Arkona offshore wind farm is a 385MW wind power project located in the Baltic Sea, approximately 35km north-east of the island of Rügen, Germany.

The offshore wind firm was developed with an estimated investment of £1.1bn ($1.4bn‎) by OWP Arkona, a 50:50 joint venture between German utility E.ON and Norwegian energy company Equinor (formerly Statoil).

E.ON led the construction and is responsible for the operation of the wind farm.

Offshore construction on the project started with the first monopile installation in September 2017.

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Arkona offshore wind farm produced its first electricity in September 2018, with 44 out of the total 60 turbines installed.

Fully commissioned in April 2019, the wind farm is expected to generate up to 1.5TWh of clean electricity a year, which is enough to power 400.000 German households.

The project is estimated to offset approximately 1.2 million tons of CO2 emissions a year.

Arkona offshore wind farm make-up

Spread over an area of 40km², the Arkona wind farm is equipped with 60 SWT-6.0-154 Siemens Gamesa wind turbines installed in water depths ranging from 23m to 37m.

With 154m diameter rotor and 75m-long blades, each three-bladed direct drive offshore wind turbine has a swept area of 18,600m². The rated capacity of each turbine is 6MW.

The steel monopile for each turbine has a diameter ranging from 7m to 7.75m and weighs up to 1,200t.

The wind turbines are interconnected by 76km of offshore array cables.

Electricity generated from each turbine is gathered and sent to the Arkona high-voltage alternating current (HVAC) offshore substation located in 30m-deep water in the wind farm site.

Installed in April 2018, the Arkona electrical offshore substation is jointly operated by OWP Arkona and 50Hertz, a German transmission system operator.

The 4,000t topside and 1,000t jacket for the offshore substation were manufactured at STX France's Saint-Nazaire yard.

Electricity transmission from Arkona offshore wind farm

The wind power generated by the Arkona project is fed to the national grid via the 93km-long Ostwind 1 cable system connecting 50Hertz’s onshore substation at Lubmin in Mecklenburg-Vorpommern.

Comprising a 90km offshore section and a 3km onshore section, the Ostwind 1 cable system provides grid connections to both Arkona and Iberdrola's Wikinger project.

Wikinger is a 350MW offshore wind farm commissioned in December 2017 in the German waters of the Baltic Sea.

Power purchase agreement (PPA) for the German wind farm

French multi-national electric utility Engie off-takes the entire electricity output from the Arkona wind project, under a four-year power purchase agreement (PPA) signed with OWP Arkona in September 2018.

Contractors involved

Siemens was contracted to supply, install and commission the turbines for the Arkona wind farm, in April 2016. The contract also includes a two-year service agreement for the wind turbines.

A2SEA, in the same month, was awarded the contract to install the turbines of the wind farm using its offshore installation vessel Sea Challenger.

STX France (now Chantiers de l'Atlantique) was awarded the engineering, procurement, construction and installation (EPCI) contract for the Arkona electrical offshore substation in April 2016.

The scope of the contract also includes maintenance of the substation for 12 months, following the delivery in 2018.

Seaway Heavy Lifting (SHL) was engaged for the transport and installation of the offshore substation.

Schneider Electric provided the full electrical package, while ABB was subcontracted for the supply of electrical transformers for the offshore substation.

Nexans was contracted to provide 76km of inter-array energy cables for the Arkona wind farm in April 2016. VBMS was awarded the inter-array cabling contract in the same month.

VBMS subcontracted Vroon Offshore Services in October 2017 for supporting the inter-array cabling operations with the use of subsea-support walk-to-work (W2W) vessel VOS Stone.

Ampelmann was subcontracted to provide its A400 gangway system for W2W operations during array cabling work and commissioning of the Arkona offshore wind farm, in January 2018.

EEW Special Pipe Constructions was contracted to provide the monopile foundations, while Van Oord was contracted to transport and install the monopile foundations, including the transition pieces, using its heavy lift installation vessel Svaven, in April 2016.

DNV GL received the project certification contract for the Arkona offshore wind farm in June 2016.