Project Overview

The Kaskasi Offshore Wind Farm, also known as Kaskasi II (formerly Hochsee Testfeld Helgoland), is an offshore wind farm off the coast of Heligoland in the North Sea, Germany. The wind power plant project is developed and operated by RWE Renewables. The wind farm consists of 38 Siemens Gamesa wind turbines with a total installed capacity of 342 MW.

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Construction of this renewable energy project started in 2021 and achieved commercial operation by December 2022. The wind farm is developed in a single phase capable of producing green electricity to power more than 400,000 households. Earlier in 2024, RWE AG has signed six new power purchase agreements (PPAs) with major industrial customers starting from 2026.

Project Background

Kaskasi II offshore wind farm is part of the German Offshore Wind Energy Act to reduce dependency on fossil fuels and promote clean energy. The act aims to increase the installed capacity of offshore wind power to at least 30 gigawatts and at least 70 gigawatts by 2045.

The German Federal Maritime and Hydrographic Agency (BSH) granted planning permission for the Kaskasi II offshore wind farm in December 2020. The development of the Kaskasi offshore wind farm marked a milestone in Germany’s offshore wind sector, becoming the first project to receive planning permission under the new offshore wind law (WindSeeG). 

In April 2020, the final investment decision (FID) of the wind power plant project was made. Also, CAPE Holland was awarded a contract by Seaway7 to supply a CAPE VLT for the installation of the monopiles in the same month. Fabrication and construction work began in late 2021 following the FID. 

The offshore substation of the wind farm was installed in March 2022 and the first turbine connected to the grid in August 2022. All the 38 turbines were installed and final testing was completed over four months by November 2022.

The offshore wind farm Kaskasi was constructed in nine months with more than 100 people from RWE and other 70 suppliers working to implement this project. The sixth wind farm of RWE in the German north sea started its commercial operation in December 2022 and entered regular operation in March 2023.

Kaskasi Offshore Wind Farm Location Details

Kaskasi offshore wind farm is located 35 km off the German coast of Heligoland (North Sea). The wind farm has an area of approximately 17.4 sq. km and water depths ranging between 18m and 25m.

The average wind speed at the site is reported to be 10 m/s. Additionally, Kaskasi OWF (offshore wind farm) is a part of the Heligoland cluster along with Amrumbank and Nordsee Ost.

Project cost

The estimated project cost of the Kaskasi offshore wind farm is around EUR 800 million.

Technical Specifications

The Kaskasi Offshore Wind Farm features 38 Siemens Gamesa SG 8.0-167 DD wind turbines. Each turbine has a rotor diameter of 167 meters and utilizes three 81.5-meter-long B81 Integral Blades. The rotor blades made from fiberglass-reinforced epoxy use RecyclableBlade technology designed to be recycled at the end of their lifecycle.

Each turbine operates at a hub height of 107.5 meters and has a swept area of 21,900 square meters. The turbines have Siemens Gamesa Power Boost technology, enabling them to reach a rated capacity of up to 9 MW. As part of the Siemens Gamesa Direct Drive platform, these turbines are made without gearbox reducing maintenance cost.

The offshore wind turbines are mounted on 64-meter-high monopile foundations. These are installed using “vibro piling technology” developed by Dutch specialist CAPE Holland. Vibro pile driving ensures a quieter and faster installation process compared to traditional hammering methods. The monopile foundations are reinforced with support collars developed by RWE patent technology to enhance stability and durability.

The electricity generated by the turbines is collected via 52 kilometers of 33kV inner array grid cables and transmitted to an offshore transformer substation. This substation gathers the generated electricity and sends it to the onshore grid via the HelWin2 converter platform. The HelWin2 platform connects the offshore wind farm to Germany's mainland grid infrastructure.

Contractors Involved

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Project Timeline

Project Benefits

The Kaskasi offshore wind project will provide several project benefits including clean electricity for more than 40,000 German homes. Also, the innovative recyclable rotor blades used in the wind turbine are a positive step towards a sustainable future.

Current and Future Outlook

The Kaskasi offshore wind is in regular operation phase since the project completion in 2022. The retail divisions of Schwarz Group are the first corporate customers to sign a purchase agreement (PPA) for green energy from the Kaskasi wind farm in April 2023. 

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RWE has signed six new PPAs with major industrial customers in April 2024. The PPA includes the supply of around 1,000 GW/h of green power per year from its Kaskasi offshore wind farm, starting from 2026. 

The PPAs have been signed between RWE Supply & Trading, DHL Group, Ensinger, Evonik, Infraserv Höchst, Thyssenkrupp Steel Europe, and Vodafone. RWE also plans regular maintenance to ensure optimal performance over its operational lifespan of 25 years.

In October 2024, RWE has initiated the SeaMe (Sustainable Ecosystem Approach in Monitoring the Marine Environment) project at the Kaskasi offshore wind farm. The goal of the initiative is to understand the offshore wind farms’ impacts on the marine ecosystem using scientific methods and CO?-reducing, AI-based monitoring technology. 

Summary

The Kaskasi Offshore Wind Farm (Kaskasi II) is one of the most successful offshore wind projects by RWE. The wind farm with 342 MW installed capacity supports the country's offshore wind targets and delivers clean energy to approximately 400,000 households. The wind farm is a testament to growing offshore wind technology by implementing technologies like renewable wind turbine blades and vibro pile driving for installation. With secured purchase agreements with key industrial partners, Kaskasi Wind Farm will be a forerunner to offshore wind farms in Germany.

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