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Science

LEDs - Do the Benefits Outweigh the Cost? 58

Posted by Cliff from the assessing-the-risks-versus-the-rewards dept.
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?"
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LEDs - Do the Benefits Outweigh the Cost? More

LEDs - Do the Benefits Outweigh the Cost?

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  • Fluorescent lights are much more cost-effective and last just as long.
    • 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 tha

    • Re:LED lighting? You must be kidding (Score:2, Informative)

      by Anonymous Coward
      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. Wh
      • 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 t

  • Sure. (Score:5, Insightful)

    by Polo ( 30659 ) * on Monday April 28, 2003 @07:02PM (#5829887) Homepage
    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.
    • mine are the same... But i've seen pages around that show you how to replace the old light module with a couple LEDs. I haven't gotten around to it yet though

      • mine are the same... But i've seen pages around that show you how to replace the old light module with a couple LEDs. I haven't gotten around to it yet though

        These guys sell LEDs mounted in standard plugs specifically for easy replacement of incandescent lamps; they might have something that doesn't require custom wiring: http://www.superbrightleds.com/led_prods.htm [superbrightleds.com].

    • 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 s
      • Unfortunately, the problem in my case was that the "check engine" light wouldnt' function. And here in California, a functioning "check engine" light is required to pass the emissions test.

        But the truck is a '91 model so it's possible they hadn't ironed out bright yellow-led's yet back then. ;)
        • the suv which was formerly mine (sold it, because of college being in milwaukee, and it being in california) passed smog tests as late as last summer, and it had neither a functional check engine light, nor a catalytic converter...

          it did fail once because the gas cap didn't seal though. (although there is no way in hell that the gas cap sealing made any difference in the actual operation of the vehicle (as opposed to the seal on the seal tester device))

          of course, it was a '78 international scout.... so th
    • So replace it with one. I changed out the backlighting bulbs on the A/C controls and clock in my old car to green LEDs. They'll probably be the last things still working in that car. :-) Only caveat is that LEDs are more directional; the centers of those LCDs ended up being illuminated much more than the edges.

  • only from flashlights (Score:5, Interesting)

    by zogger ( 617870 ) on Monday April 28, 2003 @07:09PM (#5829934) Homepage Journal
    --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.
    • Do any of them throw nearly as much light as a battery operated miners light? If so it would seem to be ideal for spelunking and hiking use. Of course one of my headlights is on its second battery after like 6 years of intermitant use so it's not a huge deal but I always freak about being without power for my headlamp at night as I have had to make two night descents (one was altitude sickness after consuming dinner at base camp where the oxegen use from digesting food worsened the condition and the other w
      • Hate to reply to myself but I decided to do some research and Petzl the guys who make my headlamp (the Zoom, the most popular headlamp around for good reason) have a new product coming out. It's their Myo series and it has an interesting set of features. For the Myo 5 they have two bulbs systems in one lamp, a bright halogen bulb for extremely bright light, but it will only last about 4 hours running on this bulb. They also have a 5 LED array that has 3 settings, normal for most walking, max for quick walki
        • I have a headlamp that uses LEDs or an incandescent in the same reflector. The choice is made by rocking the on/off button to the left or the right. A tap in the center is the full on/off. Girlfriend got it for me, came off the rack at walmart, around 20$. It is "cyclops" brand.
    • ...as soon as the LEDs get a scosh cheaper in a normal 12 vdc config for area lighting I will switch to them instead.

      You might not want to be hasty in switching from fluorescent to LED. In the several Slashdot articles about LEDs recently, the consensus is that fluorescents are actually more effecient for area lighting. E.g., the main central ceiling light in your RV should probably remain fluorescent, but nook and cranny lights can certainly go LED. Combining both technologies would probably give you
      • E.g., the main central ceiling light in your RV should probably remain fluorescent, but nook and cranny lights can certainly go LED.

        Quite insightful :), but another idea would be to set up LEDs in a grid on the cieling. Perhaps each LED could be in its own little canister recess. The coolness factor would outweigh any inefficiencies, then.
        • DEFINETLY a consideration!

          I was looking after last Christmas for LED in christmas strings but never found them on the shelf local. I think that would be the way to go, either string them around the ceiling or pack them into a home brewed fixture.
          • Noma "Forever Bright"

            UPC # 0 63407 13802 8

            Bought them on Clearance from Canadian Tire one year for $3.00

            They are really quite cool. There are three strands of wire, one neutral, one string of red leds wired in one "direction" and another string of green LEDs wired in the other "direction".

            The 120Hz flicker is actually quite fetching. As long as they are not in your peripheral vision though, otherwise they might just drive you batty...

            John
        • Another bonus with using LEDs for home lighting is the fact that you can dim them. Try that with fluoresent lighting! I hate changing burnt out bulbs but I've been holding off on buying fluoro stuff since it isn't compatible with my X10 setup. (It would work, but not support dimming) LED fixtures sound like the solution.
      • ... as soon as I either buy or make one. It's still cheaper to just purchase a finished product that trying to mod your own with those LEDs in a lot of cases. I've seen various strip 12 volt models but are still too expensive (60$ as opposed to under 10$ for similar). I figure whenever the first fluorescent burns out, that will be the time to look hard again and buy one LED replacement for trials. I have several backup of the fluorescents already, so that really isn't the problem. I tend to more use spot-di

  • Previously on Ask Slashdot (Score:4, Informative)

    by Nighttime ( 231023 ) on Monday April 28, 2003 @07:19PM (#5830013) Homepage Journal
    Previous Ask Slashdot discussions on LED lighting, LED Light Fixtures for the Home? [slashdot.org] and Which LED Flashlight Do You Use? [slashdot.org]

  • Power usage (Score:3, Insightful)

    by orkysoft ( 93727 ) <orkysoft@m y r e a l b ox.com> on Monday April 28, 2003 @07:23PM (#5830043) Journal
    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.

