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Technology Science

Jet Engine on a Chip 463

Posted by michael from the go-go-gadget-jet-engine dept.
Roland Piquepaille writes "Today, our handheld devices are powered by batteries, which are heavy and inconvenient. Fuel cells are just arriving on the market as a replacement. But there is a new contender: micro gas turbine engines under development at the MIT. Engineers there shrunk jet engines to the size of a coat button. And their blades which span an area smaller than a dime can spin a million times per minute and produce enough electricity to power your PDA or your cell phone. While there are still a few hurdles to overcome, these micro turbine engines should be operational in two or three years, with commercial products available four years from now. These micro jet engines also have the potential to free soldiers or travelers from carrying heavy batteries. The engineers even think their engines on a chip could be used in poor countries to bring electricity there. This summary gives you the essential details about a technology which promises to free us to carry extra fuel instead of batteries."
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Jet Engine on a Chip More

Jet Engine on a Chip

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  • Fear... (Score:4, Funny)

    by grub ( 11606 ) <slashdot@grub.net> on Tuesday October 19, 2004 @01:54PM (#10567904) Homepage Journal

    Engineers there shrunk jet engines to the size of a coat button

    Naturally the Department of Homeland Security will declare that people with 4 or more buttons on their coat are 'terrorists'

  • Cool, but misleading title (Score:5, Interesting)

    by AKAImBatman ( 238306 ) * <<moc.liamg> <ta> <namtabmiaka>> on Tuesday October 19, 2004 @01:54PM (#10567905) Homepage Journal
    1. That's pretty damned cool. Gas Turbines are some of the most efficient fuel -> energy converters known to man.

    2. Saying that a Gas Turbine == a Jet Engine is a bit misleading. It's a bit like saying "Scientists have shrunk an electric motor to 4 nanmometers", then before you even finish thinking about all the MEMS devices, you read "Scientists have produced a 4 nanometer electric genertor for use in making power for MEMS devices." Still very cool, but not the same thing.

    • Re:Cool, but misleading title (Score:5, Interesting)

      by maeka ( 518272 ) on Tuesday October 19, 2004 @02:08PM (#10568074) Journal
      Why do you say that gas turbines are some of the most efficient fuel to energy converters known to man? Every link I can find in a google search says otherwise. http://www.britannica.com/eb/article?tocId=45726 [britannica.com] for example.

      Gas turbines seem to only become highly fuel efficient when the heat of their exhaust gas is captured by a secondary system, like a steam recovery boiler. http://www.ornl.gov/info/ornlreview/v33_1_00/turbi ne.htm [ornl.gov]

      • Re:Cool, but misleading title (Score:5, Informative)

        by AKAImBatman ( 238306 ) * <<moc.liamg> <ta> <namtabmiaka>> on Tuesday October 19, 2004 @02:22PM (#10568246) Homepage Journal
        Why do you say that gas turbines are some of the most efficient fuel to energy converters known to man? Every link I can find in a google search says otherwise.

        That used to be true, but the current breed of Gas Turbines are amazingly efficient. From wikipedia [wikipedia.org]:

        They can be particularly efficient -- up to 60 percent -- when waste heat from the gas turbine is recovered by a conventional steam turbine in a combined cycle.

        The primary issue in obtaining high efficiencies is in (as you stated) efficiently recycling the waste heat. I can only assume that the inventors would be attempting to shrink the secondary cycle along with the gas turbine. The physics really aren't all that different, so it should just be a matter of materials.

        Also from the wikipedia link above:

        Typical micro turbine efficiencies are 20 to 35 percent. When in a combined heat and power system, overall efficiencies of greater than 90 percent may be achieved.

        • Two lessons for you: (Score:5, Informative)

          by Engineer-Poet ( 795260 ) on Tuesday October 19, 2004 @02:40PM (#10568459) Homepage Journal
          1. Wikipedia is not [volokh.com] trustworthy. [volokh.com]
          2. The microturbines the authors appear to be talking about are in the neighborhood of 30 kilowatts and bigger, not 15 watts. A non-micro turbine would have an output of megawatts; some are capable of hundreds of megawatts. [gepower.com]
        • There are two reasons big gas turbines have low efficiency. The first is that gas compression is expensive in terms of work. It's also tricky, and it took decades to make working models even though the materials and techniques were well known. The second problem is that you are typically blowing lots of hot and unexpanded gas back into the environment.

