Diversity in renewables, diversity in their placement (it's unlikely for the wind to be zero everywhere), and stuff like energy storage (which Australia is very successfully experimenting with on moderate scales: https://www.theguardian.com/technology/2019/feb/18/tesla-big...) goes a long way.
Storage, I think, is where our existing grids will need to invest in heavily. I'm thinking "Batman villain with a warehouse full of giant capacitors" storage.
Or, at the very least, a system where excess grid power is used to store gravitational potential energy in a reservoir.
Diversity in renewables, diversity in their placement (it's unlikely for the wind to be zero everywhere), and stuff like energy storage (which Australia is very successfully experimenting with on moderate scales: https://www.theguardian.com/technology/2019/feb/18/tesla-big...) goes a long way.