A innovative pilot floating wind turbine is set to be commissioned in Norway in the coming weeks after French contractor Bourbon Subsea Services completed installation and hook-up operations.
Designed by Denmark-based Stiesdal Offshore Technologies — with backing from Anglo-Dutch supermajor Shell, Germany's RWE and Tepco Renewable Power of Japan — the 3.6 megawatt TetraSpar demonstrator unit involves a turbine installed atop of a sub-structure in the shape of a tetrahedron.
After pre-installing mooring lines in 200 metres of water in June, Bourbon Subsea towed the facility to its test location at the Marine Energy Test Centre near Stavanger, hooking up the turbine in July before laying and connecting a power cable earlier this week.
The French company said it has installed most of the semi-submersible floating wind turbines — ranging in size from 2.5MW to 8.3MW — in Europe since 2011, and built on that experience for the Spar-based solution.
Henrik Stiesdal, inventor of the TetraSpar concept and chairman of TetraSpar Demonstrator ApS — the Shell, RWE, Tepco and Stiesdal joint venture — said: “We value the expertise of Bourbon engineers.
"Their experience with floating wind is already impressive and with (their) contribution, we and our partners have been able to execute the cable installation safely and within budget.”
Bourbon Subsea chief executive Patrick Belenfant described the project as "a challenge," adding that "we are now looking forward to (the development of) pre-industrial floating wind farms particularly in France, UK, Portugal, Spain, Norway, Japan and South Korea”.
Steisdal's website describes the TetraSpar foundation as a tetrahedral structure assembled from tubular steel components that is "expected to offer important competitive advantages with its potential for lean manufacturing, lean assembly and installation processes, and low material costs."
The foundation components were fabricated by Danish wind turbine tower manufacturer Welcon and transported to the port of Grenaa in Denmark in summer 2020.
Assembly took place faster than expected at Grenaa in October and November 2020, using no welding.
The turbine from Siemens Gamesa was mounted on the sub-structure following its launch in Denmark.
The terahedral sub-structure is designed to operate safely in water depths between 100 metres and more than 1000 metres, although the pilot facility will confirm the validity of these estimates.
Tepco said earlier this year that the streamlined fabrication and assembly process for the pilot facility "indicates that the standardisation and industrialisation approach of the TetraSpar concept could deliver cost and logistics advantages in comparison to other existing floating concepts."
Shell has a 46.2% stake in the TetraSpar Demonstrator joint venture, with Tepco on 30%. RWE on 23.1% and Stiesdal holding 0.7%.