Floating ‘Counter-Rotating’ Wind Turbines Promise Unprecedented Power Output

éolienne flottante axe vertical contrarotative

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A new Norwegian company, called World Wide Wind, has developed technology to improve the performance of offshore wind projects. These are floating turbines with a vertical axis, made up of two sets of blades that rotate in the opposite direction. According to the designers, these wind turbines could generate more than twice the power provided by current offshore wind turbines.

Offshore wind farms typically rely on Horizontal Axis Wind Turbines (or HAWTs). Horizontal axis wind turbine), whose axes of rotation are parallel to the ground. The blades rotate in a plane perpendicular to the ground, and the longer they are, the higher the masts must be. However, installing them off the coast, where the ocean gets deeper, represents a real challenge: the heaviest components (engine and blades) are at the top of the mast and therefore their mounting on a floating platform is particularly complex. .

Vertical axis turbines (or VAWT, for Vertical axis wind turbine) of the World Wide Wind (WWW) allow us to overcome these difficulties. The generator and the rotor are located at the foot of the wind turbine, underwater, serving as stabilizers and counterweights; the upper turbine rotates in one direction, while the lower turbine and the outside of the mast rotate in the other direction. The structure tilts in the wind. WWW says its heavy-bottom, tiltable, counter-rotating coaxial turbines can solve the scale limitations of offshore wind power.

Reduced wake effect, higher turbine density

These wind turbines are distinguished by their double turbine: the upper turbine is fixed to a shaft placed in the center of the mast (and which joins the foot, up to the rotor), while the lower turbine is fixed to the outer shell of the mast (he itself linked to the stator). Each part rotates in the opposite direction to the other. This configuration makes it possible to double the relative speed of rotation with respect to a static stator.

Schematic of the vertical axis floating wind turbine designed by World Wide Wind. © world wind

The other advantage of these wind turbines is that they can take advantage of the wind from any direction. The blades are not facing into the wind: the two sets of three blades are arranged in a cone shape. WWW also notes that this design leads to a significant reduction in wake effect, which corresponds to the reduction in wind speed downstream of a wind turbine, after capturing some of its kinetic energy.

This effect makes it necessary to sufficiently space HAWT from each other in wind farms, to limit production reductions. Here, the distance between the turbines can be reduced by 50%, allowing four times as many turbines to be installed in a given marine area.

Another advantage of this technology: less impact on wildlife, as the rotating turbine is perceived as a natural obstacle. ” The low wingtip speed of the rotor blade prevents bird strikes and our design also allows for more recyclable materials to be used. “, specifies the company on its website.

Masts 400 meters high, for a capacity of 40 MW

The fact that these floating towers can tilt in the wind allows them to withstand strong winds, limiting damage. The parts that require the most maintenance are located at the foot of the wind turbine, under the floating platform, which makes maintenance easier, unlike HAWTs. It remains to be shown that these wind turbines are as resistant as expected in the open.

Currently, the trend is more towards giant offshore wind turbines. GE Wind Energy (a subsidiary of General Electric) stood out in 2019 with its Haliade-X wind turbine, with a capacity of 12 MW. It recently unveiled its new prototype, the 14 MW Haliade-X, which can generate up to 74 GWh of annual gross energy production, saving up to 52,000 tons of CO2 in the process. ” The ability to produce more electricity from a single turbine means that fewer turbines need to be installed in each wind farm. In addition to reducing capital expenses, it also simplifies operations and maintenance. said Vincent Schellings, chief technology officer for GE Renewable Energy Offshore Wind.

The largest wind turbine in the world to date remains the MySE 16.0-242 (16 MW) wind turbine, unveiled by the Chinese company MingYang Smart Energy in August 2021: at a height of 264 meters, it has a rotor diameter of 242 meters , and 118 meter long blades that allow it to sweep an area of ​​almost 46,000 mtwo. It is designed to withstand strong winds, including typhoons. Such a turbine can generate 80,000 MWh of electricity each year, enough to power more than 20,000 homes.

But WWW wind turbines could completely overshadow these already impressive projects: according to the company, they could reach 400 meters in height with a capacity of 40 MW! These vertical counter-rotating turbines could radically improve efficiency and reduce LCoE (levelized cost of energy, that is, the levelized cost of energy) of floating offshore wind projects; the latter could cost less than $50 per megawatt, according to company representatives.

WWW promises rapid prototyping. It plans to have a 3 MW model operational by 2026; the 40 MW giant could be ready by 2029.

Source: World Wide Wind

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