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The End Of The Light Bulb? 434

sdmonroe wrote to mention an MSNBC article discussing the likely eventual replacement of common light bulbs by LEDs. That replacement is likely to come quicker thanks to an accidental discovery announced this week. From the article: "Michael Bowers, a graduate student at Vanderbilt University, was just trying to make really small quantum dots, which are crystals generally only a few nanometers big. ... When you shine a light on quantum dots or apply electricity to them, they react by producing their own light, normally a bright, vibrant color. But when Bowers shined a laser on his batch of dots, something unexpected happened. 'I was surprised when a white glow covered the table,' Bowers said. 'The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow.'"
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The End Of The Light Bulb?

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  • by xanadu113 ( 657977 ) on Saturday October 22, 2005 @12:55PM (#13852827) Homepage
    Something new for moths to fly in to?
    • well, likely not. (Score:5, Interesting)

      by way2trivial ( 601132 ) on Saturday October 22, 2005 @01:04PM (#13852867) Homepage Journal
      at my workplace, a hotel on the beach.

      We had for many years yellow colored standard bulbs, as they don't attract bugs.

      we started replacement with yello fluro twist bulbs, to save on electricity and replacement costs.

      in research, it turns out, we can use white fluro-- as they only emit light in a very narrow spectrum of white light, unlike an ordinary filament bulb.. and the range they do emit light on, suitable for humans, does not attract bugs.

      I'd guess these low power led lights also emit white light on a very narrow band....
        • that was an excellent pic of the distribution.

          so these would still attract insects, but provide a fuller light experience for humans as well, than fluro..
        • This is awesome! (Score:3, Interesting)

          by Dr. Spork ( 142693 )
          The frequency distribution of this light is so much more natural than the other low-energy alternatives! I wonder if it could be made to match the frequency distribution of sunlight more closely by just rearranging the mixture of the sizes of the quantum dots. Anyway, this is excellent news. It's because of the spectrum distribution of fluorescent bulbs that I refuse to use them. It's not that I like wasting energy, but even without ugly light, winter is depressing enough in upstate New York!
    • by Simonetta ( 207550 ) on Saturday October 22, 2005 @01:22PM (#13852958)
      One of the unfortunate side effects of the 1970s was the replacement of all the soft white street light bulbs with orange-yellow sodium vapor bulbs. Sodium vapor bulbs use less energy. All the night lighting went from soothing soft white to light orange. Orange, as you may recall, is the color of madness.

          I've never liked yellow-orange streetlights. It's one of those things that never gets noticed. But the difference can be really appreciated if you go to a wealthy neighborhood where white light bulbs are still used. However, unless you're older and white, it's going to be a short time before the 'security guards' drive up with tasers and ask you what you're doing. If you're truthful and tell them that 'you're digging the cool white groove of the light, baby', then they will do what all mercenaries do when encountering a civilian harmlessly enjoying life, they will kidnap and assault you for their amusement.

          Anyway, a return to soft white lighting in the night will be most welcome.
      • There is another advantage to the yellow orange high preasure sodium lights. They aren't as big of a problem when it comes to light polution, because it is easier to filter their narrow spectrum. That makes astronomers happy because they can put fitlers on their telescopes. A lot of dark sky advocates will ask people to switch to high preasure sodium, if they have to have a light.

        I know what you mean though. I do hate the way they look. The orange glow even makes trees look creepy.

      • I disagree with your like. I find the white lights to be over
        bright and obnoxious. I much prefer the muted look of the
        sodium vapor lights. Especially from the air. The yellow
        lights are much more pleasant to view. What would be really
        nice is if we could change them to our liking. I have one
        of those bright white lights in the street outside my house.
        If it had knobs on it where I could change its spectrum, that
        would be cool. My ex-wife's neightborhood has no street
        lights at all - which I really prefer
  • LED lights (Score:5, Interesting)

    by totallygeek ( 263191 ) <> on Saturday October 22, 2005 @12:55PM (#13852828) Homepage
    I have been impressed with the LED lights over florescent or incandescent. The subdued lighting is fine with me and the energy consumption / bulb longevity is the best part. When my wife and I move (build a house), we will go 100% LED.
    • Then you (and your wife) might want to have a look at Modern Optical Engineering [], or if you are into math and can also appreciate the theoretical background of LEDs, hunt for Light Emitting Diodes [], by Fred Schubert, who is somewhat of the pope in this field.
    • by Tau Zero ( 75868 ) on Saturday October 22, 2005 @01:41PM (#13853038) Journal
      I wonder how many people are going to read this in the article and assume that LEDs are not just more efficient than other types of lamp, but 100% efficient?

