Slashdot Mirror
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.
No mercury = huge improvement
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.
LED light bulbs are coming along. I've been keeping my eye on the GeoBulb sold by C Crane, but it's about $120 and always seems to be listed as out of stock. It is available in three color temperatures, however, so perhaps that's been worked out. There are a few others, including some T8 replacements. Unfortunately, they're all expensive and the ones that fit standard sockets max out at about the equivalent of a 60 watt incandescent. But these things will get worked out. On the plus side, advantages include not just electrical savings and longevity, but also less heat (less risk of fire) and less vulnerability to things like vibration and moderate temperature changes. Unlike compact fluorescents, they contain no mercury and turn on/off instantly. I believe some are dimmable, but I'm not sure. In any case, it seems clear that it will only take a few years of fairly routine development for LED bulbs to be much more practical than all the alternatives. There doesn't seem to be a down side.
The summary would seem to imply only modest electrical savings. I'm pretty sure the 10% figure just reflects the fact that light bulbs are only part of your electrical picture. The rated wattage for a 60-watt equivalent is about 8 watts. Correcting for overoptimism, that's about 80% savings wherever you plug one of these in.
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.
Take a hint from the car manufacturers. Today, high-end cars are using LED tail lights. They are also used on trucks. The main advantage is they do not burn out.
However, for most people in the world a burned-out tail light bulb is a minor safety issue and a minor expense. Replacing the bulb takes 10 minutes and maybe the owner's manual if you are truely clueless about how to do it. Also, many people own a car for 5+ years without ever having to replace a single bulb.
Compare this to the cost of a minor traffic accident where a tail light is cracked. No, you cannot replace the lens or any individual part, just the whole assembly. Instead of $100-$200 for an incandescent bulb assembly expect to pay $1500-$2000 for the LED tail light.
Sure, over the life of many vehicles it is a minor issue that bulbs will never burn out. But over the same number of vehicles it is far, far more likely that a lamp assembly will have to be replaced. The result is a far more expensive part to replace.
With trucks there is a certain amount of sense to be made with claiming that the bulbs do not have to be replaced. Replacing a bulb on a truck or semi-trailer can be a real hassle requiring a ladder and tools. However, again the likelyhood the bulb would ever need to be replaced vs. the lens being damaged is about the same as for cars. Basically, it is a complete rip-off.
Expect to see wired-in LED systems in household lamps where the fixture must be replaced because the bulbs cannot be. Expect to see the fixtures sold to builders with non-replacable bulbs will cost the builder only slightly more when bought in huge quantities but the homeowner will be faced with $1000 lamp fixtures should they ever need or desire to replace them.
I smell some FUD
As for the replacement cost of a LED light component on a car. I personally can replace BOTH left and right sides of my cars LED light assemblies (which consists of 4 separate pieces) for $450. The leap from incandescent assemblies is only about $100. And yes, this is OEM, not a 3rd party solution. And to top this off, it takes about the same 10 minutes to replace these assemblies.
As for it being a complete rip-off, the odds of it needing to be replaced is not the only implication. Most LED components on cars that I know of are more visible, take lest time to be "on." Additionally, they draw less current thus putting less strain on the power generation and results in a slight efficiency and MPG boost.
From a build-out perspective you can even use smaller, more compact alternators that don't need to put out as much energy to run conventional lighting. I don't know much about the LED's manufacturing process but suspect you get a smaller carbon footprint there too as you don't need to melt a bunch of glass to make bulbs with... etc.
Even tho I am not a tree-hugging sprout-munching environmentalist, I can see the bigger picture with LED lighting.
Can LED's be dimmed? As far as I've seen it's not possible.
Not so. LEDs can be dimmed either by regulating the forward DC current (then they don't flicker at all) or by pulse-modulating some fixed current; the LEDs in the latter case will flicker only if the frequency of the pulses is too low. LEDs have very low capacitance and inductance, so they can be easily pulsed with any high frequency of your choice, though 1 kHz would be more than enough. And as I said the DC source works also.
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.
It takes a man to suffer ignorance and smile
Be yourself no matter what they say
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.
You're missing the "Roland Piquepaille" link just on top of the summary.
Yes, the only way to vary the brightness reliably is to use PWM (Pulse width modulation, aka "duty cycle"). There is some variance from voltage, but the best way is to operate them at a constant voltage.
All "breathing" LEDS (like on sleep mode for laptops) is accomplished this way. Duty cycle is controlled by a simple sin() or cos() function.
Slashdot's rate-of-post filter: Preventing you from posting too many great ideas at once.
Perceptions.
Direct unfiltered sunlight indoors doesn't look yellow, it's almost pure white.
Sun's spectrum is very close to the ideal black-body spectrum with the color temperature is about 5000K. So 5000K CFL will look almost exactly like the real sunlight.
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...
MP3 Search Engine
They are already more efficient. I have a 3W MagLite that runs on 2AA and will blind you.
Mercury in the CFL's are not as much of a concern as mercury in those 4' flouro's of the commercial buildings, but maybe they are more likely to be recycled.
Eating tuna might be more of a problem though.
http://www.gotmercury.org/article.php?list=type&type=75
because they aren't going to exist much longer into the future. http://www.idtechex.com/products/en/articles/00000591.asp
I also find it ironic that everyone seems to love that mercury is not contained in LED's, yet is it essential to the extraction of gallium from ore.
Not perceptions... Quanta
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.
The LF version flickers with 50 or 60 Hz (depending on where you live) while the HF version has a lot higher frequency and will be almost flicker-free.
LED:s also suffers from flickering if you feed them with AC, but if you use DC and a low-pass filter you will get rid of the flickering.
The color spectrum is also different depending on the type of light source.
If builders built buildings the way programmers wrote programs, then the first woodpecker would destroy civilization.
LED lighting doesn't exceed the efficiency of fluorescent lighting in terms of lumens per watt yet.
Your description of the problem displays a level of ignorance which could easily be corrected by simply reading wikipedia. The simple truth is that there are numerous LED lights which are more efficient than flourescents, but there is a very good reason why the bulk of them are not.
This reason is that white LEDs are fluorescent lights. Not all of them, but all the cheap ones. That's because the alternative is to use multiple junctions in a package to produce a mixture of light to produce the whitest possible light. There are bicolor and tricolor (and for all I know quadcolor) LEDs, some of which are tuned for the closest thing you can get to white, and some of which are tunable.
The typical white LED is a blue LED (the most expensive single-color visible LED) doped with a material which emits yellow light when the blue light strikes it. This method does not produce the brightest light nor the whitest, but it is by far the cheapest way to produce a "white" LED.
The 3W mag-lite may not be more efficient than an imaginary flourescent that would produce the same amount of light, but they do illustrate a different point; the flourescent has a glass tube filled with toxic shit and a ballast to drive it. You can build the voltage regulation hardware right into an LED and just hook it up to some LVDC. I would be extremely amazed if the total lifetime energy cost of flourescent lighting were not significantly higher than that of LED lighting.
In short, [typical] white LEDs are not more efficient than fluorescent lighting because they are fluorescent lighting. When the cost of blue LEDs come down, and tricolor LEDs become more ubiquitous, then the price of the more-efficient "white" (in this case, tricolor) LED lighting will come down.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"