5 ms·

Windmills and electric motors don't actually require strong permanent magnets - electromagnetism/induction is somewhat more complex to manage but potentially mo

Windmills and electric motors don't actually require strong permanent magnets - electromagnetism/induction is somewhat more complex to manage but potentially more powerful and efficient. This is not theory or speculation - Tesla car motors don't involve strong permanent magnets [1] Large wind turbines do not require large rare earth magnets [2] (Im not saying powerful magnets are not very valuable, but requirements for them can be overrated) [1] https://forums.tesla.com/de_AT/forum/forums/no-rare-earth-metals-model-s https://forums.tesla.com/de_AT/forum/forums/no-rare-earth-me... [2] https://www.mathworks.com/help/physmod/sps/powersys/ug/wind-farm-using-doubly-fed-induction-generators.html https://www.mathworks.com/help/physmod/sps/powersys/ug/wind-...

abricot 9y ago
Sure, the turbines themselves down't require rare earths, but that doesn't mean it isn't used for windmills. "In Vestas, rare earth elements are used in the magnets found in the towers of all new models of Vestas turbines" - Vestas[1] [1]https://www.vestas.com/en/about/sustainability#!material-use https://www.vestas.com/en/about/sustainability#!material-use
- strainer 9y ago
  Rare earth magnets 'found in the towers' is a rather mysterious idea. I can only guess this is about relatively modest requirements of direction control motors.
  - jessaustin 9y ago
    ISTM a generator, even if it were set up to use induction, first would need to generate a small current using permanent magnets to "jump-start" the process. Without magnets, if no current is flowing, no magnetic field is created, and no power is generated.
    - sjburt 9y ago
      Industrial wind turbines just use power from the grid to start up.
      - Robotbeat 9y ago
        Correct, and you could also use a battery to start up.
    - strainer 9y ago
      It was not a great reference to clarify matters, its promotional language, but they state "Vestas’ current turbine range does not use rare earth elements in the generator. "
  - dwyerm 9y ago
    Actually, I just learned the answer a few weeks ago when I toured a wind-farm: Vestas uses magnets to secure ladders, lights, and other items to the inside of the tower instead of drilling holes. This neatly heads off problems with water egress and rust. It is a little daunting to see that ladder going up into the dizzying heights and see that it is held in place by the same technology that keeps the kids' art stuck on the fridge. Here's their patent on it: https://www.google.com/patents/US8567131 https://www.google.com/patents/US8567131
    - strainer 9y ago
      Thanks for this - I never would have guessed it!
mfrykman 9y ago
Not positive, but I think there are scaling issues w AC induction motors. My understanding is that for smaller applications, they don't make sense. Anyone have more insight on this?
- ChuckMcM 9y ago
  Power dissipation in the electromagnets is the limiting factor. The more current you push through them the more power you dissipate in the windings. To offset the resistance you can make 'thicker' (current is a surface area effect but mass is a thermal sink) wires but that reduces you Ampere turns which reduces flux. Since room temp superconductors aren't an answer, you top out.
hwillis 9y ago
With windmills, strong magnets are useful because they reduce or eliminate the gearbox. PM motors can be efficient at lower speeds than induction motor so it simplifies and shrinks the nacelle, raises efficiency a bit, and might lower maintenance. That said, it's totally not necessary. >electromagnetism/induction is somewhat more complex to manage but potentially more powerful and efficient. Quibble- at certain RPM ranges an induction motor can be more efficient than a PM motor of equal cost, but in general a PM motor will always be smaller and more efficient than an induction motor if built to the same quality. For most applications, the cost of the motor is very minor. Wind turbines are an exception because the converter is cheaper than the motor at that scale. Tesla uses induction motors for several reasons but the primary one is probably cost. The cost is actually more in materials handling and assembly than the magnets themselves, since magnets will always find a way to fuck up your life eventually. PM motors also have much more demanding requirements of controllers and more cogging, but in general they can only be as good as a PM motor at high speed and low load.
- strainer 9y ago
  Interesting but I am not sure you are not over generalising the legacy experience. With Tesla motors lately using induction motors for their top performance as well as their top economy models, that is a fair suggestion that 'PM free' can be superior, perhaps enabled by capabilities of modern power controllers.
  - hwillis 9y ago
    Tesla has very specific applications that make induction motors almost as good, but 3x cheaper. The efficiency of the motor is most important under that high-speed low-load point, when on the highway. PM motors have very large advantages over induction. They have half the iron laminations of an induction motor, so they have half the hysteresis losses. On an overall basis there is no way for an induction motor to make that up. Even at high RPMs I've only seen indications (papers/FEMM sims) that induction motors can roughly match PM motors, not surpass them.
    - 9y ago