      (I hate scientifically-illiterate journalists.)

  • by Anonymous Coward on Saturday October 22, 2005 @12:56PM (#13852833)
    How many cats does it take to change a quantum dot?
  • leds (Score:2, Interesting)

    by jsmucker ( 812692 )
    I will go to leds when they meet my budget....just a matter of time.
    • I will go to leds when they meet my budget....just a matter of time.

      Or the time of matter, since you can't measure both due to Heisenberg.
  • by Mysticalfruit ( 533341 ) on Saturday October 22, 2005 @12:58PM (#13852842) Homepage Journal
    Considering that the average lightbulb creates more heat than light, this is great!
    • by winkydink ( 650484 ) * <> on Saturday October 22, 2005 @01:03PM (#13852860) Homepage Journal
      Considering that the average lightbulb creates more heat than light...

      Kind of like most slashdotters!
    • by joostje ( 126457 ) on Saturday October 22, 2005 @01:13PM (#13852911)
      Considering that the average lightbulb creates more heat than light, this is great!
      As lightbulbs create about 95% to 98% heat (the rest is light), and modern LEDs about 85% to 96% heat, the LEDs still create more heat than light.

      reference []

      • by Hedon ( 192607 )
        When I was finishing up my PhD (on InfraRed LED's) about 5 years ago, HP was making high-efficiency Red LED's with 50% light output efficiency. At the same time commercially available blue (GaN) LED's were only 10% efficient. Green LED's were somewhere inbetween.

        I should really google for the state-of-the art visible LED efficiency, but am hoping for someone to post a more informative post following this one.
        • by rco3 ( 198978 )
          Cree [] are claiming a white (phosphor-based) LED with 50% wallplug efficiency, according to Don Klipstein's Lighting Site []. The link from his site is dead, though. Cree are also claiming that lab versions of a current LED achieve 70 lumens/watt [], and a total of 85 lumens at 350 mA. You'd still need about 25 of these to get the light output of a 100W incandescent, though. Probably cheaper to drop 300 5mm LEDs into a dedicated fixture - Chi Wing's [] eBay store will sell you 300 16,000 mcd (maybe...) white LEDs
    • Yeah, technically the LED itself doesn't throw out heat with the light it produces...however the "driver" (similar to a ballast on a flourescent fixture) or the electronics behind running/controlling the LED does produce a lot of heat. Reducing this ancillary heat production is another limiting factor to the adaptation of A Lamp replacement LED "bulbs".
      • by DrLex ( 811382 )
        Actually LEDs do produce heat, albeit the ratio of heat/light is much lower than with incandescent bulbs. The common LED is designed for a maximum current of 20 ~ 30mA, and at these currents the heat production is negligible. You can drive them at a higher current, but then the heat production becomes significant and can cause the LED to burn out (and at real high currents, the junction simply breaks down immediately). The more performant Luxeon LEDs are attached to a tiny heatsink and the high power ones (
    • Unless you give in a cold place -- where its nice of have as many sources of heat as you can get. Also, what about the fate of Easy Bake Ovens?!
  • by gvc ( 167165 ) on Saturday October 22, 2005 @12:58PM (#13852844)
    White LEDs are already 3 times as efficient as mercury fluorescent, and fluorescent tubes are 3 times as efficient as incandescent. They (fluorscent and LEDs) can get pretty good colour accuracy, too, if they want to. The only thing holding them back is price. I'm not sure what this new invention might bring to the table in that regard.
    • Can you point me to documentation of LEDs being 3 times as efficient as fluorescent? What I have mostly seen is that they are about the same efficiency. With the LEDs being about 3 to 4 times the cost.
    • No, actaully, the thing holding back LEDs from practical home applications is the color of the light they produce. More specifically the color temperature [].

