Follow Slashdot stories on Twitter


Forgot your password?
Power Science

Laser Blast Makes Regular Light Bulbs Super-Efficient 559

guruevi writes with news that a process using an ultra-powerful laser can crank up the efficiency of everyday incandescent light bulbs. Using the same laser process covered several years ago, the tungsten filament has an array of nano- and micro-scale structures formed on the surface making the resulting light as bright as a 100-watt bulb while consuming less electricity than a 60-watt bulb and remaining much cheaper to produce. "The key to creating the super-filament is an ultra-brief, ultra-intense beam of light called a femtosecond laser pulse. The laser burst lasts only a few quadrillionths of a second. To get a grasp of that kind of speed, consider that a femtosecond is to a second what a second is to about 32 million years. During its brief burst, Guo's laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point. That intense blast forces the surface of the metal to form nanostructures and microstructures that dramatically alter how efficiently light can radiate from the filament."
This discussion has been archived. No new comments can be posted.

Laser Blast Makes Regular Light Bulbs Super-Efficient

Comments Filter:
  • by Verteiron ( 224042 ) on Monday June 01, 2009 @04:44PM (#28173291) Homepage

    But it doesn't matter (at least to those of us in the USA), because in 2014 incandescent bulbs will be banned.

  • by B5_geek ( 638928 ) on Monday June 01, 2009 @04:49PM (#28173397)

    This is the might Slash. We can understand proper units.

    Femto = 10^-15

  • by freedumb2000 ( 966222 ) on Monday June 01, 2009 @04:52PM (#28173459)
    Same in europe.
  • Re:Super Efficient? (Score:5, Informative)

    by tjstork ( 137384 ) <todd.bandrowsky@gma i l .com> on Monday June 01, 2009 @04:53PM (#28173471) Homepage Journal

    Perhaps it operates more efficiently, but it doesn't sound like it is so efficient to produce. Unless I'm misunderstanding or misrepresenting the verbiage from the summary.

    You forgot that femtosecond part. The usage of the whole USA grid is for an incredibly tiny fraction of a second, 10^15 of a second. The USA grid is 4x10^15 watts. So really, if you want to translate it into a more sane energy understanding, its about four watts per bulb to do this.

  • Re:Too late (Score:4, Informative)

    by digsbo ( 1292334 ) on Monday June 01, 2009 @04:54PM (#28173493)
    Yeah, and they contain enough mercury to poison 4000 gallons of drinking water! Yay!
  • Re:Super Efficient? (Score:5, Informative)

    by clone53421 ( 1310749 ) on Monday June 01, 2009 @04:59PM (#28173579) Journal

    You screwed up your units, there. (watts)x(seconds) = joules [].

    You also forgot the negative on the exponent, but I'll forgive you for that...

  • Re:Consistency (Score:5, Informative)

    by sjames ( 1099 ) on Monday June 01, 2009 @05:04PM (#28173639) Homepage Journal

    ... Guo's laser unleashes as much power as the entire grid of North America onto a spot the size of a needle point.


    For one femtosecond (10^-15 seconds). Rough figure from the world factbook shows the U.S. + Canada averaging 497 GW. So, if the laser fired one thousand pulses per second, it would only draw 5 W from the wall (assuming 100% efficiency). It's another case of really big numbers combining with really small numbers to yield nothing spectacular.

  • Re:Consistency (Score:3, Informative)

    by artg ( 24127 ) on Monday June 01, 2009 @05:05PM (#28173655)
    Approx. energy used by NA grid in one year, 4x10^12 kWh Approx. mean power to achieve this, 4.5x10^11 W Approx. energy used in one femtosecond pulse 4.5x10^-4 Ws = 1.26x10^-10 kWh So quite a high repetition rate is allowed before the energy usage is noticeable.
  • by Grishnakh ( 216268 ) on Monday June 01, 2009 @05:14PM (#28173803)

    Since most power plants in the US (and many other countries too) burn coal, which contains mercury, these slightly-more-efficient incandescent lights will most likely end up dumping more mercury straight into the atmosphere (and then into the waterways with rain) over their lifetime than CFLs, which contain the mercury within the bulbs.

