h a l f b a k e r yMy hatstand runneth over
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Flywheels are a great way to store energy; unlike
most other large scale energy storage systems,
energy can be stored/retrieved at any
quantity/rate, and with unlimited
recharge/discharge cycling. This makes them
perfect for providing an energy buffer to
electrical networks. But flywheels
have a
problem: their capacity is limited by the
bearings.
Rolling bearings have weight and speed
limitations. Because the friction is proportional
to weight, increase in weight of flywheel suffers
from an increase in friction.
Magnetic bearings and air bearings are being
investigated, but these have their own
limitations: It is difficult to make permanent
magnetic bearings stable over a range of
velocities, while electromagnetic bearing and air
bearings consume significant amount of energy.
So I propose a flywheel that is supported by its
buoyancy. In this way no energy is being
expended to support the weight of the flywheel.
Of course there are still other energy losses (e.g.
drag and constraining lateral movement) that
will partially (and perhaps completely) offset the
advantages.
For example, consider a torus made of PVC
with a wall 1cm thick filled with helium, having a
cross section diameter if 5 meters, and main
diameter of 100 meters. This would float in
slightly bigger chamber filled with sulphur
hexafluoride (SF6). Spinning just below the
speed of sound in SF6, this would store about
1MWh. Not sure how to calculate drag loss.
Alternatively the flywheel ring could instead
float in a low viscosity slippery liquid.
Skin friction drag
https://en.wikipedi.../Skin_friction_drag
[xaviergisz, Mar 01 2016]
Ultracentrifugal satellite launcher
Mentioned in my anno [notexactly, Mar 03 2016]
Hydrodynamic bearing demo by Steve Mould
https://youtube.com...si=-t5VXw3ZFLE6yy18
[xaviergisz, Jan 20 2024]
[link]
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I like it. Drag is going to be the main reason for loss. I am so hopeful there will be some math bandied about as regards what medium would be best and how to prove that is the case. |
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Just looking at viscosities of standard gases, hydrogen is lowest. A problem using puny little molecules as the medium is that it will be hard to get the flywheel buoyant and also have enough mass to store energy without wheel-sundering velocities. But those big molecules get gooey and draggy. |
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Why not just put the flywheel in freefall and high vacuum ? Three discs, one twice the mass of the other two that are contratotating, thus cancelling the gyroscope effect. |
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/flywheel in freefall and high vacuum/ |
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Imagine an orbiting flywheel as suggested. If the engine is in the big one can it push against the little ones and spin them both? |
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One would want some sort of magnetic no touch clutch. I wonder if that exists. |
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Pondering scifi uses for this scheme: one would use the entire habitat as the flywheel, tapping rotational energy to do various tasks. This results in gravitational fluctuation for the inhabitants. I can imagine that during the crisis, standard industrial uses for the energy are incapacitated with the result that gravity gets stronger and stronger as the habitat speeds up. Then all the pent up energy needs to be expended in something spectacular. |
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I think that liquid Helium might be friction-free. There might
be a slight power loss in the cooling system, but I'm
prepared to ignore that. |
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Hang on a minute....idea! |
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Assuming turbulent flow it wouldn't even stay spinning for an hour. |
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Assuming laminar flow I get a loss of 8% per hour, i.e. it would go from maximum speed to resting after about 13 hours. Not great but not entirely useless either. |
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I am thinking of swimming in the N-prize McDuck moneybin, and an enormous flywheel balloon at high altitude. It spins up to speed then expends the accumulated energy in a mighty heave, propelling its satellite into orbit. |
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I worry thought that the structural integrity of a balloon will not allow energy to be expended in a mighty heave. It might be amenable only to slow acceleration and then deceleration. |
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[bungston], that reminds me of [MB]'s ultracentrifugal
satellite launcher idea: [link] |
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//flywheel in freefall and high vacuum// |
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Wouldn't you need a stator to extract electrical power from it? In freefall and high vacuum, how would the stator stand? |
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If the buoyant 100m torus was floating in a special medium that was slippery, but then gas was injected between the torus and the medium, like the bubbles that allow superfast torpedos to avoid drag from the water, could you spin this thing up enough for long enough to get the benefit? Maybe a texture on the torus could act as a generator of the friction-free layer you would need for a floating flywheel. |
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Could the power be extracted from the fluid directly? If so you could ‘charge’ this apparatus the same way. |
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Spinning at just below the speed of sound in thick gas, I'm pretty sure the losses due to drag will be prohibitive. And both gases mentioned can't be cheap, so there's a large capital cost. |
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And I think liquid bearings are already a thing. |
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