Word of the day:
In German, the term Dunkelflaute is used to describe the predicament. Dunkel means “dark”; solar is simply not available half the time, and solar power production is significant for only around six hours a day even when the sun is shining. Flaute is “doldrums” – when the wind is not blowing. So the “dark doldrums” are times when solar and wind power is not available in sufficient amounts.
This chart is just wind+solar for March in Germany. Red lines are periods less than 5GW.