    So in your quest to avoid mercury pollution by using incandescent bulbs, you're actually causing MORE mercury pollution in the long term.

  • by Chris Burke ( 6130 ) on Monday June 01, 2009 @05:14PM (#28173807) Homepage

    Energy and Power are not the same. Specifically, Power is Energy divided by Time. W = E/t

    Based on just the US [], which for the sake of half-arsed napkin engineering on /. I will double to get total energy usage for North America in 2005, we're talking about 58000 TWh / 8760 h = 6.621 TW average power output.

    Thus the laser pulse itself uses 6.621E12 W * 1E-12 J = 6.621 J.

    The "efficient" lightbulb saves 40W. 6.621 J / 40 W = 0.165 s.

    So it takes less than a second to recover the energy used by the laser. I'm sure the laser system itself uses more power than what is just in the beam, but the point is, ridiculous amounts of power in ridiculously short amounts of time results in quite rational and manageable power levels.

  • Re:Too late (Score:3, Informative)

    by Locke2005 ( 849178 ) on Monday June 01, 2009 @05:14PM (#28173809)
    Compact florescents emit audible noise. Incandescents only emit noise if you but a cheap dimmer switch on them that chops up the sine wave. LEDs, as far I can tell, are silent. LEDs have good enough light now, they just need to be cheaper.
  • by Chris Burke ( 6130 ) on Monday June 01, 2009 @05:17PM (#28173855) Homepage

    6.621E12 W * 1E-12 s = 6.621 J.


    Also, I said "power" instead of "energy" at the end of my post. Heh.

  • Re:Too late (Score:4, Informative)

    by rev_sanchez ( 691443 ) on Monday June 01, 2009 @05:18PM (#28173877)
    A lot of mercury is released into the atmosphere from burning coal for electricity. According to the Australian version of the EPA [], powering a traditional incandescent light bulb will release of about 13.4mg of mercury over its lifetime versus 2.7mg for a CF bulb. CF bulbs contain 5mg of mercury or less so if you didn't recycle any you'd still release less mercury than would have been released by an incandescent bulb.

    Home Depot recycles them for free now and infrastructure to recycle them is spreading all of the time.
  • by confused one ( 671304 ) on Monday June 01, 2009 @05:22PM (#28173931)
    CFL's seem to have a finite number of on-off cycles. Well, that's not completely true... What seems to happen is that if you turn it on for only short periods of time, the life expectancy is reduced. the reduction goes something like 20% loss at 15 min. cycles, 80% loss at 5 min cycles. Counter-intuitive and seems to violate the principle that you should turn off the lamp when you're not in the room.
  • by DragonWriter ( 970822 ) on Monday June 01, 2009 @05:23PM (#28173943)

    But it doesn't matter (at least to those of us in the USA), because in 2014 incandescent bulbs will be banned.

    This is not correct, and, in fact, the restriction that motivates this misconception is, in fact, the reason why it matters particularly to those of us in the USA. There is no restriction, first of all, of incandescent bulbs meeting one or more of the exclusions or exceptions in Section 321 of the Energy
    Independence and Security Act of 2007 (Pub.L. 110-140) [] (the law imposing the new restrictions), including:
    * Bulbs producing less than 310 lumens
    * Bulbs producing more than 2600 lumens
    * Bulbs whose operating range is not with 110 V - 130 V
    * Bulbs not intended for "general service" use
    * Bulbs that don't have a "medium screw base"
    * appliance lamps
    * black light lamps
    * bug lamps
    * infrared lamps
    * left-hand thread lamps
    * marine lamps
    * marine signal service lamps
    * mine service lamps
    * plant light lamps
    * reflector lamps
    * rough service lamps
    * shatter-resistant (including shatter-proof and shatter-protected) lamps
    * sign service lamps
    * silver bowl lamps
    * 3-way incadescent lamps
    * traffic signal lamps
    * G shape lamps with a diameter of 5 inches or more
    * T shape lamps using not more than 40 watts or having a length of not more than 10 inches
    * A B, BA, CA, F, G16-1/2, G-25, G30, S, or M-14 lamps using 40 watts or less

    But, more importantly, even for the bulbs those that don't meet one of those exclusions, they aren't banned, they just need to be significantly more efficient than they currently are. Which the improved efficiency claimed by this process (more than meet.

