Nordsee Ost is a 295MW offshore wind farm developed off the German coast around 30km north of the Heligoland Island in the North Sea.

The project is operated by German energy company RWE.

The construction of the offshore wind farm commenced in 2011 and it was completed in late 2014. The wind farm was officially inaugurated in May 2015.

Nordsee Ost is capable of providing renewable power to 320,000 households, making it one of the largest commercial wind projects off the coast of Germany.

The project entailed an investment of more than €1bn.

Nordsee Ost project details

The Nordsee Ost Project is located in water depths of up to 25m, around 60km from the shore. Overall, the wind farm covers an area of 24km2.

It features a total of 48 wind turbines, each with a capacity of 6.15MW. The turbines are mounted on four-legged steel jacket foundations.

There are a total of 49 foundations, including 48 for turbines and one for a transformer substation. They are fixed to the seabed using BASF’s Exagrout Masterflow 9500 cement-based grout.

The foundations are up to 50m high and weigh around 550tonnes. Each of these includes an area of almost 400m2.

The wind turbines are around 160m from sea level to the tip of the blade. Each nacelle weigh around 350tonnes, while the 60m long rotor blades weigh more than 23 tonnes.

The wind turbines and the substation are connected by inter-array cables. The offshore substation converts the electricity produced by the wind turbines to the transmission voltage. The electricity is then transferred to the shore through a high voltage cable.

More than 60km of underwater cables were laid for the project.

All construction was conducted from the base port in Bremerhaven. Key components of the project including foundations, tower segments, nacelles and rotor blades were stored, pre-assembled and loaded onto ‘Victoria Mathias’ and ‘Friedrich Ernestine’ vessels at the Eurogate Container Terminal for transportation and installation.

Nordsee Ost Project can produce 1.1TW-hours of electricity a year. The project helps in offsetting 850,000tonnes of carbon dioxide emissions annually.

The wind farm is operated and serviced from Heligoland island. Around 50 service technicians, engineers, and nautical personnel are involved with the operation and maintenance of the project.

Power Purchase Agreements

In January 2023, RWE Supply & Trading signed power purchase agreements (PPAs) with 11 industrial customers and one large municipal utility.

As agreed, Nordsee Ost and Amrumbank West offshore wind farms will supply the customers with some 1,500GWh of electricity annually from 2025 and 2026 respectively.

The agreements were signed with Badische Stahlwerke, Freudenberg group, Infraserv Höchst, Mainova, Messer, Schott, Telefónica, Verallia, Vodafone, Wacker and ZF.

Most of the agreements have a term of ten years.

Previously, the two wind farms sold power to Deutsche Bahn in 2019, 2020, and 2021.

Contractors involved

The Nordsee Ost wind turbines were delivered by wind turbine manufacturer Senvion. The company was also responsible for the operation and maintenance of the wind turbine generators during the installation.

Aker Solutions won the engineering, procurement and construction (EPC) contract to supply 48 steel jackets and piles for the offshore wind farm.

The consortium of Siemens and cable manufacturer Prysmian won the contract to connect the Nordsee-Ost offshore wind farm to the German national grid.

In June 2011, ABS Group, an affiliate of ABS Consulting, was selected for conducting inspections of 49 offshore foundations of the wind farm. This included assembly and welding processes of the steel foundation, compliance check with the manufacturer’s design documentation, and inspection of transition pieces, pile clusters, lattice steelwork, and interface flanges.

In January 2012, RWE Innogy awarded the foundation grouting contract for Nordsee Ost wind farm to FoundOcean.

Visser & Smit Marine Contractors (VSMC) secured the inter-array cable installation contract. Subsequently, VSMC contracted ARC for a conceptual design of the cable pull-in frame, which was used for the infield cable pull-ins at the offshore substation.

Five Wölfel wind turbine generators are equipped with a comprehensive monitoring system to permanently monitor jacket, foundation, grout connections, and tower. Also, three other wind turbines were equipped to monitor structural behaviour.

Wireless connectivity specialist Citymesh was contracted to provide a solution to enable internet onboard and inside the turbines.

In September 2016, classification society DNV GL certified Nordsee Ost offshore wind project. The certification was carried out according to the German Federal Maritime and Hydrographic Agency Standard and covers all phases of project development.

BWTS signed a contract in January 2020 to take over the statutory inspection, maintenance and repair of all safety equipment in the offshore wind farm.

Rockwool Technical Insulation delivered SeaRox wired mats and sabs for bulkheads and decks.

Corrosion protection services were delivered by CWind, while Xervon Wind provided annual maintenance services for Nordsee Ost wind farm.