What is a Dunkelflaute?
Dunkelflaute (German: "dark doldrums") describes extended periods when both wind and solar generation are very low — typically during cold, cloudy, windless winter days. During these events, renewable energy cannot meet electricity demand, requiring backup power from fossil plants, imports, or stored energy.
Learn more...
The model uses real generation and load data from the ENTSO-E Transparency Platform and runs a PyPSA power system optimization. Dunkelflaute hours = hours where backup fossil plants must run even after all battery, import, and V2G capacity is exhausted.
Hours vs. days: Batteries and EVs bridge short gaps well. But a 30 GWh V2G fleet covers ~25% of a 24-hour deficit and only ~8% of a 72-hour event. Multi-day events need interconnectors, dispatchable generation, and long-duration storage.
Did you know? In 2025, new BEVs added ~35 GWh of battery capacity to Germany's roads — 5× more than all new stationary grid batteries combined (6.6 GWh).