Energy

Offshore wind turbine platform pivots downwind like a weathervane

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A 1:3 scale prototype of X1 Wind's floating platform was installed at the PLOCAN test site in the Canary Islands in 2023
X1 Wind
A 1:3 scale prototype of X1 Wind's floating platform was installed at the PLOCAN test site in the Canary Islands in 2023
X1 Wind
The X90 design is intended for mass production
X-Wind
The X90 is designed to meet the wind backwards
X-Wind
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A new offshore wind farm system that promises faster, cheaper installation and operations will be tested in the Mediterranean. Called the NextFloat+ Project, it received a €13.4-million (US$14.4-million) grant from the European Commission.

Setting up wind farms at sea seems like a logical idea. Sea breezes tend to blow regularly and open water provides a more predictable and dependable wind pattern than on land. Plus you don't have to worry so much about compulsory purchase of the building site.

However, the engineering challenges of setting up turbines at sea are so great that they often outweigh the benefits. This is because not only do the turbines need to be very robust, with blades that won't bend under load and strike their own mast, they also require heavy mooring systems to keep them in place that are expensive to install.

NextFloat+ is a consortium led by Barcelona-based X1 Wind and includes Technip Energies and NextFloat Plus SAS. Its purpose is to build a prototype 6-MW wind station called X90. This is a triangular floating platform with a single turbine that is assembled onshore and then towed to the installation site.

The X90 uses Single Point Mooring (SPM) and a Tension Leg Platform (TLP) system that doesn't require special heavy equipment to install. In a TLP, the triangular structure floats on the surface and three cables connect to a mooring on the seabed at depths of over 1,600 ft (500 m). These are then tensioned to keep the platform precisely in place. For the X90, the TLP uses a SPM to the cable trio that allows the platform to passively turn into the wind. Before the platform is floated out, the SPM is installed with a quick-connect system that lets the platform be snapped into place on arrival.

The X90 is designed to meet the wind backwards
X-Wind

This setup is designed around what at first seems like a backward turbine. Conventionally, wind turbines face into the wind and the assembly turns on top of a mast as the wind shifts. This means that the mast must be able to withstand a lot of strain and the rotor blades must bend as little as possible or they could end up striking the mast, which would be most unfortunate.

With the X90, the rotor is fixed on the platform, which does all the turning. In addition, the turbine pivots like a weathervane and faces away from the wind, so the air pushes the blade from behind. Since there's no mast to strike, the blades can pretty much bend as they please. This not only makes for a simpler and lighter design, but one that is cheaper and easier to maintain.

In all, the platform, mooring arrangements, and turbine reduce the installation's seabed footprint. It also lends itself to scalability thanks to its modular design, with a new mass-produced commercial platform of over 20 MW already on the drawing board.

"We’re thrilled to receive support from the Innovation Fund," said X1 Wind CEO and co-founder Alex Raventos. "The grant represents a cornerstone in the fundraising for the NextFloat+ Project, adding to finance already secured through the European Commission under the Horizon Europe program, finance secured through the French Government as part of the France 2030 plan operated by ADEME, plus private funding from partners and shareholders. Crucially, it will provide an opportunity to drive substantial improvements in the competitiveness of floating wind as we prepare for long-term mass deployment in locations around the world."

The video below shows a prototype of X1 Wind's PivotBuoy system in storm conditions.

Source: X-Wind

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8 comments
Bob Stuart
I am glad that somebody has finally had a look at water as offering opportunities rather than just problems to overcome to make a land-like foundation. I am astonished, dismayed, and baffled that anything was built before such questions were asked. There is a lot more improvement available in this whole area.
John S
This system looks like it may be one of the best ways to solve many issues of ocean wind farms. Let's hope so.
1stClassOPP
Good plan. I think if the winds were stronger than the structure could handle, it will probably dip into the sea, dumping some of the wind’s energy.
Global
I imagine the mooring lines would pivot around the anchored end, and also possibly link farms together, to feed back power to land?
Global
Forgot to add, wave and solar generation, since you already have a platform, could even self clean.
SteveG64
Would it be safer in high wave conditions if nearly all of the buoyancy was underwater, to minimize wind-age and wave action above the water? Rather than the generator being attached directly to the blades at the top of the mast as normal, could the generator be located in one of the legs, connected to the blades via hydraulics. Piping easily placed inside the main airfoil shaped leg.
martinwinlow
@ SteveG64 - A hydrostatic (hydraulic) drive connection between turbine and generator introduces at least a 10% loss of efficiency (typically more like 15%). That said, given the application, the advantages of simpler maintenance and potential construction cost savings (arguable; extra cost of hydrostatic drive Vs less weight at the nacelle, for starters) might make it worth doing.
pete-y
video is a waste of time and the mooring arrangements are not clear.
But backward blades and single anchor to pivot are good ideas.