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Robert Wilson's picture
University of Strathclyde

Robert Wilson is a PhD Student in Mathematical Ecology at the University of Strathclyde.

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Graph of the Day: German Solar Energy Exports

Here is a rather obvious cycle. Solar power output goes up during the day, and down to zero at night. Remarkably, Germany’s electricity imports and exports now follow an identical cycle. Electricity is exported when the sun comes out and is imported when it goes down. At least during summer. Here is what happened in June this year:



The peak in exports and the peak in solar power is more or less identical. So, when the sun comes up German power prices go down (relative to its neighbours) and it starts exporting power. When it goes down German power prices go up (relatively speaking) and Germany starts importing power again.

You can also see that exports increase significantly when it is very windy on the 2nd June.

This shows just how difficult it is to work with high accuracy how much renewables, or nuclear, reduce emissions. Not only do you need to consider what renewables are displacing within a country, but also what is displaced via exports. And if you want a real mental challenge try estimating how much Danish wind farms reduce emissions. Denmark more or less has two electricity grids, and often imports and exports from and to Sweden and Germany at the same time. And does a MWh from a Danish wind farm that displaces a MWh of Norwegian hydro reduce emissions at all?Energinet

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John Miller's picture
John Miller on Jul 16, 2013

Interesting power supply trends.  I wonder if the variable import/export power balances benefit or penalize the fossil fuels consumption and associated carbon emissions of the neighboring countries tied into their international power grids?

Robert Wilson's picture
Robert Wilson on Jul 16, 2013


That’s a pretty difficult thing to figure out. If you look at daily German fossil fuel output there is evidence of gas and coal ramping down a bit to accomodate solar. But quantifying this overall is far from easy. I’m not aware of any analysis into the issue. It’s also very ambiguous at times where electricity is actually coming from just by looking at the data. German exports to Denmark in particular are tricky. Two IC cables and at times one is exporting to Denmark, and the other is importing. Not easy accounting for this.

Pieter Siegers's picture
Pieter Siegers on Jul 16, 2013

Interesting stuff but not complete; I’d also like to see some graphs comparing all countries within a specific grid, and see how green enegy exported to other countries can lower fossil fuel consumption of that other country. This is likely to happen nowadays, so we need to see the overall net result and if possible something like a before – after picture.

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