Can the Earth's magnetic field be used to generate electricity?

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Solution 1

Not really. A magnetic field alone doesn't create electricity. A changing magnetic field does. The Earth's magnetic field does change a tiny bit but not enough to really generate much.

The other option is to move the inductor in the magnetic field. The Earth's magnetic field is quite homogeneous over short distances though so the coil would need to move fast and very far to generate much. This would use more energy than it creates (at least on the surface of the Earth).

Several years back there was an experiment (the Space Tether Experiment) to drag a conductor through the Earth's magnetic field with the Space Shuttle. I don't know how viable this is though because I think it saps orbital energy.

Solution 2

Actually, it's possible to use the Earth's magnetic field to generate electricity. A satellite in the form of large diameter loop in orbit around the Earth will generate a current in that loop, and could be used to power something, but at the cost of a rapidly degrading orbit. On the other hand, solar panels creating a current in that same loop could boost the satellite into a higher orbit.

Transferring power out of an orbiting system of this type to somewhere else , and the technical issues involving superconductors are large.

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hmir
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Updated on August 01, 2022

Comments

  • hmir
    hmir over 1 year

    Since the Earth has a magnetic field, can it, in theory, be run through a conductive metal coil to create electricity?

  • Admin
    Admin over 10 years
    "The Earth's magnetic field is quite homogeneous over short distances though so the coil would need to move fast and very far to generate much." You can just spin a coil. The issues are that: (1) the earth's field is weak, and it's easier to use the field of a stronger permanent magnet; and (2) as with any generator, it requires an input of energy to turn the crank.
  • Brandon Enright
    Brandon Enright over 10 years
    @BenCrowell I think we're in agreement. I was not imagining the coil spinning. I was imagining it on a train or something like that. But my point was that you'd have to make it move really fast and really far to generate anything useful and the energy needed to move it would use far more than in generated.
  • Alan Rominger
    Alan Rominger over 10 years
    If you put in energy into the coil, there seems to me no reason that you couldn't then get momentum out of it. I don't know how viable this would be in practice, but in theory it seems like you could use a coil to push against the Earth and slowly raise or maintain your orbit.
  • Admin
    Admin over 10 years
    The efficiency would depend on the quality of the bearing. There is no fundamental reason that it has to be inefficient. The coil doesn't have to move far or fast. If it has some large number of loops, you can generate a large emf by spinning it slowly.
  • anna v
    anna v over 10 years
    @AlanSE also as far as efficiency goes for keeping the orbit one should do the energy balance between small rockets/jets and spending it in rotating a gismo.
  • JanKanis
    JanKanis about 6 years
    Space tethers can be used to generate electricity, but at the cost of orbital energy. Conversely if you send electric energy into a space tether you can raise your orbit without using fuel. This is still research stage tech because doing research in space is very expensive and there have been problems with the tether getting tangled or starting to oscilate uncontrollably from (what are assumed to be) inhomogenities in the earth magnetic field.
  • Hisham
    Hisham over 4 years
    How is variation of flux density better achieved at the equator?