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Will a superconducting dynamo in space produce free energy?

  1. Dec 4, 2007 #1
    I have read in several places that superconducting materials are the closest phenomenon to perpetual motion known to science (constant flowing electrons within a circuit without resistance). The problem is that the energy required to cool the inducting material to its superconducting temperature would be far more than would be produced. However in space we have two advantages. One is the fact that it is a frictionless vacuum environment (you could rotate a disk with magnets on it without friction resistance) and the second is that parts of space are near absolute zero. Therefore theoretically you can have a free rotating dynamo inducting on a superconducting material at the surrounding ambient temperature. There would be no EMF feedback to slow the rotation of the disk. The freely moving magnets would induce a current on the superconducting coils without resistance. The energy could then be stored or used. And no energy would have been consumed in cooling the coils to superconducting temperatures. I must have missed something? Won’t this work?
     
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  3. Dec 4, 2007 #2

    stewartcs

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    Sounds like a violation of Lenz's Law and thus the conservation of energy. Don't think it will work.
     
  4. Dec 4, 2007 #3
    Definitely NO.
    How come you could store the electrical energy if the whole circuit is of zero resistance? or more correctly zero impedance? So, assume that you could create some current, but the current should make no work (or energy), it's there, but does nothing.
     
  5. Dec 4, 2007 #4

    LURCH

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    Superconductors lose almost none of the energy that is put into them. But
    a) the energy they contain must come from somewhere, and
    b) any enrgy you remove for storage or use will be subtracted from the energy in the system.

    IOW, if you do nothing to this system, the dynamo would continue to rotate for a very long time (practically forever), but as soon as you take energy from it for storage or use, that energy is subtracted from the system, and it slows to an eventual stop.

    IOOW, superconductors don't generate energy, they just store it and transport it extremely well.
     
  6. Dec 4, 2007 #5
    I think you will not be able to create a "Free Energy" source as it is a violation of Conservation of Energy Law. But I think what you will have is a near 100% efficient system. Which means no energy loss. So your system may be 99.99% efficient.
     
  7. Dec 4, 2007 #6

    f95toli

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    No, there is no "free energy". Superconductors can be used to STORE energy, that is all.
    The easiest way to use superconductors for energy storage is actually to store "mechanical energy" using a flywheel with superconducting bearings. This works like a very efficient "battery" and has actually been considered for satellite applications (meaning you would actually launch a spinning flywheel into space).
    The amount of energy you can "store" in a superconductor in the form of a circulating current is quite small, although if you instead use a coil it is enough for a very efficient SMES (these are actually used commerically).
     
  8. Dec 4, 2007 #7
    If what I suggest did work then yes it would be an outright break of the law of conservation of energy. Therefore we start on the premise that I must not be accounting for something or have overlooked something. Unfortunately the reason I am posting here is because my physics understanding is limited. The way I have understood it is that a current is induced on a coil when a magnetic flux passes through it at right angles. The problem with making efficient dynamos is that the resistance of the coil slows the dynamo meaning that more work is needed to overcome that resistance. According to my understanding you could in theory make a 100% efficient windmill for example if it was contained within a vacuum and had superconducting coils. In space the natural environment can provide both. Now, am I getting confused about the difference between resistance and the feedback Electro Magnetic Flux (EMF)? Is there no resistance but the coil still generates an EMF? Or are they both the same thing? Or is it that when you connect a load to the other end of the coils (say a light bulb for example) the superconducting coils start producing an EMF that repels the rotating magnets and thus brings the system to a standstill? I thought it was like this: The magnets push current through the coil as they pass them. If the coils were made of copper at room temperature then the resistance within the coil produces a magnetic field that acts against the magnets and slows the magnets down, but if the coils were superconducting then they wouldn't have any resistance and wouldn't produce any magnetic flux and the magnets would continue to move freely, without resistance, inducing current flow through the coils!?

    In layman terms can anyone explain to me what I have got wrong or not understood?
     
  9. Dec 4, 2007 #8

    Mentz114

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    Hi John,
    No, the current in the coil produces the field. Electrical resistance will produce heat if a current flows.

    In any generator, when it is loaded there is a back EMF which produces mechanical resistance to the rotation. You have to work harder to make it rotate when current is circulating.
     
  10. Dec 4, 2007 #9

    stewartcs

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    EMF stands for Electromotive Force.

    http://en.wikipedia.org/wiki/Electromotive_force


    What will cause the relative motion between your rotating conductor and the flux field?

    Whatever it is will require an energy input to the system, so there is no "free energy".

    Lenz's law states that any induced electromotive force will be in the direction such that the flux it creates will oppose the change in the flux that produced it. Read the source below, it describes why what you are describing would be a conservation of energy violation.

