When periods without wind happen at night, there is no energy output from wind turbines and solar panels. Despite growing use of renewables, the English language has no single precise technical term for this challenging phenomenon yet. The German term for a period of renewables being becalmed at night is Dunkelflaute and has come to prominence due to the example of Germany’s advanced energiewende programme. Maintaining a steady energy supply requires addressing this problem, usually by developing or refining energy storage methods, so the German term is breezing into English language technical literature.
Dunkel means dark, here as in the darkness of night, and the noun Flaute means both an absence of wind or an absence of demand from purchasers in a market. English translations might best be Dark Interval or Dark Pause, as English struggles to find its own term for the absence of wind, offering such terms as windlessness, becalmed, stillness and so on.