You might find AA-CAES (Advanced Abiabatic Compressed Air Energy Storage) interesting. ColdFusion talks about it in the video I just shared (Solar Power Plants | The Next Big Thing?) at 3:30.
Geeky people who study things like red-shift found that the stretching of the very fabric of the universe is accelerating. When you stretch something like a rubber band or the fabric space time you store energy.
http://www.calphysics.org/zpe.html "Zero-point energy is the energy that remains when all other energy is removed from a system. This behaviour is demonstrated by, for example, liquid helium. As the temperature is lowered to absolute zero, helium remains a liquid, rather than freezing to a solid, owing to the irremovable zero-point energy of its atomic motions. (Increasing the pressure to 25 atmospheres will cause helium to freeze.)" So Helium does more then make people talk like Daffy Duck! Who'd a thunk it??
I didn’t look at the vid, not enough time. But I have read of storing energy in old oil wells using compressed air. Also compressed air stored in bladders under water.