Above is a flywheel energy storage used for electrical peak demand. 

The Energy Storage Industry Is Exploding

DYI:  Energy storage is not a cure all for our future energy needs; however, it is an excellent stretched out for our diminishing hydrocarbons.  Unfortunately the article does not go into the many forms of energy storage that is fascinating all by itself simply stating the amount of dollars many countries are spending on these technologies.  If you want more simply google up energy storage devices the articles are almost endless.

DYI