Changes in Simultaneous Low-Wind and Low-Solar Events (Dunkelflauten) under Global Warming: A High-Resolution Simulation Study for Germany

The usage of renewable energies is essential for achieving climate neutrality, as outlined in the Paris Agreement and the European Green Deal's target of net-zero emissions by 2050. However, the electricity grid faces significant challenges due to the temporal variability and uneven spatial distribution of renewable energy production. Periods of particularly high or low generation present problems for grid operators. So-called “Dunkelflauten”, periods of little sunshine and low wind speeds, result in a low power supply. These fluctuations emphasise the importance of examining how climate change itself may affect renewable energy sources. Understanding such impacts is crucial for developing effective adaptation strategies. This study investigates changes in the frequency and duration of Dunkelflauten in Germany under climate change by utilising the CMIP6-based high-resolution NUKLEUS ensemble. Unlike previous studies, we do not consider specific installations in order to focus on the change across the entire country. We evaluate changes in wind and photovoltaic capacity factors under 2 K and 3 K global warming scenarios, using two representative wind turbines to illustrate sensitivity to technical specifications. The results show a moderate decline in average wind speed, particularly in northern Germany, which results in a lower wind capacity factor. In contrast, only minimal changes in the photovoltaic capacity factor are projected. Consequently, we conclude that the frequency of Dunkelflauten will increase slightly in the context of a stronger climate change signal. This work highlights the value of high-resolution climate model ensembles for assessing the resilience of renewable energies sources under climate change.