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buoyant flywheel

float and spin
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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.

xaviergisz, Mar 01 2016

Skin friction drag https://en.wikipedi.../Skin_friction_drag
[xaviergisz, Mar 01 2016]

Ultracentrifugal satellite launcher Mentioned in my anno [notexactly, Mar 03 2016]

[link]






       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.   

       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.
bungston, Mar 01 2016
  

       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.
8th of 7, Mar 01 2016
  

       /flywheel in freefall and high vacuum/   

       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?   

       One would want some sort of magnetic no touch clutch. I wonder if that exists.
bungston, Mar 01 2016
  

       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.
bungston, Mar 01 2016
  

       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.   

       Hang on a minute....idea!
Ling, Mar 01 2016
  

       Assuming turbulent flow it wouldn't even stay spinning for an hour.   

       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.
xaviergisz, Mar 01 2016
  

       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.   

       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.
bungston, Mar 02 2016
  

       hmmm   

       [bungston], that reminds me of [MB]'s ultracentrifugal satellite launcher idea: [link]
notexactly, Mar 03 2016
  
      
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