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Making Strides Toward Low-Cost LED Lighting
Roland Piquepaille writes "You all know that incandescent bulbs are pretty inefficient, converting only 10% of electricity into light — and 90% into heat. Light-emitting diodes, or LEDs, could soon replace incandescent and compact fluorescent bulbs in our homes. They are more efficient and environmentally friendly. But LED lights are currently too expensive because they are using a sapphire-based technology. Now, Purdue University researchers have found a way to build low-cost and bright LEDs for home lighting. According to the researchers, the LED lights now on the market cost about $100 while LED lights based on their new technology could be commercially available within a couple of years for a cost of about $5. It would also help to cut our electricity bill by about 10%."
They will be way more environmentally friendly. No mercury involved.
But how much of an improvement will they be over fluorescent lights, which we already have at an affordable price?
Well, they won't flicker, they won't contain mercury, and they won't be too big to fit in many light fixtures.
Even if LEDs aren't any more efficient than current CFLs, they'll be a lot more attractive to people who don't like or can't use fluorescent lights.
How can I believe you when you tell me what I don't want to hear?
Many of these white LEDs are blue or UV LEDs that stimulate a phosphor coating to produce white light.
Having three Red Green Blue LEDs to create white light might produce a light that appears white to the eye, but might not have the same effect when reflected off material.
The white from the phosphor would generate more of a broad spectrum white, whereas the Red, Green and Blue LEDs would probably create spikes in the Red, Green and Blue spectrum.
So you might have a green material that appears black when you use the "RGB white" LED - just because it does not reflect the Green LED's narrow green, whereas it will appear green in the white from the phosphor white LED.
The phosphor means one more step in light conversion, and that probably means less efficiency.
In addition the no mercuary as already noted, they will have a longer life, be less fragile, and be smaller.
Infuriate left and right
I realise it's customary not to RTFA, but I would think that the submitters would at least read what they submit. Roland wrote:
The article says:
Far from the same thing. But I suppose that's another reason people don't like Roland.
We do not live in the 21st century. We live in the 20 second century.
Another article http://pubs.acs.org/isubscribe/journals/cen/86/i28/html/8628cover4.html provides some interesting information on organic LEDs - OLEDs have interesting design applications since you can make them in flat sheets
(I think an illuminating wall would be way cool, but maybe thats just me :-))
Right now efficiencies are similar to the inorganic LEDs and fluorescent bulbs.
2003 called, it wants it's CFL stereotypes back.
CFLs don't flicker like old ballast-type fluorescent tubes of decades ago. And the newer ultra-compact ones are actually smaller than the incandescent bulbs they replace. I have one in the swing-arm desk lamp in front of me right now, and the tip of the bulb no longer protrudes past the end of the shade like the old bulbs I used in it long ago. In my bathroom I have CFL bulbs made to look identical to G25 globe lights, in the same fixture with the actual incandescent bulb I am slowly replacing. They appear the same except the CFLs are brighter and their light isn't as yellow.
I will give you the mercury, though.
Trucks use LED taillights because they are more visible in the daytime. It never ceases to amaze me how often a 4-wheeler (car driver) will rear-end a truck that is braking for a stoplight or turn, then claim that they didn't see the truck's brake lights.
The LED taillights you see on a lot of semi-trailers are held in place by metal bezels that are riveted in place by the manufacturer. To replace one, you have to drill out the rivets. Then of course you can simply use self-tapping screws to put the bezel back on once you have replaced the light. Incandescents tend to be held in place by a rubber cup-like thing that I don't know the name for, and can be removed by prying on the light with a flathead screwdriver, much like dismounting a tubeless tire from a wheel.
The reason for riveting the things in place is to deter theft. Incandescent lights don't get stolen nearly as often as LED's for some reason.
"Alcohol, Tobacco, & Firearms" should be a convenience store, not a government agency.
The mercury depends on efficiency aswell. Modern CFLs have <=2mg mercury content, (at least the CFLs I own). Over a 5 year period, the electricity needed for CFLs, generated by coal based power plants in some portion, releases 2.4mg of mercury into the air. For incandescents the number is 10mg over a 5 year period. LED lighting is currently less efficient than CFL, so more mercury gets into the air.
The question is really, whether you prefer 2.4mg of mercury in air plus 2mg in the landfills, or more than 2.4mg of mercury in the air. Until LEDs become more efficient than CFLs, I'll opt for CFLs.
Note, there is a confusion over LED vs CFL efficiency. LEDs generate light more efficiently than CFLs, but they do so in a narrow arc. To make it useful for everday applications conversion to a wider arc takes place and that causes efficiency loss.
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As far as I know, the most used variant is the blue LED + yellow phosphor one. In this case, the blue light, emitted by the LED, is cast directly, besides the yellow light coming from the phosphor. The mix of blue and yellow produces white light.
Unfortunately, these LEDs don't produce a very broad spectrum of light either. The spectrum has a sharp peak in the blue range, and a bit broader yellow range, as can be seen on this graph on the Wikipedia page.
LED lighting is already cost effective in certain situations. I priced a cable-hung low-voltage lighting system using LED-based MR-16 socket bulbs vs. 12 volt halogen incandescent and the system pays back in less than a year in electricity savings. That doesn't even count the significantly smaller number of bulb changes that are required.
If you have a large number of low wattage/low voltage light sources, CFL is not viable, but LED is. The power requirements are so much lower that smaller transformers can be spec'd, you can string piles more of them on a circuit, saving even more money.
There are some neat bulbs available at http://www.theledlight.com.
I have a new way to deal with Roland Piquepaille spam, every time I see an article by him I go away for 3 days.
So, see you on the 24th...
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Look at the sun and at a CFL though a spectroscope. With the sun, you'll see even intensity across the spectrum. When you look at the CFL, you'll see several distinct bars of light at specific wavelengths. While both average out to about the same color temperature, the sun will have a black-body spectrum, evenly illuminating the pigments in the items in your room, while the CFL will make certain colors in the room jump out more than others.
I loathed the xenon high beams when they first came out a few years ago. You know, those tiny very concentrated blue lights ? Leaves a retina trail that lasts for 20 seconds. I'm so glad that they are gone now. I've never heard if they were made illegal or if they just went out of fashion [snip]
Xenon HID headlights never went away. They're still standard equipment on higher end Japanese and some German luxury cars and optional on many others. If anything, their use by car manufacturers are expanding, not contracting.
What YOU'RE complaining about, and thankfully seem to have gone away, are those high intensity blue color lights that dropped into a standard headlight assembly. Like you mention, I don't know if they were made illegal or became "uncool" but I hated them as well. True Xenon HIDs have a completely different reflector assembly than standard halogen headlights and spread the light far more evenly and are actually less annoying that a slightly misaimed halogen headlight, and you probably see them all the time and don't even realize it. They look "blue" only compared to what turns out to be the yellow tinge of a regular headlamp, but at a glance just appear very white.