Without permanent anchoring, wind energy could be generated much more cheaply at sea. Floating platforms can be used in deep water. A French company is now building a prototype with 5 megawatts of power.
Wind energy at sea, the concept solves many problems – above all, acceptance. There are no stubborn neighbors on the water who feel disturbed by the large industrial buildings. Most rotors at sea are similar in construction to turbines on land: the rotor is mounted on a single tall mast and the mast is anchored to a foundation on the seabed.
The French company Eolink wants to completely break with this concept. Its wind turbines are built on a pyramid-shaped structure and float on the waves. They are not floor mounted.
Less construction effort
Compared to land, the mast of conventional systems on the water is longer and more complex. Added to this is the stretch below the surface, and it must be designed to withstand the force of the water. This is only possible in shallow areas at sea, such constructions are not possible in deep sea. The floating turbine should solve the dilemma. Because it doesn’t require an underwater structure or foundation, it takes 30 percent less material to produce it. In addition, the ocean regions where you can harvest the most wind are too deep for ground anchoring.
Construction of a plant with 5 megawatts
Several companies are working on such floating models. However, Eolink is already building a large demonstrator with 5 megawatts of power. The platform is anchored to the ground with a cable and thus automatically rotates optimally into the wind. The rotor itself can therefore be mounted rigidly on the support frame. Four base supports form the shape of a pyramid, the rotor sits on the head, and ballast tanks are located at the lower end of the struts, which balance the island.
Because of the pyramid design, the inclined support masts are significantly less stressed than with a vertical construction. There is a special feature: The rotor does not move outside the construction like in an old windmill, but rotates inside at the top of the pyramid. Two struts each form a V-shaped suspension, the rotor hangs between the two. This brings the following advantage: The struts move away from the rotor. In strong winds, it can deflect much more than a rotor attached to a vertical mast. This saves expensive material and reduces the inertia of the propeller.
Eolink states that the loading of the tanks with pumps can be dynamically controlled in order to be able to deal with difficult wind and current conditions.
In principle, the construction and maintenance of such mobile systems are much easier than with wind turbines installed at sea. The whole construction can be assembled in a shipyard and then only has to be towed to the place of use. An extensive revision can also be carried out again in the shipyard.
Will the pyramid defy the sea?
Eolink has raised $23 million to begin manufacturing a full-scale prototype. The pyramid has a bottom edge length of 52 meters and weighs 1100 tons. It is scheduled to go into operation as early as 2024. According to Eolink, these systems can be scaled up to 20 megawatts. The production costs of the electricity should be 20 to 25 percent lower than with conventional construction. The price does not express the main advantage of the concept. Floating plants can produce electricity where anchored pylons cannot be erected. The prototype must prove that the floating pyramid can survive heavy seas.