If the first prototypes were born ten years ago, three families of floats coexist. Research is still necessary to develop the underwater electric cables.
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Steel or concrete, the companies that today want to raise the bet of the floating wind power still hesitate on the material to be used. If it is made of steel, the float weighs, with the turbine, between 2,500 and 4,000 tonnes. If it is concrete, it is rather around 10,000 tonnes. A real subject for ports, where the bearing capacities of the quays, lifting and towing equipment, as well as storage spaces are insufficient.
But weight is not the only criterion. The draft is also decisive. A concrete float will need a deeper port for its launching than a steel model. This is one of the reasons why the Eolmed pilot farm, off Gruissan (Aude), finally preferred to choose the metal version.
Concrete, however, has advantages. “In Europe, it is complicated to obtain competitive steel, while concrete can be prepared with cement, sand and local aggregates. Its price is, moreover, less volatile, it is an important element In the current inflationary context, “underlines Paul de la Guérivière, CEO of the company BW Ideol, which has developed the floats of Eolmed.
The family of the” Bottle of milk “
This float is a type of barge 40 to 60 meters side by 10 meters high, the size of a four -story building, hung at the bottom by chains and sea anchors. The center of the parallelepiped, empty, absorbed the energy of the swell and the currents. The turbine is based on one of the four sides.
This solution was chosen for the wind turbine thatideol commissioned in 2018 in Japan, and for a Scottish floating farm attributed to the French start-up in early 2022 for a power of 1 Gigawatt, double the field Get-based wind from Saint-Nazaire.
Other designs compete with the float in the ring. All are made of steel or cylindrical or prismatic (welded plates to form parallelepipedes). There is the so -called “bottle of milk” family, a single -weighted cylinder of several hundred tonnes of concrete, maintained vertical by the thrust of Archimedes and stabilized, again, by traditional anchors. The semi-submersible family consists of giant barrels connected by tendons. The turbine is based on one of them and the other two are ballasted. Or the three are surmounted by a tripod in the middle of which the wind turbine sits.
This is the choice of renewable EDF in Port-Saint-Louis-du-Rhône, on a concept developed by the Dutch SBM offshore. Except that the anchor lines will be tense, to increase general stability. And that the anchors, bells 9 meters in diameter inside which the void will be made, will never move.