the LED semiconductors on a sphere, then enclose the sphere with a phosphor coated envelope, they may be onto something.
Well I'm nearly sold on buying some, question though. How are you supposed to 'dispose' of them, when they do wear out?
Thanks for the compliment. I'd like to add something to demonstrate the long life of LEDs. I bought a clock radio in March of 1982 (nearly 25 years ago). The clock radio has an LED display for the time. I still use it. The display has been on continuously for nearly the entire 25 years and it still works as well as it did when I took it out of the box in 1982. I've never had any parts replaced. That means that the LEDs in that display have been on continuously for nearly a quarter of a million hours and are still going strong. I don't think that even the Energizer Bunny can last that long.
Well I'm nearly sold on buying some, question though. How are you supposed to 'dispose' of them, when they do wear out?
Has anyone purchased those energy saving lightbulbs? You've seen them, they look like little pigtails. I replaced all of my incandescents with them and they seem to work just fine...
Are these florecent? I need the warm yellow light since I live in WI.
(Go Bears!) 
Greg, ummm, cheese doesn't glow!
The obvious question is, where is the break-even point between a radiant barrier and more insulation? I recently increased the insulation in my attic to R60 or so, and that was very cheap.Experiments with various levels of conventional insulation show that the percentage reduction in ceiling heat flow due to the addition of a radiant barrier is larger with lower amounts of insulation. Since the fraction of the whole-house heating and cooling load that comes from the ceiling is larger when the amount of insulation is small, radiant barriers produce the most energy savings when used in combination with lower levels of insulation. Similarly, radiant barriers produce significantly less energy savings when used in combination with high levels of insulation.
