By: Teun Schröder The Norwegian start-up World Wide Wind advocates a radical new model of offshore wind turbines. The floating wind turbines have two sets of blades that rotate vertically in opposite directions about an axis in the mast. With this design, the company expects to generate much more power than traditional models can generate. Last week, World Wide Wind presented drawings of floating vertical wind turbines intended for the sea. Their windmill consists of two sets of turbine blades that rotate in opposite directions. The idea of ​​the counter-rotating vertical turbine is that it doubles the rotational speed of the blades. The result: much more energy yield than we are used to from vertical wind turbines. Potential vertical windmills For Gerard van Bussel, emeritus professor of wind energy at TU Delft, the design of World Wide Wind is a feast of recognition. “Ten years ago we did research into the same kind of design together with the Danish Technical University. The further you go out to sea, the more complicated the maintenance of a wind farm is. That is why you want to design a turbine that is as simple as possible. A floating vertical mill offers that simplicity.” Testing in Denmark At the time, the research team of the Deepwind project, of which Van Bussel was part, was working on a vertical floating windmill according to the Darrieus design: 'little whipped cream whipper model'. Van Bussel: “Actually, all the research results were positive. We even conducted tests on the water. First in the wave basin of the MARIN in Wageningen and later in practice in the Roskildefjord in Denmark. But due to a lack of funding, the concept has never been tested on a large scale.” Giant wind turbine Now World Wide Wind is breathing new life into the idea of ​​the vertically floating windmill. And there is no lack of ambition. From 2026, the company says it will start operation with turbines with a capacity of 3 megawatts. Ultimately, World Wide Wind wants to build a model in 2029 with a capacity of 40 megawatts that will reach 400 meters into the air. For comparison, the largest windmill of MingYang Smart Energy today is 'only' 242 meters long and has a capacity of 16 megawatts. World Wide Wind builds on the expectations by claiming that they expect a cost of about 50 euros per generated megawatt hour. In the direction of 2030, the EU assumes a cost price of 65 euros per megawatt hour. In its estimates up to 2027, the US Department of Energy even assumes more than 100 euros per megawatt hour generated. For a long time it was thought that windmills with a vertical axis produce less energy than turbines with a horizontal axis. But that idea is outdated, says Van Bussel. More experts are now seeing the potential of vertical mills. Challenges enough For the time being, World Wide Wind has not revealed much about the technical details of its ambitions. There are also no practical tests on a small scale yet. It is striking that World Wide Wind deviates from the proven Darrieus design and opts for a turbine with more rotating parts. These can have a hard time in the salty seawater. In addition, floating wind turbines often lose energy due to the swaying of the mast. The question is how big this loss will be if the turbines become longer and wider. Another challenge is getting the electricity generated from the wind turbines to land. The further the wind turbines are out to sea, the longer the cables that connect the park to the land must be. Not in the North Sea Still, Van Bussel does not want to get rid of the idea immediately. “The principle remains more or less the same as we tested ten years ago with positive results. Although I don't think we will eventually encounter them in the North Sea. It is much too shallow, so we can get by with wind turbines that are attached to the seabed.” And whether a wind turbine with a capacity of 40 megawatts is possible? “I will no longer comment on that,” laughs Van Bussel. “Twenty years ago we thought 20 megawatt turbines were impossible. It now seems very likely that we are going in that direction.”