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Power Hardware Science

MIT Produces Electricity Using Thermopower Waves 157

Posted by Soulskill from the set-on-fire-to-begin-current-flow dept.
MikeChino writes "MIT scientists have discovered a never-before-known phenomenon wherein carbon nanotubes can be used to harness energy from 'thermopower waves.' To do this they coated the nanotubes with a reactive fuel and then lit one end, causing a fast-moving thermal wave to speed down the length of the tube. The heat from the fuel rises to a temperature of 3,000 kelvins, and can speed along the tube 10,000 times faster than the normal spread of this chemical reaction. The heat also pushes electrons down the tube, which creates a substantial electrical current. The system can output energy (in proportion to its weight) about 100x greater than an equivalent weight lithium-ion battery, and according to MIT the discovery 'opens up a new area of energy research, which is rare.'"
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MIT Produces Electricity Using Thermopower Waves More

MIT Produces Electricity Using Thermopower Waves

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  • 3000 K? What about cooling? Refueling? 100x seems... optimistic.

    • Re: (Score:2)

      by Phrogman ( 80473 )

      Yeah they mention a possible implementation of this in producing laptop batteries. I for one am not all that happy with contemplating using a laptop whose battery reaches 3000 Kelvin :P

      • Can you imagine trying to take it on a plane? It'd be worse than laptop batteries [xkcd.com]...

      • 3000k at the nanotube level.

      • Re: (Score:3, Informative)

        by ircmaxell ( 1117387 )
        Well, on the scale of the tube, we're not talking about that much thermal energy. Sure, it's a high temperature, but something the size of a nanotube (around 1/50,000 the width of a human hair) won't have a significant amount of energy. It really depends on the density of these tubes that's needed to achieve a usable amount of energy. And don't forget, we're talking about localized heating here... It's not that the tubes and structure need to get to 3000*k, that's just the temperature of the flame front

      • Re: (Score:3, Funny)

        by omarius ( 52253 )

        I agree--but I am *really* looking forward to my flaming electric car. Better start trying to snag the GHST RDR plate now....

      • Re: (Score:2)

        by icebike ( 68054 )

        This doesn't look like a battery solution.

        It looks like a railgun power source to me.

        You need immense pulses of power for railguns, and having a ready supply of preloaded nonotube "cartridges" could reduce the need for huge and dangerous capacitors.

    • Re:That's some hot stuff... (Score:4, Insightful)

      by Xerolooper ( 1247258 ) on Monday March 08, 2010 @03:01PM (#31403632)
      They never said it was practical yet. It is a new area of research. Only time will tell if they discovered something useful or if they were rolling something else in a "tube" shape and smoking... ehm I mean lighting it.

    • 100x seems... optimistic.

      indeed. but only 2x or 3x means the end of the combustion engine, if the cost can be kept under control.

      • Re: (Score:2)

        by Nadaka ( 224565 )

        This IS a combustion engine. Or more accurately a combustion generator.

      • but only 2x or 3x means the end of the combustion engine, if the cost can be kept under control.

        If I had a dime for every time I'd heard this on Slashdot.... wow. Anyhow, it's not only cost that has to be solved, of course, this is very basic research and I'm sure there are a whole host of practcal problems to overcome, any one of which could be a show stopper. Once they are all addressed, then we can start talking about cost.

    • Re:That's some hot stuff... (Score:5, Interesting)

      by profplump ( 309017 ) <zach-slashjunk@kotlarek.com> on Monday March 08, 2010 @03:09PM (#31403742)

      Refueling could be as simple as pouring more fuel on the nanotubes. But it may also be irrelevant -- not all power systems need to be reusable. For example, an emergency beacon is not likely to be used frequently, so refueling is not nearly as important as shelf life. And even in applications where refueling is desirable, the increased power density may be worth it -- if you phone battery lasted 200 days instead of 2 days you might not care that the battery can only be refueled with special equipment.

      That being said, 100x might well be optimistic. Or it might be wildly conservative. Since this is a brand new field it seems unlikely that an estimate will be terribly accurate.

