Global energy storage owner-operator BW ESS has officially commenced construction of the 1,000MW/5,700MWh Klostermansfeld Battery Energy Storage System (BESS) in Saxony-Anhalt, marking the start of one of Europe’s largest battery storage projects and the biggest BESS development in Germany.
Located in the Mansfeld-Südharz district near the Klostermansfeld substation, the project is designed to deliver up to 5,700MWh of energy storage capacity. Once operational, it will be capable of supplying electricity to approximately three million German households for at least four hours, significantly enhancing the country’s energy storage infrastructure.
BW ESS initially invested in the project in 2024 before acquiring full ownership earlier this year. Project developer Zelos Energy Developments, which originated and sold the project, will continue supporting BW ESS on local site-related matters until construction progresses further toward the end of 2026.
The battery storage facility is expected to play a critical role in strengthening Germany’s electricity grid by improving energy security, enhancing grid stability, and enabling greater integration of renewable energy. The Klostermansfeld substation serves as one of Germany’s key transmission nodes and has recently undergone expansion to accommodate higher volumes of electricity transferred from the distribution network to the high-voltage transmission grid. The large-scale BESS will help absorb excess renewable electricity during periods of high generation and discharge stored energy during peak demand, improving grid flexibility and reliability.
Commenting on the milestone, Roberto Jiménez, Executive Director of BW ESS, said the company remains committed to supporting Germany’s energy transition through long-term investments in energy storage. He noted that the Klostermansfeld project represents BW ESS’s first battery storage asset in Germany to enter the construction phase and highlighted the company’s strategy of applying operational expertise gained from mature global energy storage markets across its international portfolio. He also acknowledged development partner Zelos Energy Developments and thanked Saxony-Anhalt’s Minister Prof. Dr. Armin Willingmann and Klostermansfeld Mayor Frank Ochsner for participating in the groundbreaking ceremony.
Prof. Dr. Armin Willingmann, Minister for Science, Energy, Climate Protection and the Environment and Deputy Prime Minister of Saxony-Anhalt, stated that battery energy storage systems are essential for stabilising power grids as renewable energy generation continues to expand. He said the Klostermansfeld BESS will become an important component of the state’s energy transition by enabling larger volumes of renewable electricity to be stored and efficiently integrated into the grid while strengthening supply security and operational flexibility.
Mayor Frank Ochsner welcomed the investment, describing the groundbreaking as a landmark moment for Klostermansfeld. He said the establishment of Germany’s largest battery storage facility would deliver long-term economic benefits to the local community while reinforcing the region’s role in supporting the country’s clean energy transition.
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