I came across this interesting graph presented in a tweet by Martien Visser:
It shows the comparison between the average daily production of electricity produced by solar and the average daily electricity export of the Netherlands over a one year period. Basically, each hour on the x-axis of the graph is the average of the values of that hour of every day of the year. For example, the value for 1 pm in the graph is the average of all values on 1 pm of every day of that one year period.
Looking at the graph, it is clear that the averaged export of electricity seems to follow the averaged solar electricity production for most of the day, except in the last six hours when export levels off instead of declining further.
The graph is an illustration of the relationship between export and solar production in the Netherlands. This is how the tweet explains it (translated from Dutch):
Over the past 12 months, the Netherlands has (indirectly) exported approximately 25% of its total (!) solar PV yield.
#graphoftheday
This export continues to count as renewable for the Netherlands. The subsidies (SDE) and network costs for this exported solar PV are also for the account of the Netherlands.
Exporting 25% of the solar electricity production, that seems quite a lot.
It reminds me of a post that I made eight years ago when I was looking into the claim that the electricity produced by lignite is the cause of Germany’s increased electricity exports. To figure this out, I compared German electricity exports with production of electricity by lignite, by solar and by solar plus wind. The electricity produced by lignite didn’t match electricity exports at all, the production of solar power matched way better, but it was the production of solar plus wind that matched electricity export best. I only used one week of data back then, but the amount of electricity being exported during that week was significant, maybe also somewhere in the neighborhood of 25% of the solar plus wind yield.
That made me wonder how this would play out in Belgium? Would there be the same correlation of electricity exports with solar here? Or with both solar and wind as I found in the post from eight years ago?
Time to look into the data. All relevant data can be found on the Elia website (import/export balance, solar and wind).
I first started re-creating the graph of the Netherlands. This is the Belgian average daily import/export balance compared to the average daily solar production in the year 2023 (quarter hour interval, so a higher resolution than the graph of the Netherlands):
The average daily import/export balance also follows solar production, but not as pronounced as in the graph of the Netherlands. There are however not that many times during which the balance switches to export. The import/export balance only slightly switches to export roughly between noon and 3 pm (which coincides with the highest production of electricity by solar).
Also here, there are the slightly elevated values during the last six hours of the day, similar to what I saw in the graph of the Netherlands. Based on my previous experiences, I assumed that it might be the effect of wind, so let’s look at the wind data. This is what wind did over the same period:
The averaged wind values are pretty stable over the day. There is on average slightly less wind around noon and slightly more in the evening.
Let’s now compare the import/export balance with the sum of solar and wind electricity production:
That seems a better match than solar alone. Electricity production by solar and wind is on average lowest in the night/early morning, then picks up towards early afternoon, after which it gradually decreasing but staying slightly elevated during the evening. That is similar to what the import/export balance does, confirming my earlier findings that export is related to the sum of solar and wind production, rather than solar alone. My guess is that when the graph of the Netherlands would also include wind, that it would be an even better match.
Why such a difference between the Netherlands (25% solar exported) and Belgium (less than 2% solar exported)? I guess it is a combination of several factors. For example, the Netherlands has a higher share of renewables than Belgium and it also has relatively more solar in the mix. This means that the solar/export connection will be more pronounced in the Netherlands. Also, Belgium has an aging grid infrastructure and current policies favor import more than domestic (dispatchable) production. Therefore, more solar and wind production in Belgium on average seem to translate into less reliance on import rather than more export.
The reason why the Netherlands, but also Germany and, to a lesser extent, Belgium export more when it is sunny and/or windy has I think to do with (a lack of) balancing capacity. The larger the share of intermittent power sources without the ability to balance that power, the more electricity needs to get rid of during times of plenty of sun and/or wind. Exporting it abroad apparently seem to be cheaper than building the necessary balancing capacity to actually deal with the intermittency.
via Trust, yet verify
August 31, 2024 at 01:53PM
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