Previous post detailed the Dunkelflautes in Germany during the period 1 November 2024 until 28 March 2025. Belgium being a neighbor country of Germany and having the same energy strategy (increasing solar and wind while decreasing dispatchable electricity sources) will most likely going through similar periods of Dunkelflautes.
Let’s just compare both countries in the same period with the same methodology (Dunkelflaute = period in which total daily production of solar and wind is less than 10% of its installed capacity).
This is the graph depicting the Belgian electricity production of solar and wind compared to the 10% threshold in the same period:
There is some similarity with the graph of the situation in Germany from previous post. This is the comparison of both below each other with roughly the same height (attention: the volumes are vastly different in both countries, Germany has roughly ten times more production – this graph is just meant to compare the frequency of days with a low production in both countries):
The appearance of both graphs is rather similar. The share of solar in electricity production is pretty small from November through January and picks up speed starting at the end of January.
Those graphs are maybe not that clear when it comes to the Dunkelflaute periods and how much these overlap. Let now just focus on the length of the Dunkelflaute periods and compare both:
Although there are some differences, the general direction is the same for both and the figures are in the same ball park. The average capacity factor of solar and wind in this period is roughly the same (12.2% vs 11.8%) as well as the maximum number of consecutive days (15 vs 14). The total number of days of Dunkelflaute in the period is however somewhat higher (67 vs 59).
The differences might depend (at least partly) on the share of solar and wind in the mix. Belgium has a larger share of solar relative to Germany, so when the sun is the biggest contributor to the Dunkelflaute, then Belgium will be more affected than Germany.
That reminded me of a statement made at the end of 2022 by our then Minister of Energy, claiming that Dunkelflautes only last for a few hours and can be solved with battery storage. However, in this case there were several periods with a total daily solar and wind production of less than 10% of its installed capacity, one of them even lasted for two weeks. I doubt that these Dunkelflaute periods could be solved with battery storage. Not even close.
via Trust, yet verify
April 30, 2025 at 02:45PM
Iowa Climate Science Education 