Assessing ‘Dunkelflaute’ as an extraordinary weather event for the energy sector in Germany using precise power plant data

Achieving Germany's national climate targets requires efforts to reduce emissions in all sectors. The German Ministry for Digital and Transport (BMDV) established the ‘Network of Experts’ (BMDV-Expertennetzwerk), a network of German government agencies focused on the future-oriented transformation of transport in Germany. The focus of the topic area “Renewable energies” is the assessment of renewable energy potential along the transportation infrastructure. In this topic area, Germany’s national meteorological service DWD (Deutscher Wetterdienst), the Federal Highway and Transport Research Institute (BASt) and the German Centre for Rail Traffic Research at the Federal Railway Authority (DZSF/EBA) work closely together.

The transport infrastructure offers significant potential for renewable energy production. To optimize energy management, it is crucial to analyze the variability of renewable energy in Germany. Earlier studies of DWD showed that solar radiation and wind speed complement each other well throughout the year, but extraordinary weather events can strain the energy system. An example is the so-called “Dunkelflaute”, a period of very low wind and solar energy production. Specific weather patterns can cause regional conditions of minimal wind and low solar radiation. Key factors when defining a Dunkelflaute are the renewable energy production, demand, the area of interest, duration and critical thresholds of the capacity factors.

The new analysis is based on capacity factors for wind and solar energy. Solar radiation is obtained from the SARAH-3 satellite dataset from CM SAF, as it provides high temporal and spatial resolution. Additionally, the 10 m wind speed and the 2 m temperature from the new regional reanalysis COSMO-R6G2, the follow-up product of DWD’s COSMO-REA6, are used to estimate the temperature-dependent efficiency of the PV modules. For the wind capacity factors, wind speeds near hub-height are required and are taken from COSMO-R6G2 as well as from the other new reanalysis ICON-DREAM.

Unlike previous studies of DWD, this analysis incorporates precise power plant location data from the German ‘Marktstammdatenregister’ to derive energy production values from the capacity factors. This allows for assessing the frequency and timing of low solar and wind energy production and estimating the occurrence of Dunkelflauten. Additionally, other extraordinary weather events for the energy sector are collected.