      Typical incandescent lighting comes in somewhere around 2800-3200K. White LEDs live somewhere around the 5000-7000K range. When an efficent LED source can be made at a color temperature similar to that of incandescent lighting...then you'll see it take off in as a replacement for a standard A Lamp.

      This same color issue relates to the slow adaptation of Co
      • by gvc ( 167165 ) on Saturday October 22, 2005 @01:20PM (#13852949)
        It is the incandescent colour that is the wrong temperature, not the LEDs. Mid-day sun is nominally 5600K, and morning/evening higher. So why do you want to emulate candle-light?

        Completeness of spectrum is another issue. Cheap fluorescent tubes have huge mercury spikes and little red - maybe 55% on the accuracy scale. Good tubes achieve 95% - a marked difference. This is independent of the colour temperature.

        White LEDs (at leat the ones you commonly buy today) are also fluorescent, but with pretty decent spectral accuracy. It would at least in theory be possible to build an RGB array of monochrome LEDS that would produce apparent white light.
        • So why do you want to emulate candle-light?
          I never said it was a good idea, just that IMO this is what is holding up the adoption of white LEDs. This is what people expect.

          Completeness of spectrum is another issue.
          Yes, Color Rendering Index rating is also an important factor that I did not mention. However, isn't the CRI index also tuned to incandescent lighting, because this is what the eye expects?
          • The eye can adjust to color temperatures quite well. What the CRI measures is the completeness of the spectrum, not the temperature. The color temperature is based on only the summed effect of the different frequencies. You can have vastly different spectrums that result in the same color temperature, for example in a television where only three different fairly narrow bands are used to produce a wide range of colors.

            Two problems with using such narrow bands is that different people have different frequ

      • > Only recently have they produced flourscent fixtures that have a
        > similar color temperature to incandescent lighting.

        I specified flourscent fixtures that have a similar color temperature to incandescent lighting more than thirty years ago.
    • Not to mention that laser is just about the least efficient source of light.
    • The very best white LEDs are only as efficient as CFLs under ideal conditions. LEDs are best used for low light levels. When used for higher light levels the LEDs overheat producing less light per watt. CFLs are still the best for household lighting.
    • White LEDs are already 3 times as efficient as mercury fluorescent, and fluorescent tubes are 3 times as efficient as incandescent.

      From the article, LEDs produce twice as much light as a regular 60 watt bulb. I'm really not sure how to think about all of this. If LEDs produce twice as much light as a regular 60 watt bulb, how does that make LED lights better than compact fluorescent bulbs, which can produce four to five times as much light as an incandescent bulb of the same wattage?

      What is missing i

      • There's no wattage listed for the LED bulbs. However, they do specify the light source was a bright blue LED. If we assume it is the most power hungry LED currently available, it's about 5 watts. That means this bulb is producing light equivalent to a 120 watt incandescent bulb at 5 watts, or roughly 24 times as much light per watt as incandescent.
    • Ultimately it's not pure price (initial cost) that will determine the success or failure of alternative lighting. Cost is obviously a factor, but there are enough situations where the up-front costs are secondary to the lifetime costs in determining whether a purchase will be made. And in many situations the replacement cost includes substantial extra costs (manpower, equipment, etc) over and above the light's purchase price, which make fluorescents and LED lighting relatively attractive.

      As yet, LED light
    • by SuperBanana ( 662181 ) on Saturday October 22, 2005 @02:03PM (#13853158)
      The only thing holding them back is price.

      No- many things are holding back LEDs.

