‘Dunkelflaute’ sends wind power generation plummeting in UK and Germany

Meteorological phenomenon is highlighting the difficulties of transition to renewable energy

A “Dunkelflaute” period of weather has sent wind power generation tumbling in the UK, Germany and other parts of northern Europe.

The phenomenon – which translates roughly as “dark wind lull” – describes periods when wind speeds plunge, leading to little to no generation from turbines.

On Tuesday, it meant wind farms were only able to meet 3-4pc of the UK’s electricity demand during the morning and evening peaks, with gas-fired plants instead fired up to meet around 60pc of demand.

The remainder was met by nuclear and biomass power plants, along with solar farms and imports via interconnectors, according to grid transparency data.

A similar phenomenon was seen in Germany, where low wind speeds left the country’s wind farms generating barely 7pc of their nameplate capacity.

There, grid operators had warmed up coal-fired power plants to meet 30pc of the morning’s demand, with another 18pc coming from gas and 12pc coming from solar farms.

Wind is created when two masses of air have a difference in pressure, which is in turn caused by differences in temperature.

Dunkelflautes are caused by static, high-pressure systems that cause weaker-than-normal winds in the areas they cover, along with cloudy weather.

Andrea Bishop, a spokesman for the Met Office, said: “At the moment, we have high pressure dominating the weather and this is helping to keep the wind quite gentle.

“This high pressure is centred to the east of the UK. Furthest away from the high pressure across Northern Ireland and western Scotland, there is slightly more of a southerly breeze blowing.”

Complete drops in wind generation are extremely rare, but sharp declines in output are a well-known issue and one of the central problems grid planners are grappling with as they switch over to weather-dependent renewables.

The scale of the challenge in Britain was laid bare on Monday when the National Energy System Operator (Neso) published a report setting out “pathways” to the Government’s target of reaching clean power by 2030.

It warned that a “Herculean effort” was required, including a doubling of onshore wind capacity, a tripling of offshore wind and a quadrupling of solar power – all in the next five years.

This is to ensure renewables are built to such an extent that there is always enough residual capacity, even on low-wind or darker days.

On top of this, Neso said wind and solar farms would need to be bolstered by nuclear power plants, a huge amount of battery storage and large amounts of system “flexibility” provided by consumers by shifting their electricity use to different times.

The goal also cannot be achieved unless the planning system is rewritten and thousands of extra miles of cables and pylons are built to connect everything together, the report said.

Gas would still be used to back the system up, Neso said, but would provide less than 5pc of capacity.

On Tuesday, Chris Stark, head of the Government’s “mission control” for clean power, said a “clear priority” that had emerged from the report was “the need for more energy storage”.

“Gas, in effect, provides most of our ‘backup’ service today, but we want to replace it with something low-carbon,” he wrote on the social network X.

“Even small amounts of low-carbon flex can displace a lot of gas. We’ll also need to support the build of a lot of new renewable generation – of all types, but especially offshore wind.”