While the „dunkelflaute“ (a period of low wind and solar power generation) has long been known as a critical scenario for energy supply, its meteorological counterpart is increasingly coming into focus: the Hellbrunn. This refers to a weather situation with simultaneous high wind and solar power production. What initially sounds like an ideal picture of the energy transition is increasingly posing enormous challenges for public power grids. Possible consequences include overproduction, negative electricity prices, and bottlenecks in grid operation.
What is a Hellbrise?
The term "Hellbrise" originates from the energy industry and describes a weather condition with a lot of solar radiation and strong wind simultaneously. This combination leads to exceptionally high feed-in volumes in an energy system with a high proportion of renewable energies – often more than is actually demanded or can be absorbed by the power grid. Thus, the Hellbrise, in contrast to the Dark doldrums, to a Surplus electricity.
The light breeze mostly occurs in the Spring or Fall When energy consumption by industry and commerce is low on weekends or holidays, the sun is high at low temperatures, and the wind is blowing strongly, this phenomenon occurs. Then, the energy supply exceeds demand, or too much electricity is generated at the wrong time and place. Thus, the "Hellbrise" (a German term for an oversupply of renewable energy) is increasingly becoming a systemic challenge in Germany, rather than an exceptional case.
Impact of a light breeze on the power system
The oversupply of electricity during a bright breeze affects the power system and grid stability in multiple ways:
Overproduction & electricity surpluses
During heat wave phases, feed-in from renewables can temporarily exceed demand by a multiple. This poses the risk of Instabilities all the way to Blackouts, because power grids rely on the immediate balancing of generation and consumption to keep the grid frequency stable. Any surplus electricity must therefore either be exported, stored, or curtailed. The latter is often done by Redispatch, where wind turbines in northern Germany and increasingly also controllable PV systems are being shut down – with corresponding follow-up costs.
Negative electricity prices
When the supply of electricity significantly exceeds demand in the spot market, negative electricity prices on the stock exchanges. This means that non-curtailable power generators may have to pay to have their electricity taken, and operators of EEG-subsidized plants will not receive feed-in tariffs during these hours. In 2024, for example, there were around 457 hours with electricity prices at or below 0 EUR/kWh, which was about five times more frequent than the occurrence of a dark doldrum. Forecasts assume that light breezes could occur significantly more frequently in the future – according to a study by the Öko-Institut, possibly up to 40 % the year's hours in the year 2045.
Network bottlenecks and load shifting
The current power grid is still not designed to efficiently transport large quantities of electricity from the wind-rich regions in the north and solar peaks in the south to where it is needed. The consequence is regional network bottlenecks, which prevent the transport of renewable electricity – even though theoretically sufficient energy would be available. Without sufficient grid expansion, this leads to system-critical situations, which also the Security of supply can impair. Experts estimate the necessary expansion at around 700 billion euros.
The light breeze puts pressure on the network stability
The light breeze poses not only logistical challenges for the power grid, but also Physical limitations. Because an oversupply of renewable electricity directly affects grid stability – especially frequency control, voltage regulation, and system management.
50 Hertz even with high feed-in
The European power grid must constantly be supplied with a Mains frequency of 50 Hertz operated. This frequency is a sensitive indicator of the balance between generation and consumption. While a power shortage leads to a frequency drop, a strong breeze can cause a Frequency increase especially if feed-in and load are not closely coordinated. Automated protective mechanisms and primary control power must intervene rapidly in such cases to avoid grid damage.
Voltage and reactive power in a light breeze
Besides the frequency, also the Voltage regulation a central task in network operation. With very high decentralized feed-in, it can lead to local Voltage increases come, provided that there are no flexible connectable consumers. In addition, there is often a lack of controllable Reactive current resp. Reactive power, which is necessary to stabilize the power flow. Conventional power plants, which have provided these services, are often not on the grid during Hellbrise phases. Replacement by new technologies, such as Large-scale battery storage with network support function are not yet in widespread use.
More Complex System Management
The more volatile energy producers feed high power levels into the grid simultaneously, the more complex load management becomes for grid operators. The demand for forward-looking planning, real-time data, automated switching operations, and regional coordination is increasing massively. This is increasingly pushing distribution network operators into an active role – away from passive power distribution towards active grid operation with real-time control.
Perspectives & Solutions for Health Brink
To utilize offshore wind not as a risk but as an opportunity for the energy transition, structural adjustments are needed at multiple levels. Grids, markets, and technologies must be capable of flexibly and efficiently integrating large amounts of renewable electricity.
Network expansion & network optimization
A central building block is the need-based expansion the power grids, especially the transmission lines between northern and southern Germany. In addition to new routes, however, also Smart grid technologies The meaning is: Bottleneck management, controllable local grid transformers, automated switching technology, and digital grid control can make more efficient use of existing infrastructure. cross-border electricity trading helps to balance generation peaks across national markets.
Flexible Demand & More Storage
To make sensible use of electricity surpluses from wind turbines, various approaches are being discussed and implemented. These technologies help relieve the grid and convert generation peaks into consumption:
- Large-scale battery storage for short-term grid services and expansion of further pumped-storage power plants
- Power-to-X technologies such as electrolyzers for hydrogen production
- Demand Side Management, meaning the temporal shifting of electricity consumption through intelligent control (e.g., for industrial processes, heat pumps, or charging infrastructure)
Opportunities for Sector Coupling
A key lever lies in the linking of different energy sectors. The intelligent Sector coupling between electricity, heat, mobility, and industry, it enables needs-based energy utilization where it is needed. This consumption option is also extremely flexible and grid-friendly. These include the combinations of:
- Power-to-X Technologies (Power-to-Heat, Power-to-Gas, Power-to-Liquid)
- EV Charging Infrastructure
- energy-intensive industrial processes with electricity consumption
- Heat storage
Market Incentives & Price Signals at Hellbrisen
The German electricity market Selbst muss better able to react to Hellbrise phases. The recently introduced dynamic electricity tariffs In Germany, initial incentives are already being set in motion. Time-variable grid fees or local market prices are further options that aim in the same direction. Currently, however, strong dynamic price signals are still missing, which also flexible consumers motivate the targeted use of electricity during times of high availability. Short-term and regional flexibility markets offer another way to activate or curtail excess generation in real-time. The effects are currently being tested in model regions.
Hellbrise - The weather phenomenon with systemic relevance
The "bright breeze" is a new but increasingly relevant phenomenon in the energy transition. It represents a stressful moment for the power system. What initially appears to be an ideal state turns out to be a challenge upon closer inspection: grid congestion, negative electricity prices, and complex system management demonstrate that abundance can be just as critical as scarcity. The bright breeze will occur more frequently and highlights the importance of expanding storage, flexible consumers, and grid infrastructure. However, with sensible integration and combination, it can transform from a risk into a cornerstone of a stable, climate-friendly energy supply.