          Combined cycle generation overcomes these limits by using water as a working fluid for the gas turbine's "waste heat". Water is much easier to compress,

    • Re:Cool, but misleading title (Score:5, Informative)

      by kaszeta ( 322161 ) <rich@kaszeta.org> on Tuesday October 19, 2004 @02:12PM (#10568131) Homepage
      Gas Turbines are some of the most efficient fuel -> energy converters known to man.

      Actually, in terms of the overall thermodynamic efficiency, they aren't all that great. 40% efficiency is *very* good for a Brayton cycle (i.e. turbine engine) system, but is fairly easily done with a large-scale steam system. Microturbines tend to run around 25%, which means that (a) you need a fairly big recuperator to run efficiently (which doesn't seem to be part of the MIT design), and (b) you need to be able to reject a lot of waste heat (so running your laptop on one of these means you'll be blowed 200+ watts out the back).

      Not that gas turbines are without their advantages. Their specific power (weight per kW) is very good, so for the same amount of power the engine is very light compared to most other engine types (which is why they use them in aircraft). They also start and stop quickly compared to steam turbine systems. And they can be nicely combined with other systems like a steam system to make a combined cycle, the whole system can be fairly efficient.

      But, by themselves, they aren't all that efficient.

      • Trying to make an efficient micro-turbine like this should be quite interesting. Viscosity will play a much bigger role - your entire flow regime will have the effects normally confined to the boundary layers on larger turbines. I wonder if they had to modify their CFD analysis programs to be able to handle the sort of flows you get inside such a tiny turbine.

        • Re:Cool, but misleading title (Score:5, Interesting)

          by kaszeta ( 322161 ) <rich@kaszeta.org> on Tuesday October 19, 2004 @02:27PM (#10568320) Homepage
          Trying to make an efficient micro-turbine like this should be quite interesting. Viscosity will play a much bigger role - your entire flow regime will have the effects normally confined to the boundary layers on larger turbines.

          You are correct. However, much of the fluid mechanics of very small microturbines is rather well understood, so the basic goal isn't unreasonable. And usually the answer to viscosity is speed---small turbines generally spin very, very fast.

          (Disclaimer, I work for a company that makes very small turbines [creare.com].)

    • size and efficiency (Score:5, Interesting)

      by TamMan2000 ( 578899 ) on Tuesday October 19, 2004 @02:19PM (#10568224) Journal
      1. That's pretty damned cool. Gas Turbines are some of the most efficient fuel -> energy converters known to man.
      You will also notice that (in general) the smaller the gas turbine, the less efficient.

      I have been to multiple talks on these engines, I used to work for one of the industry colaborators on the project as an aerodynamicist. These engines are no exception to that rule. The turbine on these engines hardly extracts enough work to run the compresser when you are running the combuster just below the melting point of the engine.

      Also (addressing the summary, not the parent post), these things have been "2-3 years away" for at least 6 years.
      • I'd like to add something to what you said...

        Jet engines are relatively inefficient at low speeds but once they get up to speed, the efficency goes back up and the process feeds on itself becoming a self-sustaining process.

        Combustion engines are the opposite, they run fine at regular speeds but at high speeds, you get the same effect as the economic term "diminished returns" where it states that with additional units of work provide lesser and lesser additional power. In other words, it requires more and

    • Gas Turbines are some of the most efficient fuel -> energy converters known to man.

      False!

      I work in the energy sector. Gas turbines are, for the most part, only turned on when there is either (a) a sudden increase in demand or (b) nothing else available. Believe it or not, a steam-powered plant will generally do the job on as much as 50% less fuel than a gas turbine, but may take several hours to get up to speed.

  • exaust (Score:5, Funny)

    by tubbtubb ( 781286 ) * on Tuesday October 19, 2004 @01:55PM (#10567915)

    What about the exaust?
    I can't wait to get kicked out of a snooty coffee shop because my dual core G5 laptop was asphyxiating the customers . . .

    • Re:exaust (Score:4, Informative)

      by AKAImBatman ( 238306 ) * <<moc.liamg> <ta> <namtabmiaka>> on Tuesday October 19, 2004 @02:02PM (#10568003) Homepage Journal
      What about the exaust?

      Well, your cell phone only needs about a watt, a PDA about 2-10 watts, and your laptop about 20-100 watts. If you consider that cars produce kilowatts of constant power output, you should realize that the amount of exhaust shouldn't be anywhere close to what your car puts out.

