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Method note · measured

The Dunkelflaute spell detector

What it measures

A Dunkelflaute is a spell when wind and solar together nearly stop generating, found by testing how long their combined share of demand stays low.

Inputs

  • ENTSO-E actual generation per production type for the DE-LU bidding zone (Germany and Luxembourg, which share one wholesale price), hourly, grouped into wind and solar
  • ENTSO-E actual load for DE-LU, hourly

Method and weighting

A Dunkelflaute is a spell when Germany's wind and solar generation together nearly disappear, leaving demand to be met from other sources. The detector takes the combined wind and solar generation as a share of electricity demand for every hour, then smooths that share with a rolling mean over the smoothing window stated on the view, so a single sunny spell inside an otherwise low stretch does not split it in two.

A spell is any run of hours where the smoothed share stays under the threshold stated on the view, for at least the minimum length stated there. The view pads the spell it displays by a few hours on each side so the entry and the exit are visible on the chart.

Window

The rolling 12 months to the last complete day, refreshed on the 1st and 15th of each month. The current window runs from to . Data last refreshed on .

Known limits

  • The threshold and the minimum spell length are choices stated on the view; a different pair would count spells differently.
  • The share is of demand, so a day with very little wind or solar and equally low demand can show a share high enough to escape the threshold, leaving a genuine low-renewable day uncounted.

Used on

Sources: ENTSO-E. Each is described on the Data sources page.