      • They produce light efficiently (not THAT efficiently) but don't produce that much light compared to a very simple single-bulb HID or fluorescent tube (by the way, which tube are you basing that "3x" on? T12, T10, or T8? Because T8's are MUCH more efficient that T12's). It takes a HUGE number of LEDs to replace ONE T8 fluorescent tube- and that tube costs a few dollars tops, because it is very easy to make. Right now, a single Luxeon white LED sells in 100-1000 unit quantities for well over $10-20, and produces 1-5W. A T8 bulb will produce 30-40W, and costs RETAIL about $5.
      • They require new reflector designs and light spreaders, since they are a VERY small point source. A lot of work goes into making light sources produce even, smooth lighting that won't generate harsh shadows- point sources make this job a real bitch. Point source also means that despite relatively low heat output the heat is very localized, and that means PCBs must also be heat spreaders, complicating assembly/design/manufacture further. You can't just toss them on a PCB. Companies like Luxeon now sell them on little PCBs with the necessary spreader etc, but now you're not just talking about buying an LED, you're buying a whole assembly for your product...$$$.
      • Related- while they have a long life before failure, most of the high-output LEDs drop in light output very significantly, within a year or two of continuous operation 10-20 degrees above room temperature. VERY few LED manufacturers disclose this upfront- and virtually ALL the companies hawking LED products fail to mention this nice little caveat. Furthermore, just because the LED is rated to, say, 100,000 hours- doesn't mean it won't burn out because the company that made the device it is part of didn't botch the job on current+voltage regulation, heat dissipation, etc.

      I know everyone thinks they are the second coming of Christ, and they do have some wonderful applications (like traffic signals and car brake lights)...but they're not the end-all be-all.

  • Oh no! (Score:4, Funny)

    by Trip Ericson ( 864747 ) on Saturday October 22, 2005 @12:59PM (#13852846) Homepage
    But now we'll have to change our "how many x does it take the change a lightbulb" jokes!

    "How many /. readers does it take the change a lightbulb? They don't have to because it's LED!"
  • No Effing Way!!! (Score:3, Interesting)

    by Anonymous Coward on Saturday October 22, 2005 @12:59PM (#13852853)
    Have you ever tried an LED light? They suck!!! They do not cast nearly enough light. The light color is a disturbing and unnatural color, usually with too much blue in it.

    Florescent tubes are FAR superior to LED lights and yet so many people prefer good old incandescent lights to even florescent tubes. Hell, even something as simple as a flash light. Try an LED flash light and then try a xenon Mag Light and tell me which one rocks your socks.

    LED lighting is one of those technology "revolutions" that are for the sake of technology. They are NOT better.
  • by PGC ( 880972 ) on Saturday October 22, 2005 @01:01PM (#13852857)
    are not followed by 'Eureka' , but by "Hey, that's funny" .
  • by dada21 ( 163177 ) * <> on Saturday October 22, 2005 @01:03PM (#13852863) Homepage Journal
    If I close my bedroom door, my quantum bulb will neither be working nor burnt out.
  • From the FAQ on LEDs (Score:5, Informative)

    by jkind ( 922585 ) on Saturday October 22, 2005 @01:04PM (#13852871) Homepage
    Answer: there are several obvious advantages LEDs have over traditional incandescent light bulbs, they are as follows:
    Low power consumption - energy saving,
    Long lasting,
    Cold lighting,
    Small size and weight,
    Fast switch times,
    Simple to use.
    This is from the FAQ, but it doesn't list any disadvantages..
    anyone care to share?
    • by Rob the Bold ( 788862 ) on Saturday October 22, 2005 @01:25PM (#13852972)
      Some Disadvantages:

      Like Fluorescent, requires supporting circuitry -- doesn't plug directly into AC wiring.
      Cost (initial investment)
      Harder to dim -- can't use simple rheostat
      Flicker (if using less than 100% on time)

      I don't have anything against LED lighting, and none of these disadvantages are insurmountable. Indeed, these could be viewed as business opportunities instead. Most of the disadvantages are shared with fluorescents, and adequate solutions already exist there. I know a guy who lights his whole off-grid house with LEDs (using low voltage DC wiring). I particularly like the possibility of creating variable color lighting with LEDs, emulating daylight, sunlight, tungsten or whatever.

