Floating offshore wind mooring turbines are the future of renewable wind energy. Bigger and further offshore to maximise their efficiency, they face significant mooring challenges, however. With over 20 years experience in deepwater mooring, Lankhorst Offshore is taking a lead in developing the mooring technologies that will be needed for the successful deployment of what is ultimately predicted to be the largest source of offshore wind energy globally.
Over the past 5 years, Lankhorst Offshore has supplied mooring lines for many floating turbine offshore trials. These include WindFloat Atlantic located offshore Viana, Portugal. The three 8,4 MW floating turbines are moored with Gama98® Dyneema® DM20, 103mm diameter mooring lines. This was the first ever Dyneema Long Term Mooring (LTM) System.
Offshore Aberdeen, Scotland, Gama98® Dyneema® DM20, 118mm diameter mooring lines, have been used to moor five 9,4 MW turbines at the Kincardine Floating Wind farm. While the TetraSpar® Demo, offshore Stavanger, Norway, developed by Stiesdal is a 3,6 MW floating turbine that uses 144mm diameter Gama98® Dyneema® DM2 with for its three mooring lines.
Advances in Fibre Rope Technology
The Offshore renewables energy market brings many new challenges for mooring systems in shallow waters. Depending on the type of the floater concept used, it requires ropes that are moderately stiff, or very stiff and in some other cases they may require ropes with high elongation in low loads. Meeting these demands is where the Gama98® Dyneema® DM20 rope construction has emerged as the mooring line of choice for floating offshore wind.
Beyond the mooring line characteristics, there are practical considerations such as enabling sea-bed installation of the rope ahead of the wind turbine platform arriving on station, thereby streamlining mooring operations. For this Lankhorst has developed and qualified filter barriers that protect the rope strength members from seabed particles penetrating the rope and causing internal abrasion.
Cut Resistant Mooring Lines
Cut resistance jackets too have become a necessary addition to protect the polyester mooring tethers from fishing activity surrounding the floating turbine platform. Lankhorst has established the qualification criteria for cut resistant jackets to assess resistance to a trawler steel wire running across a mooring line.
With increasing experience of the floating offshore wind market, Lankhorst has used its technical know-how to produce innovations that reflect the diversity of floating offshore wind turbine platform designs and mooring environments. These include new rope designs for different floater concepts such as Gama98® Dyneema® DM20 for a stiffer Station Keeping System (SKS).
“The floating offshore wind market is innovation driven. Turbine development continues apace with bigger and more efficient turbines, this in turn impacts the design of the floating platform. In addition to offshore wind platform rope developments, we are now broadening our research to include IoT applications that provide greater insights into the mooring line service life,” says Alberto Leao, Mooring Systems sales director, Lankhorst Offshore.