West of Orkney Wind Farm, Scotland

The West of Orkney Wind Farm is a proposed around 2GW wind project within N1 Plan Option in Offshore Wind Sectoral Wind Plan, offshore west coast of Orkney in Scotland.

The N1 option plan is one of the 15 areas around Scotland which are suitable for the development of commercial offshore wind farms, as considered by the Scottish Government.

The wind project is proposed by Offshore Wind Power Limited (OWPL), a joint venture of Macquarie’s Green Investment Group (46.75%), now lead by Corio Generation, a GIG portfolio company and a specialist in offshore wind business, TotalEnergies (38.25%), and Renewable Infrastructure Development Group (RIDG) (15%).

The Crown Estate Scotland awarded option agreement to the joint venture in January 2022 after the commencement of ScotWind leasing round in late 2019.

According to OWPL, the project will entail a potential investment of more than £4bn. The partners will invest £140m to support local supply chain development, ports enhancement, and harbor infrastructure in Caithness and Orkney.

In April 2022, the Supply Chain Development Statement (SCDS) Outlook document was submitted by the joint venture to the Crown Estate Scotland. The Crown Estate Scotland officially signed the Option to Lease Agreement with the partners of the joint venture.

As per the document, the partners commit to spend a minimum of £932m during the development, construction, and operation of the project for six years in Scotland.

The offshore and onshore construction of the wind farm will take around four years to complete. The offshore construction will be completed between 2028 to 2031 and the onshore construction between 2027 and 2030.

West of Orkney Wind Farm Location

The wind farm will be located in 28km from Hoy west coast, Orkney, and at least 23km from Caithness north coast, and around 25km Sutherland north coast in Scotland.

Across the Option Agreement Area (OAA), the water depths range from 45m to 100m, and the area has two shallow bank areas, Stormy Bank and Whiten Head Bank.

West of Orkney Wind Farm Details

The West of Orkney Wind Farm will have offshore and onshore infrastructure. The offshore infrastructure, Wind Turbine Generators (WTGs) and associated structures, inter array cables, and Offshore Substation Platforms (OSPs), will be located in the array area known as Option Agreement Area (OAA).

Up to 125 WTGs, with horizontal axis turbines, are expected to be installed. Each WTG will have a hub height of up to 200m, rotor diameter of up to 330m, and maximum rotor tip height (above LAT) of up to 370m.

The WTGs will be separated by a minimum of 1km from each other, as indicated in the WTG layout.

The WTGs will be supported by fixed-bottom foundations or floating substructures where over 55m water depth will support floating foundations and under 70m will support fixed-bottom foundations. The type of foundations has not been decided yet.

The fixed-bottom foundations will have up to four legs per foundation and monopiles with up to 18m base diameter and pile diameter.

Scour protection may be needed to prevent erosion of the structures.

A maximum of five OSPs will be needed which will receive power from WTGs and convert and transfer it. Each substation will have anticipated height (above mean sea level) of up to 26m, topsides dimensions of 45*38m (length*width) and piled jacket foundations with base diameter of up to 35*35m having up to eight piles per foundation.

Power Transmission

The power from WTGs will be delivered to OSPs via inter-array cables. These cables will have an anticipated length of up to 750km, up to 132kV voltage, and 225mm external cable diameter. The project will also have up to six interconnector cables, as anticipated, of 150km total length.

The array area will be connected to the Caithness landfall and Flotta landfall with up to ten offshore export cables where up to five will connect array area to Caithness landfall and up to five to Flotta landfall, crossing Orkney west and Scapa Flow through onshore routes across Hoy and Fara.

These cables will have anticipated voltage of up to 600kV, and external diameter of 330mm. The cables connecting offshore Caithness will be up to 320km long, up to 340km long connecting offshore Orkney (Hoy), and up to 60km long connecting Scapa Flow.

The offshore export cables will be installed at the landfall areas by using one of the three techniques being considered: Horizontal Directional Drilling (HDD), open-cut trench, and rock pinning technique.

By using open-cut trenching, as anticipated, up to 10 onshore export cables will be installed underground. Up to five will be installed at Caitness and up to five at Orkney, including installation of five cables across Hoy, Flotta, and Fara, with no overhead transmission lines planned yet.

Each cable will have a voltage of up to 600kV and will be up to 175km long connecting Caithness and up to 155km long across Hoy, Fara, and Flotta in Orkney.

There will be up to two new onshore substations located at Spittal (Caithness) and/or at Flotta (Orkney). These stations will connect to the project, grid, and/or Flotta Hydrogen Hub. The substations will have anticipated footprint of 20 hectares (ha) located at Spittal and 15ha located at Flotta.

Contractors Involved

The Environmental Impact Assessment (EIA) Scoping Report of the wind farm was prepared by Xodus Group Ltd.

Scottish Hydrogen Electric Transmission plc (SHET-L) will be responsible for construction and operation of the grid infrastructure.

In October 2022, Ocean Infinity, a robotic technology company, and Spectrum Offshore, a company specialising in offshore marine surveys, geophysical surveys, and crew transfer services, conducted the offshore and nearshore survey campaigns at the project site.

TotalEnergies UK Offshore Wind Hub, an offshore wind developer in the UK, acted as the survey manager of the campaigns.

The Offshore Wind Consultants (OWC), a part of ABL Group and headquartered in London, UK, was the adviser of survey campaigns.

Power Purchase Agreements

In October 2021, a power purchase agreement was signed by the joint venture with National Grid in Caithness to deliver renewable power to the proposed Flotta Hydrogen Hub, a green hydrogen production facility located at the Flotta Terminal.

To connect Spittal substation’s existing network, OWPL has signed another grid connection agreement with National Grid.