Dunkelflauten in Germany: Climatology and Relation to Weather Regimes

It is scientific consensus that the Paris Agreement (COP21) can only be achieved by drastically reducing the emissions of anthropogenic greenhouse gases, in particular those related to burning fossil energy sources. Succesfully providing the required energy with renewable energy sources, such as wind and solar power, is dependant on the weather conditions. Dunkelflauten, periods during which only little energy is available by wind and solar power, can put strain on the energy system based on high shares of variable renewables. Particularly, cold Dunkelflauten with coinciding low renewable energy generation and high heat demand are critical. To mitigate the risk of such critical conditions, energy storage systems are an important component in the future energy system. The appropriate dimensioning of energy storage requires knowledge about the typical duration and frequency of Dunkelflauten.

This study presents a climatological analysis of Dunkelflauten that would have occurred in Germany from 1979 until 2018, with the assumption of a 100% renewable energy scenario. On average four Dunkelflauten are detected per year, with durations of up to nine days. To forecast the chances of a Dunkelflauten event several weeks ahead of time, it is helpful to unveil the long-lasting weather conditions, called weather regimes, during which Dunkelflauten occur. We show that Dunkelflauten are more likely to occur during blocked regimes than during cyclonic regimes. The particularly critical cold Dunkelflaute occurs predominantly during the Greenland blocking. Accordingly, accurate predictions of weather regimes are key to manage energy storage systems and to eventually avoid temporary shortages in energy supply.