Agreed, I'm shocked I missed this when it was released in 2014. Rare earths no longer needed for magnets strong and light enough for windmills and electric motors? I remember the reports on how vulnerable our infrastructure was to neodymium supply disruptions, it was really high on the priority list. This is fantastic if it can be manufactured reasonably!
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)
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.
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.
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.
When I wrote the point of contention, i was thinking how it is possible to produce stronger magnetic fields electrically than ~materially, and what that should mean to ultimate motor performance. But I can see your correction is likely sound, that in practice PM options keep a performance edge -at least until the age of high temp superconductors arrive or other magic :)
A purely (doubly fed) superconductive motor would probably resemble a PM motor more than an inductive motor, but I'm not 100% sure. It would be for the same reduction in hysteresis losses. An air-core motor would also be possible, but that would result in 30 Tesla fields swinging around wildly, which would be a Bad thing.
You could probably get good gains with metal glass laminations, if you were gonna make a hilariously expensive motor. It's got very low core loss and extremely high permeability, which lets you shrink the motor and have a higher ratio of copper/iron, lowering winding resistance.
Still, electrical machines are so efficient it's kind of just not worth it. The friction in the bearings and the viscosity of air are significant factors in a motor's efficiency.
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.
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.
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.
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. "
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.
Indeed, Hyperloop Transportation Technologies (the crowdsourced one) said they'd use Inductrack technology for their version of Hyperloop:
https://en.wikipedia.org/wiki/Inductrack
This uses permanent magnets arranged in a Halbach Array for levitation.
This method of levitating a pod is incredibly efficient and gets more efficient at higher speeds (in a vacuum). You can actually exceed typical rail efficiency (rolling resistance of 1:1000, i.e. an effective coefficient of friction of 0.001 or a lift-to-drag ratio of 1000) at 300m/s since levitation power remains basically constant above a certain speed (as opposed to increasing linearly in the case of friction or rolling-resistance). And because you're in a vacuum, you're far exceeding what could be possible in a non-hyperloop/vactrain design:
https://www.google.com/patents/US20100064929
This might be a case where no one has actually tried it with a maker mentality. Musk was saying the other day that you need 1 atmosphere of pressure capability to create a vacuum, but 5-6 to hold back the watertable related to his tunneling network. Seems like from a first principles perspective making a vacuum should be much easier than an underwater tunnel. I'm guessing that you could create a partial vacuum in such a tunnel fairly easily. But I haven't 'done it' and that's the rub.
I don't think the problem is the pressure - holding up one atmosphere is not big deal - I think it's the porosity. It just takes one hole, anywhere, and pscchht you start losing your vaccum. You have to continuously run pumps to get rid of the air that finds its way in, and their efficiency is inversely proportional to the pressure difference.
This is also true of below-water-table tunnels and pipelines of various sort, which are often at much higher pressure and with much greater environmental risk.
It is quite a bit easier to hold back a liquid than a gas. Different minimum pore size and you get hydrophobic chemistry and surface tension on your side.
Especially at such big pipe diameters as required.
You can use cheap materials like modified concrete to patch a hole in an underwater tunnel, not so in a vacuum tube - that needs something much better and more expensive.
Not true. You can use concrete to hold back a vacuum and cheap materials like a thin polymer coating, too. Remember, Hyperloop does not require an ultra hard vacuum.
It's a 'soft' vacuum, so doesn't have anywhere near the difficulty of a 'hard' vacuum. IIRC the detailed specs of what they intend to do aren't out, so it's all just speculation.
I could come up with electrical motors and generators. Before that I saw them for controlling the arm of spinning hard drives, and those aren't used that much anymore. What else is there?
> spinning hard drives, and those aren't used that much anymore
Hey! Are you basing this statement on your own experience of your personal/business hardware? Because spinning rust has never been more heavily used, for bulk on/near-line storage.
Judging by the list of alumni from Prof. Wang's group, HDD manufacturers have a strong demand for advanced applications of magnets, plus a tiny fraction from biomedical techs.
There's still a lot of active research going into magnetic tape storage, I find it very difficult to believe research into hard drive storage is going to slow any time soon.
At least earphones and speakers use permanent magnets[1], though according to Wikipedia[2] the early ones actually used electromagnets. I agree though that relays and maglev use electromagnets. I'm not sure about the rest.
Last time I checked speakers and headphones still had a single permanent magnet + an electromagnet. However, for speakers, the "old" iron permanent magnets generally work just fine - they just have to be bigger.
Inverter-based power supplies are sufficiently light that a guitar amp should only be the weight of the wood and the speakers.
And, the speakers have to be a certain size to move the correct amount of air--so the copper coil is probably the limiting weight. It's remarkable how much air you have to actually move to get decent sound volume.
Hm...sounds plausible from a physics POV, but maybe there's something else? Since, in practice (at least as far as I can speak from experience), old-school ferrit 15" speakers are ~7-8kgs, while you can get similarly specced neodymium speakers that weigh about half (3-4kgs).
And, yes, you will find that the values are all over the map in terms of weight. There are some much less powerful speakers that are quite a bit heavier.
Most commercial drones have 4 motors w about 12 magnets each.
Some others:
electric bikes, electric skateboards, power tools, blow dryers, iPad cases.
If I recall correctly, one of the earlier iPhones was basically held together w rare earth magnets, with the screen module magnetically stuck into the case. Can't find info to verify this though, so take it w a grain of salt.
Why is this being downvoted? Prev post said you don't realize how many magnets are around you, so the parent is asking. I wanna know too. I additionally came up with speakers/headphones, connectors, reed switches.
"MRI" covers a very wide variety of imaging and analysis techniques under the general category NMR (Nuclear Magnetic Resonance). Some forms of NMR analysis actually use the Earth's magnetic field (https://en.wikipedia.org/wiki/Earth%27s_field_NMR).
Basically, the stronger the fixed magnetic field, the more you can see and do.
Exactly. Super conductors are the ones I use and high temperature superconduction will likely make maintaining a super conductor much cheaper (after you spent lots on a whole new system).
> This technology for producing iron nitride permanent magnets has been exclusively licensed.
Interesting — I wonder to whom.