Van Oord installed the Slip Joint foundation in the 19 MW Borssele V offshore wind site last week, using its installation vessel Aeolus. It is one of several innovations that are applied at the innovation site which is part of the Borssele wind farm zone.
It was the first time a submerged Slip Joint was used on a full-sized offshore wind turbine on a fully commercial basis.
The Slip Joint connects a monopile and a transition piece by means of two conical sections placed on top of each other which can be produced using standard manufacturing methods. It is based on friction, with the weight ensuring firmness and stability. Installation takes place by sliding the wind turbine’s foundation elements over the monopile, without having to use grout or bolts. According to Van Oord, the Slip Joint provides a rapid, simple and safe installation solution in combination with reduced maintenance for the duration of the project.
The Slip Joint makes a submerged connection possible, allowing for a more balanced weight distribution between monopile and trasition piece. As a result, the installation of larger foundations for the next generation of wind turbines is made possible, using existing vessels.
The design and production of the Slip Joint was certified by DNVGL in the autumn of 2019, with MottMcDonald assessing it on bankability aspects.
The Borssele V project, located around 20 km off the coast of Zeeland, consists of two 9.5 MW wind turbines. The site was assigned as innovation site to introduce advanced technologies for commercial application in future offshore wind farms with larger turbines and in deeper waters and to demonstrate the practical value. The technologies should contribute to decrease the Levelized Cost of Energy (LCoE).
The other technologies demonstrated are Thermally Sprayed Aluminium (TSA), Impressed Current Cathodic Protection (ICCP) optimisation, oval cable entry holes and Eco-friendly scour protection.
Two Towers BV, consisting of Van Oord, Investri Offshore and Green Giraffe, has been awarded the project in 2018. Van Oord is was awarded the Balance of Plant scope for this project which is planned to become operational in 2021.