Hydrogen fuel cells also. Use the excess to make hydrogen which is simple to store and then use it as a fuel to burn when you have demand. These have started to be put at the bottom of wind turbines so they don’t need to be stopped when the wind is blowing but there is no grid demand.

All these systems help balance the grid too meaning these renewables can be used as base loads instead of dirtier base load generators like coal or gas fire stations.