    IOW, if the results claimed are accurate and the process is commercially viable and this efficient for incandescent lamps generally, its quite likely that all classes of incandescent lamps (provided this process was applied to the manufacture of those covered by the Act) could continue to used in the US after the restrictions in the Energy Independence and Security Act of 2007 go into effect, because this would make those bulbs covered by the Act efficient enough to continue to be used under the limits imposed by the Act.

  • by Chris Burke ( 6130 ) on Monday June 01, 2009 @05:23PM (#28173949) Homepage

    LOL and I screwed up the exponent for "femtosecond"! At least my title is still accurate, but it's really less than a millisecond that it would take to save the energy. I didn't mean to be that half-arsed!

  • by whiledo ( 1515553 ) * on Monday June 01, 2009 @05:24PM (#28173965)

    Were these in a bathroom, by chance? Humidity will shorten the life of CFLs. They never say how much, though. I stick with incandescents in the bathroom and outdoors (very cold winters that cause the flourescents to take forever). You may also have some funky electrical problems in your house that the CFLs dying are simply a symptom of. I've bought the cheap home depot ones for years and have replaced maybe one CFL since. That's opposed to the bathroom, where the incandescents have been replaced over and over.

  • by Dare nMc ( 468959 ) on Monday June 01, 2009 @05:24PM (#28173975)

    FYI the best Flourcent bulb is 100 lm/Watt (CFL is 60-72) while the best white LED is 131 lm/Watt (over 150 lm/Watt for some other colors.) []

    so while currently most CFL beat most LED in efficiency, inherently it looks like LED has a better future. Especially with LED lights having a longer (best case) lifetime, and being instant on to full power, and no high voltages present.
    The LED at home being a new trend, with in-efficient transformers, and cheap production units likely causing damage to their reputation. Much like Fluorescent is still trying to get over the poor initial products reputation (with odd colors, poor life, and several minutes of power up, with constantly buzzing transformers, and odd harmonics with monitors, video cameras, and TV's.)

  • by JSBiff ( 87824 ) on Monday June 01, 2009 @05:30PM (#28174085) Journal

    Dunno if this is gonna happen yet, or not, but I've seen articles about the use of oLed sheets as light sources - instead of being a 'bulb' in the usual sense, think more like those ceiling mounted fluorescent light fixtures with diffusers so common in schools, office buildings, and retail. Or, think of a computer monitor that is all white (although, the light need not be pure white - could be offwhite colors - could even change the color when you want, maybe), but brighter. They also say that OLEDs will become thin and flexible, so you could take your OLED 'film' and wrap it around a curved surface or something.

    So, you could have lighting that looks like a sort of 'standard' table-lamp with a lampshade - except the 'lampshade' is actually the OLED 'film', giving off light directly into the room, with no bulb inside the lampshade.

    That's still a number of years into the future, if it ever happens. OLEDs have to become many times cheaper than they are now before that'll happen.

  • by ShadowRangerRIT ( 1301549 ) on Monday June 01, 2009 @05:33PM (#28174139)
    Assuming you're old enough to have used them, have you ever broken one of the old school mercury thermometers? If so, you've already released the same amount of mercury found in 100 fluorescent bulbs []. 95% of the mercury in one of those bulbs can be recycled, so if you do recycle them, it would take 2000 bulbs to equal the mercury in that single broken thermometer. And of course, the additional power consumption means using more power, usually from coal, which is "the largest source of human-caused mercury emissions in the United States," [] making that incandescent release far more mercury over its lifespan than the fluorescent.
  • How's the power quality on those lines? Spikes and strong fluctuations can be pretty bad for any electronics device.

  • by Anonymous Coward on Monday June 01, 2009 @05:43PM (#28174283)

    Never. Incandescent light bulbs are banned from Europe in a coupe of months.

  • by Chris Burke ( 6130 ) on Monday June 01, 2009 @05:46PM (#28174327) Homepage

    So in your quest to avoid mercury pollution by using incandescent bulbs, you're actually causing MORE mercury pollution in the long term.

