Kaskasi, also known as Kaskasi II, is a 342MW offshore wind farm being developed in the German North Sea by RWE, a multi-national energy company.

The planning permission for the project was awarded by the German Federal Maritime and Hydrographic Agency (BSH) in December 2020. The wind farm will support Germany’s goal of achieving 20GW of offshore wind energy capacity by 2030 and 40GW by 2040.

Construction of the new offshore wind farm is anticipated to begin in the fourth quarter (Q4) of 2021, while commissioning is expected in Q4 2022. The project will generate enough clean energy to meet the electricity needs of approximately 400,000 households a year. It is expected to have an operational life of at least 25 years.

Kaskasi offshore wind farm details

The Kaskasi wind farm site is located in the North Sea, approximately 35km north of Heligoland, Germany. It will be installed with 38 Siemens Gamesa SG 8.0-167 DD Flex wind turbines featuring 81m-long B81 IntegralBlades, which are the world’s first recyclable wind turbine blades. Made with the breakthrough RecyclableBlade technology, the blades can be recycled at the end of their lifecycle.

The turbines will also feature Siemens Gamesa’s Direct Drive platform, which ensures stability and reduces associated costs and risks.

Kaskasi offshore wind farm construction

The wind turbines will be installed on monopile structures. Three special collars, which are based on RWE’s patented technology, will be installed around the monopile foundations on the seabed at water depths of up to 25m. The collared monopile is expected to provide additional support for lateral loading while increasing the bearing capacity of the foundation.

The installation will be performed using the ‘vibro pile driving’ method, which is expected to reduce installation time as well as noise levels.

The offshore substation is scheduled for installation in the first half of 2022.

Power transmission from the wind farm

The Kaskasi wind farm will be connected to the same grid connection cluster as the 295MW Nordsee Ost wind farm, which is also operated by RWE.

The power generated from the Kaskasi wind farm will be collected using 52km-long 33kV aluminium core inner array grid cables that will be installed in water depths ranging between 18m and 25m. The cables will transmit the power to the offshore substation. The topside of the substation will weigh 1,250t.

The three-phase electric power from the offshore substation will be transmitted through two export cables to Helwin Beta, a high-voltage direct current (HVDC) platform that further transmits wind power through a 130km-long connection to the land-based substation in Schleswig-Holstein.

Contractors involved

Siemens Gamesa was selected to supply the wind turbines for the Kaskasi wind farm in April 2020. Danish steel contractor Bladt Industries was appointed to manufacture and supply 39 monopile foundation structures for the project. It will also provide the offshore substation in collaboration with Semco Maritime and ISC Engineering.

Bladt Industries will build the substation while ISC Engineering will be responsible for the substation design and Semco Maritime for the electrical installations. DEME Offshore was engaged to transport the three monopile collars from Denmark to the Kaskasi construction site. The company will also be responsible for the installation of the steel collars using the jack-up vessel Neptune.

Subsea 7 secured the contract for the transportation and installation of the offshore substation foundation, the monopile foundations and the inner array grid cables at the wind farm in April 2020. Dutch subsea cabling specialist TKF was contracted by Seaway 7, a subsidiary of Subsea 7, to supply 33kV aluminium core inner array grid cables with different cross-sections for the wind farm.

Subsea cable protection systems (CPS) provider Tekmar received a contract to supply its patented TekLink CPS to protect the export cables of the wind farm in February 2021.

Dutch transmission system operator TenneT was selected to provide the offshore grid connection. The company appointed global subsea cable manufacturer Zhongtian Technology Submarine Cable (ZTT) to manufacture the cable systems, which will be installed by Greek company Asso.subsea.

Correll Services was, in turn, selected by ZTT to perform cable routing and testing of the 155kV subsea cables. Spanish firm Sener provided the preliminary tender design of the offshore substation for the project, while Vos Prodect Innovations was engaged to provide cable hang-off systems for the installation of the turbines.

Other contractors involved in the project include Trelleborg, CAPE Holland and ProCon Wind Energy.

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