Gemini: a detailed look

 

The consortium of Northland Power, Siemens, Van Oord and HVC is

bringing intelligent energy to The Netherlands

Back to overview

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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.

 

On location

Gemini will employ best-in-class technology to optimize safety and efficiency throughout construction and operations.

 

Navigation

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.

 

Operation systems

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.

 

Heli-access

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.

 

Corrosion protection

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

of Gemini

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

installation crane

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)

 

 

600

2.6

785,000

1.5

 

2

 

 

75–100

 

2.8

 

6

 

36

85

68

 

28–36

5

 

24–36

 

1.25

 

500

 

1

59–73

 

7–11

 

 

5–13

88.5

990

 

2

5,000

 

110

33

 

 

220

 

 

450

 

1,347

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