I've been enthusiastic about flywheels for a long time. With magnetic
bearings, in an evacuated chamber, you are right, losses are
negligible. Of course, there are inefficiencies at input and output,
but much less than for any other storage system. As you say, initial
cost is high.
My only worry would be in an earthquake-prone area. Damage could have
horrendous effects.
:)
Bob

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Dr Bob Rich
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