What is a dark doldrums?
A dark doldrums describes periods in which both wind and solar energy contribute only minimally to electricity generation. Particularly in the winter months, when dense clouds and calm winds combine, electricity production from renewable sources can drop sharply. Battery storage systems are becoming increasingly important as a flexible solution to ensure security of supply in an electricity system that is increasingly geared towards renewable energies.
Current situation in Germany
- In 2024, around 60 percent of the electricity generated in Germany will come from renewable sources such as wind, solar, biomass and hydropower.
- Germany is part of a closely networked European electricity market. During dark doldrums, electricity can be imported from neighboring countries, especially if the weather conditions there are better. Imports covered around 6% of electricity demand during critical phases in 2025.
- Despite the strong expansion of renewable energies, the electricity grid has remained stable even during long periods of darkness. Trotz des starken Ausbaus der erneuerbaren Energien ist das Stromnetz auch bei längerer Dunkelheit stabil geblieben.
- In November 2024, one of the longest dark doldrums in recent years was recorded at almost eleven days. Nevertheless, security of supply remained guaranteed as fossil fuel power plants and imports stepped in.
Energy storage to bridge dark doldrums
Battery storage in the German energy system
- Strong expansion: By 2025, more than two million solar power storage systems will have been installed in Germany, reaching a total capacity of over 20 gigawatt hours. This storage capacity is enough to supply two to four million households with electricity for a day.
- Direct connection: Battery storage systems are increasingly being installed directly at wind and solar parks in order to store locally generated energy efficiently and make it available when needed.
- Flexible use: During periods of darkness, stored electricity can be made available to bridge gaps in supply.
- Electricity price stabilization: The targeted use of battery storage systems can cushion electricity price fluctuations during times of shortage, which stabilizes supply costs for consumers.
Advantages of battery storage
- Rapid scalability: In contrast to traditional storage technologies such as pumped storage power plants, battery storage systems can be expanded flexibly and modularly.
- Space-saving solution: They require comparatively little space and can be installed decentrally in residential areas, business parks or directly at power generation plants.
- High reaction speed: Battery storage systems can compensate for grid fluctuations within seconds and thus make an important contribution to grid stability.
- Integration of renewable energies: They enable the efficient use of solar and wind power by absorbing surpluses and releasing them as required.
- Economic development: The costs of battery storage systems have fallen significantly in recent years, further improving their distribution and cost-effectiveness.
Future perspectives
As the proportion of renewable energies increases, the need for flexible storage solutions will continue to grow. Battery storage systems are a key element in ensuring security of supply even in times of volatile feed-in. The combination with digital control systems and the connection to the European electricity market further increase the energy system’s resilience to dark doldrums.
The continuous development of storage technologies and innovative business models will further strengthen the role of battery storage systems in the coming years. It is already clear that the German electricity system remains one of the most stable in the world, despite occasional dark doldrums, and the number of power outages continues to fall.
Conclusion
Battery storage systems are indispensable for a reliable power supply in an energy system based on renewable sources. They enable a flexible, efficient and fast supply even in times of low wind and solar power and thus ensure the stability and future viability of the energy supply.