      In addition, these turbines will probably use something a smidge cleaner than gasoline. Even kerosine is better, but ethanol would probably rank the cleanest.

      Speaking of kerosine, these turbines shouldn't even be as back as burning a kerosine lamp. :-)

      • Re:exaust (Score:2, Insightful)

        by Anonymous Coward

        Well, your cell phone only needs about a watt, a PDA about 2-10 watts, and your laptop about 20-100 watts. If you consider that cars produce kilowatts of constant power output, you should realize that the amount of exhaust shouldn't be anywhere close to what your car puts out.

        Which is quite good, as they don't let you run your car on a plane. But using your numbers, 20 or so people using laptops on a plane would be the same as someone running a car in the passenger cabin. That's not good.

      • Re:exaust (Score:3, Interesting)

        by drinkypoo ( 153816 )

        In addition, these turbines will probably use something a smidge cleaner than gasoline. Even kerosine is better, but ethanol would probably rank the cleanest.

        What about hydrogen? I know that's kind of a played-out concept but look at the possibilities. You could have your own electrolyser at home and bottle your own hydrogen, then slap it into your laptop and go. You could generate the electricity off the grid, or whatever. Output is water vapor, which is pretty harmless as long as it's exhausted outs


        • And please don't forget to mod *down* all the muppets that think that Hydrogen is in any way more dangerous than Petrol(gasoline), Kerosine or Ethanol ;)

        • Storage (Score:5, Informative)

          by Andy Dodd ( 701 ) <atd7@[ ]nell.edu ['cor' in gap]> on Tuesday October 19, 2004 @02:17PM (#10568197) Homepage
          Long-term storage of hydrogen is still a bit of a problem. Hydrogen has a tendency to penetrate ANYTHING you try to store it in, resulting in hydrogen embrittlement. In short, anything you store hydrogen in (esp. pressurized hydrogen) will eventually become weakened by the hydrogen permeating it.

          • Re:Storage (Score:3, Insightful)

            by AKAImBatman ( 238306 ) *
            That's a good point. Hydrogen embrittlement is a serious issue with rocket engine design. I hadn't considered that it would be an issue with fuel cells. That may be why many laptop cells utilize methanol as a hydrogen storage medium.
      • waste heat?

        getting rid of some 300w+ of heat on your lappy..

      • Re:exaust (Score:3, Informative)

        by Feanturi ( 99866 )
        In addition, these turbines will probably use something a smidge cleaner than gasoline.

        The article mentions diesel, which makes the whole thing sound like it will be messy and smelly. Changing cartridges you'd probably get some in the air, and it doesn't smell good. Using the device, then (because you're in a hurry, say) quickly sticking it in your shirt pocket while the engine is still winding down, you'd be smelling like diesel exhaust the rest of the day. Yuck...

    • You also planning to use this excuse in elevators? (Score:5, Funny)

      by StressGuy ( 472374 ) on Tuesday October 19, 2004 @02:05PM (#10568047)
      Beats blaming it on the dog I guess... :)

      • Or at dinner... (Score:5, Funny)

        by jpetts ( 208163 ) on Tuesday October 19, 2004 @02:51PM (#10568579)
        Beats blaming it on the dog I guess... :)

        A guy goes to dinner with his girlfriend's family, and finds he is a bit windy about the arse. Anyway, he is sitting down at table, and the family dog is lying down behind his chair, so he figures he'll try a little experiment. So, he shifts his weight to his left cheek, and squeezes out a fairly quiet fart.

        The mother looks up at the noise, and says "Baron!" (this being the dog's name). Encouraged, the guy lets out another one, quite a bit louder this time.

        Again, the mother looks up, and exclaims "Baron!" in a more urgent tone.

        By now the guy figures he's got carte blanche for whatever trouser stunts he wants to pull, so he let's rip with all his might, and lets one go that sounds like the curtains are being ripped in half!

        At this, the mother stands up, panic-stricken, and shouts "Baron! Get away from that man before he shits all over you!"

    • Re:exaust (Score:3, Insightful)

      by upsidedown_duck ( 788782 )

      Why not use a small tank of compressed gas (i.e., nitrogen) to drive the turbine? For small portable power, the inefficiency inherent in compressing the gas in the first place isn't that big of a deal.