      • From a senior project I did in a few years ago, we dimmed an array of 300 high-powered LEDs (Lumileds)with no flicker at any level. They definitely didn't run totally cool, though they did have a fair amount of heat. As far as dimmers go, most standard dimmers use SCRs or triacs for dimming instead ofa rheostat anyhow, and that should work just fine for LEDs. Whatever supporting circuitry is used can easily provide dimming capabilities already built-in.
      • AC vs DC (Score:5, Interesting)

        by MDMurphy ( 208495 ) on Saturday October 22, 2005 @02:11PM (#13853192)
        AC has it's advantages, especially for long distance transmission. But in a house, it's gradually losing out. If you don't count lightbulbs, I'd say I have more DC things plugged in than AC. So many of the outlets are connected to "bricks" or "wall warts" to change the high voltage AC to low voltage DC. Things that don't have an exterior brick, like the DVD player or TiVo just do the conversion internally. While the higher voltage AC might have some benefits of lower loss in the wires, I'd think that umpteen separate transformers and rectifiers are negating a large percentage of that benefit.

        If lighting were go to DC, then a re-think of the home wiring would really be in order. If there were a "standard" DC voltage and current available to lower power devices, we might not have wall transformers with anything from 3v-12v hanging off our surge supressors.

        So in-house DC makes lots of sense. Send the AC to things like ovens and clothes dryers, and DC to most everything else.
    • LED disadvantages (Score:5, Interesting)

      by Temeraire ( 913731 ) on Saturday October 22, 2005 @01:37PM (#13853026)
      Anyone who tries (like me) to build small lighting devices with LEDs rapidly discovers lots of practical difficulties. To equal the light output of one cheapo fluorescent tube you need hundreds of the little blighters. It is not easy to make their output look even, rather than dotty. And with that large number, reliability is a real problem. Even a 1% failure rate (amplified to 3% or 5% by the LEDs often being in series) rapidly translates into major unevenness. Even production lines struggle to make large arrays of LEDs stay 100% alight, but little people often get sold the bin ends, which fail rapidly in service.
            Also LEDs are NOT yet more efficient than fluorescents. Their data sheets never give the one number that really matters: what percentage of input energy actually emerges as light? The answer is usually frighteningly low. Therefore LED devices tend to cook themselves to death if run really bright.
            To run LEDs stably requires either a wasteful series resistor or an expensive semiconductor constant-current device. And cheap low-voltage power supplies are actually badly life-limited by their electrolytic capacitors. In my experience many LEDs die prematurely because of a failing power supply and hot sunshine.
            Don't get me wrong. LEDs are the future, but you must be wary of calling them energy-saving, long-lasting, or easy to use!
  • by Anonymous Coward on Saturday October 22, 2005 @01:06PM (#13852882)
    A LED Zeppelin, of course.
  • FTFA (Score:3, Funny)

    by Associate ( 317603 ) on Saturday October 22, 2005 @01:09PM (#13852888) Homepage
    When a brilliant idea pops into your mind in the future, what will appear over your head?

    Answer: $$$
  • by Garridan ( 597129 ) on Saturday October 22, 2005 @01:09PM (#13852889)
    "One big question remains: When a brilliant idea pops into your mind in the future, what will appear over your head?"

    Smoke. That's one thing that I don't see changing any time soon. Not for me, anyway.
  • Thinkgeek (Score:4, Informative)

    by Eightyford ( 893696 ) on Saturday October 22, 2005 @01:14PM (#13852913) Homepage
    I'm totally surprised that they OSTG didn't pimp their LED bulb from thinkgeek. 35 bucks is a little steep though. []

    Of course, you could always make your own. htm []
  • by lancejjj ( 924211 ) on Saturday October 22, 2005 @01:15PM (#13852922) Homepage
    This could be a big advance for LEDs. But as of now, commercially available LEDs do NOT produce as many lumens per watt as Compact Fluorescent Light bulbs (CFLs.) [] Of course, this new LED discovery may improve LED efficiency to the point where they exceed CFL efficiency. We'll have to wait and see.

