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Power Science Technology

Heat Engines Shrunk By Seven Orders of Magnitude 168

Posted by kdawson
from the gimme-a-v8-of-those dept.
KentuckyFC writes "The vast majority of motors that power our planes, trains, and automobiles are heat engines. They rely on the rapid expansion of gas as it heats up to generate movement. But attempts to shrink them by any significant amount have mostly ended in failure. Today, the smallest heat engines have a volume of some 10^7 cubic micrometers. Now group of Dutch engineers has built a heat engine that is seven orders of magnitude smaller than this. The engine consists of a piezoelectric bar that expands and contracts in the normal piezoelectric way. However it also heats up and cools at the same time causing a thermal expansion and contraction, which lags the piezoelectric displacement. By carefully choosing the frequency of the driving AC current, the Dutch team found a resonant effect in which the thermal expansion and contraction amplifies the mechanical motion, making it a true heat engine. Operating the thermodynamic cycle in reverse turns the device into a heat pump or refrigerator. The total volume of the device is just 0.5 cubic micrometres."
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Heat Engines Shrunk By Seven Orders of Magnitude

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  • Great, let's make this 500 times bigger and power my car!
    • Re: (Score:3, Funny)

      by Parlett316 (112473)

      Yeah a Beowulf cluster of them

    • by von_rick (944421)
      Don't do it unless you know the efficiency of this heat engine. Something tells me that a micro engine (or an array of those micro engines) wouldn't help you much.
  • On Chip cooling? (Score:2, Insightful)

    by camperdave (969942)

    Operating the thermodynamic cycle in reverse turns the device into a heat pump or refrigerator. The total volume of the device is just 0.5 cubic micrometres.

    Great! When can I get these built into my CPUs?

    • Re: (Score:3, Insightful)

      by Anonymous Coward

      It's not like a heat pump turns heat into nothing. One side of a heat pump gets cold, the other side gets hot. At half a micron across, it's hard to see how such a device could help evacuate heat from a CPU.

      • by AaxelB (1034884)

        It's not like a heat pump turns heat into nothing. One side of a heat pump gets cold, the other side gets hot. At half a micron across, it's hard to see how such a device could help evacuate heat from a CPU.

        Just stick 100,000 of them end-to-end, naturally. Of course, I've no idea how efficient or effective they really are, but it seems like it *could* work.

      • Stack arrays of them on top of each other between the CPU and the heat sync. Even if the temperature gradient is tiny over each layer it will add up, and even 1000 of them would be less than a millimeter thick.

      • Re:On Chip cooling? (Score:5, Interesting)

        by coolsnowmen (695297) on Friday January 22, 2010 @11:59AM (#30860168)

        Already done: see peltier device. They are already made to the correct size and probably better efficiency.
        http://www.peltier-info.com/ [peltier-info.com]
        http://en.wikipedia.org/wiki/Thermoelectric_cooling [wikipedia.org]

        • by ElectricTurtle (1171201) on Friday January 22, 2010 @12:56PM (#30860872)
          It always amuses me when people try to raise performance as a point against a first generation lab prototype vs. a tenth generation refined technology in production. The question is not whether these piezoelectric heat engines/pumps are more efficient than peltiers now, but rather can they be more efficient than peltiers in the future after further development, or is there a foreseeable upper limit to the technology that makes such an application unlikely even with development?

          There *is* a need for heat reduction at very small scales, especially in mobile devices or even the implant devices of the future. Of course heat has to go somewhere, the only issue is that the destination of the heat be better able to deal with it than the source.
          • And even the performance scale is just one of many axes in the space of the question, whether that concept is useful.
            The size, for example, is another one.

            Why do people always think in one-dimensional absolute extremes?
            (Yes, I know that the “always“ is ironic. ^^)

        • Peltier junctions are 'cool', but irrelevant to this. Unless my memory fails me, Peltier devices are not heat engines. They are solid-state thermoelectric devices. The devices here involve the Carnot Cycle of exchanging temperature and pressure in a four-sided cycle as do all heat engines. It's a bit weird at least for me to think about because they are also using the piezoelectric effect to drive or be driven by the cycle, so it's hard to think of these as simple heat engines. I will have to reread TF

      • by bill_kress (99356)

        I love how a lack of imagination these days = impossible. I've decided to try responding to posts that claim "I can't imagine it, so since it's not possible..."