    • I wouldn't worry about the exhaust, I would worry about shock. What are the implications of having a relatively tiny turbine spinning that fast and be dropped / jostled / jiggled / wiggled? Would that interrupt the rhythm and therefore the power output?

  • Roland Piquepaille! (Score:3, Interesting)

    by recursiv ( 324497 ) on Tuesday October 19, 2004 @01:55PM (#10567923) Homepage Journal
    Fantastic! Glad to see a post by you Roland! You see, I really enjoy absolute shit, so I am glad to see another of your presumably bought and paid for fluff stories.

    • MOD PARENT UP (Score:3, Interesting)

      by jmays ( 450770 )
      This is exactly true. Roland Piquepaille submits fluff stories to /. over and over and over just to generate traffic to his blog. Slashdot ... come on. You can do better.

      • Re:MOD PARENT UP (Score:5, Interesting)

        by AbbyNormal ( 216235 ) on Tuesday October 19, 2004 @02:25PM (#10568293) Homepage
        Fluff?

        I dunno, I found this article very interesting.

        Also, did you actually read some of the other stories on his blog? Mongolian monks and fish? Hydrogen Economy? Phoning Home from the Bottom of the Ocean?

        I actually found that blog to be quite interesting and unlike most, he took the time to post illustrations. I say: Good job Slashdot! That was indeed a "News for Nerds" article.

        • Re:MOD PARENT UP (Score:5, Insightful)

          by jmays ( 450770 ) on Tuesday October 19, 2004 @02:42PM (#10568476)
          Roland generally posts a link to an (interesting) article on a technology site and then paraphrases it under the guise of a 'useful summary'. He offers zero insight and could instead just submit the original article without his unnecessary boring commentary. It is filtered and it is bullshit.
  • What about pollution from this? Has that even been considered?

    • Re:What about pollution? (Score:5, Insightful)

      by djh101010 ( 656795 ) * on Tuesday October 19, 2004 @02:01PM (#10567985) Homepage Journal
      If the fuel is a clean hydrocarbon, the exhaust will be CO2 and H2O. Using batteries pollutes too, you just don't see it right there because it's either at the power plant where your battery charger got it's energy from, or it's in the chemical pollution of used dead batteries, or both.
    • I'd bet it is neglectible compared to the pollution caused by regular alkaline batteries that end up in the dumpyard.

      At most the pollutants would be CO2 and some other carbon based compounds.

    • Re:What about pollution? (Score:5, Insightful)

      by pclminion ( 145572 ) on Tuesday October 19, 2004 @02:05PM (#10568048)
      What about pollution from this? Has that even been considered?

      Compare with traditional rechargable batteries.

      First, there is the one-time environmental cost of manufacturing the batteries. Making a battery requires fuel for mining equipment, transporting the materials, running the manufacturing equipment, and producing the electrolyte.

      Second, there is the energy required to charge the battery. This energy comes from the power grid. Ultimately, it comes from burning fossil fuels in power plants. This energy must be transmitted via wires to an electrical outlet, turned into DC by a rectifier, and finally, used to charge the battery.

      In other words, here's the energy path for the turbine:

      Fossil fuel ---> Combustion ---> Turn turbine ---> Generate DC power

      And for the rechargable batteries:

      Fossil fuel ---> Combustion ---> Turn turbine ---> Generate AC current ---> Transform to high voltage ---> Transmit down wires ---> Transform back to low voltage ---> Rectify to DC power

      Which do you think is more efficient?

      • Except my batteries (mouse batteries) are rechargeable ones I recharge from a grid that gets its power from hydroelectricity if I'm not mistaken. Of course, there's probably pollution from that still, but minor compared to other methods.

      • Re:What about pollution? (Score:5, Insightful)

        by Ignignot ( 782335 ) on Tuesday October 19, 2004 @02:25PM (#10568290) Journal
        Well, IAAEE (I am an electrical engineer) and I'm gunna have to say that the turbine is going to have to transform its output voltage somehow anyway. Not that transformers deplete much power at all, but still, it is almost certainly more efficient to use a transformer after the turbine than screwing with the turbine to produce different voltage / frequencies. Also, the tiny turbine is going to have to rectify to dc power also. AC power is the "natural" form of electricity produced by power plants. It always requires an extra step to get dc. Finally, there is an economy of scale involved. A small turbine is simply not going to be as efficient as a large one. I would expect one that small to be nowhere near as efficient as a power plant. I would expect that the difference in efficiency of turbines would more than equal out the benefit of avoiding transformation (which is a very efficient process, for good transformers at least).