    CFLs are inexpensive and readily available today. CFLs have a long life, and they save a ton of energy when compared to traditional light bulbs. Even more importantly, they don't suck like the CFLs of a few years ago that had a noticeable/painful "warm up" time.

    I save quite a bit off of my energy bill [] by using CFLs. They really cut down on electricity consumption, and I've never had one "burn out" on me. Ever. Yet.

    • I've replaced most of the bulbs in our house with CFLs and generally my wife and I love them. There are just two issues which are pretty darn annoying at times (basides their appearance, which isn't a problem given that I've put them in lamps that have shades or other covers).

      The first is that the bulbs still have a warm-up time. Sure, they light right away, but it can take several minutes before they're at maximum brightness. This can be annoying, say, in a kitchen or other work area where I need all the
    • CFL's do not like enclosed fixtures - I live in a rental, so I am not inclined to change them, but *every* cfl I put in those fixtures failed. I did post-mortens on them, some seemed to have unsoldered themselves (wires off the board) and others just seemed to have died. They never seemed to feel hot enough to melt solder, but the conditions in the base while running might have been pretty rough. So 15 have failed, 2 survived (in open socket applications). Many rooms in my house have regular tube fluore
  • Costly Quantum Dots (Score:5, Interesting)

    by ObligatoryUserName ( 126027 ) on Saturday October 22, 2005 @01:18PM (#13852935) Journal
    If the manufacturing breakthough talked about in this article [] pans out, the cost of Quantum Dot manufacture will drop from $2,000 to $400 per gram. That's huge improvement, but I still wouldn't expect to see Quantum Dot lightbulbs on ThinkGeek anytime soon...
  • by The Optimizer ( 14168 ) on Saturday October 22, 2005 @01:25PM (#13852973)
    I just finished converting the lighting in my house to save energy, and learned a few things in the process. Most of the incandescent bulbs were replaced with compact fluorescents, but I did install 4 LED light bulbs in one application.

    The current generation of compact fluorescent bulbs has come a long way from the ones I remember 10-20 years ago. They don't have the flicker or startup problem anymore, and they are available in a variety of color temperatures from 2700 degrees (yellowish, comparable to incandescent) to 6100 degrees (white, sterile). For the same light output (lumens), energy consumption is normally 22% to 27% of the incandescent bulbs they replace. They very slightly in things like color and wattage depending on the manufacturer.

    Nobody who has visited my home has yet noticed the difference.

    Since you can find common CF bulbs sizes for under $2 per unit (try Sams Club, etc), and they should last 4 to 8 times as long as an incandescent, the economic case is pretty sound even before factoring in the energy savings.

    I replaced 4x 7.5 watt bulbs with LED bulbs and noticed a few things. The LED bulb itself is about twice as large, and as others have mentioned, the light emitted is an eerie blue-white light. You defiantly notice it. These bulbs consume 0.8 watts and produce an output pretty close to the 7.5 watt bulbs they replaced, though I could not find the output in lumens for either bulb anywhere. They were about $7 a bulb, and are rated to last 100K hours, or about 50 times as long the bulbs they replaced. Since the bulb is actually made of up 18 individual LEDs inside, I believe the rating is for the mean time until 50% of the LEDs are no longer functioning.

    After converting 152 of 160 bulbs in my home, my electric bill happy.
    • I've switched a lot of my bulbs over to the CFs available at my local home store (Feit Electric; their websites down right now or I'd link it). The problems I have with them:
      1. Most of them start nearly instantly, but dimly. They get brighter as they go, usually peaking after a minute or so.
      2. At least half of them smell like magic smoke when you get close to them. One of them had me looking for an electrical fire inside my walls until I figured it out.

      Once they're up and running, they're bright, ni

      • Are these "features" of all CF bulbs, or is the brand I've been buying really crummy?

        I've recently converted my apartment to CF bulbs as well, and I've noticed mixed results in this regard. The Noma 60W equivalent bulbs in my hall and bedroom lighting fixtures don't exhibit this problem -- or if they do, the brightness differential is so minimal that I don't notice. They come on immediately and are at full brightness immediately (or at least as fast as I can perceive).

