Energy storage at the utility level is now accomplished almost entirely with
the old-fashioned method of pumping water uphill at low electricity demand
times, then letting it spin a turbine when demand is high. But there aren't
too many more places to build new pumped hydroelectric projects – and
integrating intermittent renewable resources like wind and solar power will
require a lot more storage.
While solutions like compressed air energy storage are being promised at
prices approaching those
