How to Store AC Power?

This article describes some indirect AC storage methods. As far as I know AC cannot be stored directly in batteries, but must be converted from DC.

http://en.wikipedia.org/wiki/Grid_energy_storage#Flywheel

Thank you for your guidance

I think, Using LC circuit, Can do it.

1. Rectify; store in batteries or capacitors; invert.

2. Pumped hydro or flywheel storage.

OK. How about a large flywheel with fixed magnets around its circumference? When the magnets pass pick-up coils attached to the stator, AC is taken off the coils' output terminals.

Power for the flywheel could be stored on a mountaintop in the form of snow and guided by a stream, and as a bonus, perhaps loaded with trout, to your location.

You can store AC by spinning up a flywheel, and tapping its momentum with a variable speed transmission driving an alternator at the desired frequency.