There is, ironically, one technology that might allow wind power to work without backup fossil fuel generation, but it's one that the greens killed years ago: pumped storage. Way back when, it was planned as a way to reduce the need for peaking generation and to allow hard-to-adjust nuclear plants to provide more of the power need. Now it would be used for the opposite purpose: to ride out irregularities in power production.
Imagine giant concrete tanks offshore near wind farms, capable of maintaining billions of gallons of seawater with heads of 100 feet or more. With multiple tanks, it would even be possible to use tidal effects to good purpose, pumping at high tide and releasing at low tide.