Most of us, when we think about storage, think first of batteries, but though batteries may be good for bringing electricity with you, they have not, until recently, been very good for storing power at grid scale. At the moment there is only one battery on our grid: a 22,000-square-foot, 1,300-ton nickel-cadmium battery that was built outside Fairbanks in 2003. This can supply 40 MW of power for about seven minutes, though it is most often used for twice as long at half the power.
this has already changed. as of jan 2017 there were three installations each being worlss largest at install. one was 20MW/80MWH