      • And another application might be to use this to charge a supercapacitor, allowing time for the cell to regenerate/refuel/cool down, and repeat as necessary.

        Really interesting. Power density is the new frontier. If this can increase density usably by just a factor or 10, it is a tremendous advance. And I'm just thinking about portable electronics. For a vehicle, this really could be a good fit. Temperature could be manageable if you have space to put some insulation and cooling structures in...

    • Re:That's some hot stuff... (Score:5, Informative)

      by jellomizer ( 103300 ) on Monday March 08, 2010 @03:12PM (#31403786)

      For some perspective that is about the heat that a filament in a lightbulb is at.

      • The temperature, you mean.
    • Small quantities could mean self-heating meals; larger implementations could be used to replace commercial boilers. Sounds promising but I'll wait for someone else to test the 'laptop battery' version, TYVM.
    • 100x energy density? Can I haz flying car naow?!!!

    • Re: (Score:2)

      by mcgrew ( 92797 ) *

      2727c, 4940f for thos of us who aren't physicists. For those who aren't nerds, that's "damned hot". IIRC that's hot enough to melt steel. I don't think you'll be running your cell phone on these "batteries".

    • Re: (Score:2)

      by Greyfox ( 87712 )
      Yeah! 3000K is almost as hot as the Macbook Pro [penny-arcade.com] when it gets cranking!

    • Chemical reactions are very hot, but the heat dissipates (spreads out) quickly.

      This sounds like it'd be good for car batteries, where capacity vs weight vs drain/charge speed are all important considerations.

  • Heh (Score:2)

    by Pojut ( 1027544 )

    Images of Wile E. Coyote sitting on a nano-tube rocket trying to light a fuse are taking over my mind's eye.

  • So basically they cut out the middleman (Score:5, Funny)

    by Shadow of Eternity ( 795165 ) on Monday March 08, 2010 @03:00PM (#31403624)

    Instead of having a Lion battery that explodes we now have a deliberately exploding battery.

  • is this gonna put Bloom Energy out of business?

  • The heat from the fuel rises to a temperature of 3,000 kelvins

    Since it presumably didn’t start at absolute zero, wouldn’t it have made more sense just to give the temperature in degrees Celsius?

    • Re:Kelvins are degrees on an absolute scale... (Score:4, Informative)

      by wizardforce ( 1005805 ) on Monday March 08, 2010 @03:33PM (#31404034) Journal

      3000-273=2727C They were rounding. Also thermodynamic efficiency is easier to calculate in kelvins and is standard practice in thermodynamics; see carnot cycle for details.

      • If they’re rounding once, they might as well round twice. These numbers are for laypersons... 2700C would be close enough.

        • Thermodynamic systems are more often than not quoted in Kelvin. The only times they're ever really converted to Fahrenheit or Celcius is for the public's convenience. Very nearly every equation in thermodynamics works best in Kelvin as it is an absolute scale from absolute zero.

          • Yes, but the only time it makes more sense to give the public a temperature in Kelvins is when you have some good reason for which to set the reference at absolute zero. In this case, I think it would have made more sense to convert it to Celsius, since the public will at least be somewhat familiar with that scale.

            • Yes, but the only time it makes more sense to give the public a temperature in Kelvins is when you have some good reason for which to set the reference at absolute zero.

              As opposed to the freezing point of water? Sure, people are familiar with the properties of water, but does it really make sense to translate anyway? "You know how water freezes? Well, this reaction takes place 5400 Fahrenheit above that." Informative.

              I think it would have made more sense to convert it to Celsius, since the public will

              • As opposed to the freezing point of water?

                The reason Celsius (or Fahrenheit) makes more sense than Kelvins is because people are more familiar with it. They probably have no idea what 3000 Kelvins is. Unless you have a good reason for basing it at absolute zero (they probably have at least heard of absolute zero), there’s no good reason to use Kelvins.

                Oh, you're not American.

