Fixed, Floating, or Both? Major Offshore Wind Project Weighing Options

The developers of the 2 GW West of Orkney wind farm offshore Scotland have shared more information on the project through the recently published documents.

In January, the Offshore Wind Power Limited (OWPL) consortium comprising Macquarie’s Green Investment Group, TotalEnergies, and Scottish offshore wind developer RIDG secured rights in the Crown Estate Scotland’s ScotWind leasing round to develop the offshore windfarm around 30 kilometres off the west coast of Orkney and around 25 kilometres from the north Caithness coast.

The consortium has already undertaken surveys and studies, especially in relation to the environment, to ensure that the project fully meets its sustainable development objectives, and last week they submitted an Environmental Impact Assessment (EIA) Scoping Report to Marine Scotland, Orkney Islands Council and The Highland Council detailing all of the studies and surveys they will undertake in the years ahead.

The project is currently considering both fixed-bottom foundations and floating substructures for the wind turbines. The water depths across the site range from 45 metres to 100 metres.

At present, it is anticipated that water depths under 70 metres will be suitable for fixed-bottom foundations and depths of over 55 metres are suitable for floating foundations.

There is an overlap in the viability of fixed-bottom foundations and floating foundations in relation to water depth.

The final technology selection will be driven by a series of environmental, technical and commercial variables. There is the potential for each foundation technology to be used for all the wind turbines or a combination of both technologies, according to the scoping report.

The wind farm will comprise up to 125 wind turbines, meaning the minimum individual capacity of the turbines will be 16 MW, up to five offshore substation platforms and up to two onshore substations, up to 750 kilometres of inter-array cables, and up to ten export cables, including up to five to a landfall at Caithness, up to five to a landfall at Flotta via onshore sections across Hoy and potentially Fara.

The maximum rotor diameter of the wind turbines will be up to 330 metres, and the maximum rotor tip height up to 370 metres.

As part of the proposal, the consortium said that it designed a supply chain strategy specifically to bring together a unique combination of stakeholders to maximise the opportunities for the region.

The partners have already committed to a GBP 140 million initiative during the initial phase of the project to develop the supply chain, drive skills development and create opportunities for businesses and organisations in Caithness and Orkney, across Scotland and the rest of the UK.

The consortium has also finalised a grid connection agreement with National Grid, with a connection point in Caithness, and once built, the offshore wind farm could also deliver renewable power to the Flotta Hydrogen Hub, a proposed large-scale green hydrogen production facility on Orkney.

Developers are now launching a series of public consultation events where local communities and stakeholders can find out more about the project and ask questions.

The first virtual public exhibition is scheduled for March 21.

”We are really keen to hear local views on our proposals,” said Stephen Kerr, Project Director of the West of Orkney Windfarm.

”The virtual exhibition will open on March 21 and will include two live question and answer sessions on March 29 – where people can hear directly from project staff and ask any questions they may have.”

The consortium plans to produce first power at the wind farm in 2029.

Once fully commissioned, the project will be capable of powering the equivalent of more than two million homes.

There is currently only one wind farm in operation that combines fixed-bottom and floating wind technology.

Last year, China’s China Three Gorges commissioned the pilot anti-typhoon floating wind turbine at the Yangxi Shapa III wind farm.

This was also the first project globally where a floating wind turbine was connected to a fixed-bottom turbine.

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