        The important question is actually, which one weighs more? Which one is cheaper to use? Seriously, who cares about the environmental effects. We have millions and millions of big engines in the form of cars, a few hundred thousand small gas turbines aren't going to matter much.

      • You forgot a step (Score:3, Insightful)

        by TyrranzzX ( 617713 )
        It takes energy to transport materials, ya know.
    • "What about pollution from this? Has that even been considered?"

      Compared to all the old batteries now sitting in landfills?
    • I think the key will be how high they can get the efficiency. Some other commenters have said that turbines can be really efficient, but I don't know how well that will scale, and the article IMHO didn't really give us much to go on.

      It is, however, encouraging that they are seriously discussing putting these into laptops. Since waste energy almost always comes out as heat, and while a lot of that will presumably come out the exhaust, a lot will also go into the laptop itself. If they aren't going to toast

    • Re:What about pollution? (Score:3, Interesting)

      by sbaker ( 47485 ) *
      It is certainly ironic that the world seems to be rushing to convert cars from internal combustion to battery/electric - whilst rushing in the exact opposite direction (in this case) to convert laptops from battery/electric to internal combustion.

      Is there something inherent in the scale of these devices that means that this kind of reversal makes sense?

  • Am I going to need to crary jet fuel around with me, because that could become real inconvenient. Also, is it going to make that jet engine noise? Am I going to have to deal with exhaust? If I were to attach one to a balloon, would it be able to propel the thing around the room?

    Geh, what a weird idea.

  • Roland Piquepaille (Score:4, Interesting)

    by Anonymous Coward on Tuesday October 19, 2004 @01:57PM (#10567944)

    http://science.slashdot.org/search.pl?query=Roland +Piquepaille [slashdot.org]


  • Noise? (Score:2, Insightful)

    by Paster Of Muppets ( 787158 )
    What about the noise created? Last time I was near a jet engine, it made quite a racket...
    • "Yeah, honey, I'll be home around [nnnnnnuuuuuuuuaa] just a second [aaaaaaAAAAAAAAAA] my phone is recharging!!! [...AAAAAAAAAA...] I said just [...AAAAAAAAAA...] a [...AAAAAAAAAA...] second! no, [...AAAAAAAAAA...] NOT SEVEN, [...AAAAAAAAAA...] SECOND![...AAAAAAAAAA....]"

  • Vaporware (Score:4, Insightful)

    by n1ywb ( 555767 ) on Tuesday October 19, 2004 @02:01PM (#10567980) Homepage Journal
    How many years now have we been hearing about miniature turbine power sources? Too many. Just because some kids at MIT did it doesn't mean it's even close to being commercially viable, and even if it is viable doesn't mean anybody will adopt it. That aside, I do think it's a great concept and I hope it DOES eventually get adopted, especially if they can make the turbines run on vegetable oil :)

  • no kidding dept. (Score:5, Funny)

    by lottameez ( 816335 ) on Tuesday October 19, 2004 @02:01PM (#10567984)
    While there are still a few hurdles to overcome...
    Ya think?

  • This sounds promising (Score:2, Insightful)

    by Anonymous Coward
    "a technology which promises to free us to carry extra fuel instead of batteries"

    That's just what we need, more dependence on combustable fuel. Besides that I feel MUCH safer carrying around extra batteries then a highly explosive fuel.

  • gas powered calculator (Score:5, Funny)

    by morcheeba ( 260908 ) * on Tuesday October 19, 2004 @02:02PM (#10568000) Journal
    There was a bit of calculator one-up-manship in some of my classes, so I always wanted to connect a little model airplane engine to a little generator and use it to power my calculator during exams. Besides the roar of the non-mufflered engine (dropping in RPMs during every keypress as it consumes more power), there would be the smell half-burnt gas coming out of that little two-stroke. The intimidation factor alone would have skewed the curve in my direction.

    So, wow, my silly dreams could become reality!
    • One of my friends at college (1981) had a solar powered scientific calculator. It was his pride and joy.

      One term we had to do an extra maths test and it was scheduled for 7pm. It was winter and we were in an outbuilding with basic lighting.

