h a l f b a k e r yNaturally, seismology provides the answer.
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A flywheel is a relatively easy way of storing energy. And the more energy you want to store the bigger the flywheel (OK, not quite correct: more energy can be stored by making the flywheel larger, heavier and/or faster, but you get my drift)
A flywheel can be mounted on gimbals which allows the structure
holding the flywheel to tilt while the flywheel itself remains in the same orientation.
Although gimbals work quite well for relatively small gyroscopes, I don't think they would be practical for relatively large flywheels (weighing several tons) for storing energy.
I hear you ask, "Why would I want a large flywheel to allow for changes in tilt? Surely a flywheel of that size would be stationary and thus not need a gimbal?"
A large flywheel is influenced by the effects of the Earth's precession around the sun. Although the effect is small, I believe it should be taken into account when designing a flywheel. Failing to account for precession will cause stress and fatigue on the flywheel's axles and bearings. See "Foucault's Flywheel" for discussion on this point.
So I propose a gyroscope/flywheel without gimbals. Basically this is a disk that spins inside a spherical housing. The disk is covered in rollers/bearings which allow the disk to freely move within the housing. See illustration.
The disk contains an array of permanent magnets on the its periphery, while the spherical housing has corresponding coils of wire. The coils can act to impart energy into the disk (by applying an electrical current), or the coils can act to tap energy from the disk (by applying a load to the ends of the coil).
The flywheel could be used in buildings to store energy from solar panels, windmills, or mains electricity. The flywheel could be used as a UPS or for living off-the-grid.
Foucault_27s_20Flywheel
[xaviergisz, Aug 13 2009]
Event Horion
http://www.imdb.com/title/tt0119081/
Be warned .... [8th of 7, Aug 13 2009]
(?) Katabatic wind power
Katabatic_20Wind_20Power_20Generation
[bungston, Aug 14 2009]
(?) illustration on SketchUp
http://sketchup.goo...45fc201&prevstart=0
[xaviergisz, Aug 23 2009]
Archived copy of the above-linked "Katabatic Wind Power Generation" idea
https://web.archive...0Power_20Generation
[notexactly, Aug 26 2019]
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I know Foucault about flywheels. |
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I don't think failure of the rollers/bearings would necessarily be catastrophic. If the flywheel was big enough it wouldn't need to spin too fast, so a bearing failure could lead to the flywheel grinding to a halt rather than exploding. |
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I like the idea of a flywheel on casters but when precession causes it to spin horizontally all of the stress and friction will be on the lowest bearings. |
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I think this is much worse than a regular gimball. All of your
bearings are on the fastest-moving part of the flywheel, and
therefore will create the greatest possible drag. |
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OooH! I just noticed that Ubie's back! |
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Isn't your spherical housing simply a gimbal with more frictional contact points? |
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The illustration: Bearings that look like this exist, but they are rated for low speeds only. In your design they would burn up quickly, and in catastrophic fashion. |
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are two bearings (one resting inside the other) more efficient than one bearing? If we add a third bearing, do we gain even more efficiency? What problems arise with plural wear surfaces? discuss. |
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Go watch "Event Horizon" ....... <link> |
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// I just noticed that Ubie's back! // |
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Yeah, like hemorrhoids ...... gr8. |
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Play nicely children, or you'll have to go and sit on the naughty step. |
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There is always going to be some induced magnetic drag on the flywheel from the presence of the coils. Remember the trick where you drop a magnet through a steel tube and it slows? |
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/I envisage it carving an inexorable path of destruction through floor after floor of a highrise, before it exits to the street and takes out a streetful, or two, of rush hour traffic./ |
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If such a flywheel were depicted in a movie that is certainly what would happen. I like the idea of someone making it happen on purpose so that the flywheel might be used as a weapon to slow an advancing army of alien robots. This is akin to my action movie scheme of rejiggering an open MRI facility so that the scanners could be used as coilguns firing steel tanks of chlorine gas. |
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But thinking of civility and the advancement of humankind, UB is right that /gravity and friction finally get the better / of everything. |
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Solution: No rollers, unless this is steampunk Victorian england. Evacuate the sphere. Magnetically levitate the flywheel. Spin would be imparted electromagnetically and energy removed electromagnetically. I think this could be accomplished by making the sphere asymmetrically magnetic. Need I mention that the wheel is actually a sphere itself: more volume, more mass. |
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In the event of failure of the maglev, the ball will roll inside its sphere. The inside of the sphere is itself very low friction and high heat conduction, so the ball will gradually lose its energy without destroying the neighborhood. Maybe failure of the magnets would also cause the sphere to be flooded with water, to facilitate slowing of the ball. |
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These devices would best be installed at the poles to capture and store energy generated by kadabatic windmills, as previously proposed on this site. Aircraft would visit, land atop a sphere and juice up their batteries by tapping the flyball within. |
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The goal of this idea was low-tech power storage. So although bearings/rollers have some frictional losses, they have the advantage of being readily available. |
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My back-of-an-envelope calculations suggest that a concrete ring flywheel with 2 metre diameter (with the centre 1 metre diameter hollow) would weigh 5 tonnes. |
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Spinning at 30 rev/sec (outer edge traveling at 300km/h) it could store 15kWh. Assuming a rolling resistance coefficient of 0.0002 between rollers and sphere and also within the rollers themselves, the flywheel would consume 60W in friction losses @1rev/sec up to 1800W @30rev/sec (OK, that is huge and not really practical). |
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Well, I for one am glad to see Ubie here. Gives this place
more of an international/interspecific feel. |
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Air bearings are going to need a lot of power for something big enough to store useful amounts of energy. And you have the problem that if the airflow fails, the rotor drops against the stator ..... rollerball ! |
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The maglev-sphere-in-sphere idea seems to have the most mileage in it as the levitation system can double up as the power input-extraction mechanism. Why not float the thing in liquid helium ? It's a superfluid (no measurable viscosity) and it would keep superconducting elements nice and cool. |
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I like the idea of using maglev, superfluids and air cushioning, but they all seem too complicated for the intended purpose. |
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I've made an alteration to the idea wherein the flywheel rotates around a central sphere. This would cut down the fiction by an order of magnitude (since the rollers are travelling much slower for a given flywheel speed). This is pretty similar to a regular flywheel on an axle, but would still allow for precession. see additional illustrations. |
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I think this level of energy loss to friction is reasonable. The heat due to friction could be transferred away from the flywheel through the axial support (and the heat could be used to heat a hot water cylinder). |
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//Solar trickle currents are unlikely to provide enough grunt to move it at all// |
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I disagree. It seems fairly simple to convert a current from a solar array into well timed electromagnetic impulses to spin the flywheel. |
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Pun of the month award to [coprocephalous] |
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I have a way to improve the bearing and commutation situations. The flywheel
does not bear on the spherical shell. Instead, it has a conventional rotary
bearing at its center, which connects it to a frame. This frame is what rolls
inside the spherical shell. It only rolls to account for the change in axis of the
flywheel, while the flywheel rotates relative to the frame and shell to store
energy. The frame's edge has wheels that only roll in a direction perpendicular
to the frame's/flywheel's plane, so that the flywheel doesn't drag the frame into
rotation about its axis. Then, coils for adding energy to and removing energy
from the flywheel are mounted in the frame instead of in the shell, eliminating
the difficulty of choosing which coils to use based on the current angle of the
flywheel, as well as the cost of many more coils. |
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