In athe 60s when fusion was predicted to be the energy source of the future it was believed that when power demands were minimal during the night that the excess capacity would be used to hydrolize water and the Hydrogen Age would be born. Fusion never happened but hydrolizing water might be one way to "store" excess wind energy. A power plant in Michigan, (I think), uses a similar technique to store energy. Its battery is a lake on top of a mountain. At night water is pumped up the hill. During the day the water flows down the hill. The motor generators that pumped the water, (mechanical energy creating potential energy) become the generators when the water flows down the hill pass them. Yes there are system losses but the vast majority of energy is harvested.
Since variable energy sources might be a problem then overbuild the system so that expected base load production is always available. In 1991 the Scientific American measured the wind resources of the US and stated that North and South Dakota could produce 17% of US's electricity. In 1996 this estimate in Scientific American was increased to 78%. Why the increase. The room temperature superconducting technology had matured to the point where motor generators hwere much more efficient. That's the same technology which has improved memory storage devices. In 1990 if your hard drive stored 50Mb you were with it. Now a 100 Gig hard drive is passe! Go figure.