“Dark doldrums” – a real threat or just a political bogeyman? Carsten Pfeiffer, Head of Strategy & Politics at bne, explains why supply gaps are nothing to worry about.
He tells us how “dark doldrums” can be bridged and why the energy transition is actually making our energy supply cheaper and more resistant.
Mr. Pfeiffer, you are the Head of Politics & Strategy at the German Association of Energy Market Innovators (bne): Why are you and the bne working so hard on figuring out how we can make it through “dark doldrums”?
Because “dark doldrums” have become the favorite bogeyman of energy transition sceptics who stir up fears of a blackout and make up absurd examples of how much it would cost to completely depend on a battery for two weeks. Their goal is clear: sow doubt and undermine trust in renewables and the energy transition. Of course, no one has to worry about supply gaps.
As an association, our task is to fight back with an honest, straightforward explanation: “Dark doldrums” represent a natural and expected weather variability, and they can be managed using available technologies when all parts of the energy system are taken into account. To explain how this is done, we have published the website Sicher durch die dunkelflaute. And for the same reason, The smarter E Europe will display the special exhibit Renewables 24/7.
Are you saying that this phenomenon is already well-known, it is not a new threat?
Exactly, and we are actually reducing risks overall. There have always been “dark doldrums”, long before the energy transition was ever mentioned. Barely anyone took interest in them before because the system was based on continuously burning fossil energy carriers. The actual concern was – and this is still true to a certain extent today – an energy supply that depends on only these fuels. Just think about the 1980s oil crisis or current geopolitical conflicts like in Ukraine or the blockade of oil and LNG tankers in the Strait of Hormuz.
Today we are intentionally reshaping the system because we want to protect the climate, but also because renewable energy is the cheapest and safest power source. It is important to stress that we already have the technology needed to overcome the challenge: storage, further flexibility options as well as motors and turbines. The latter are still predominantly powered by coal and natural gas. Over time, this will shift to green fuels.
To get more specific, when both wind and solar systems are not generating much electricity, what happens within the system?
This is where the importance of system-wide coordination becomes clearly evident. For large parts of the year, wind and solar sustain the supply directly, and sometimes we even produce more electricity than we need. This surplus energy can be stored in batteries or in chemical form like hydrogen or biomethane.
In periods when this is not sufficient, several additional mechanisms are activated and coordinated through the electricity market: Short-term storage offsets fluctuations and residual peak loads, flexible consumers adjust their electricity use, we exchange electricity with our neighbors through the European grids, and – as a last resort – we use controllable power plants. In the future, power plants could resort to renewable fuels generated during sunny hours. Agriculture has been using this type of storage for thousands of years: Corn is harvested in the fall and stored for the rest of the year to provide fresh bread every day.
Batteries are a great example of how discussions can become distorted and misleading. Today, no one would seriously claim that standard lithium-ion batteries alone can bridge “dark doldrums” for multiple days. That is not what they are made for. Their strength lies in the short-term. During “dark doldrums”, they shift electricity from times with lower residual loads to hours with higher ones. A residual load is the share of electricity consumption which wind and solar power cannot cover. Batteries stabilize the grid’s frequency and voltage and reduce peak loads.
It does not sound like a big deal, but it is extremely important for the system as during the day, load demand fluctuates by several gigawatts. For example, covering 10 GW of residual peak load saves having to build 20 large gas-fired power plants. The market is driving the expansion of battery storage at all levels, such as residential storage, large-scale storage systems and e-cars, without any subsidies. Together, they will soon be able to close the storage gap in the German electricity system, reducing the need for grid expansion, and saving money in the process. As a result, times with negative electricity prices will also decrease.
New technologies such as redox flow batteries will soon enable longer storage durations. The United States is already planning its first 100-hour energy storage system.
Flexible demand is also a frequent topic of debate. How much potential is there really?
The potential is huge, yet it remains underutilized. Previously, electricity consumption was largely inflexible. Even today, supported by high-demand privileges, the industry is effectively incentivized to maintain constant electricity use to match the inherent inflexibility of power plants. These outdated incentives are being abolished and replaced by modern flexibility incentives.
A look abroad shows what is possible: The flexibility potential of Sweden’s industry is estimated at around 30 percent, and Great Britain’s at around 16 percent. Due to existing misdirected incentives, Germany’s is much lower. At the same time, more and more flexible loads such as heat pumps and electric cars are being integrated into the system. Combined with dynamic electricity tariffs, consumption can be shifted to times when much cheaper energy from renewable sources is available.
The accusation that it creates an economy of scarcity is nothing more than blatant populism. On the contrary: This system upholds the core principle of a free market economy – the efficient allocation of limited resources. Why should you convert expensive gas into electricity when you can just postpone charging your electric car by a couple of hours?
A flexible electricity system is a bit like a group of dancers, all moving in harmony.
A very important one. Supply security is often viewed through a national lens, although it has actually long been organized at a European level. Weather conditions vary across regions – when there is no wind in Germany, conditions may be entirely different elsewhere. These differences are balanced out cost-effectively by the Continental Europe Synchronous Area, which improves efficiency and lowers costs. Therefore it is important to further strengthen this market with new cross-border interconnectors.
Electricity imports are often portrayed as something negative, but they are not. Electricity consumers benefit from cheap electricity that could not have been produced in Germany at that time. Besides this, we are talking about net imports of around two percent, whereas 98 percent of fossil energy carriers are imported. This does not seem to bother anyone. Surprising, right?
No system is free. It is important to compare costs, and comparing them shows that alternative approaches, such as building new nuclear power plants, would be significantly more expensive. We are already seeing this in France and Great Britain, where costs are spiraling out of control.
Generating power from wind and solar is very cost-effective and the same goes for short-duration energy storage and other flexibility options. Generating electricity during “dark doldrums”, on the other hand, is relatively expensive. But this should not lead us to the conclusion that we need expensive combined cycle gas turbine power plants – relatively cheap engines and turbines are sufficient. This results in a system in which electricity is generated very cheaply for most of the year, but is relatively expensive for only a few weeks. Overall, that is significantly cheaper than maintaining an expensive system all year round. Even a system predominantly based on baseload power plants would still have to be able to cover peaks. The only way of doing this without carbon emissions would be extremely expensive nuclear power plants.
As a result, numerous analyses suggest that a flexible renewable system offers lower long-term costs while also improving resilience.
Would you like to learn more about how a renewable energy supply can work around the clock, all year round? The special exhibit “Renewables 24/7” at The smarter E Europe 2026 shows how a renewable energy system can be operated reliably, economically and flexibly. The focus is on real-world applications in industry, commerce, residential use and mobility, demonstrating how generation, storage, flexibility and digitalization interact and work together. Visitors experience technological innovations, best practices and expert insights.
