Germany’s largest battery storage system officially went into operation in June 2025. The system is located in Bollingstedt (Schleswig-Holstein). According to the operators, it stores surplus electricity from wind and solar power plants, and feeds the renewable power into the grid during peak demand. The project is run by ECO STOR, and is connected to the distribution network of Schleswig-Holstein Netz GmbH (SH Netz). The storage device has an output capacity of 103.5 MW and a storage capacity of 238 MWh, allowing it to make a significant contribution to the urgently needed energy transition. A so-called digital twin gives the project a special innovative twist.
Nadine Bethge explains what makes this project special, and talks about its economic benefit and the potential of the technology used here.
A digital twin combines weather and generation data from wind and solar with historical load values, enabling a realistic forecast of grid load. It simulates real-world systems and is constantly fed the latest data as a basis for simulations, forecasts and optimized decisions. In other words, it is a virtual copy of a real energy system. In this case, it is the virtual copy of a grid node in Bollingstedt that combines renewable generation and battery storage.
It helps us understand the energy system better and manage it more precisely. A digital twin allows us to run various scenarios without having to interfere with the real-world energy infrastructure – the power grid and the actual storage behavior. The project designer, ECO STOR, operates the digital twin in Bollingstedt to generate data on how the system can be used most effectively – both in terms of marketing and grid operation.
This makes it possible to determine in advance how much electricity can be fed into the grid without causing congestion. At times of high feed-in from renewables, the storage system automatically reduces its discharge rating.
Another benefit is SH Netz’s ability to reduce possible peak loads, while ECO STOR can optimize the utilization of the storage device. This makes grid utilization more efficient and saves costs. The integration of renewable energies becomes easier because we can balance out intermittent power feed-in. In this situation, everybody wins – the project designer, the operator and the energy system as a whole.
A digital twin continuously maps the real-world energy system in a digital model. The latest forecast for the feed-in volumes of renewable power are constantly fed into a grid model, which allows us to follow the current state of the system in real time. We can also run targeted simulations to analyze how specific actions or situations – the integration of a storage device or load shifting – would affect the system. The digital twin is a useful tool to make grid operation more transparent and to better support operative decisions.
The key economic benefit is the more efficient utilization of the existing energy infrastructure; this saves costs. For grid operators, the digital twin makes it easier to recognize bottlenecks early on and to manage them with precision. This will reduce the need for grid expansion, lowering system costs in the long run. What’s more, SH Netz can now optimize its energy planning, reduce peak loads and control the expansion of sustainable technologies.
ECO STOR benefits from being able to optimize storage system usage. The digital twin shows when storing electricity and feeding it back into the grid can serve the system, and when it makes financial sense.
Absolutely! In principle, the concept can be transferred to all levels of the energy system – from individual grid areas to entire regions. Digital twins can be used beyond grid operation itself. They can be useful in planning new systems, utilizing flexible assets and in creating local energy markets. In the long term, they will provide a key element for a smart, digital energy system.
A fully integrated digital twin of the complete German power system is a long-term vision rather than a short-term goal. We have the technology to do this, but we would also need to have comprehensive data and standardized systems and processes. A step-by-step approach is more likely, meaning that digital twins are integrated with each other at a regional level.
But there are also some risks, particularly with respect to data security and system stability. These risks can be managed with the right architecture and clear rules, though. It is key to apply digitalization in a way that makes the system more robust rather than more susceptible.