      My friend was some way into a complex calculation when the examiner, who had been walking around, passed by his desk, throwing his shadow over the calculator - the display gracefully faded as the calculator powered down. My friend jumped up uttering a burst of expleti
  • Sweet! All I need for my self-powered computer is a fan mount! Cools my processor and powers it at the same time ;)

  • Runs on Fart Gas? (Score:3, Funny)

    by zungu ( 588387 ) on Tuesday October 19, 2004 @02:03PM (#10568013) Journal
    I read somewhere that farting releases methane. May be these micro-jet engines can be powered by far gas. On an airplane, the PDA can be inserted in a pocket on the seat and just a fart will power the PDA micro-jet ;-)
    • Would somebody care to geek out for me, and estimate how much power is contained in a standard fart's methane content, if you conventionally combust it? (Remember, even the worst farts aren't 100% methane, although if you do the math based on that assumption it'd be trivial to scale, if you tell us.)

      This invention could be the best thing that ever happened to the baked beans market, no?

      • Re:Somebody want to geek out for me? (Score:4, Informative)

        by WormholeFiend ( 674934 ) on Tuesday October 19, 2004 @03:07PM (#10568746)
        Remember, even the worst farts aren't 100% methane

        The sun is a mass of incandescent gas... ^H^H oops sorry... wrong comment.

        Here's the lowdown on fart gas content, for those interested in such things:

        (source: Facts on Farts [heptune.com])

        What is fart gas made of?
        The composition of fart gas is highly variable.
        Most of the air we swallow, especially the oxygen component, is absorbed by the body before the gas gets into the intestines. By the time the air reaches the large intestine, most of what is left is nitrogen. Chemical reactions between stomach acid and intestinal fluids may produce carbon dioxide, which is also a component of air and a product of bacterial action. Bacteria also produce hydrogen and methane.
        But the relative proportions of these gases that emerge from our anal opening depend on several factors: what we ate, how much air we swallowed, what kinds of bacteria we have in our intestines, and how long we hold in the fart.
        The longer a fart is held in, the larger the proportion of inert nitrogen it contains, because the other gases tend to be absorbed into the bloodstream through the walls of the intestine.
        A nervous person who swallows a lot of air and who moves stuff through his digestive system rapidly may have a lot of oxygen in his farts, because his body didn't have time to absorb the oxygen.
        According to Dr. James L. A. Roth, the author of Gastrointestinal Gas (Ch. 17 in Gastroenterology, v. 4, 1976) most people (2/3 of adults) pass farts that contain no methane. If both parents are methane producers, their children have a 95% chance of being producers as well. The reason for this is apparently unknown. Some researchers suspect a genetic influence, whereas others think the ability is due to environmental factors. However, all methane in any farts comes from bacterial action and not from human cells.

  • Good Laptop Power Source for Travelers? (Score:4, Insightful)

    by xxxJonBoyxxx ( 565205 ) on Tuesday October 19, 2004 @02:03PM (#10568017)
    TSA Drone: "What do you have in that bottle?"
    You: "Oh, it's just some gasoline for my laptop."

    Sure...this technology will be a GREAT laptop power source for travelers...

  • Geese (Score:5, Funny)

    by Anonymous Coward on Tuesday October 19, 2004 @02:04PM (#10568029)
    Do these things still make a horrid mess when they accidentally suck geese in through the intake?

  • Real Beanie Jet Engine Hat (Score:2, Funny)

    by Anonymous Coward
    If I can take 1000 of these microjets, I can convert my Beanie Propeller hat to a Beanie Jet Engine Hat and fly. Since this is posted freely and publicly, this can't be patented anymore.

    Ready to take off
    5
    4
    3
    2
    1

    Where did my body go?

    WhatMeWorry!

  • Conspicuous omission (Score:5, Insightful)

    by Engineer-Poet ( 795260 ) on Tuesday October 19, 2004 @02:05PM (#10568045) Homepage Journal
    Neither "reference" (they aren't worthy of the term) mentions a thing about efficiency.

    This matters a lot, because small turbines suffer much more from viscous flow losses and heat-transfer losses than large ones. If a 50 W microturbine is 10% efficient, its waste heat will amount to 450 watts; if it is 5% efficient, the waste heat will be 950 watts! This could easily lead to them being banned from commercial aircraft, because the extra heat load and oxygen consumption would drive A/C loading too high (not to mention the discomfort of adjacent passengers).

    • Also, nothing is mentioned about wear. From my understanding, the rate of wear is a real killer for these tiny devices.

      Just think, if 0.5mm wears off the sliding surfaces in a conventional turbine, not big deal... if 0.5mm wears off the surfaces of this device you have nothing left.

