The floating wind farm on track to be the largest in the world when it comes online in 2026 will be built using the next-generation platform design from Stiesdal Offshore now being prototyped in the North Sea, following the signing a deal by project consortium Highland Wind.

The Pentland Floating Offshore Wind Farm (PFOWF), being built 7.5km off the coast of Dounreay in the Scottish Highlands in waters as deep as 100 metres, will use a variant of Stiesdal Offshore’s TetraSpar concept called the TetraSub for the 100MW project, which will power 70,000 homes once fully operational.

“The objectives of Pentland are to demonstrate new floating wind technologies which will enable industrialisation, develop local supply chains and reduce costs, allowing deployment of floating wind in the UK and globally at scale,” said PFOWF project director Richard Copeland.

“For us, the Stiesdal Offshore TetraSub concept ticks all of these boxes,” he stated, specifying “simple modules… which tap into existing highly industrialised steel tubular [and] turbine tower supply chain; fast-assembly jointing technology; and limited requirement for specialist port facilities or infrastructure” as winning the day for the design.

Stiesdal Offshore CEO Peder Riis Nickelsen said: “This project will support us to meet market demands for low-cost and fast deployment of floating wind technology, advancing the next generation of floating offshore wind turbines with capacity of 14MW and more.”

Copeland told Recharge the PFOWF development team was “still engaging the market on steel supply, [with] the project committed to assembling the units at a UK port but still finalising location selection”.

“In addition, PFOWF has been working closely with [business development agency] Scottish Enterprise via its Scottish Development International and Scottish Manufacturing Advisory Service teams and DeepWind Offshore Wind cluster to introduce Scottish companies for supply opportunities at all levels,” he said.

The TetraSub is a semisubmersible version of the original TetraSpar concept, first revealed exclusively by Recharge in 2015, which was devised by industry pioneer Henrik Stiesdal for factory-fabrication and quayside assembly, with an innovative ‘keel’ feature that allows the units to be constructed in shallow-water ports and installed in deepwater with the stabiliser lowered.

“The TetraSub [as a] semisubmersible variant of the Tetra[Spar] concept... is better suited for the relatively shallow water conditions at [PFOWF] and the marine operations are easier. The last part is very important in the rough waters off the north coast of Scotland,” said Stiesdal.

A prototype of the design installed last year at the MetCentre R&D centre off western Norway as part of a demonstrator project backed by international energy players Shell, RWE and TEPCO is in the midst of a one-year testing programme.

Late last year, Highland Wind revealed plans to use Scrabster Harbour on the far northern tip of Scotland as an operations and maintenance support base for PFOWF, which is to be built in two phases, with a flagship turbine deployed offshore as early as 2023 and construction of the full development complete three years later.

Scottish Enterprise director of economic opportunities and climate Suzanne Sosna said: “Floating wind presents huge potential not only for Scotland’s economy, but for companies the length and breadth of the country to take advantage of significant manufacturing and supply chain opportunities.

“Scotland can lead the way in floating wind. We look forward to working with developers, manufacturers and industry partners to maximise future opportunities and showcase Scotland’s unique global strengths in this sector.”

The project – being led by Copenhagen Infrastructure Partners and engineered by Copenhagen Offshore Partners under the Highland Wind banner – is set to be built on the site of the vanguard Dounreay Trì demonstrator launched in 2016 and so is boosted by already having a number of consents granted by Marine Scotland for the first project.

Consultancy DNV calculates floating wind projects currently make up over 15% of the total offshore wind deployment in the pipeline for switch-on by mid-century, equal to some 264GW of the 1,750GW slated to be installed.