Dunkelflaute is German for “dark doldrums”, a period when little or no renewable energy can be generated from wind and solar.
A paper last week in Nature said that renewables developers must stop focusing solely on the resource availability of wind and solar farms. They are missing two parts of what is actually a “trilemma” of competing factors – resource availability, variability, and extremeness.
The authors said that failure to address and plan for dunkelflautes “may threaten efforts to accelerate renewable energy deployment by sapping investor, public or policy support for these technologies.” There is currently too metric to describe these periods.
There is also a need to focus on variability, how stable the resource is, measured by the standard deviation of the capacity factor.
They stress the difference between variability, which can be managed with short-duration battery storage; and resource droughts, which require backup generation and long-duration energy storage to prevent blackouts.
The authors note a “lack of sites that excel in all three quality attributes”.
Very much to the point but the authors miss the effect of distribution. Before solar very few homes and businesses had their own generation and storage. Renewables rely less on central power, on public utilities. What is very much needed is massive energy storage.
The original post was about an academic research paper appearing in Nature. Coincidentally, it can be noted that Germany is currently experiencing dunkelflaute conditions so far this month.
Early November has brought a prolonged period of little wind and sunshine in Germany and many other parts of Europe, bringing down renewable power generation and leading to a spike in electricity prices and the use of fossil fuels. A so-called ‘Dunkelflaute’ (dark doldrums) with minimal output by solar panels and wind turbines is not uncommon at this time of the year and does not pose a risk of blackouts to Germany’s power system, researcher Bruno Burger of institute Fraunhofer ISEtold public broadcaster WDR. “We’ve got sufficient [backup] capacity for this,” Burger said.
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Looking at the electricity generation data for Germany for this month, output from the intermittent renewables (wind, solar) is indeed down compared to November of last year. Output from natural gas and coal-fired power plants is up this month. Also, electricity imports are up significantly in Germany. Since shutting down the nuclear plants, Germany has become a net importer of power, and that trend seems to be increasing. Many of those imports come from France, which has a large nuclear power fleet.
True, but how much less? The majority of people in both developed and developing countries live in large cities. Few of the 11+ million who live in Jakarta, for example, could have distributed power. Also, if you live in a northern latitude country such as Germany, Denmark or the UK renewable power is much more dependent on wind than solar, and wind turbines on one’s house or apartment building don’t seem to be practical.
It’s not just the power you produce but also the power you get from the grid cheap at night (low use) which you sell back at a profit during daytime (high use). You just need batteries for storage.
Britain’s wind power output fell to just above zero on Wednesday, which, combined with the cold, dark weather, caused the market price for electricity to climb to almost £250 per megawatt-hour at auction, or almost seven times the average price before the pandemic. The sudden drop-off in renewable energy due to dull windless winter weather, known as dunkelflaute in German, has also forced the system operator to pay gas power stations more than £500/MWh to run on Wednesday evening when household demand is expected to reach its peak.
The weather conditions – the third dunkelflaute of the winter so far – left Britain’s electricity grid reliant on gas-fired power stations. They accounted for more than 70% of power generation at points on Wednesday…
Akshay Kaul, a director at Ofgem, the energy industry regulator, said: “We’ve seen this winter that when you have a period of still, cold, cloudy weather batteries on their own, and interconnectors on their own, are not sufficient.”
It is remarkable how quickly the argument for fossil fuels in grid electricity is evolving to simply providing an emergency backup.
This is happening even in China.
In China, coal plants are running at 50% capacity with a majority of the large plants losing money in the first half of 2022. It appears that China is shifting coal from providing baseload energy to more of a peaker plant role. China is building more coal plants but might burn less coal
China may well have over-built plants as they have with other construction, but coal consumption has still increased. How does a shift to peaker plants square with continued growth in coal consumption? The IEA projected that Chinese coal use would increase by 1% in 2024, reaching a record of 4.9 billion metric tons. We’ll see what the actual numbers turn out to be.
(On a side note, the IEA expected India to see demand growth of over 5% to reach 1.3 billion metric tons.)
Of the new liscenced plants, Greenpeace notes
“These facilities are quite large. Coal facilities do not nimbly switch on and offline. And large facilities are particularly inefficient coming online in terms of time, money, or total emissions. This somewhat contradicts the stated purpose of using these facilities to support periods of peak energy demand. We are seeing a positive trend in decreasing new approvals. But the new approvals themselves are quite concerning,” Gao said.
Pretty reasonably I think. China has clearly built too many coal plants so a shift of many to peakers makes sense. Xi in 2021 declared that China peak coal would be reached in 2026. Now a lot of folks believe it will be in 2025.
Coal plants running at half capacity and losing money, a plummeting decline in coal plant permits, and accelerating conversion of coal plants to peaker plants are all consistent with coal consumption approaching a peak.
I’ve seen figures where China’s electricity demand in 2024 rose about 5% while coal consumption rose 1%. This suggests that renewables are taking on a larger share of grid electricity production. Renewable energy generation in China continues to grow while most estimates show an easing in electricity demand in the coming years.
Now add the possibility of a slowdown in the China’s economy due to tariffs or other such nonsense and peak coal in 2025 is very plausible. If that is the case, China has to do something with all those coal plants.
Britain faces bidding war with Europe to keep lights on amid wind power slump https://www.telegraph.co.uk/business/2025/01/22/britain-faces-bidding-war-europe-keep-lights-on-power-slump/ The UK is typically able to rely on interconnector cables linking it to France, Belgium, Holland, Denmark and Norway when in need of bolstering energy supplies. However, those countries have also been hit by the same still and gloomy weather in recent weeks, meaning they have less spare power to export…
The UK’s growing reliance on intermittent renewables means low wind conditions offer a prime opportunity for electricity traders to make money. Some, like Geneva-based Vitol, or Germany-based Uniper, own gas-fired power stations, switching them on and off according to the prices offered via Neso.