Norfolk Marine’s Scour Prevention System for Elisa Floater

Norfolk Marine’s Tyre Filled Net (TFN) scour prevention system will be installed as scour protection for the foundation of the 5MW Elisa prototype under construction in the Canary Islands.

The TFN system will be installed on the turbine foundation inshore in controlled port conditions complimenting the projects “Off Site Construction” technology, Norfolk Marine said.

Esteyco, leader of the developer’s consortium, said: “TFNs have been chosen as scour protection for the project as they perfectly match with its core objective: minimising offshore tasks and the dependence on expensive and scarce offshore means. And pre-installing the TFNs in-harbour eliminates the traditional anti-scour offshore activity using rock armour.”

The TFN system is fabricated from recycled materials reducing the environment impact of offshore developments, Norfolk Marine said.

Each TFN consists of recycled tyres held inside a marine grade net. The tyres are tied together inside the net with ropes that provide a backup method of securing and recovering the tyres from the seabed. The tyres inside each net trap material which is suspended in the tidal water flow and prevent it escaping so the seabed is reinstated with naturally occurring sediment.

The 5MW Elisa prototype uses a gravity foundation, which essentially serves as a floating platform on which an automatic telescopic deployment tower with a wind turbine is anchored in water depths between 20 and 55 metres.

Each unit consists of a concrete platform, a mast, and a turbine, assembled onshore. It is then towed into the open sea to its site, using conventional tugs.

Once deployed at sea, the platform is weighted and anchored to the seabed. Then, once the platform is secured, the tower is erected in its final position by means of cables and heavy-duty cable-pulling cylinders.

Esteyco has developed the technology and is building the prototype with three partner companies, Gamesa (now Siemens Gamesa), ALE Heavy-Lift and DEWI-UL.