                I said somewhat familiar. They know that degrees C is a temperature scale. Some of them might even know that 0 is freezing and 100 is boiling, if you’re lucky.

    • There are other reasons to use kelvins. When doing calculations about the energy and stuff, the temperature needs to be in kelvins. They just didn't bother converting to celsius.

      • Re: (Score:2)

        by JSBiff ( 87824 )

        Since the 'size' of a Kelvin and a degree Celsius are the same, I've noticed it seems to be common practice in science that when dealing with any values larger than about 1000 deg. C, to just use Kelvins. As the parent points out, all the physics equations are based on Kelvin anyhow (since Kelvin 0 == absolute Zero), but there's also the fact that, when dealing with 'large' temperatures, the difference between Kelvin and Celsius is basically negligible.

        Kelvin is the 'more correct' scale to use for science,

  • Fricken Lasers (Score:5, Interesting)

    by Gotung ( 571984 ) on Monday March 08, 2010 @03:19PM (#31403884)
    This sounds like a niche energy product. Basically nano-combustion that very quickly creates a very strong electrical charge.

    Doesn't sound too great as a battery. But as "ammo" for hand held laser weapons? Could be perfect for that.

    • Re:Fricken Lasers (Score:5, Insightful)

      by girlintraining ( 1395911 ) on Monday March 08, 2010 @03:26PM (#31403982)

      Basically nano-combustion that very quickly creates a very strong electrical charge.

      EMP in a suitcase.

    • Re: (Score:2)

      by rotide ( 1015173 )

      I was actually thinking about vehicles.

      What if you had enough of these in an "engine" where you have enough nanotubes to spread fuel onto to create energy. Instead of powering pistons you could push the energy to an electric motor and perhaps a battery.

      I know, I know, we want to get away from fossil fuels and we may potentially be able to with this but even if we can't, if this is more energy efficient it may still be worth it.

    • Re: (Score:2)

      by jockeys ( 753885 )
      cue the sharks!

    • Screw Lasers - I want to fire the actual electrons at the guy. The target will be so staticly charge his pubic hair will shoot out of his crotch causing him to double over in physical and emotional pain, thereby rendering him neutralized but not killed, an effective non-lethal weapon.

      • Re: (Score:2)

        by danlip ( 737336 )

        what if your target shaves down there?

        • Unless they shave all over, the effect should also take place in Arm-pits, the head, arms, legs, etc.

          So this weapon is essentially useless on professional swimmers.

          • Re: (Score:3, Funny)

            by ColdWetDog ( 752185 )

            So this weapon is essentially useless on professional swimmers.

            Not to worry. That's what the sharks with lasers are for.

    • It's more like a fuel cell in that it uses fuel to produce a current but it is small enough and light enough to be potentially usable in devices that otherwise would use a battery. Also, the mechanism by which it produces a current implies that it can use a variety of fuels; pretty much anything that burns hot enough which is extremely useful.

    • Re: (Score:2)

      by AP31R0N ( 723649 )

      How could a battery be too great?

    • Re: (Score:2)

      by Yvanhoe ( 564877 )
      Add a capacitor, have ten thousand of these wires in a box and lit one of them when the capacitor is empty.

      But what it lacks is a recharging mechanism...

  • Link to the Nature Materials article (Score:5, Informative)

    by reverseengineer ( 580922 ) on Monday March 08, 2010 @03:20PM (#31403890)
    The orignal article may be found here [nature.com]- subscription to Nature Materials or payment required for full text. Abstract:

    Theoretical calculations predict that by coupling an exothermic chemical reaction with a nanotube or nanowire possessing a high axial thermal conductivity, a self-propagating reactive wave can be driven along its length. Herein, such waves are realized using a 7-nm cyclotrimethylene trinitramine annular shell around a multiwalled carbon nanotube and are amplified by more than 104 times the bulk value, propagating faster than 2 m s-1, with an effective thermal conductivity of 1.28±0.2kWm-1K-1 at 2,860K. This wave produces a concomitant electrical pulse of disproportionately high specific power, as large as 7kW kg-1, which we identify as a thermopower wave. Thermally excited carriers flow in the direction of the propagating reaction with a specific power that scales inversely with system size. The reaction also evolves an anisotropic pressure wave of high total impulse per mass (300 N s kg-1). Such waves of high power density may find uses as unique energy sources.

