Gemini

Location and Overview

The Gemini Wind Farm is an offshore wind farm located in the Dutch part of the North Sea, approximately 85 kilometers north of the coast of Groningen, Netherlands. It is one of the largest offshore wind farms globally.

Capacity and Turbines

The wind farm has a total capacity of 600 megawatts (MW) and consists of 150 Siemens SWT-4.0-130 wind turbines, each with a capacity of 4 MW. The turbines have a rotor diameter of 130 meters and blade lengths of 65 meters. They are equipped with high-wind ride-through (HWRT) technology, enabling operation at high wind speeds.

Layout and Construction

The wind farm is divided into two parts:

• The first part, located north of Ameland, comprises 75 turbines.
• The second part, located 55 kilometers north of Schiermonnikoog, also includes 75 turbines.

Construction began in early 2015, with the installation of the first monopile foundation in July 2015. The turbines were installed starting in February 2016, and all 150 turbines began producing power by the first week of December 2016. The project was fully commissioned in May 2017.

Water Depth and Foundations

The wind farm is built in an area with water depths ranging between 28 and 36 meters. The monopiles, which are the foundations for the turbines, have a total length of 65 meters, with 30 meters resting on the seabed. Each monopile has a diameter of 7.5 meters, a thickness of 7 cm, and weighs between 750 and 850 tons depending on the position and final design.

Electrical Infrastructure

The electricity generated by the turbines is transferred to two offshore substations via a network of cables. It is then converted into a 200kV alternating current and transported to the transformer station in Eemshaven by two 120km-long export cables. The power is further stepped up to 380kV and transmitted to the national power grid via cables to Oude Schild.

Ownership and Operation

The Gemini Wind Farm is developed by a consortium led by Northland Power, a Canadian power producer. Other consortium members include Siemens, a German technology firm; Van Oord, a Dutch marine contractor; and HVC (Hollandsche Vastgoed Campanjen), a public utility company. Northland Power is the operator of the wind farm.

Environmental Impact and Benefits

The Gemini Wind Farm is expected to produce approximately 2.6 TWh of clean and renewable electricity annually, which is enough to power around 785,000 households. It is estimated to offset about 1.25 million tonnes of carbon dioxide emissions per year.

Jobs and Economic Impact

The project created around 500 construction jobs and 120 operations and maintenance jobs.

Financing

The total construction cost of the Gemini project is estimated at around €2.8 billion. The project received significant financing, including loans worth more than €2 billion from banks, export development agencies, and credit insurance companies. Northland Power and PKA, a Danish pension fund, also provided subordinated loans of €80 million and €120 million, respectively.

Subsidies

The project is eligible for a maximum subsidy of €4.4 billion over 15 years to cover the difference between the cost price of the renewable electricity produced and the market price of non-renewable electricity.

Licenses and Decommissioning

The wind farm has licenses to operate for 20 years. After this period, the wind farm and all structures introduced onto the seabed must be removed. A bank security of €40 million has been made available for this purpose.

Service and Maintenance

The wind farm is serviced by an offshore service vessel with an inverted bow and X-Stern, launched by the Ulstein Group in April 2016, which houses 40 workers. The maintenance and operations are supported by various contractors, including Siemens, which provides maintenance services for the turbine generators over a period of 15 years.

Transmission and Power Purchase

The electricity generated is primarily purchased by Zeeland-based energy company Delta, which buys 85% of the power produced, while the remaining 15% is supplied to HVC.