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# Tension-Compression balanced Flywheel

For very high rotation speeds and high energy storage
 (+3, -1) [vote for, against]

There are several Ideas here about using flywheels for energy storage. It is, I think, generally acknowledged that to reduce friction, the flywheel should be spun up in a vacuum, and maglev should be used to support its weight.

However, that's not all that "maglev" (in quotes for a reason!) can be used for. Let's approach this design by first considering the original flywheel design: a fairly simple spoked wheel, with most of the mass in the wheel. Its purpose was basically to smooth out any irregularities in the rotational motion of any machine that converted reciprocating motion into rotary motion.

When people began thinking about using flywheels for energy storage (see link), calculations showed that that design was far from ideal at any practical rotation speed. A design that could store rather more energy was a sort of solid disk with significant bulges in the middle, where the axle was.

As you probably know, the problem with a high-speed flywheel is that the material from which it is constructed typically needs to have tremendous tensile strength, to hold the wheel together against the forces that appear as a result of its rotation.

This Idea is about a different way to balance those forces: maglev.

Let's construct our flywheel in the form of a simple cylinder. Let the outer curved surface of the cylinder be covered with very strong permanent magnets. A simple cutaway side view ASCII sketch, of the cylinder tipped on its side:
= axle
|
| body of cylinder (edge below)
|______________________
N S N S N S N S N S N S (magnetic polarities)
N S N S N S N S N S N S
______________________ (wall of cylindrical container)

Since the HalfBakery does not support HTML underlining, there is a gap portrayed between the wall electromagnets and the wall; actually those electromagnets are in the wall, the same as the cylinder permanent magnets are in the cylinder. As portrayed, there is magnetic repulsion between the cylinder and the container wall. The magnets, of course, are so numerous as to be located all the way around both the exterior of the cylinder and the interior of the flywheel container body (one should think of them as continuous magnetic rings).

When oriented vertically, the weight of our massive flywheel cylinder floats on more magnets (not portrayed) --and that weight ensures that the cylinder doesn't "shift" so that the portrayed repulsion becomes attraction.

What happens when we start rotating this flywheel/cylinder at high speed? Obviously stresses will begin to appear, attempting to cause the cylinder to fly to pieces. However, because the container wall magnets are electromagnets, we can power them up and increase the magnetic repulsion between them and the cylinder. (Obviously we also want these electromagnets to be of the superconductive variety, in order to not waste energy.)

The more magnetic repulsion we can create, the faster our flywheel/cylinder can be spun, and the more energy it will store. All the force that tries to tear the cylinder apart is effectively transmitted through the magnetic fields to the body of the container, and that body can be constructed of materials that can hugely resist compressive forces, like reinforced concrete.

Because of the total weight, it would probably be unwise to put this sort of flywheel in any vehicle smaller than a ship, but to use it anywhere on land would be perfectly practical, for temporary energy storage purposes (such to hold solar power gathered during daytime for use at night).

 — Vernon, Jun 30 2010

Flywheel energy storage for a car http://books.google...wheel%20car&f=false
As mentioned in the main text. The article, if I recall right, has quite a bit to say about flywheel design. [Vernon, Jun 30 2010]

Forced quantum singularity http://memory-alpha...quantum_singularity
Small, yet perfectly formed. [8th of 7, Jun 30 2010]

The forces involved http://www.piercene...entrifuge-speed.pdf
[mouseposture, Jun 30 2010]

[link]

 Several problems Vern.

 1. You are going to induce magnetic drag due to the proximity of the rings to the opposite poles beside them.

2. Magnetic forces simply aren't terribly strong in relation to the stresses that the material sees at speed, at least not at reasonably-sized continuous electrical input levels. Pound for pound with the system you've described here you'd might as well wrap a few layers of heat shrink around the wheel.
 — RayfordSteele, Jun 30 2010

It seems to me that if maglev is good enough to hold in the air tons of train, then it is good enough to hold up against tons of "centrifugal" force.
 — Vernon, Jun 30 2010

There's no reason you actually need opposing poles. Simply make the flywheel bar magnets with all the South pointing in, and the walls with the south pointing out. It essentially becomes two very large magnets with a very strong flux wrapping around the ends.
 — MechE, Jun 30 2010

Why not just use a forced quantum singularity ?
 — 8th of 7, Jun 30 2010

seems to me that one of the products of this is going to be a giant quantity of heat.
 — WcW, Jun 30 2010

You say that like it's a bad thing. Go look up "over unity machine".
 — 8th of 7, Jun 30 2010

 //tons of "centrifugal" force// Why the quotes? Just because it's fictitious doesn't mean it isn't real.

Also, I think maybe it's not tons, but hundreds of tons, if we take a standard ultracentrifuge as an example of the sort of flywheel requiring specially strong material in order to avoid shattering when spun up. <link>
 — mouseposture, Jun 30 2010

 [MechE], any magnetic field so far that we know how to make MUST feature a complete "field loop" such that if we look "into" the loop anywhere --say like cutting a hula-hoop--, we will see a North pole at the face of one cut and a South pole at the face of the other cut. I would have done it the way you suggested, except for the preceding fact.

[mouseposture], I used the quotes just so nobody would complain about me saying the wrong thing. Note that the electromagnets used for maglev of trains are nowhere near as powerful as we know how to make, and could make in a relatively small facility such as an energy-storage flywheel. Note we could use maximum-strength maglev on the axle end of the cylinder, to support the weight of a rather long cylinder, and equally strong magnets all along that length....
 — Vernon, Jul 01 2010

[+] neat: the flywheel is it's own containment. Sounds pretty draggy though.
 — FlyingToaster, Jul 01 2010

Vernon, with proper layout, the flux is entirely out of the end of the rotating cylinder. The Wall flux is out the sides of the swept back edges. You have some possible field turbulence around these edges, but nowhere near the level you would with close packed alternating poles.
 — MechE, Jul 01 2010

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