        So, how about placing them together side-by-side so the cold side points down at the CPU and the hot side points up to the heat sink. This keeps the CPU cooler and the heat sink hotter (allowing it to dissipate more heat).

        How about a tube made of the stuff--outside is hot, inside cool, through which you blow air? The tube itself can sit outside th

    • If it's anything like pretty much every other really useful technological development that's occured in the last decade? You probably won't, but they'll always say it's N years away from commercial application.

      Also they mention the ability to use it for refridgeration, but not whether it's still moving when they do that. Even on a microscopic scale having these things moving pretty much anywhere could cause problems.

  • Its a heat engine but it does not use gas, so maybe this could be the engine for a train of nano bots! Or we can use them to cool our CPUs. Interesting indeed, now we need to find an use for it

  • by Anonymous Coward

    Can the physics gurus please put cubic micrometers in perspective for us common mortals? Is that as big as a grain of rice or a head of a pin?
    10^7 micrometers is.... a spehrical cow? a toaster?

    • by Red Flayer (890720) on Friday January 22, 2010 @11:47AM (#30860012) Journal
      You know how big a millimeter is, right? A micrometer is one thousandth the length of a millimeter.

      A cubic micrometer is the volume occupied by a cube one micrometer on each side.

      10^7 cubic micrometers would fill a cube about one-fifth of a millimeter on a side. Smaller than a pinhead.
      • by xaxa (988988) on Friday January 22, 2010 @12:03PM (#30860234)

        about one-fifth of a millimeter on a side

        That's about the thickness of a sheet of paper. (Round here, and probably in a lot of the world, the thickness and density of paper is specified, for instance "160 g/m^2, 200 micrometres".)

      • by MagicM (85041)

        (10^7) (cubic micrometers) = 0.01 cubic millimeters

    • by Atraxen (790188) on Friday January 22, 2010 @11:51AM (#30860074)

      Fun fact - Wolfram Alpha can serve as your 'self-checkout line' for things like this.
      http://www.wolframalpha.com/input/?i=1+cubic+micrometer [wolframalpha.com]

      Here's a bit of scale - a cubic micrometer is about the same size as a calibration bead for microscopy. A red blood cell is about 8 micrometers across. http://learn.genetics.utah.edu/content/begin/cells/scale/ [utah.edu] Or, there's this video showing the "powers of ten" (also its title...): http://www.youtube.com/watch?v=A2cmlhfdxuY [youtube.com]

      Also, chemists work at these dimensions, too! (So do biologists. And others.) :*P Don't snub the other disciplines!!! Or I'll weep. And not gently, nor to a guitar.

    • Can the physics gurus please put cubic micrometers in perspective for us common mortals? Is that as big as a grain of rice or a head of a pin?
      10^7 micrometers is.... a spehrical cow? a toaster?

      Yes, someone explain how many of them would fit into the library of congress.

    • I agree that using cubic micrometers is nowhere near intuitive.

      1 um (replace "u" with the Greek letter "mu" please) is 1e-6 metres.
      So, 1 cubic um is 1e-18 cubic metres. So, the smallest conventional heat engines are 1e7 of these 1e-18 cubic metres, or 1e-11 cubic metres.

      Not that intuitive either. So we'll use cubic mm.

      1mm is 1e-3 metres, so 1 cubic mm is 1e-9 cubic metres.

      Something that's 1e-11 cubic m (1e7 cubic um) is 1e-2 cubic mm. So, it's 1% of 1 cubic millimetre.

      That's pretty small.

    • A centimeter is about as far across as your pinky finger fingernail.
      A centimeter is about half the distance across a penny (1.9cm), nickle(2.1cm), or dime (1.7cm).
      So a square the size of a stack of pennies, 6 high (1.55mm each), would be 1 centimeter high, 4 centimeters square (2x2) and have 4 cubic centimeters.

      A typical grain of rice appears to be about .2centimeters by 1 centimeter. So each grain of rice has roughly 1/25th of a cubic centimeter of material. So 25 grains of rice would roughly fill a cubi

  • by Anonymous Coward

    Can it be used for other things?

