Slashdot Mirror
LEDs - Do the Benefits Outweigh the Cost?
7x7 asks: "We keep hearing about the latest and greatest thing to come out of LED technology, and every article seems to give an over-view of the topic. How LEDs consume little electricity and last a long time, etc. However the manufacturing process involves super hot ovens and expensive componants. Do the requirements necessary in the manufacture LEDs and LED componants out-weight the requirements for standard bulbs over 10 years? One LED light can last ten years, but contains dozens of LEDs. Has anyone seen or performed an evalutation to see if the trade-off is really anything to speak of?"
I wish the bulb that burned out in my truck's dashboard had been an LED to begin with.
It cost $95 to change it.
--I am an extreme flashlight fiend, I mean I got dozens of them. My LED flashlights are just a sheer joy. The bulbs don't burn out or pop in temp extremes, I got literally years of normal use off a set of batteries. Most of them will run for days if you just turn them on and leave them on, I've tried it. a regular flashlight lasts a couple of hours max usually. I took one of my first ones, a ccrane model, and read several books at night on one set of batts, just to see how they did "real world". Just outstanding.
I switched several years ago from 12 vdc incandescents to fluorescents for my interior lighting in my RV I live in,got a good boost in performance, but as soon as the LEDs get a scosh cheaper in a normal 12 vdc config for area lighting I will switch to them instead.
Previous Ask Slashdot discussions on LED lighting, LED Light Fixtures for the Home? and Which LED Flashlight Do You Use?
I've got a fever and the only prescription is more COBOL.
It seems to me that if the power usage of those LEDs is much lower than that of a bulb, then yes, there is a very good chance of the LEDs being less damaging to the environment.
Don't underestimate the power savings you can achieve over a ten year period.
I suffer from attention surplus disorder.
Incandescent light bulbs, as we all know, are highly inefficient, emitting ~95% of their energy as heat. Fluorescent bulbs are much better, but still emit radiation in a line-emission spectrum far wider than that of visible light. As far as I know, LEDs are geared to one frequency, and are therefore very power-efficient. No matter how much it takes to manufacture something (within reason), if it is more efficient, it will pay off in the end.
I think the question asks about the total cost of manufacturing/consumables used to run LEDs vs fluorescent vs incandescent bulbs. I'd also throw in the environmental impact as well.
Incandescence are pretty simple to make now and don't contain much in the way of harmful chemicals, just glass and tungsten (older ones used a leaded compound for the base.) But the monetary and environment costs of the electricity are high.
fluorescents contain mercury, but I don't believe they are too hard to manufacture (correct me if I'm wrong.) They are currently the cheapest to run from an electricity point of view, but LEDs are rapidly (yes, there is more electrically efficient lighting out there, but not in the brightness range that most offices and homes require.)
LEDs use some nasty chemicals to manufacture, but the end product is fairly harmless (it contains tiny amounts of some harmful things, but the LEDs last such as long time that, imho, the impact is very small when depreciated over its lifespan.
From a battery-operated point of view, LEDs are the way to go. Fluorescents require some bulky voltage and signal conversion and don't run the battery completely empty. LEDs are strong, light weight, and very energy efficient. Plus batteries contain their own nasty chemicals. I just can't wait for portable fuel-cells!
Very true, but it depends on the purpose of the light.
In the kitchen, use Flourescents. Cheap & effective.
But how about for your car dashbord or some other DC-powered device? Seems like an LED light in your car roof could solve that "Ooops, I left the interior light on all last night, and now the battery is dead" problem.
That said, I still think LED installations have a way to go. Whenever it rains, I see a bunch of cars where 30% of the LED lamps are dark. The LED's probably work fine, but I bet that the connections have corroded due to the rain and smog.
"Can of worms? The can is open... the worms are everywhere."
As always, it depends on the use.
I haven't seen anything about manufacturing costs, so maybe I'm not answering your question, but in use:
In traffic lights, a burned out bulb is a hazard, and expensive to change.
Brake lights and taillights are dangerous to lose, and they get shaken around. That's why in many cars if your brake or taillights go out, your dash lights go out too as a reminder.
Flashlights are typically low temperature bulbs where incandescents are more inefficient, especially after the battery voltage starts to drop off. Besides, they get dropped, so LEDs are a win there too.
Fluorescents are the most effecient, but for household lighting I don't like their color or sixty Hertz visible hum. (Any specific recommendations for a compact fluorescent that has a good color & a nice ballast that doesn't flicker sixty times a second?)
The LED geeks know LEDs aren't always better as far as power consumption goes.
http://www.pioneernet.net/optoeng/LED_FAQ.html#Q7
http://misty.com/people/don/lede.html
I saw a nice use of LEDs in a remote campsite. There were solar collectors on the roof of the bathroom, and little banks of a few LEDs that lit the bathrooms at night.
An LED seems smaller, but the incandescent in a mini-maglite puts out much more light than a white LED of the same size.
Assembly is the reverse of disassembly.
Same here. Most of the x-many (16?) bulbs in the dashboard of my 1995 Escort were burned out, and I resorted to a clipped-on LED flashlight for a while (the light from which is actually much more pleasing than the stock, "working" lightbulb situation -- the LED cast a very nice pool of light). Girlfriend pressure --> 'fixed' but what a hassle. Even with the borrowed labor of a car-fixing friend, it was a royal pain.
...
