Technical description

​Offshore Projects Elements
​Maximum number of turbines​Up to 240 offshore wind turbines
​Individual turbine capacity​Between 5MW and 8MW
​Turbine rotor diametersUp to ​178 metres (depending on the size of the turbine used)
​Maximum blade tip height​ Up to 200 metres above MHWS
​Turbine clearance above sea level ​At least 22 metres above MHWS
​Water depth​Between 20 and 40 metres below LAT at the wind farm site
​Foundations

​The following foundation options are being considered (the chosen option depending on the size of selected turbines and a number of other variables):

  • Pile driven or drill/driven single steel monopole (cylindrical steel tube)
  • Gravity base (similar to a concrete foot)
  • Piled steel jacket (metal matrix of cross joints)
  • Steel jacket on suction caissons (steel foot that sucks itself into the sediment during installation)
​Inter-array network, substation and transmission

​Up to five HVAC collector substations will be constructed within the wind farm, connected by inter-array cables of 30 to 70kV. Interlink cables will connect the offshore substations directly to each other to provide redundancy capability.

If HVAC tranmission is employed:

  • A Reactive Compensation platform will be required, aproximately half way along the cable route, to compensate for reactive losses in the export cable
  • Up to four subsea HVAC export circuits, each of up to 140km in length, running from the offshore substations to landfall, each with a voltage between 132 and 400kV. The offshore export cables will be joined to the onshore cables at the transition joint bay located in the vicinity of the landfall, from where the cables will run underground for approximately 40km to the onshore substation located at Killingholme

 

If HVDC transmission is employed:

  • Array cables and HVAC collector substations as above, plus up to two HVDC convertor stations
  • No Reactive Compensation platform would be required in the case of HVDC transmission
  • Up to to 2 HVDC circuits, running 140km to landfall and an additional, underground, 40km to the onshore substation located at Killingholme
​Offshore construction

​The offshsore construction works could take up to four years to complete; foundation installation (i.e piling/driving etc.) is anticipated to be completed in 24 months

 

Safety zones, typically up to 500m, will most likely be applied for around construction vessels and/or offshore structures during the construction phase

 

The wind farm will have a ife span of approximately 25 years

​Onshore Project Elements
​​Cable landfall​​The offshore cables will make landfall in the vicinity of Horseshoe Point, south of Grimsby, where they will be jointed to the onshore underground cables in transition joint bays. The cables at the landfall will be installed by horizontal directional drilling (HDD) beneath the saltmarsh and sea defence.
​​Onshore cable works​Onshore cables will run a distance of about 40km from landfall to the onshore substation. All of the onshore cables will be installed underground, mostly using open cut trenching techniques. Either HDD or open cut trenching will be used to cross roads, with method statements to be agreed with the Highways Agency

 

Jointing bays will be constructed at regular intervals (approx. every 750m to 2.5km) along the onshore cable route. Maximum dimensions of these jointing bays 25m x 6m, 2m deep.

 

The working width of the onshore cable route corridor will be up to 40m wide. Temporary construction compounds will also be created along the onshore cable route.

​​Onshore substation

​The onshore substation will be located adjacent to the National Grid Killingholme substation, and will have a site footprint of up to 32,200 m2. It will include the equipment required to transfer electricity from the offshore wind farm to the national grid and is likely to include the following:

  • Onshore transformers (likely to be 400/220kV)
  • Reactors (likely to be connected on 220kV)
  • High voltage gas insulted switch gear systems (likely to be 220kV and 400kV)
  • Static VAR compensators (SVC) or static synchronous compensator (STATCOM) (likely to be connected on 16kV)
  • Harmonic filters (HF)

In the event that an HVDC solution is chosen, the onshore substation site would be a Convertor Station, and would likely consist of the following:

  • 1200MW bi-pole VSC HVDC convertor station
  • High Voltage gas insulted switchgear systems