dark doldrum

thumb|upright=1.4|A dunkelflaute of three days in Germany 2023 (wind in light blue and solar in yellow) In the renewable energy sector, a dunkelflaute (, , plural dunkelflauten) is a period of time in which little or no energy can be generated with wind and solar power, because there is neither wind nor sunlight. In meteorology, this is known as anticyclonic gloom.

== Meteorology == thumb|A cloudy and foggy January evening in Austria, one hour before sunset Unlike a typical anticyclone, dunkelflauten are associated not with clear skies, but with very dense cloud cover (0.7–0.9), consisting of stratus, stratocumulus, and fog. there is no agreed quantitative definition of dunkelflaute. Li et al. define it as wind and solar both below 20% of capacity during a particular 60-minute period. High albedo of low-level stratocumulus clouds in particularsometimes the cloud base height is just 400 meterscan reduce solar irradiation by half.