  • Starting a turbine engine is a complicated procedure. How will we be supposed to start such a tiny engine ? Perhaps using the generator in motor mode to give it enough RPM ?

    It could be a nice replacement for hydrogen fuel cells, if it can be tuned to run on hydrogen like some real turbine engines out there. No pollution ! And the hot steam could be used for something else.
    • take a deep breath and blow on it.

    • Using the generator as a starter motor is probably the absolute best way to go. This is probably coming on automobiles, too; we'll end up with a combination AC motor/alternator-generator for starting and charging. This will be driven by everything and I mean everything on the car going electric. No more vacuum lines, no more hydraulic system. The system will be higher-voltage (automobiles are about to go 48V, even in the US) and that will reduce the gauge of wire necessary for the electrical system, furthe

  • Energy = energy, danger = danger (Score:5, Insightful)

    by dpbsmith ( 263124 ) on Tuesday October 19, 2004 @02:09PM (#10568082) Homepage
    "Each disposable cartridge would pack as much energy as a few heavy handfuls of lithium-ion batteries."

    We don't really want to carry larger and larger packages of energy on our person. As it is, we are seeing accidents like this one [zwire.com] due to today's ordinary lithium-ion batteries. And I recently got a recall notice from Verizon about the kind of batteries used in my cell phone, so this isn't an isolated incident.

    When someone tosses a 9V battery in their pocket and it gets shorted out by a coin, they are startled, yell, and pick the hot coin out of their pocket.

    When a cell phone battery acts up, Shelley Kaehr got a handful of battery acid and set fire to the floor.

    Multiply that by "a few heavy handfuls" and you start to get the possibility of really serious personal injury.

    What we need are breakthroughs on the power consumption side, not ever-increasing power supplies
  • From the article: Spearing estimates a version capable of putting out enough power to run devices would take two to three years more, with another year or two beyond that to produce a marketable version.

    So, it's 5 years away, like flying cars and jet packs and everything else that stays 5 years away. Why don't I feel good about this?

    By the way, so anyone else remember seeing TV comercials in the 60's that showed a new miracle insulation material (made of low tech aluminum foil and cardboard) that they

  • Nanobots, tiny jet engines. Has anyone warned Dennis Quaid [imdb.com]?

  • Obvious joke (Score:5, Funny)

    by SuperKendall ( 25149 ) * on Tuesday October 19, 2004 @02:12PM (#10568124)
    "Hey, what is that?"

    "WHAT?"

    "I said, what is that"

    "MY NEW JET-POWERED MP3 PLAYER"

    "cool , what are you playing?"

    "I'M NOT SURE"
  • What developing countries (and us) really need is NOT another technology that requires petroleum/gas refinery infrastructure. I don't have the background but it would be interesting to do a cost-benefit tradeoff between existing lithium-ion battery technology vs. portable turbine generator technology. Costs, of course, include the energy put into making the batteries and turbine/generators, as well as the industrial effluent from the plants that make the parts for both.

    Real progress will be made when you

  • Can we PLEASE STOP linking to this guy's blog??? (Score:5, Informative)

    by sczimme ( 603413 ) on Tuesday October 19, 2004 @02:15PM (#10568167)

    In all seriousness, why does /. continue to link to his ramblings instead of to articles that contain real, useful, technical content?

    Yes, this is probably off-topic (as in "not about tiny turbines") but it is still relevant. At least give us the option to ignore him.

  • Roland... (Score:5, Insightful)

    by addie ( 470476 ) on Tuesday October 19, 2004 @02:15PM (#10568170)
    Can we please stop posting directly to stories on this guy's weblog? It's embarassing for Slashdot. The real news link you're looking for is:

    here [technologyreview.com]

  • Roland (Score:5, Insightful)

    by Lord_Dweomer ( 648696 ) on Tuesday October 19, 2004 @02:17PM (#10568189) Homepage
    Yet another Roland story. You know, you'd think that if there was enough outrage about this (which I'm SURE the editors are more than aware of) they would have the common decency to listen to their readership instead of just posting more Roland stories.

    For as much as I love Slashdot, there exists little recourse for people who want their input on the site to be heard, even when its on as large a scale as the current hatred of Roland posts.

