Ars Technica, By John Timmer, 18 July 2017
Renewable power sources’ intermittency could eventually cause problems as our electric grids become increasingly reliant on them. While it’s always sunny somewhere, and always windy somewhere (often somewhere else), relying on weather variations for generating consistent power means integrating power sources across a large geographic region. Many countries, including several leaders in renewable power, don’t have that luxury.
A Swiss-UK research team has now looked at what this means for Europe, where renewable energy has boomed primarily among countries with access to the wind resources of the North Sea. They’ve found that certain weather patterns leave the North Sea region underproducing for over a week. But those same patterns would boost production relatively nearby—in the Balkans, Spain, and Scandinavia. While that would be enough to offset the North Sea’s power slump, it won’t do much to help until Europe integrates its grids.
The authors focus on what they call “weather regimes,” periods of similar weather that tend to stick around for five days or more. Most weather services recognize a handful of distinct European regimes, like having a low-pressure system parked south of Iceland, or high pressure just to the west of Ireland. The authors consider seven of these, nearly twice as many as most weather services recognize, because the relatively subtle differences among them can make a big difference to wind power generation.
The wind speeds and cloud cover generated by these weather regimes were then plugged into a model that tracks the aggregate capacity of wind and solar in each country in Europe. With current installations, the different weather regimes could mean a production of anywhere from 22 to 44 gigawatts in Europe. In the North Sea alone, production could range from half its mean value when the weather’s bad, up to 1.5 times the mean when the weather locks high winds in place.
Plans are also in place to boost renewables to cover 25 percent of Europe’s electricity needs by 2030, which would exacerbate the problem. Right now, the difference between high- and low-production regimes is 22GW; the authors estimate that in 2030, the difference would be over 50GW.
Since it’s always windy somewhere, the researchers decided to figure out where that somewhere is. And it turns out there were several options. One of them is northern Scandinavia, where wind production went up under any of the weather regimes under consideration (presumably, it’s lower during more variable weather). Another is the western Mediterranean near Spain, where production varied among the seven regimes with no clear pattern.
But the key potential is in southeast Europe—the Balkans. Here, the activity was nearly a mirror image of that in the North Sea, meaning when it was calm there, the Balkans would produce 1.5 times the typical amount of wind power.
Renewing the grid
There are two small problems with this finding. One is that northern Scandinavia and the Balkans have almost no wind generation installed at the moment. And, even if there were, you’d run into issue two: there’s not much transmission capacity between there and the countries that border the North Sea.
Still, since the authors had a model, they decided to see what would happen if Europe installed the transmission lines and built their future wind power outside the North Sea region. With the right installation plan, by 2030, the mean generation would be similar to what you would get out of continued development in the North Sea area: a mean of a bit over 75GW of power. But, instead of varying by as much as 25GW above or below that, the variability dropped to a third of that (±8GW). The minimum amount of renewable power produced would also be shifted upward, allowing renewables to be managed more like a source of baseline power.
While the report mostly focused on wind, there’s some good and bad news for solar. In many locations, solar and wind are anti-correlated, meaning when one’s low, the other tends to produce more. That’s the case for Europe, where you tend to get more solar power when wind speeds are low. But solar is also far less variable than wind, and there’s a lot less of it right now. As a result, for solar to balance out the variability of wind, European countries would have to install ten times the existing capacity.
The authors consider that level of expansion unlikely, which is why most of the analysis is focused on wind. Of course, getting wind to help balance out the grid in Europe would require a significant expansion of the transmission capacity from Scandinavia and the Balkans.
It would also require a different approach to planning. Right now, economic forces and national priorities are dictating that most new installations are going into the North Sea, because that’s where the best wind resources are. Installations in the areas identified by this study have value not because they produce as much power, but simply because they produce power when the North Sea region goes quiet. At the moment, there’s no obvious way to make wind installations in other countries a national priority for places like the UK and Germany and little market inducement to install hardware where it would produce less overall.