abricot 9y ago

Sure, the turbines themselves down't require rare earths, but that doesn't mean it isn't used for windmills. "In Vestas, rare earth elements are used in the magnets found in the towers of all new models of Vestas turbines" - Vestas[1] [1]https://www.vestas.com/en/about/sustainability#!material-use https://www.vestas.com/en/about/sustainability#!material-use

strainer 9y ago
Rare earth magnets 'found in the towers' is a rather mysterious idea. I can only guess this is about relatively modest requirements of direction control motors.
- jessaustin 9y ago
  ISTM a generator, even if it were set up to use induction, first would need to generate a small current using permanent magnets to "jump-start" the process. Without magnets, if no current is flowing, no magnetic field is created, and no power is generated.
  - sjburt 9y ago
    Industrial wind turbines just use power from the grid to start up.
    - Robotbeat 9y ago
      Correct, and you could also use a battery to start up.
  - strainer 9y ago
    It was not a great reference to clarify matters, its promotional language, but they state "Vestas’ current turbine range does not use rare earth elements in the generator. "
- dwyerm 9y ago
  Actually, I just learned the answer a few weeks ago when I toured a wind-farm: Vestas uses magnets to secure ladders, lights, and other items to the inside of the tower instead of drilling holes. This neatly heads off problems with water egress and rust. It is a little daunting to see that ladder going up into the dizzying heights and see that it is held in place by the same technology that keeps the kids' art stuck on the fridge. Here's their patent on it: https://www.google.com/patents/US8567131 https://www.google.com/patents/US8567131
  - strainer 9y ago
    Thanks for this - I never would have guessed it!

mfrykman 9y ago

Not positive, but I think there are scaling issues w AC induction motors. My understanding is that for smaller applications, they don't make sense. Anyone have more insight on this?

ChuckMcM 9y ago
Power dissipation in the electromagnets is the limiting factor. The more current you push through them the more power you dissipate in the windings. To offset the resistance you can make 'thicker' (current is a surface area effect but mass is a thermal sink) wires but that reduces you Ampere turns which reduces flux. Since room temp superconductors aren't an answer, you top out.

hwillis 9y ago

With windmills, strong magnets are useful because they reduce or eliminate the gearbox. PM motors can be efficient at lower speeds than induction motor so it simplifies and shrinks the nacelle, raises efficiency a bit, and might lower maintenance. That said, it's totally not necessary. >electromagnetism/induction is somewhat more complex to manage but potentially more powerful and efficient. Quibble- at certain RPM ranges an induction motor can be more efficient than a PM motor of equal cost, but in general a PM motor will always be smaller and more efficient than an induction motor if built to the same quality. For most applications, the cost of the motor is very minor. Wind turbines are an exception because the converter is cheaper than the motor at that scale. Tesla uses induction motors for several reasons but the primary one is probably cost. The cost is actually more in materials handling and assembly than the magnets themselves, since magnets will always find a way to fuck up your life eventually. PM motors also have much more demanding requirements of controllers and more cogging, but in general they can only be as good as a PM motor at high speed and low load.

strainer 9y ago
Interesting but I am not sure you are not over generalising the legacy experience. With Tesla motors lately using induction motors for their top performance as well as their top economy models, that is a fair suggestion that 'PM free' can be superior, perhaps enabled by capabilities of modern power controllers.
- hwillis 9y ago
  Tesla has very specific applications that make induction motors almost as good, but 3x cheaper. The efficiency of the motor is most important under that high-speed low-load point, when on the highway. PM motors have very large advantages over induction. They have half the iron laminations of an induction motor, so they have half the hysteresis losses. On an overall basis there is no way for an induction motor to make that up. Even at high RPMs I've only seen indications (papers/FEMM sims) that induction motors can roughly match PM motors, not surpass them.
  - 9y ago