It's unconscionable to stick such inherently perishable parts (incandescent bulbs) into such an inherently inaccessable, inherently expensive (in time and money) spot. Many (most?) new cars are at least using some sort of electroluminescent stuff instead, maybe some are using banks of LEDs, I don't know
And rube goldberg as it sounds, I liked the flashlight for one other reason: it was simpler to click it off when I wanted than to find the rheostat for my dashboard, which is located in a tricky spot.
timothy
jrnl: http://tinyurl.com/c2l8yr / foes: http://tinyurl.com/ckjno5
ya, the flicker can be bad, and fluorescents really mess up radio reception and transmission if they are close to the antenna. Ditto for over the air TV, too. I use 12vdc ones I get from the auto parts store, they don't *seem* quite as bad as 120 vac fluorescents of similar wattage, but I can't really say that for a fact, as if there is a difference it's marginal. Definetly better mileage from the storage batteries though, went several years with the incandescents (and little TV, radios, etc), that meant re charging the storage batts every day, with the fluorescents switch over I can have twice as much light and the batts only really need topping off every few days. But now I have solar PV so they get topped off quietly anyway. Hate having to run the engine or genny if it's not necessary.
I think for most purposes LEDs are much better though. One place I really want bright incandecent is working at the bench, need that bright hot light, just no substitute for that fine detail work, soldering, etc.
A high-efficiency red LED puts out about 2.5 mW of luminous energy in its emission band, and consumes 120 mW of power. That's 3% efficiency. The rest is dissapated as heat. Incidentally, that's why LEDs have a large footprint (the luminous area is very small); so the heat can spread out and the junction characteristics don't change. Incandescents emit light energy outside the visible band, unlike LEDs. This is where most of the power goes, not heat. Thus, incadescent lights achieve about 15 lumens per watt, flourscents get about 50 per watt. Contrary to popular belief, LEDs are in between, the high efficiency models get about 25 lumens per watt.
The most efficient LED right now is %32. You can't buy these yet... they will be used in lights that operate like flourescent lights since they emit UV. This will be the ideal, long-lasting but low power light source.
LEDs are not economical when a flourscent light with electronic ballast can be used in the same situation. In scenarios where the extra electronics required by a flourscent light are too bulky or not enough power is available- this is where LEDs shine. That is why they are the flash-light champs.
Fuck Beta. Fuck Dice
Bike lights (taillights, headmarkers and on some models of high-end headlights, instrument lights) have used LEDs for years. They really conserve on batteries and are quite bright (I can see the glare of my LED taillights on the road behind me in my helmet mirror at night). Most of the cities in northwest Oregon and ODOT have changed to LED arrays for traffic signals, since they don't burn out as often as incandescent, even when being bounced around by a storm (most intersections have traffic lights on overhead stringer lines, not poles, so they can properly position the signals over each lane). TriMet is phasing in LED signals on busses (they hate driving around busses with a burned out left blinker as much as you hate getting stuck behind them that way), and has
Help us build a better map!
LED lights are getting better
http:\\www.limileds.com
main points to know about lumileds
the light is cold to touch (heat is still generated - but through a heat sink)
coloured lights are alot more efficiant then any other type i know of
the 5W white leds are not rated for a very long life but all the other 5W and all the 1W are rated for 100,000 hours.
a swith mode power supply will probabily be need to drive them efficaintly which adds to the already high cost.
Did you misread the part where I said LEDs are the winner in flashlight choice? This is because they beat incadescent lights in lumens per watt numbers (the numbers get worse for incadescents too as they get smaller, like in flashlight bulbs). They don't beat flourescent lights, though. That was my point.
Light bulbs emit infrared, radio, microwave, and ultraviolet light (as they are blackbody sources). The heat from the filament is not easily conducted away into the base of the bulb or through the gas inside. Hence, much of it radiates away in the form of photons. The infrared radiation is re-absorbed by the glass in the bulb itself and causes it to heat up some (in addition to heat transfered by conduction). But it still passes much of the infrared, ultraviolet, etc. energy out into the room. They don't heat up as much PER WATT when compared to LEDs.
LEDs don't emit anything but a narrow wavelength. Unfortunately, many of the photons get re-abosrbed by the substrate. All of this gets converted into heat. Some of it is converted into microwaves and radio waves, but not much. This is because the large package area (and small power output compared to a light bulb) allow it to conduct the heat into the environment, either through the plastic package or through the thick metal leads allow into whatever its attached to. They don't get hot to the touch unless you put a lot in a small space.
Fuck Beta. Fuck Dice
People say this a lot here, but can you cite a source. A super-bright (2 candella) LED takes 15mA at 1.7 volts, that's about 25mW of power, so 1 Watt powers 40 LEDs. A standard 4-foot fluorescent tube is 40 Watts, so you can power 1,600 super-bright LEDs with the same power as the 40 Watt tube. I've never used more than 50 of the LEDs at once, but it sure seems like a few hundred would match the light output of the fluorescent.
From what I said, we know 40 Watts gives us 3,200 candella with the LEDs. What's the output of the 40 Watt tube? I have a 20 Watt ring-shaped compact fluoresent that gives under 1000 candella, so the LEDs are more efficient than that.
Jason
ProfQuotes
From the voltage drop you quote (1.7 V) that must be a single colour (probably red?) LED. The 20W flourescent is (I assume) closer to white. If you look at white leds they're far less efficient than the basic red and green varieties. The loss of efficiency puts them below flourescent lighting. I don't have any sources to hand to back this up I'm afraid.
Of course, LEDs can be used to make very cool light enclosures that can't be achieved with other technologies.
If we're talking car lighting (brake or tail lights) then LEDs win out easily, 'cos they've got to be red anyway.