BalWin1 and BalWin2 are two large-scale offshore grid connection projects being developed in the German North Sea.
The two grid connection systems will be designed to transmit 2GW of offshore wind power each to the onshore grid. The combined 4GW power supply can meet power requirements of nearly 4 million people.
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The projects are being developed by Amprion Offshore, a subsidiary of transmission system operator Amprion. The company is responsible for planning, building, and operating the grid connection systems, including both offshore and onshore infrastructure.
In June 2025, Amprion secured planning approval for the two offshore grid connections in the coastal waters of Lower Saxony. Construction work for the submarine cable laying of the BalWin1 and BalWin2 began in July 2025.
The two grid connection projects are expected to become operational in 2030 and 2031, respectively.
The projects will support Germany’s broader effort to accelerate renewable energy integration and achieve national climate targets.
BalWin1 and BalWin2 Route
BalWin1 and BalWin2 will connect planned wind farm clusters in the German Exclusive Economic Zone (EEZ) of the North Sea to onshore converter stations in Lower Saxony and North Rhine-Westphalia.
BalWin1 will connect to an onshore converter station in Wehrendorf, Lower Saxony. Its total route length is approximately 360km, with around 155km offshore and the remainder on land.
BalWin2 will connect to an onshore converter station near Westerkappeln, also in Lower Saxony. Its total length is about 380km, with roughly 165km offshore.
The two grid connections will pass under the island of Norderney and reach the coast at Hilgenriedersiel.
Both the routes will bury the cables for protection, and use specialised horizontal directional drilling (HDD) crossings at sensitive points such as shipping channels or coastal dunes.
BalWin1 and BalWin2 Infrastructure
The BalWin systems will use High-Voltage Direct Current (HVDC) technology to transport the electricity.
Key infrastructure will include offshore converter platform each— located near the wind farm clusters, housing HVDC technology to convert AC from the wind farms to DC for long-distance transmission.
The offshore converter platforms, referred to in project documentation as ‘BalWin alpha’ and ‘BalWin beta’, will each weigh in the order of 56,500 tonnes including substructure. They are designed to withstand harsh offshore conditions while housing complex electrical equipment, including transformers, reactors, and converters.
The platforms will be supports by a steel foundation, anchored to the seabed. An onshore converter station will convert the DC back to AC for grid integration.
HVDC export cables — subsea and land cables- are designed for high-capacity, long-distance transmission.
Each cable system will comprise two single-core ±525 kV HVDC copper cables. The submarine section of the cable will have XLPE insulation, while P-Laser insulation was selected for the land underground sections.
It will also include a dedicated metallic return cable and a fibre optic cable.
Overall, BalWin1 will utilise around 1,070 km of cables along a 358km route and BalWin2 will use approximately 1,100 km of cables over a route of 376km.
The subsea cables will be installed from the offshore converter platforms to landfall points on the German coast, using horizontal directional drilling (HDD) to minimise coastal impact.
From there, high-voltage underground cables will transmit the electricity to the inland converter stations, where the direct current (DC) will be converted to alternating current (AC) for integration into the national grid.
Contracts Awarded
In August 2023, Prysmian Group was named preferred bidder for the HVDC cable packages for both BalWin1 and BalWin2. The contracts, along with the underground cable project DC34, have a combined value of around €5bn.
Dragados Offshore, in consortium with Siemens Energy Global, will develop, build and deliver the HVDC Grid Stations for both the connection projects.
Papenburg-based Meyer Werft will carry out significant portion of the steel construction work (approximately 32,000 tons) for the topside, the upper part of the platform.
In February 2025, Aker Solutions secured a contract, valued between NOK1.5bn and NOK2.5bn, to deliver the steel substructure for the HVDC converter station for the BalWin1. The company was subsequently selected to deliver the steel substructure for the 2GW HVDC converter station for the BalWin2 in May 2025.
Swiss offshore construction specialist Allseas will be involved in the transport and installation of the converter platforms for these projects. The company will also lift, stab and drive 24 foundation piles with 5000-tonne crane among other works.
In July 2025, Amprion initiated a market research process for waste heat utilisation at the converters of the BalWin1 and BalWin2. It plans to launch a tender at the end of 2025.