  • How many beer cans fit in a 0.5 micrometers refrigerator?
    • by AaxelB (1034884) on Friday January 22, 2010 @11:44AM (#30859972)

      How many beer cans fit in a 0.5 micrometers refrigerator?

      Depends. Are we talking micro- or macrobrews?

      • Sorry, I didn't specify. I was talking about nanobrews.
    • Re: (Score:2, Funny)

      by Red Flayer (890720)

      How many beer cans fit in a 0.5 micrometers refrigerator?

      You're thinking too small.

      The correct question is, how many beer kegs fit in a 0.5 micrometer fridge?

      • by krnpimpsta (906084) on Friday January 22, 2010 @12:24PM (#30860488)

        You're thinking too small.

        The correct question is, how many beer kegs fit in a 0.5 micrometer fridge?

        0.00000000000000000852167911 beer kegs

        If the fridge interior happens to be shaped optimally so that no space is wasted and the entire 0.5 micrometer fridge is filled with keg, then.. exactly 8.52167911 * 10^-18 beer kegs (if each keg is 15.5 gallons). [Incase someone wants to out-pedant me: Yeah, I understand you can't optimally shape a 0.5 micrometer fridge for a keg, when the size of 1 unit of keg > 0.5 micrometer fridge.]

        Citation: http://www.google.com/search?hl=en&q=(0.5+micrometers%5E3)%2F(1+keg)&aq=f&aql=&aqi=&oq= [google.com]

        • Re: (Score:2, Insightful)

          by gsarnold (52800)
          No, no, no! You don't put the beer in the fridge, you put the fridge in the beer! Take that disk thingy Guinness uses in their cans to make it all foamy and add the refrigerator to that! Take it off the shelf, pop it open, wait two minutes and Voila! -- it's ice cold AND foamy! Brilliant!
    • by mcgrew (92797) *

      That depends. Are we talking about actual beers? [angryflower.com]

      In a less huumorous vein, how many of these refrigerators does it take to cool a can of beer? It would be nice to have cold beer with a built in refrigerator in every can. Provided it could be done cheaply enough.

  • by Dilligent (1616247) on Friday January 22, 2010 @11:42AM (#30859952) Homepage
    Somehow "heat engine" directly translates into "internal combustion engine" for me. But this piece uses electricity, exactly how useful is that? This is bound to be less efficient than to use the electricity to just power an ordinary electric motor. I suppose scaling a motor down to that size might be kinda difficult, though, if that was the point, why emphasize that it is a heat engine?
    • by Scrameustache (459504) on Friday January 22, 2010 @12:03PM (#30860220) Homepage Journal

      Somehow "heat engine" directly translates into "internal combustion engine" for me.

      That's too bad, I hope this article will be enough to let you correct your thought

      why emphasize that it is a heat engine?

      Because they figure it's mostly usefull as a heat pump, not as a mechanical actuator.

      • I RTFA, and I still have serious doubts about the terminology used here and there.

        What TFA describes is actually an electric motor. They apply AC & DC, and got mechanical work :

        The new heat engine is essentially a bar of piezoelectric material whihc expands and contracts when an alternating current is applied

        Well guess what? That's no heat engine, that's an electric motor. It also happens to release some heat, but so does every motor.

        They didn't describe the reverse process (heat engine or refrigerator).

        Maybe this product really *is* a heat engine, but that's not what's described in TFA.

    • by qazwart (261667) on Friday January 22, 2010 @12:15PM (#30860368) Homepage

      The internal combustion engine is only one class of heat engines. The Sterling Engine and the External Combustion Engine (used in old steam locomotives) are also heat engines. Heat engines use heat to create power either by taking advantage of temperature differences or the expansion of heated air.

    • Re: (Score:2, Funny)

      by Rogerborg (306625)

      why emphasize that it is a heat engine?

      Probably just trying to get some free publicity when California bans it.

    • by mcgrew (92797) * on Friday January 22, 2010 @12:28PM (#30860560) Homepage Journal

      Somehow "heat engine" directly translates into "internal combustion engine" for me.

      A steam engine is an external combustion engine, yet is is still a heat engine. The thing with this teensy engine is that it reuses waste heat rather than throwing it away, making it far more efficient than your ordinary electric motor.

