The green future of offshore wind hubs and hybrid connections



50Hertz and Energinet have joined forces to fully harvest the offshore wind potential held in the Baltic Sea, power the green transition in Germany and Denmark, and spearhead a new idea for connecting offshore wind farms across borders: the Bornholm Energy Island (BEI) project. This innovative and visionary project will connect multiple wind farms together via a single hub and transport the green electricity that they generate to consumers in both countries while providing transmission capacity for cross-border trading.


Together, 50Hertz and Energinet want to establish a power hub on the island of Bornholm that is able to provide electricity to consumers in either country, depending on the market and demand in Germany, Denmark and Europe more widely. Electricity generated by the wind farms located off the coast of the island will be centralised at this hub and then converted into high-voltage direct current (HVDC) and transported via 525 kV HVDC sea and land cable systems to onshore substations in Zealand (in Denmark) and Mecklenburg-Western Pomerania (in Germany). In addition, the BEI project will enable the local community on the island to be connected to both Zealand and continental Europe.  

Cooperation between countries is the way forward

50Hertz and Energinet are pioneering innovators. BEI will pave the way to a future in which offshore wind energy is no longer harvested by individual countries alone. Instead, in line with the offshore wind potential held by different countries and electricity demand in these, two or more countries will cooperate to efficiently integrate the green electricity generated by offshore wind farms into their energy systems.

We at 50Hertz and Energinet hold a significant amount of expertise in feeding electricity from offshore wind farms into our power grids. The Kriegers Flak - Combined Grid Solution (KF CGS), our joint project which has been fully operational since 2021, laid the foundations for making hybrid interconnectors a reality in both the Baltic Sea and the North Sea. We will continue to use our know-how to implement ever-evolving, more complex and more efficient on- and offshore energy hubs.


Energinet and 50Hertz start tendering for Bornholm Energy Island

30.11.2023 – Danish and German TSO’s Energinet and 50Hertz have started the tendering process for key technologies of the joint project Bornholm Energy Island that will bring 3 GW of green power to German and Danish energy consumers. As a result of a market dialogue with possible vendors this summer, the partners decided to speed up the tendering in order to reserve production capacity as early as possible. Next step will be receiving bids and starting negotiations until contracts can be signed in the second half of 2024.

The market dialogue with interested vendors have shown that the Energy Island project needs start tendering early in order to reserve production capacity and keep to the project timeline. Another direct consequence of the market dialogue is that 50Hertz and Energinet will split the tender into multiple contracts in order to enable vendors interested in bidding on the HVDC stations and cables the possibility to bid on contracts within their core business, while other parts of the project will be tendered separately.

HDVC equipment for the stations in Germany and Denmark will be tendered as one joint contract which has been sent to prequalified vendors today. 50Hertz and Energinet has designed the procurement of the HVDC-breakers – a future key technology for the energy island - as an option, which can either be built as part of the initial construction – or as a separate tender at a later phase. The reason for this is that some vendors are highly interested in supplying the breakers, while others prefer to focus on their core products.

”We cannot ignore the current market situation. HVDC circuit breakers will play an important part in the operation of our Energy Island but are not crucial in the initial phase. Therefore, we have decided that it is more important to ensure a competitive bidding process and to keep up the pace of the green transition in order to secure the supply of clean electricity to consumers in Germany and Denmark.”, says Hanne Storm Edlefsen, vice president for Energy Islands at Energinet.

50Hertz has already signed a contract for the procurement of HVDC cables for Bornholm Energy Island and several other projects. Energinet has started the tender of one contract for production of cables as well as offshore installation. Onshore installation and horizontal directional drillings (HDD) will be a separate contract as well as surveying and removal of unexploded ordnance (UXO) which will also be tendered as a separate contract at a later time. Civil works and the buildings for the HDVC stations will be tendered for Denmark and Germany respectively, at a later time.

Construction on Energinets part of the project in Denmark can start once it has received an environmental permit and archaeological excavations have been completed in 2025.  In Germany installation and construction can start after permits are granted by the authorities.


Bornholm Energy Island is one of two Energy Islands being planned in Danish waters as a result of the Danish Climate Agreement adopted by the Danish Parliament in June 2020. Bornholm Energy Island will have a production capacity of 3 GW.


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