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# ring flywheel 2

 (+3) [vote for, against]

I posted a ring flywheel idea a while ago and, having thought a bit more about it, have made a few improvements.

The key elements of both designs are that the flywheel is a ring shape (thus maximizing the rotational inertia) and the ring levitates above the stationary housing (thus no contact, thus minimizing friction).

I'll briefly discuss three aspects to the invention: shape, levitation and propulsion.

Shape
My idea is to use a half toroidal shell as a housing around the ring flywheel (see illustration). Using a half toroidal shell will restrain the flywheel's horizontal and vertical movements while allowing rotation. I think the ring will be stable and levitate at any speed - even when not moving.

The ring is lumpy and has coils spaced around its inner periphery. The coils are for propulsion, the lumpiness is so the ring has uniform resistivity all the way round.

Levitation
The toroidal shell (purple) has current traveling in one direction (say clockwise), while the ring (silver) has current traveling in the other direction (counter-clockwise); the opposing currents causes repulsive magnetic fields hence levitation. The current in the shell is sustained by a current generator. The current in the ring is induced into the ring by a changing magnetic field (generated by an alternating (sawtooth) current in concentric non-touching wire loop (orange)).

Propulsion (i.e. spinning the flywheel)
Some of the current that is traveling around the ring will flow through the coils. These coils create a magnetic field that can be pushed against by carefully timed magnetic field pulses produced by the stationary coils (green) thus propelling the ring to store energy, or to induce current in the green coils to draw energy from the flywheel.

There will be energy losses from the electrical resistance in both the toroidal shell and the ring. However, my rough calculations from my previous idea showed that the resistive losses would be acceptable for a suitably dimensioned flywheel.

As before, the whole apparatus could be mounted on a tilt according to latitude to prevent precession forces due to the Earth's rotation causing destabilization or unnecessary energy drain on the flywheel.

I realize that there are other magnetic bearing flywheel systems, however they suffer from two disadvantages. Firstly, they usually rely on permanent magnets which tend to produce counterproductive eddy currents in the flywheel; secondly, they usually require active electromagnetic control to keep the flywheel levitating. My design is relatively simple and avoids both of these issues.

 — xaviergisz, Sep 03 2011

ring flywheel
[xaviergisz, Sep 03 2011]

illustrations http://imgur.com/a/vTdjf
[xaviergisz, Sep 03 2011]

illustrations http://imgur.com/a/UGwZi
ring flywheel set at an incline corresponding to the latitude. [xaviergisz, Jul 22 2012]

[xaviergisz, Mar 09 2015]

Don't know how this stayed dormant for so long, but (+)
 — 2 fries shy of a happy meal, Apr 08 2012

Yes, but how do you fly it. The propulsion bit makes sense but there's nowhere for the pilot to sit!
 — saedi, Apr 08 2012

I've added a slight variation on the previous illustration that properly takes into account the inclination of the ring flywheel. Each ring flywheel shell (purple) would need to be designed specifically to take into account the latitude at which it would be installed.
 — xaviergisz, Jul 22 2012

My rough calculations indicate that the heat dissipated through electrical resistivity remains the same regardless of the weight of the flywheel ring - increasing the thickness of the ring lowers its resistivity which directly compensates for the increased current necessary to levitate the ring. So although there is a constant 3.5kW loss in the system (for an aluminium ring with 15m radius, levitating 1cm above the housing/shell) the weight can be increased such that (at maximum speed) it could store hundreds of kWh. At the very least this would make a good alternative to using load banks in power generation and distribution.
 — xaviergisz, Jul 23 2012

I think you'll want an atmospheric shield shell around the thing as well; vacuum or hydrogen filled. [+] the same as for Ring Flywheel: The Original.
 — FlyingToaster, Jul 23 2012

"The Ringworld is unstable".
 — normzone, Jul 23 2012

 Yep, the shell would be capped to form a hollow torus to allow a low drag environment for the ring to spin in.

One question I have is whether the heat of the ring could be properly dissipated. The resistive loss of the ring is 1.5kW; if the ring was enclosed in a vacuum this heat would have to be dissipated through radiation alone, whereas a gas surrounding would allow convection heat dissipation.
 — xaviergisz, Jul 23 2012

maybe keep just enough gas pressure in there to keep it cooled off.
 — FlyingToaster, Jul 25 2012

 Just a correction to previous anno. My initial calculations were based on ring and shell having essentially no thickness. Obviously this is not the case, and when added into the calculations (for a toroidal ring) increases the losses for the ring significantly (for the aluminum ring from 1.5kW to 6.4kW). For this reason, increasing the weight of the ring will also increase the losses further (contrary to my previous anno).

 Ways of decreasing this loss would be: a) changing the shape of the ring from torus to thin and wide tube, b) make the whole thing with bigger radius, c) use denser metal (copper rather than aluminum).

sorry for the churn.
 — xaviergisz, Jul 29 2012

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