    Considering that the average American's face contains more mercury than 100 CFLs (~0.5g per filling, ~0.4mg per CFL), and CFLs are recyclable anyway, this truly smacks of a red herring like the environmental costs of the battery packs in hybrids/EVs.

  • by MyLongNickName ( 822545 ) on Monday June 01, 2009 @05:47PM (#28174355) Journal

    I think we might have the answer

    (from Wikipedia)
    "The life of a CFL is significantly shorter if it is only turned on for a few minutes at a time: In the case of a 5-minute on/off cycle the lifespan of a CFL can be up to 85% shorter, reducing its lifespan to the level of an incandescent lamp.[10][11][12]The US Energy Star program says to leave them on at least 15 minutes at a time to mitigate this problem."

    And here I am programmed to turn off lights when I leave the room. This being the case, I am more of an environmentalist for turning off my incandescent lights than I would be converting my whole house to CFL. With the exception of my living room, I am wasting money buying the CFLs. And they will be banned in the name of environmentalism.

  • by Grishnakh ( 216268 ) on Monday June 01, 2009 @05:54PM (#28174439)

    Maybe you need to get a better brand. I've got plenty of CFLs that are 2-5 years old, some more. I usually buy Sylvania. I once got some "Commercial Electric" ones from Home Despot but they were terrible, taking several minutes to warm up to full brightness.

  • Anal for units (Score:3, Informative)

    by RichardJenkins ( 1362463 ) on Monday June 01, 2009 @05:57PM (#28174477)

    Watts is a measurement of joules per second, so if you multiple power by time (as in applying 4x10^15 Watts for 10^-15 seconds) you get 4 joules.

  • by hardburn ( 141468 ) <hardburn&wumpus-cave,net> on Monday June 01, 2009 @05:57PM (#28174479)

    Carnot Efficiency goes up with the temperature [] you're adding to the system. At the temps nukes run at, it can be quite a bit better than 40%, and a lot better than the best photovoltaic cells in a labratory.

    The most efficient use of solar power doesn't come from photovoltaics, but from solar reflectors [], which are also limited by Carnot Efficiency.

  • by Grishnakh ( 216268 ) on Monday June 01, 2009 @05:59PM (#28174501)

    You don't need to "dispose" of fly ash from coal burning. You give it to concrete makers and they use it as filler in concrete.

    But yes, reprocessing is the best use of nuclear waste. It's a lot better than pouring tons of carbon dioxide and various pollutants (including mercury) into the atmosphere.

  • by Xtifr ( 1323 ) on Monday June 01, 2009 @06:29PM (#28174921) Homepage

    My experience is just about the opposite of yours. We began replacing incandescent with CFLs a little under three years ago, replacing bulbs only as the old ones died, and it took about six months to go all-CFL. Since we started the experiment, to date, we have had one CFL die. The first CFL we installed, nearly three years ago, is still going strong. It's too soon for any hard numbers, but the current data we have says that in our house, CFLs typically last at least six times as long as incandescents.

    This is in California, so it's not like the house wiring was originally installed by Ben Franklin himself, but it's hardly brand-new either, and CA is somewhat notorious for its flaky power supply. (Unlike the population, which includes both flakes and nuts.) :)

  • by sexconker ( 1179573 ) on Monday June 01, 2009 @06:37PM (#28175011)

    Uh, nuclear "waste" isn't a problem.

    If it's radioactive we use it smaller plants.
    There are "portable" nuclear reactors designed for neighborhoods, blocks, etc.

    Lower yield material is still useful.
    When it becomes too low-yield to be useful, simply bury it. It won't cause cancer or awaken latent mutant powers in angsty teenagers, even if it got exposed, released, etc.

  • by Anonymous Coward on Monday June 01, 2009 @06:45PM (#28175087)

    Power plants produce millions of tons of fly ash every year. Not all of it can be used in concrete filler (maybe 35% nationwide). In many cases, the fly ash needs to be post-processed before it can be used, which is added cost.

  • Re:This just in... (Score:1, Informative)

    by Anonymous Coward on Monday June 01, 2009 @07:01PM (#28175265)

    Efficiency also means less full-time people are needed for the same amount of work.

    Fewer, not less.

    HTH. HAND.

