Belgium benefits “extra” from surplus German solar and wind

Central in the tweet of our Minister of Energy (see previous post) is the role of Germany in the event of July 29, when Belgian offshore windmills were shut down: (translated from Dutch, my emphasis)

Due to a lot of German wind & sun + imports, Belgium has the lowest prices.
Due to negative prices, a lack of flexibility and storage, offshore wind is currently being shut down.
100% renewable via flex & storage. Look to the future, instead of recipes from the past. 1/5

Followed by (translated from Dutch, my emphasis):

Production in Germany: 24 GW wind and 16 GW solar. Belgium benefits extra thanks to its import capacity, flow-based (flow factor competition) and the minram70%. 2/5

As I understand it, (forecast of) surplus electricity by solar and wind from Germany kept Belgian (day-ahead) prices low and Belgium benefited extra from this surplus electricity on July 29 because of its import capacity. I can understand the statement that this day-ahead price combined with a lack of flexible power sources and storage can lead to wind mills being shut down. I however find it highly unlikely that we benefited extra from import of German electricity.

The Minister of Energy provides this chart to support her claim:

Germany export on 20210729 from midnight until 9 am

Without a legend it is rather difficult to interpret that graph. It seems to be the share of the different German power sources from midnight until 9 AM and the negative numbers are export data. When I compare this with the import/export balance from Agorameter, Germany indeed exported electricity between midnight and 9 AM. The maximum value was 3,000 MW and there was no export (and even a slight import) somewhere between 6 AM and 7 AM. That seems to be a match.

So, what our Minister is showing here is the total import/export balance of Germany on July 29 from midnight until 9:00 AM, meaning that the chart stops where the actual solar and wind surge starts. This chart therefor shows that Germany was exporting electricity to (some of) its neighbors until 9 PM. It however doesn’t show what happened during the actual surge of solar and wind, nor that Belgium was the beneficiary of that flow and to what extent.

Time to have a look at the import/export balance of the Belgium-Germany flow on July 29 (my annotations in blue):

Belgium: electricity import from Germany on 20210729


During most of the day, the import/export balance with Germany was heavily skewed towards export. Belgium didn’t import electricity from Germany until 8 PM, well after the surge of solar and wind production in Germany. Then what is that all about benefiting extra from this surplus when import from Germany started almost 7 hours after she send her tweet, lasting only for a short period and the imported amount was rather insignificant?

We see the same trend at the other borders: Belgium was mostly exporting electricity to the Netherlands, Great-Britain and France. There was however some electricity import from France between 2 AM – 5 AM and around 10 PM, but also just a tiny amount.

Basically, Belgium was most of the time exporting its electricity on July 29, therefor not benefiting from that surplus German electricity from solar and wind. But then, why was Belgium mostly exporting at that time in the first place?

That is pretty simple to explain. Belgium is a neighbor country of Germany, so if it is sunny and windy in Germany, chances are that it is sunny and windy in Belgium too. We also are more and more relying on solar and wind power, so if Germany has an surplus of electricity from solar and wind, most likely Belgium will have a high production too.

First, July is midsummer in Belgium, so electricity production from solar/PV did excellent on July 29. It was forecast to have the highest value of the week and in reality it even exceeded that (the orange curve going higher than the gray curve):

Belgium: (forecast of) solar power on 20210729

Solar had an daily average capacity factor of 21% on July 29, that is roughly double the yearly average.

Second, there was also a fair amount of electricity from wind:

Belgium: (forecast of) wind on 20210729

The curtailment of wind power, that has been lamented on in the tweet, is clearly visible (divergence of the orange curve from the gray curve). Wind still had a daily average capacity factor of 54%, that is roughly triple the yearly average.

Third, demand was rather low. That is to expected, there is less economic activity during a vacation period. The day-ahead forecast for July 29 was that it would be among the days with the highest demand in the week, but actual demand (orange line) shows it was the lowest of the weekdays:

Belgium: (forecast of) total load on 20210729

This means that there was a lot of solar power (even more than forecast), a lot of wind power (as forecast) while having a low demand (even lower than forecast). The dispatchable power plants couldn’t go out of the way (this part of the Minister’s argument is correct), leading to export of the surplus. In fact copying the intermittent power strategy of guide country Germany. Three countries (Belgium, Germany and the Netherlands) are betting on solar and wind, so had the same problem (abundant electricity from solar and wind) at the same time. No wonder that the prices got so low. Belgium additionally has the problem of a nuclear power fleet that is more difficult to modulate (again, this part of her argument is correct).

Concluding, there was no need for import of electricity from Germany when it had a surplus of solar and wind power on July 29. Belgium was producing way too much electricity itself at that time and had to export surplus electricity during most of the day. I therefor think that it is pretty unlikely that Belgium benefited much (if anything) from Germany’s surplus solar and wind power on July 29, whatever the Belgian import capacity might be.

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