    Source: http://en.wikipedia.org/wiki/Lenz's_law

    It seems as if you are confusing the conservation of energy with the efficiency of a system.
     
  11. Dec 4, 2007 #10

    ZapperZ

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    As Mentz has said, it is the current that is producing this counter magnetic flux, not resistance. So not having any resistance is irrelevant here. When we teach students about Lenz's law, we never include any resistance factor because it is usually not that large to affect the observation.

    So yes, this is the part that you have overlooked or didn't understand that will cause your premise to fail.

    Zz.
     
  12. Dec 4, 2007 #11

    Mentz114

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    Resistance is futile !

    ( sorry, couldn't resist it )
     
  13. Dec 4, 2007 #12

    Dale

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    You are absolutely correct that there is no "free energy" in a superconductor. However, I wouldn't say that the energy is small. The energy density stored in a magnetic field is:

    1/2 B^2/u ( http://hyperphysics.phy-astr.gsu.edu/hbase/electric/indeng.html#c2 )

    A typical MRI machine, at 1.5T - 3T, in routine clinical use today, contains a few MJ of energy. That may be small if you are talking about powering a city, but it is a huge amount of energy if you are trying to get rid of it in a few seconds because the magnet quenched.
     
  14. Dec 4, 2007 #13

    russ_watters

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    Electrical energy is work, so yes, your idea is a violation of conservation of energy. Energy must be conserved across different forms (such as potential to kinetic or kinetic to electrical).
     
  15. Dec 4, 2007 #14

    russ_watters

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    ....which is just fine since a real-life generator is something like 95% efficient anyway. Ignoring the resistance for the sake of learning the concept doesn't get you too far from how it works in real life (and, in fact, would get you exactly the scenario we are looking at here).
     
  16. Dec 4, 2007 #15

    f95toli

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    Yes, even controlled quench testing tends to generate a rather large cloud (a few years ago we had problems getting enough helium, it turned out that a nearby NMR lab was quench-testing their new BIG magnet, they used up several thousand liters)...

    Anyway, you are right that the amount of energy isn't exactly small but my point was that this kind of energy storage is more useful for things like the kind of SMES (which, by the way, is short for Superconducting magnetic energy storage) that are used in power conditioning systems for the power grid; i.e. the SMES are essentially used like big smoothing capacitors. AFAIK flywheels are much better for long time storage.
     
  17. Dec 5, 2007 #16
    If no windage losses occur, current will just keep flowing around the superconductor. Hence, as others have said, it will be a energy storage device, with the energy stored equal to the input of mechanical energy that started the dynamo spinning.

    I have a question...There EXISTS back EMF right? The current will result in a force opposite to the direction of motion. Hence won't the spinning slow down and eventually stop?
     
  18. Dec 5, 2007 #17
    Thanks for helping me understand everyone. Thinking that resistance and the counter EMF was the same thing caused my confusion. Now I don't know what all the fuss about superconductors was. I thought that superconducting materials didn't produce any EMF when current was going through them (whether connected to a load or not), I thought that was what was special about superconductivity and why a room temperature superconductive material (which I don't think exists) would make free energy possible. I thought you could just spin a disk in space with magnets on it that would continue spinning forever. The input energy would have come from the one off initial spin and with no counter EMF (what I was mistaking for resistance) the coils would have conducted useable current through them indefinitely without slowing down the freely rotating disk.

    I am now ready to post a thread on atomic explosions and clear up my misunderstandings about that too. :D
     
  19. Dec 5, 2007 #18

    russ_watters

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    Superconductors are exactly what their name says they are - conductors that conduct really well. In other words: no resistance. This is useful in situations where you need an extremely large current and don't want to lose a lot of energy to resistance. Among other things, this allows for the creation of extremely strong magnets.
     
  20. Dec 6, 2007 #19

    LURCH

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    It would also mean a significant savings for pwoer utilities. As they transmit power throught the line to your houde, some is lost to make the wires warm so birds can warm their feet by perching on them. Unfortunately, these birds seldom pay for the power they use.

    If we had superconducting cables, the power companies could produce less power at the plant and still supply the same amount to the end user, because less wuold be wasted to heat loss in transit. It has also been speculated that many major blackouts could be avoided. Apparently, a lot of blackouts are caused by high current generating heat in the lines, which expand and sag, touching something that allows thwm a path to ground. In a superconducting powerline, no heat is generated.
     
  21. Dec 8, 2007 #20
    So it is like what I said right? That there will be no breaking of the law of conservation of energy but just a 100% efficient system will be created according to theory.
     
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