    The "fuel" used, cyclotrimethylene trinitramine, may be better known as the explosive RDX.

  • So, batteries are just a series of tubes? Or just tubes in series?

    • Re: (Score:2)

      by mcgrew ( 92797 ) *

      Ever take a flashlight battery apart? It's just a tube filled with carbon and stuff.

      • There are actually a few different kinds. Some have a carbon electrode at the positive terminal. Others have this silvery white goo at the negative terminal. Apparently the latter is cheaper, because back when I was actively destroying stuff (like dead batteries) I noticed that really large and really old batteries had the carbon, but cheaply made, smaller, and newer batteries did not.

        9 volt batteries also had a few different types: 6 skinny round self-enclosed batteries packed in 2 rows of 3 and connected

  • I suppose they really did start the fire.

  • Which scientist first came up with the idea of lighting these things on fire anyway?

  • If you read the description of how things work - it's almost the EXACT same design principle of the home-made EMP bomb that you could read about in an early 90's issue of Popular Science, just instead of using sequential plastique explosives and a wound copper tube, you're using a carbon nanotube and some other energy source. Same idea, though - burn from the back, go forwards, create a powerful burst of energy.

    It's about 15 years new.

    • Other than the use of explosives, the two techniques don't really have much in common. In the thermopower technology, the explosion serves to "throw" electrons toward one end of a chamber, generating a current. The movement of the electrons is the objective. In an EMP, the objective is the controlled obliteration of the conductor itself, in order to "squeeze" the magnetic field into an extremely tight packet, ultimately causing the magnetic flux to become unconstrained, generating a large EM pulse. Thermopo

    • Re: (Score:2)

      by jebrew ( 1101907 )
      So it was just 3-5 years away 15 years ago? Then you're saying it might actually only be 2-3 years away now? I look forward to having these in my cell phone sometime around 2025!

  • People should never be bored, especially smart people.

    What we have here is some idiot with access to a lot of high technology designing himself a tiny little cannon fuse. Let's burn something, this will be cool. This was obvious, but you're not doing this in your basement; the results aren't obvious, of course. But hey, we have a tiny little tube, like a string or a hair or something; let's light one end and watch it burn!

    This is why smart people should never be bored. They shouldn't sit around stari

    • Hmm, whenever I rub my little rod on a piece of cloth I never get feathers flying around.
  • What can't Carbon Nanotubes do?
  • "I need to light my laptop battery wick."
    Somehow I think this is for non-portable energy generation.

    • Somehow I think this is for non-portable energy generation.

      Unless you of course you want your junk burned with a speed that a lithium-ion battery powered Sony laptop can only dream of....

  • Can anyone who has read the journal paper comment on what kind of thermal/electric conversion efficiency they saw in this process? Did they provide any information as to whether the efficiency was proportional to temperature (i.e. with heat engines, we have the Carnot Efficiency theorem which shows that the maximum theoretical efficiency is proportional to the difference between the maximum and minimum temperatures - do these nanotubes conform to the same, or similar, principle)?

    How hot can nanotubes get be

  • More hype from the materials-science people.

    This seems to happen too frequently. Usually in Nature. Someone comes up with some bit of progress in materials science, and it's hailed as the biggest breakthrough since the transistor. Then it's never heard about again.

    This particular gimmick is kind of cute, but a general-purpose power supply it's not. They coated carbon nanotubes with RDX, which is a fast explosive, and got a big voltage spike out when they set it off. It's a one-shot device. This mi

    • Hmmm... I don't know, but if cheap enough it might replace this [wikipedia.org]. If you can design some electronics that regulate the output, then the only other consideration is cost.
  • How on earth are they going to manufacture this at an energy profit? Makes no sense.

    RS

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