Why Dunkelflaute means Britain is heading for an energy supply crunch this weekend

Energy Crisis
Energy Crisis

Thick, heavy clouds and little to no wind are in the forecast for the UK this weekend. The Germans call this type of weather “Dunkelflaute”, which literally means dark wind stillness or lull. Meteorologists prefer the term anticyclonic gloom.

Such weather conditions are hardly unusual this time of year, but they present a problem: the lack of wind means very little renewable energy will be generated from turbines, at the same time as winter ramps up demand for power as the lights come on earlier.

Wind power contributed just over a quarter of the total electricity generated in Britain over the last few months, according to National Grid data, but that will drop to sharply as “Dunkelflaute” hits.

“It’s the first test,” says Tony Jordan from energy consultancy Auxilione. “When there's a lack of wind it puts the rest of the generation under pressure. So we need to turn to other fuels to generate power, mostly gas normally. So it pushes the cost of generation up.”

This weekend will be the first real test of how Britain will navigate squeezed supplies of gas this winter, as the war in Ukraine continues to push up prices.

The National Grid warned on Wednesday that “margins are expected to be tighter this week, particularly for the next few days”. In other words, the gap between supply and demand for electricity will be uncomfortably small.

There will be more pressure on the system than usual, increasing the likelihood that the National Grid Electricity System Operator (ESO) will have to activate emergency plans to avoid blackouts, such as paying people to use less energy or encouraging large industrial users to ease off on demand.

“We're running the electricity system at the moment on much tighter margins than we have in the past,” says Kathryn Porter, an energy consultant for Watt-Logic.

Generation from wind is expected to fall considerably on Friday, Saturday and especially on Sunday before rebounding on Monday. As a result, the National Grid’s expected surplus will drop to 930 megawatts on Friday and 600 MW on Saturday – well below the 1000 MW benchmark typically considered adequate.

Tom Faulkner from Cornwall Insight says that when energy supply is as tight as it is projected to be this weekend, the market will “correct”: as demand for electricity increases, prices rise and draw more power into the market.

Coal plants would also be fired up to generate electricity if markets don’t respond, or ESO may offer consumers money for reducing their electricity use. Rolling blackouts are the “very, very last resort action” it could take.

Faulkner is not worried yet: “The system is probably going to be tested this winter. But at the moment, it's showing good signs of being fairly resilient. We'll have to see what happens in the coming days and weeks. But this cold period over the winter with low sun and low wind will be a test.”

One upside is that demand is typically much lower over the weekends, Porter says. The pressure on the National Grid would be much greater had the low wind days fallen on weekdays.

There will be some challenges, though, from people gathering in pubs and in front of the TV at home on Saturday to watch England play France in the World Cup quarter finals on Saturday.

While overall demand is expected to be lower due to the match as other activities are dropped, demand will spike at half time and full time as millions who are watching the game make a cup of tea or go to the bathroom, triggering millions of kettles and water pumps at the same time.

Experts say consumers are unlikely to notice any immediate difference. Any squeeze will only be felt behind the scenes.

“ESO has long experience of this and has power stations (usually pumped hydro) and batteries on standby to start up at the right moment,” Porter says.

However, the 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.

There have been warnings about the lack of wind and low temperatures resulting in an expensive tug-of-war with mainland Europe to secure imports.

“There's been this huge debate about if we have cold weather in winter in Britain and France at the same time what will happen to the interconnectors,” Porter says, referencing the large undersea cables that trade power back and forth with the continent.

There are fears France could suck electricity from Britain at a time of need if cold weather hits on both sides of the Channel at the same time. However, Porter believes each side would in practice try and look after its own supplies.

“Although there's no formal mechanism that has been made public about what would happen, I think that from various people I've spoken to this appears to be a sort of an unofficial consensus that probably the interconnectors wouldn't flow in either direction,” she says.

Jordan says: “We've had this kind of ease into winter. It was all very much warmer than normal. So everything's been a bit relaxed, but now we're starting to see the colder temperatures and it looks like they're going to stick around for a while.

“Things will get a bit tight. We'll have to see how the network copes.”