        I also have a dimmable 100W equiv

  • by plasmacutter ( 901737 ) on Saturday October 22, 2005 @01:26PM (#13852977)
    I have an led flashlight.

    led's emit a very cold light. Fourescent light is described as cold and "vitamin burning", but led light is even worse in this respect.

    It works for headlights, emergency beacons, and select areas, but generalized room lighting is not one of those areas.
  • by maino82 ( 851720 ) on Saturday October 22, 2005 @01:27PM (#13852984)
    I can definitely see the benefits of LEDs when compared to other forms of electric light. They do produce more lumens per watt than most other sources, but they do produce a good deal of heat when combined together into a large array, despite what people may tell you. They also have the added benefit of efficiently producing (since they only produce light in a certain wavelength) just about any color you would want through color mixing of different color LEDs (check out the tunnel in the Detroit airport if you'd like to see a well done example). Personally, though, I would love to see more daylight in spaces rather than a push for the latest and greatest in electric light. If done properly, daylighting can greatly increase light levels in the workplace and lower energy consumed by electric light. Generally, this will lead to an increase in cooling load, but this is almost always smaller than the amount of energy saved by eliminating electric lighting (again, if done properly). So while I'm all for more efficient electric lighting, it would be nice to see no electric lighting used during daylight hours when the sun is readily available.
  • That's how white LED's work if I'm not mistaken. Although instead of quantum dots, they use phosphor or some other material. Are quantum dots more efficient? Try this: Take a blue LED and shine it into a white LED that is turned off. You should see a slight white glow from the white LED, even though the originating light source is blue! Kind of a neat and simple experiment.
  • The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow.

    I bet Marie and Pierre Curie thought something similar at one point. "Hey look, this lump of weird metal that we produced is glowing so pretty... hey, if I put it in my mouth, my eyes glow too! Fun!"
  • "One big question remains: When a brilliant idea pops into your mind in the future, what will appear over your head?"

    A Dollar sign? ... or more likely since we are talking about the future, a €uro sign.
  • I'm a professional firefighter and a lot of the guys have started using LED flashlights. I had just purchased my own (out of my pocket and not the city's) rechargeable StreamLight that uses a halogen bulb. When I started seeing the LED's showing up I thought I had made a mistake. They "seem" bright but after seeing them more and more I'm convinced it's just because the light is so white (slightly blueish) and clean.

    However even though it looks brighter in fact it's less so and seems to accentuate shadows MU
  • I don't understand. Would I have to shine a laser on my new quantum dot light bulbs or could they get activated differently? Using a laser doesn't seem too practical.
  • by josephdrivein ( 924831 ) on Saturday October 22, 2005 @02:09PM (#13853185)
    The main reasons why White LEDs are still not ready for general purpose lighting are:

    Low CRI (Color Rendering Index) that means bad illumination compared to incandescent
    Low temperature of operation (120-150C max)

    Most electronic design that include hi power LEDs (such as LUXEON []) need to take in account hheat transfer.
  • by travail_jgd ( 80602 ) on Saturday October 22, 2005 @03:04PM (#13853419)
    I'm an LED flashlight geek, so I'm realistic when it comes to lighting a house with LEDs. I'd be surprised if in 20 years we weren't replacing CFLs with LED bulbs, but at the moment it's not a worthwhile investment.

    Right now, I'm happy with my CFLs: for the wattage needed to light my living room and foyer with incandescents (140 watts), I can light my whole apartment on a dark October day. It's definitely a mood-lifter to not have to worry about my electric bill, or have the place look like a funeral home.

    OTOH, incandescents may not be so quick to fade away: the efficiency of tungsten filaments can be significantly increased by using crystals instead of wires [].

  • by HermanAB ( 661181 ) on Saturday October 22, 2005 @03:27PM (#13853512)
    Hmmm, if you shine a strong enough laser on *anything*, it can give off a beautiful white glow...

The IQ of the group is the lowest IQ of a member of the group divided by the number of people in the group.