Long but interesting read, with actual numbers and math: http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-storage/ http://physics.ucsd.edu/do-the-math/20

Long but interesting read, with actual numbers and math: http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-storage/ http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-stor...