  • power factor (Score:4, Informative)

    by drDugan ( 219551 ) on Monday June 01, 2009 @07:15PM (#28175429) Homepage

    a longer description of Power Factor: []

  • Re:Production cost (Score:3, Informative)

    by Random Destruction ( 866027 ) on Monday June 01, 2009 @07:29PM (#28175563)
    Cause (huge power x femtosecond) << (small power x months).  It's right in the summary.  Femtoseconds are bloody short.
  • Re:Lifetime (Score:4, Informative)

    by snsh ( 968808 ) on Monday June 01, 2009 @07:31PM (#28175581)

    Incandescent lamps fail because the hot filament sputters off metal, gradually thinning the filament until it breaks.

    You can slow this down a little by using gases like halogens or krypton, which reverse the sputter or slow the sputter, but the benefit is not dramatic.

    To dramatically increase lifetime, you run the filament less hot. But while the lifetime goes up as the square of the voltage going down, the efficiency goes down as the cube (I think it's the cube might be more). So for the sake of efficiency, you want the hottest filament you can have.

    This is the tradeoff with double-life incandescent light bulbs. The money they save you in lamps is more than offset by the cost of electric. The filament is a colder blackbody source, it lasts longer, it's more yellow, and less efficient. Don't use them unless they're for a bulb that's hard to change, like something you have to climb a ladder to get to.

    In the opposite way, running a 75-cent lightbulb above the rated 2700k temperature, you'll get it more efficient and get whiter light. The bulb won't last as long you'll have to change it frequently. Maybe that makes sense for you, maybe not.

  • Re:Production cost (Score:5, Informative)

    by Artraze ( 600366 ) on Monday June 01, 2009 @07:54PM (#28175781)
    You don't seem to appreciate just how short a femtosecond is. As it is only 1e-15sec (1 millionth of a nanosecond), that means a pulse of 1e15W (1 million terawatts) would use only about 1 joule of energy.

    So let's say for the sake of argument that the power and pulse length are both an order of magnitude larger. Then say it's only 10% efficient, so that the process actually takes 1kJ. This energy corresponds to all of 25 seconds at 40W. In other words, the break even lifetime is under one minute.
  • by compro01 ( 777531 ) on Monday June 01, 2009 @09:04PM (#28176317)

    1. Only if you use non-dimmer compatible CFLs. These are findable at the local walmart (at least my local one, YMMV) and are easily identified by "DIMMER COMPATIBLE!!!!" on the packaging.

    2. No, they do not use that power, by definition. The power is sent through the lines and sent back. There is still transmission loss on that power and it increases plant load, but still less than an equivalent incandescent. a 100W equivalent CFL draws 23W, so 46VA (which gives us 40VAR) using his PF=0.5 figure. Let's be generous and say the grid loss is 50%. That brings the real power use to 23+(40*50%)=43W in actual power used and power company having to push out 46VA.

    Compared to a normal 100W incandescent, you're still drawing less than half.

    Compared to this new trick, we're drawing about 3/4s the power.

  • Re:This just in... (Score:3, Informative)

    by mazarin5 ( 309432 ) on Monday June 01, 2009 @09:37PM (#28176557) Journal

    Me and Steve Jobs shove iPhones up each other's asses for fun.

    Steve Jobs and I.

  • by sFurbo ( 1361249 ) on Tuesday June 02, 2009 @03:41AM (#28178735)
    Actually, most loads in normal households are inductive, and the CFL are capacitive, so the low power factor increases the overall power factor of a home (some of the unbalanced power from your fridge now only have to travel to the nearest CFL, and not to the local transformer station).

    But don't expect things like facts to convince the people who irrationally hate CFLs, you cannot reason people out of a position they have not reasoned themselves into.
  • by iroll ( 717924 ) on Tuesday June 02, 2009 @01:24PM (#28184705) Homepage

    Y is invariably a social engineering problem, not a physical engineering problem, based on fear born of ignorance and mistrust. The fact is that if we can otherwise store cubic miles of assorted dangerous industrial trash, we can certainly store cubic meters of nuclear waste.

The only function of economic forecasting is to make astrology look respectable. -- John Kenneth Galbraith