Has anyone tried storing energy in the form of compressed air ? Them danged air tools work awful hard, last forever, put out like 250 lbs of torque, and have very high rpm rates. Wouldn't be too hard to hook an air tool up to an alternator/generator and power away. Been thinking 'bout slapping together some ferro concrete air storage tanks, fill them from an air compressor running part time on surplus produced power. How much air could the tanks hold ? At what psi ? Before they blew up, and shot across the valley leaving tank sized holes in all asunder ? I dunno, depends on the depends....... Just 'bout anything would be better then wanking around with a bunch of batteries.