One Dark doldrums refers to the simultaneous occurrence of Darkness and Calmwhich drastically reduces electricity generation from wind and solar energy. This weather situation typically occurs in winter and can last for several days. Even longer phases without significant wind or solar radiation occur on average every two years. In Germany, electricity generation from wind and solar energy can drop to less than two percent the total installed capacity drop.
No uniform definition of a dark doldrums
Despite the widespread use of the term in the energy debate, there are No uniform definition with regard to the duration and extent of a dark doldrums. If two foggy days with no wind are included, the probability of dark doldrums is twice a year according to the German Weather Service. If other values are used, a period of eight days is expected on average every ten years in Germany in which less than 10 % of the installed capacity is available.
Cold dark doldrums in the winter months
It becomes particularly challenging with a so-called cold dark doldrumsin which, in addition to darkness and calm, low temperatures increase the demand for electricity. According to the Federal Environment Agency, such phases occur particularly frequently at the end of January or beginning of February. Prolonged dark doldrums represent significant periods of stress for renewable electricity systems, as they have a direct impact on the security of the electricity supply.
Risks of the dark doldrums
The dark doldrums place a considerable burden on the electricity grid, especially in a system that relies heavily on renewable or volatile energy. When wind and solar plants only supply minimal energy, conventional power plants have to step in to cover the Grid stability to ensure the stability of the grid. This imbalance between energy supply and demand makes frequency regulation more difficult and can jeopardize the stability of the entire electricity grid. The reduced load on the transmission grid during a dark doldrums also requires investment in redundant capacity from conventional energy sources, which increases overall operating costs.
Avoid CO₂ emissions
The dark doldrums therefore not only pose technical challenges, but also significant economic and environmental ones. As renewable energy sources are unable to fully exploit their potential during these phases, dependency on fossil fuelswhich in turn increases CO₂ emissions from the energy sector. This is contrary to the goals of the energy transition and the Paris Agreement. In addition, the higher production costs for natural gas and coal can have a negative impact on energy prices. In order to compensate for CO₂ emissions, expensive and energy-intensive measures such as CO₂ capture will be necessary, which will further increase the overall costs of energy supply.
These risks and challenges highlight the need for strategic planning and the development of long-term storage facilities or the use of synthetic, climate-neutral gases in order to ensure security of supply even during a dark doldrums and at the same time minimize the environmental impact.
Solutions and strategies
The Expansion of the electricity grid is a fundamental strategy for overcoming the challenges of the dark doldrums. The large-scale networking of renewable electricity generators across weather and national borders ensures efficient and balanced electricity transmission. High-voltage direct current (HVDC) transmission is particularly suitable as it has significantly lower transmission losses compared to conventional alternating current lines. This makes it possible to trade electricity over long distances without significant energy losses and thus compensate for regional differences in energy generation.
Increase storage capacities
The Increase the Storage capacities is another important measure. Long-term and short-term storage systems play a key role by storing surplus energy during periods of high generation and releasing it when needed. Large-scale battery storage for example, are excellent at absorbing short-term load peaks. Pumped storage power plants are currently the largest energy storage systems available and can compensate particularly quickly during a dark doldrums. In addition, the technology of Power-to-gas (P2G) plants increasingly relevant, as it makes it possible to store excess energy in the form of hydrogen, which can be used in the long term and contributes to decarbonization.
CO₂-neutral backup power plants against dark doldrums
Backup power plants or peak load power plants are essential to ensure security of supply during extreme dark doldrums. At present, conventional gas and sometimes coal-fired power plants are still suitable for this due to their flexibility and rapid availability. However, this increases CO₂ emissions. The use of hydro, geothermal, solar thermal and biomass power plants makes more sense here. They can also be ramped up and down quickly in order to react to sudden fluctuations.
Managing across sectors
The Sector coupling is an advanced solution that combines different energy sectors such as electricity, heat and mobility. By coordinating and integrating different energy sectors, a more efficient use of renewable resources can be achieved. In times of a dark doldrums, for example, surplus energy from one sector can be used in another to meet demand. This helps to stabilize the overall system and reduces dependence on fossil fuels.
These strategies show that a combination of technological innovation and intelligent grid control can effectively overcome the challenges of the dark doldrums in order to ensure a reliable and sustainable energy supply.
Prospects and innovations for overcoming the doldrums
Investments in Research and development play a key role in driving forward innovative technologies that can mitigate the effects of the dark doldrums. This not only includes improved weather and yield forecasting models and intelligent grid infrastructures. Scientists and engineers are working flat out on new technologies and concepts. There is constant progress in storage technology and the efficiency of solar and wind power plants. Although none of this can be developed or implemented ad hoc, the diversity and performance of alternative solutions will grow as the expansion of renewable energies continues.
Flexibilization of demand
A clever combination of different measures can make the use of conventional energy sources to cope with dark doldrums superfluous in the future. A decisive step towards this is the consistent expansion of all flexibility options in the electricity grid. In addition, the Flexibilization The electricity demand can be bridged by, for example, adapting the charging processes of electric cars or the operation of heat pumps to the fluctuating feed-in. Variable electricity tariffswhich are based on the timing of energy generation and consumption, have a controlling effect.
Reservoirs & smaller decentralized hydropower plants
Hydropoweras the world's largest renewable energy source, could solve a major problem of the energy transition as, unlike solar and wind, it is available around the clock. However, the future of hydropower is not seen in large reservoirs, but in small plants, which can be traditional run-of-river power plants or current power plants. These small hydropower plants do not interfere with the river biotope and do not change the water quality, which makes them an environmentally friendly alternative. The focus should be on the expansion of small decentralized run-of-river power plants and hydropower plants, but the modernization of old plants also offers great potential.
On-site energy generation
The Decentralized energy supplysupported by investments in networked energy systems by private individuals, municipal utilities or manufacturing companies could help to stabilize the system. Instead of investing in huge transmission systems, investments in local electricity production would be incentivized. Large electricity suppliers could in turn buy electricity from these smaller producers. This could also allow the 15,000 or so green electricity plants that will soon no longer be eligible for EEG subsidies to continue operating.
Hydrogen as storage against dark doldrums
In the long term, the solution could be a comprehensive Hydrogen economy lie. If these are optimized, the power plant output of renewable energy sources could even be kept lower than some people think. Electrolysis in the event of excessive power in the grid and fuel cells for reconversion into electricity could compensate for this throughout the year. In addition, combined heat and power generation should definitely be used to avoid wasting energy. With a hydrogen economy, we would have energy stored in the gas pipelines alone for months, which could also make it easier to prevent a blackout.
Conclusion: a dark doldrums can be overcome
In summary, dealing with the dark doldrums highlights the need for far-reaching cooperation, innovative solutions and a multifocal approach in the field of renewable energies. The strategies and solutions presented, from improving storage technologies to promoting sector coupling, offer promising ways to overcome the challenges. This underlines the importance of ongoing research and the urgent implementation of effective measures to strengthen resilience to the dark doldrums.
Future prospects in the use of renewable energies require constant adaptation of infrastructure and energy management systems in order to guarantee security of supply and accelerate the transition to a sustainable energy supply. The further development and use of new technologies together with an intelligent energy policy are fundamental to achieving the long-term goals of the energy transition and providing a responsible response to global climate challenges.