Trianel Wind Farm Borkum is a 400MW wind farm being developed off the coast of Borkum Island, Germany, in two phases. The total investment for the project is estimated to be £1.6bn  ($2bn), including £880m ($1.17bn) for phase one and £711m ($949m) for phase two.

Trianel, a network of several municipal utilities from Germany, is leading the project development.

Construction on the 200MW phase one, named Trianel Wind Farm Borkum I, was started in September 2011, while commissioning took place in September 2015.

The second phase construction, which involves the development of another 200MW wind farm, namely Trianel Wind Farm Borkum II, was commenced in June 2018, with commissioning expected by the end of 2019.

Location and site details

The Trianel Wind Farm Borkum is located in the German North Sea, approximately 45km north of the Borkum Island, in water depths ranging between 25m and 35m.

It is being developed in a 56km² site near Alpha Ventus, Germany’s first offshore wind farm.

Development partners

The Trianel Wind Farm Borkum I was developed by Trianel in association with 33 municipal utilities.

German utility company EWE owns 37.5% stake in Trianel Windkraftwerk Borkum II, the developer of the phase two.

A joint venture between the utility of the City of Zurich (Elektrizitaetswerk der Stadt Zuerich) and Fontavis, a Swiss asset manager for renewable energy and infrastructure investments, holds 24.51% interest in the project.

The remaining 37.99% stake in the project is held by Trianel and 17 German municipal utilities.

Trianel Borkum wind farm turbine details

The Trianel Wind Farm Borkum I is installed with 40 Areva M5000-116 wind turbines mounted on 45m-high tripod foundations. With 116m-diameter rotor and 90m-hub height, each turbine stands 148m-high above the water and creates 10,569m² swept area.

Designed to operate at 3.5m/s cut-in and 25m/s cut-out wind speeds, each M5000-116 has a rated capacity of 5MW.

The Trianel Wind Farm Borkum II will be equipped with 32 Senvion 6.2M152 wind turbines mounted on monopile foundations. With a 152m-diameter rotor and 74.4m-long blades, each turbine will have a swept area of 18,146m² and a rated output of 6.33MW.

The cut-in and cut-out wind speeds of the turbines 6.2M152 turbine are 3.5 m/s cut-in and 25 m/s, respectively.


The electricity generated by each turbine is gathered and evacuated to an onsite-offshore transformer platform, which houses two transformers to step-up the voltage from 33kV to 155kV.

The double-deck platform is mounted on a jacket foundation and stands 20m-tall above sea level. Operated by Infrastruktur Windkraftwerk Borkum (IWB), the platform is meant to be shared by both the 200MW wind farms.

Electricity from the Trianel wind farm’s transformer platform is further evacuated through export cables to the 800MW Dolwin Alpha offshore converter station for conversion into direct current (DC). The Dolwin Alpha converter station is also connected with Ørsted's Borkum Riffgrund II wind farm.

The DC electricity from the Dolwin Alpha converter station is converted back into alternating current (AC) at the Dörper West onshore converter station in Emsland, before being fed into the TenneT transmission grid.

Contractors involved

Areva supplied 40 M5000-116 wind turbines for Trianel Wind Farm Borkum I, under a contract awarded in December 2010.

Alstom Grid completed the construction of the offshore substation platform for the wind farm in April 2013. The company was also responsible for the supply of the electrical system for the substation.

Norddeutsche Seekabelwerke (NSW) was contracted to supply and install the inter-array cables for Trianel Wind Farm Borkum I.

Norddeutsche Seekabelwerke (NSW) is also the supplier of inter-array cables for Trianel Wind Farm Borkum II, while Seaway Heavy Lifting was contracted for the engineering, procurement, construction, and installation (EPCI) of the subsea cable system for the second wind farm in November 2016.

RECASE was subcontracted by Seaway Heavy Lifting to design the electrical equipment in transition pieces of monopile structures for the turbines, in April 2017.

Senvion was contracted to supply 32 turbines of 6.2M152 model for the Trianel Wind Farm Borkum II in May 2017.

Jan De Nul Group completed the installation of export cable that connects the Trianel Wind Farm Borkum II with the Dolwin Alpha converter station in June 2018.