What happens to renewable-energy grids when the sun doesn’t shine and the wind doesn’t blow?
There is, it sometimes seems, a German compound noun for everything.
And so, Dunkelflaute, which can be translated as “dark lull” or “dark doldrums.” This describes a weather pattern during which there is not a lot of sun and not a lot of wind. Meteorologists refer to this state of affairs as anticyclonic gloom, a magnificent term in its own right.
Over to Wikipedia:
In the North of Europe, the Dunkelflaute events originate from a static high-pressure system that causes an extremely weak wind combined with overcast weather with stratus or stratocumulus clouds. There are 2–10 Dunkelflaute events per year. Most of these events occur from October to February; typically 50 to 150 hours per year, a single event usually lasts up to 24 hours.
This report from Quartz suggests that these “events” are somewhat more prolonged than that:
Dunkelflaute events lasting a day or two are fairly common in Europe between November and January, adding up to 50-100 hours on average per month, according to a 2021 study by the Delft University of Technology.
It doesn’t take much imagination to see how shortfalls in wind and sun might be somewhat unhelpful for energy grids that have come to depend on renewables.
And there has been a touch of anticyclonic gloom in northern Europe of late. Turn to the Twitter feed for Britain’s electricity system operator, National Grid ESO (which is, apparently, ”building a clean, green and fair system for tomorrow”), to discover that on Sunday, wind generated 3.8 percent of Britain’s electricity, just ahead of, ahem, coal (3.7 percent), and well below the more than 25 percent it has averaged over the year. Solar chipped in with 0.6 percent. Without natural gas (62.1 percent) to fill in the gap (at a price), life in the U.K. would have been cold and dark.
The gloom is set to lift for now, but is set to return.
[T]he stress on the system will not be short-lived. Forecasts show that the weather is expected to be unseasonably cold until mid-January, which could put prolonged upward pressure on prices and demand.
The Telegraph quotes one energy consultant as saying that “things will get a bit tight. We’ll have to see how the network copes.”
“We’ll have to see” is not perhaps the best advertisement for the energy-supply system that the U.K.’s transition away from carbon is creating.
Meanwhile (from another report in the Daily Telegraph):
France’s electricity network operator requested emergency help from Britain as the cold snap caused demand to surge across Europe.
RTE asked the National Grid if it could halve its scheduled exports through one of its interconnectors to the UK between 8am and 9am this morning as it wrestled with a spike in demand.
A combination of the cold weather, strikes among its nuclear power workers and delayed maintenance on its fleet of reactors prompted the request.
Phil Hewitt, a director at EnAppSys, said: “The French market was particularly under stress today.
“It was always going to be in trouble because of the reduced nuclear reactor fleet, the temperature is low and there has been a big demand spike combined with low wind.”
Looking further ahead, the writer of the Quartz report refers to analysis that shows that once Germany achieves its goal of relying solely on renewables, the gap between supply and demand “during the most extreme dunkelflautes could be about 10 gigawatts. That’s equal to about a dozen typical gas or nuclear plants.”
Germany, of course, has been phasing out its nuclear plants.