  • Noise (Score:3, Interesting)

    by your_mother_sews_soc ( 528221 ) on Tuesday October 19, 2004 @02:17PM (#10568203)
    What about noise? A physical device spinning that fast is going to produce hypersonic as well as audible noise. Phase I: Put jet engine in cell phone. Phase II: ? Phase II: Profit from putting even smaller jet engines in hearing aids.
  • While there are still a few hurdles to overcome

    Is that the setting your clothes on fire hurdle, or the asphyxiation in closed in spaces hurdle?

  • I can't wait to pull into the grocery ...

    Shhhheeeeewwwoooooooooossshhhhheeeeeeeeeeee

  • I wonder what the failure mode is like. I mean, even a tiny turbine spinning at millions of RPM must contain a lot of angular momentum.

    Can you imagine the engine failing and the little turbine slicing its way out of your laptop and through the side of the building?

  • 1 million rpm? (Score:5, Interesting)

    by museumpeace ( 735109 ) on Tuesday October 19, 2004 @02:27PM (#10568312) Journal
    I saw this in TR yesteday and, given my dismal batting average with the /. eds, just let it slide.
    A better TR article blasts "hydrogen hype" [technologyreview.com] but in fact H2 would be about the best fuel for these little buzzers:
    • a fuel spill will dissapate very rapidly
    • the byproduct, in answer to the questions posted re pollution is just water.
    A set of bearings however will be an awsome thing to handle the gyroscopic reaction torques as you wave your jet powered cellphone about. You turn the corner, the phone does not. I don't have my old physics books handy but the linear velocity of a point on the tip of a blade is
    1000000*60*2*pi*0.6/(12*5280) = 3570 mile/hour
    and is changing direction 180 degrees about 2000000 times a minute. The F=MA to pull this constant direction change will be staggering unless M is damn near zero.
    And aren't you just all breathless, when the "batteries die", to take your cellphone to the out-of-work airline mechanic who got re-trained at a watch factory ?

  • See same story from 1997 (Score:5, Informative)

    by Animats ( 122034 ) on Tuesday October 19, 2004 @02:29PM (#10568335) Homepage
    Here's a very similar article from 1997 [memagazine.org], from the same guy at MIT, making about the same claims. They sounded closer to success back then.

    They've been working on this since 1993, and in 1997 they said they'd have it working in three years. In 2004, they say they'll have it working in three years.

    It doesn't work yet. They can fabricate the individual parts, but it doesn't really generate power.

    It's not an unreasonable idea, but if this was going to work, there should already be little gas turbine powerplants a few inches long, machined out of metal by standard techniques. The smallest turbines available [bairdtech.com] weight around 1.5Kg, and are used for model aircraft, and they don't have to run for very long. There's a "microturbine" industry, but they mean 10KW units taller than a man.

    Little turbines are hard. Automotive turbines and light-plane turbines have been attempted many times, but have never been cost-effective.

    • Re:See same story from 1997 (Score:5, Funny)

      by One Louder ( 595430 ) on Tuesday October 19, 2004 @03:02PM (#10568693)
      They've been working on this since 1993, and in 1997 they said they'd have it working in three years. In 2004, they say they'll have it working in three years.
      It sounds like their schedule will fit nicely with the Moller Skycar.
    • The smallest turbines available weight around 1.5Kg, and are used for model aircraft, and they don't have to run for very long.

      And, if I recall correctly, they use fuel very inefficiently; the fuel consumption is like nothing else you've ever seen. The friction losses on this thing would probably be far worse, so unless there's breakthroughs in the design elsewhere I'd be very surprised if you could carry enough fuel to keep the things powered up.

  • The potential problem with these things... (Score:4, Informative)

    by sexylicious ( 679192 ) on Tuesday October 19, 2004 @03:02PM (#10568692)
    is that many of the physicists working on the problem don't understand fluid mechanics at such a small scale. The viscous forces are huge compared to the inertial forces, and you have a completely different set of physics.

    That's why you don't see very many working concepts of small aircraft (the kind that fit in the palm of your hand) with what most people recognize as wings. They're usually equipped with small flat-plate type wings, or a ribbon-like system like on a cuttlefish.
    And the reason that many folks that do happen to understand the physics don't try and do things at such small scales is that the problem is difficult. Not impossible, but difficult.

    As a person with a background in fluid mechanics, I don't see how the approach in the article will ever work well or efficiently. It might work, but it's not using the kind of principles that you need. (The whole point of my post is that you can't scale a device down without adjusting or remaking how it does what it does. The physics change.)

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