[PSUBS-MAILIST] Flywheel energy storage

[Cliff Redus via Personal_Submersibles]

 I really think there is merit to the concept of using a high speed flywheel system as a replacement for batteries and some of the ballast.  Tim correctly points out issues associated with induced forces and moments on the boat if the flywheel is not gimbaled or if there are not two counterrotating flywheels.   I briefly looked into flywheels before I developed the R300.  One of the interesting issues is how you design for a potentially catastrophic failure where the flywheel comes apart.  Because there is so much kinetic energy that could be released over a fraction of a second if you had a flywheel come apart, a lot of advanced high speed flywheels are made with layered composites that are designed to delaminate  slowly and turn into a big bundle of strands rather than come apart in pieces.  If you like, planned failure.   I ran across an interesting book on flywheels many years ago that discussed the optimum shape of a high speed flywheel.  They used a computer model to predict the perfect shape for maximizing kinetic energy storage  while holding the stress in the flywheel more or less constant  regardless of the radius.  It turns out the shape is no where near what a low speed flywheel looks like which has a lot of mass in the rim and a then web.  Advanced high speed flywheels are thick at the axis of rotation and get thinner as the radius increases.  
For for a flywheel to work, I think you would need to couple with a motor/generator that could be driven with a small IC engine when the boat is on the surface.  
Cliff
    On Sunday, March 21, 2021, 10:30:50 AM CDT, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 I was just envelope sketching a concept design, and I was struck by a thought: would a sub design using flywheel energy storage instead of batteries be feasable? I guess it would depend on design mission duration, and how frequently one could reconnect to shore power to spin it up again, but it occurs to me that if you could achieve the necessary storage capacity (kWh), there are several advantages to mechanical energy storage over chemical in the submarine environment.

Thoughts?

Sean

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