But through the swirling chaos, a video showed the faint outline of a giant structure standing tall. Piercing through the wall of grey were the blades of two enormous turbines, and the hint of a V-shaped form supporting them from the water below.
The structure was the OceanX, described by developer Mingyang as the world’s largest single-capacity floating wind turbine (with a total capacity of 16.6MW, it is significantly larger than the floating Vestas V164 9.5MW turbines at Kincardine in Scotland). Installed only weeks before, the company claimed the device’s unconventional design enabled it to withstand the extreme conditions, emerging “as a symbol of strength and innovation” amidst the maelstrom.
“Unfazed by the storm's fury, OceanX demonstrated its superior anti-typhoon features, reinforcing Mingyang's commitment to advanced, reliable offshore wind solutions,” the firm’s announcement said.
Some other turbines fared less well. With the severity and frequency of extreme weather events increasing, could twin-turbine floating platforms provide a resilient future for the green power source?
Two heads better than one
Normally consisting of conventional single-tower turbines on buoyant platforms, floating wind farms can be installed in deeper water than fixed-bottom turbines. This opens previously unsuitable areas for wind power generation, while also enabling access to the higher wind speeds further from shore.
Zhongshan-headquartered Mingyang hopes its dual-turbine platform could capture even more of the available resource. The rotors cover a swept area of more than 52,000m2, the equivalent of more than seven football pitches. With a maximum height of 219m (roughly 66 storeys) and width of 369m, the device could generate 54 million kWh annually, enough to power 30,000 three-person houses.
Built using ‘ultra-high performance’ concrete in the floating foundation, there are reportedly 1,500 steel strands threaded through the arms to control tensioning forces.
Designed to withstand typhoon loads from any direction, OceanX has a single-point mooring system that allows the platform to adaptively yaw with the wind’s direction, consistently facing the incoming wind. This reportedly reduces the ultimate load on the support structure by 40%, improving safety and stability in typhoon conditions.
Having a structure that is anchored to the seabed at multiple points would put much higher stresses on it when sea and wind conditions are rough, said Professor Simon Hogg from Durham University to Professional Engineering. Using two smaller rotors instead of one large one allows the device to be proportionally shorter, he added, which could reduce loads on the structure.
“Maybe they feel that by having smaller diameter rotors, from a physical clearance point of view, you can come down to proportionately lower heights. And then also because it's offshore, the disruption from the terrain is not there, so that enables you to have better wind resource at a lower altitude,” said the department of engineering’s Ørsted professor of renewable energy.
“If you could have any size platform you like, I can't see why you wouldn't stick them vertically. But I guess they’re a ‘V’ to get the rotors spaced, so you can come down to as low a height as possible in order to get the moment down as much as possible.”
According to New Atlas, the OceanX was built to withstand and even harness Category 5 hurricane conditions, with winds of up to 260km/h (161mph) and waves as high as 30m. It reportedly has a higher turbulence intensity rating that conventional wind turbines, meaning it could continue operating in conditions that would cause power fluctuations and significant wear in other generators.
“That would be another benefit of having two [rotors] rather than one, because if you have a smaller structure, it becomes easier to cope with more variation in the wind resource than would be the case for one very large structure,” said Professor Hogg.
V for victory
The ‘V’ shape itself could also improve the resilience of the structure, according to Dr Luigi Di Sarno, a structural engineering specialist and reader in resilient and sustainable infrastructure at the University of Liverpool.
“The system is becoming more flexible,” he said. “It's like when you have a very thin person and you try to shake [them], they tend to interact with the movement. If you have a very stocky person, you don't do anything, you just get a small lateral movement. So that's basically what is happening in design. And of course, this has a lot of benefit in terms of resilience.”
The OceanX could also be more sustainable and cost-effective thanks to the ultra-high performance concrete that is more resistant to corrosion, he said.
Wind turbines are experiencing a similar level of progress to high-rise buildings in the late 20th century, he added, going from “clean” shapes to more unconventional forms – ones with large holes, for example – which have improved aerodynamic performance. “With this new approach [to wind turbines], we are opening up new challenges and new frontiers for the design, because if you rely on a single pile probably there are some limits, some cap that has already been reached.”
We could see more projects exploring twin-turbine configurations and single-point mooring if the potential advantages of OceanX are proven by the demonstration, Professor Hogg said. Previous projects have explored similar designs, such as EnBW’s Nezzy2.
“There's lots of potential for offshore wind in Mexico, in US areas where they do have hurricanes,” he said. “We've been asked at the university here a couple of times, ‘Could the sorts of turbines that are being deployed now in the North Sea be deployed in conditions where occasionally you have hurricane-level storms much more severe than you see here?’ And the answer is no, because they're not designed for that.
“Potentially you could design an analogous structure that would work OK, but these sort of solutions that you're looking at now are probably a better way of doing it.”
He added: “For certain areas of the world where there's the opportunity to do floating wind and they have hurricane conditions occasionally… then I think there is a market for this, and I think you will see more of these coming along.”
As the world warms and extreme weather events become more frequent – even in countries that do not typically face cyclones – we will need solutions that provide reliable power. Despite the dominance of single-tower turbines in fixed-bottom wind farms, the relative immaturity of the floating sector means there could be room for innovation, and wider adoption of twin-turbine platforms.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.