There are a variety of applications which could scale their demand up and down pretty quickly based upon fluctuating supply, especially of there was an efficient means by which the devices could vary their "priority" and be billed different amounts for electricity that they used when the grid was super-saturated with supply, versus electricity that they used when the grid did not have such an excess (which should be more expensive). For example, if the water level in a tank is supposed to remain within a certain range (e.g. 50%-100% full), cheap electricity could be used to pump water even when it's near the top of its range, while more expensive electricity would only be used if it's near the bottom. If a burst of cheap electricity becomes available when the tank is 80% full, topping it off would increase by 20% the amount of water that could be removed before it would be necessary to use expensive electricity (and if bursts of cheap electricity become available often enough, it may seldom be necessary to use the expensive electricity at all).
Show me ONE such storage facility for power using pumps, tanks, and generators. You can't. It doesn't make economic sense. That's why MILLIONS of dollars of infrastructure has been built to do peak demand management.
There's a world of difference between what is feasible from an engineering or physics perspective, and what is feasible economically.