Friday, December 07, 2007
Magnetic Energy Storage
So the other day I said to myself, "Self, magnets attract and repel each other. That sounds like work." Then I started thinking: the act of magnetizing NdFeB could be viewed as an act of energy storage. If you take a screw and crank a bunch of very strong magnets together, they should resist that arrangement until they're demagnetized. The question would be: how could this resistance be harvested? One possible way might be to compress a gas, but it'd probably be a lot easier to just compress a gas itself. With magnets, you don't have to worry about gas canisters exploding, but I'm kinda baffled as to how one can extract the energy. Maybe just a stupidly high amount of mechanical advantage?
12 comments:
The process of magnetization is the aligning of all the crystallites in the magnet, and to de-magnetize them you would have to scramble that alignment. This could be done easier if you could change the phase of the magnet from solid to a liquid, or, go to an intermediate state by partially heating the magnet.
So I think to release said energy you would have to probably put energy into the magnet to erase said magnetism...or...use that magnetic field to generate energy on something else. Probably a better way to invoke magnetic energy would be to design a magnet that does not want to stay aligned and magnetized - you "wind" it up like you're describing, and then put it next to something else where that magnetic field de-aligns but in so doing runs an alternator or solonoid system for generating electricity. I think though that you would have to design the magnet at both the macro scale (some sort of multi-layer structure) and at the molecular scale so that it both easy to align and de-align the magnetic crystalites.
Or so I think anyway.
Wouldn't extracting mechanical energy from magnetic repulsion/attraction have to demagnetize it, since that's where the energy's coming from?
Not always - many magnets can be described as "permanent" in that once the magnetic particles align in the magnet, they're in that form for just about eternity unless you melt them down, physically destroy them, or hit them with an even more powerful magnetic field and heat to scramble it.
It seems like your idea would work though, I just don't know which magnet chemistry and structure would be the right one to use for this potential task.
But wouldn't that be dangerously close to implying "free energy"? If one magnet is repelling another against (say) gravity, that's output energy, and has to come from somewhere, right?
It is, which is why so many people have attempted perpetual motion machines with magnetic devices.
Let's take Maglev for example. There really isn't much energy to float the train above the track, but you do have to put energy into the system to get it to push off and move the train forward. So the energy into the system is what you put into it to get it to move.
So in this case, the energy goes into the alignment of the magnetic particles and then assuming you can then use that to drive something else, there is your potential energy source (the magnet) putting out kinetic energy when it drives something else. In the case of permanent magnets, the field strength is quite low so you really can't drive much with it at all.
Your original question struck me as "how do I get that stored potential energy back out of the magnet" which is why I was proposing changes in the magnetic structure itself, sort of like how you write/rewrite a magnetic disk, but now enough energy to actual drive something else. At least, this is how I think it might work, but since someone hasn't made it happen yet, there must be a good reason why this may not work, or at least is not practical at this time.
And I'd been thinking of extracting it via mechanical work somehow, but maybe you're right and the stored energy is too low.
If work = energy * time, I wonder if that implies an Improbable Research paper on energy storage of various permanent magnets, based on how long it takes them to cease repelling another one?
Sure, why not do the research and publish it. I still think Andy should do his study about M&M's and survival of the fittest M&M while eating them. : )
Too bad I don't have some instrument that'll create a record of physical force over time so it can be integrated. The experiment is high-school simple, but...
Sorta like all the chemical reactions catalyzed by unobtanium!
You guys hurt my head.
Sure you do - buy a counter that records the number of revolutions of moving a crank. Or buy a torque wrench where you know how much torque you put on it when you turn it and use that to measure how much mechanical energy you are putting on one magnet as it moves against another object to be magnetized. Record the total number of turns you make and you have the total amount of energy put into the system.
And Mike - come now, it can't be that hard for you. I mean you weren't exactly skiing down the slope of liberal arts - you at least were pressing up the low incline of biology. Besides, you're going to start needing to know magnetics with the proposed "toys" I'm hearing about for the next 20 years.
Me? Oh no, I just tell them where to shoot and they do. To quote Oddball from Kelly's Heroes: "I just fight them baby, I don't know what makes them work."
Alex -- yeah, I'll find one of those in my garage somewhere ;)
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