The Stability Frame, Hywind Scotland
Equinor ASA (formerly Statoil ASA)
Aberdeenshire, United Kingdom
The world’s first installation of a fully assembled Wind Turbine Generator (WTG) onto a floating substructure. Using the Saipem Stability Frame and Semi‐Submersible Crane Vessel Saipem 7000 to install five WTGs, Statoil’s Hywind Scotland Project is the world’s first floating wind farm. The Stability Frame used 25% of the material of a traditional frame and was far more efficient in terms of execution schedule. This delivered a cost saving to the project of 1.7m euros. The assembly was carried out in Stord, Norway, then the fully assembled turbines were towed to Scotland.
In recent years, we have become used to seeing wind turbines installed in the shallow waters off the coast, allowing the UK to take advantage of our natural resources and generate low carbon electricity. The technical demands of building marine wind turbines already appear significant, but are dwarfed by those associated with deep water installations. Yet the potential of these wind farms to provide increased and extended power generation means finding engineering solutions to their safe and economical installation is a vital task.
Hywind Scotland was realised through the invention of a novel Stability Frame, allowing each fully pre-assembled wind turbine – almost 100m tall and with a blade diameter of 154m – to be lifted from their Norwegian assembly area and mated with its 10,500 tonne submerged floating base, before being towed 450km across the North Sea to the site of the new Buchan Deep wind farm. The 30 tonne fabricated steel structure included a friction collar controlled with hydraulic actuators to allow lifting, transport and installation of the 1,140 tonne wind turbine generator, safely addressing the inherently unstable temporary condition and the extreme roll, pitch and yaw motions caused by wind and wave motions in transit. The frame is reusable and allows for rapid and repeatable operations.
The solution was the product of truly innovative ‘first-principles’ engineering, which was carefully developed and rigorously tested and led to the realisation of an ambitious first for UK engineering.