      As a side note, the difference between a motor and an engine is that a motor rotates, an engine reciprocates. You can indeed have an electric engine (theyre usually called "solenoids") and a gasoline motor (Mazda had "rotary engines" back in the '70s; they were actually gasoline motors.)

      • Re: (Score:3, Informative)

        by YttriumOxide (837412)

        Mazda had "rotary engines" back in the '70s; they were actually gasoline motors.

        Had? Wouldn't "have had ... since [wikipedia.org]" be more accurate? (oh, and it's since 1963 [wikipedia.org], so the '60s...)

      • by Chris Burke (6130)

        As a side note, the difference between a motor and an engine is that a motor rotates, an engine reciprocates.

        Huh. I didn't know that.

        So I guess that means that Wankel was being a bit of a Wanker when he named his Wankel Rotary Engine, huh?

      • Re: (Score:3, Insightful)

        by sammy baby (14909)

        (Mazda had "rotary engines" back in the '70s; they were actually gasoline motors.)

        Sir, poorly played. You should never pass up the opportunity to use the word "Wankel [wikipedia.org]" in a sentence.

        • by bughunter (10093)

          As in, "I built a working model of a Wankel Engine in high school?"

          Wow. That is win.

          How 'bout this, "I had a Wankel when I was a teenage boy?"

          Hrm... Not so much.

      • by kocsonya (141716)

        "making it far more efficient than your ordinary electric motor"

        Um, electric motors are 90%+ efficient, so how much is "far more"?

        The actual details in the linked blog are a tad hazy and possibly even incorrect.
        The article says that because of the mechanical change the resistance of the crystal is changed, therefore the heat generated by the DC current changes. Then it makes a rather large hop, or more like a giant leap, and says that thus one side heats up and the other cools down. Unfortunately, this is n

    • The description in the summary is really only *half* a heat engine. It turns electricity into work, yah, but it also turns work (in the form of electricity) into temperature difference.

      What it does not do is turn a temperature difference into work, which is the other half of the equation. A heat engine must do at least one of the two, and it has been proved that the maximum efficiency occurs for reversible processes, so many heat engines are capable of both.

  • by Anonymous Coward

    Peltier diode?

  • I guess the Logopolians will have to spend even more time doing base block calculations to prevent the heat death of the universe.....

  • So thats like much smaller than a womp rat!
    • It's much smaller than a womp rat's penis, at least. Incidentally, when I fucked your girlfriend friday night she was so glad I had a normal penis, said something about yours looking like the dick on a womp rat or something....
  • Not only is 10 million much easier to understand than 10^7, but 0.01 cubic millimeters is a MUCH more common number, and measurement.

    Not exactly hidden information either.
  • Tough call (Score:2, Interesting)

    by KiwiCanuck (1075767)
    if this is useful. I've seen micro rotary and piston engine. They suffer from two problems. One is heat loss due to high surface area to volume ratio (heat leaks away before work can be extracted), and the other is charge (fuel/air) leakage. This appears to solve the leakage problem buy not using combustion. Good job!
  • by autophile (640621) on Friday January 22, 2010 @04:08PM (#30862900)

    I read the attached paper on arxiv, and from what I could tell, they passed a DC current through the thing, which caused the small engine beam to expand, causing it to heat up and move the mass. The piezoelectric effect causes the resistance in the small engine beam to change, which causes the beam to cool down and move the mass back with help from the larger spring beam. Rinse, repeat. Effectively a thermoelectric buzzer. The buzzing of this particular device was measured to be about 1.255 MHz at a DC current of 1.045 mA.

    Unlike what the Technology Review article says, the paper shows no application of an AC current to get the thing vibrating. In fact, the measured voltage is alternating because the resistance is alternating. The current remains the same. There is no complicated application of a DC current and an AC current. There's just an applied DC current.

    Am I understanding the paper correctly?

    • ... they passed a DC current through the thing, which caused the small engine beam to expand, causing it to heat up and move the mass. The piezoelectric effect causes the resistance in the small engine beam to change, which causes the beam to cool down and move the mass back with help from the larger spring beam. Rinse, repeat. Effectively a thermoelectric buzzer. ... Am I understanding the paper correctly?

      As far as you went.

      But the alternating heating/cooling doesn't have to come from current through the m

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