    • Re:Power usage (Score:3, Interesting)

      by GigsVT ( 208848 ) *
      LEDs don't save power vs fluorescents though. An 18 watt fluorescent lamp puts out around 1250 lumens. White LEDs only could put out 450 lumens max with the same 18 watts of power, about 25 lumens per watt.

      LEDs for lighting only make sense currently when you already have a low voltage DC power system, like in an RV or boat, since a fluorescent bulb transformer would waste some power and make it closer to equal.
      • What about heat output. If you are removing heat from the environment then any watts of heat cost about 4X as many watts of electricity to remove. Plus white led's are much, much more pleasing on the eyes than any fluorescent.
        • Go learn about thermodynamics.
        • Actually, it's the other way around. It costs between 1/6 to about 1/3 to remove the heat generated. For example, 1000 watts can generate 3413 BTUs of heat maximum (assuming none of the enrgy is used for anything else), and the same 1KW can power a 10,000 BTU air conditioner, which won't be running continuously, so will actually use less

          Now, if we keep in mind that we don't care about excess heat in the winter months ... (remember the articles about heating your den/office/room by overclocking?), the actua

  • Power waste (Score:2, Informative)

    by flamingspinach ( 668085 )
    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.

    • LEDs are inefficient too. (Score:4, Informative)

      by pr0ntab ( 632466 ) <pr0ntab AT gmail DOT com> on Monday April 28, 2003 @10:58PM (#5831292) Journal
      A high-efficiency red LED [vcu.edu] 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 [photonics.com]. 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.

  • Total cost of manufacturing (Score:4, Interesting)

    by FirstManOnMoon ( 613282 ) * on Monday April 28, 2003 @07:31PM (#5830094)
    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!

  • What do you want do? (Score:4, Informative)

    by obtuse ( 79208 ) on Monday April 28, 2003 @08:01PM (#5830315) Journal
    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 [pioneernet.net]
    http://misty.com/people/don/lede.html [misty.com]

    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.
    • 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
      • The 12vdc ones are probably similar to the high-frequency electronic ballast available for mains voltage (inverter-based design). Flicker is reduced so it's easier on the eyes, and tube life is increased. Operated at the design voltage, less power is used for a given light output than conventional ballasts (though when supplied under-voltage, conventional ballasts usually fare better in this respect, a fact worth considering if the power supply is unreliable). Also most HF ballasts have greater EMI problems
        • ..as my voltage drops in the storage batteries it makes the fluorescents not turn on or work as well, and yep, that flicker gets much worse then.

          Tell you a problem I have had. Gone through several of the cheaper LCD digital readout multimeters to use inline with the circuit to maintain better control/monitoring over the system. They just stop working after awhile. I know they aren't designed particularly for that task, but I am wondering now why they just stop, seeing as how they are pure battery, and I am

    • 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.       I think they makers of my car were a little over zealous. When i lose a taillight the dash lights go out the horn beeps and the breaks stop working.
    • Flourescent lights do put out a visual hum, but it is at 120 hertz, because you get light on the positive and negitave halfs of the cycle...
    • >(Any specific recommendations for a compact fluorescent that has a good color & a nice ballast that doesn't flicker sixty times a second?)

      I like the GE ones I bought at target in a 3 pack, they're slightly magenta colored, very pleasing, they are definitely electronic ballast and don't flicker.

      The Philips ones I bought at Home Depot are pretty good as well. Very bright, but they are very orange, almost exactly like an incandescent. They also take up to 10 minutes or so to come up to full brightnes

  • Cyclist tested, city approved (Score:3, Informative)

    by Baloo Ursidae ( 29355 ) <dead@address.com> on Tuesday April 29, 2003 @12:39AM (#5831737) Journal
    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

  • lumileds (Score:2, Informative)

    by kartel1 ( 444641 )
    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.

  • Yes. (Score:2)

    by pmz ( 462998 )
    Do the requirements necessary in the manufacture LEDs and LED componants out-weight the requirements for standard bulbs over 10 years?

    Have faith in the free market. From a cost-payoff point of view, the only thing you should care about is the price you see on the shelf at Wal-Mart. Built into this price are all the costs associated with manufacturing, packaging, distributing, and selling the LED.

    From an environmental point-of-view, I really don't know. The fact that LEDs are so durable and compact mig
  • For flashlights, where incandescents typically have very low bulb life and you often are VERY screwed if the bulb pops - LEDs are king, and unless you want the equivalent of the largest of SureFires, they're more than bright enough thanks to Lumileds Luxeon line (Mentioned a few posts up, they make 1 watt and 5 watt LEDs.) I have a MiniMag that has had the bulb assembly replaced with a 1W Luxeon and DC/DC current-regulated stepup converter, it ROCKS. It can tangle with a 2D Mag in brightness, and handily
  • One day, we will be able to apply a photonic band gap material to the surrounding area of the LED material itself. This will hopefully reduce the wasted heat, and instead perfectly reflect those photons back at the LED material, where they can be reabsorbed and then remitted till they get emitted in the right direction. This could increase the efficiency to near 95+%.

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