Gemini: a detailed look
The consortium of Northland Power, Siemens, Van Oord and HVC is
bringing intelligent energy to The Netherlands
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As we build Gemini, we will apply our proven construction and risk mitigation strategies on a greater scale. Working closely with our turbine supply and construction partners, Siemens and Van Oord, we will help the Netherlands achieve their renewable energy targets by powering 785,000 Dutch households. That’s intelligent energy.
Gemini will employ best-in-class technology to optimize safety and efficiency throughout construction and operations.
Vessel location at sea is tracked through the deployment of an automatic identification transponder system (AIS). To ensure the safety of the various installation and maintenance vessels, each ship’s transponder transmits its position, heading, speed and registered maritime identification number every 2 to 10 seconds. This data is received by ships in the vicinity and can be plotted automatically on a digital map or radar screen.
Project management on the open sea
A web-based site management tool enables a real-time interactive map application. The tool features dynamic real-time wind farm asset status and the tracking of personnel and vessels (AIS) overlaid on a nautical chart. All data is stored for the lifetime of the project, creating a clear audit trail of site activity.
Each wind turbine self-starts when the average wind speed reaches 3 to 5 m/s (metres per second). The output increases proportionately with the wind speed up to 12 to 13 m/s, at which point the power is regulated at a rated power of 4 MW.
When wind speed exceeds the maximum operational limit of
25 m/s, the turbine will shut down by pitching its blades (turning them parallel to the air flow). When the wind speed drops back below the maximum limit, the turbine’s systems automatically reset and begin to generate electricity again.
Current permits allow for daylight helicopter deployment, which will allow delivery of service teams directly to the turbine platform. The project has been designed and will be built for
24/7 helicopter access.
When steel structures are submerged in seawater, corrosion occurs. To prevent this, Gemini will employ an advanced impressed current cathodic protection system. Four electrical anodes will be premounted equidistant around the exterior circumference of the transition piece, and four more will be mounted to the interior. The combination of seawater, steel and the direct electrical current passing through the anodes will create a neutral, non-corrosive environment on the TP and the MP to the mudline.
Gemini facts & figures
Megawatt production capacity
Terawatt hours of electricity produced per year
Households whose electricity needs will be met
Million citizens who will have their electricity requirements met
Participating companies in the construction contract structure (Van Oord is the EPC contractor; Siemens is supplying the turbines)
Full-time operational jobs over the lifetime of
the wind farm
Billion euros of project financing (debt and
equity), completed in record time
Months to reach financial close – an unprecedented
time frame for a project of this scope
Kilometres per hour average wind speed for the area
Kilometres offshore (from Groningen)
Square kilometres of area occupied by the wind farm
in the North Sea
Metre variation of water depth at the wind farm site
Years between receiving Water Act permits and
financial close in May 2014
Months required to complete environmental
assessments and to get required project permits
Million tonnes of CO₂ reduction per year because
Local jobs expected to be created during construction
Land station being built in Eemshaven
Metres – range of monopile lengths, with each
built specifically for the installation depth
dictated by the conditions of each location.
Centimetres – range of monopile wall thicknesses,
which vary to support the structure where the sea
exerts the most stress
Revolutions per minute – range of rated rotor speeds
Metres - turbine hub height above sea level
Tonnes of lift capacity of the Aeolus offshore
Offshore high-voltage substations
Tonnes – weight of a full cable carousel on the Nexus
Kilometres of export cable laid from each
offshore substation to the land (approximately)
Rated kilovoltage of the smallest infield cable
(108 mm diameter) that connects the turbines
to the substations
Rated kilovoltage of the largest export cables
(267 mm diameter) that can each carry up to 75%
of the electricity Gemini will produce
Turbine blades, each weighing 18 tonnes,
required to complete the wind farm
Tonnes – total weight of the heaviest installed
turbine (including the monopile, transition piece,
nacelle and rotor with blades)
Siemens Wind Power
The Gemini Management Team
Magazine Living on Wind
Facts | figures
Gemini in figures
Design + realisation 8-13 Graphic designers