Two years after Vestas introduced its V163-4.5 MW onshore wind turbine aimed specifically at grid-constrained sites in the US, Nordex Group has followed this summer with its own ‘US-turbine’, slightly bigger and more powerful – and with flexible power ratings.
Earlier this year we discussed the first contours of this Nordex ‘US-turbine’ that finally became the N169/5.X, on display at the company’s WindEurope 2024 booth in Bilbao, Spain.
Vestas has enjoyed huge success with its V163-4.5 MW (216W/m2), boasting a reported US order intake of more than 5GW by late 2023. This evolutionary product development stems directly from the V150-4.5 MW and is part of Vestas’ 4MW platform, with a track record of nearly 20,000 units since the initial V112-3.0 MW model introduced in 2010.
The V163-4.5 MW retained the 4.5MW rating and added an enlarged 163-metre rotor size, representing an increment of 18% in the swept area against the V150-4.5 MW.
Meeting specific requirements
It is also configured for sites with grid-capacity constraints and to achieve high capacity factors – with corresponding competitive annual energy production performance – when grid limitations occur.
The N169/5.X is the latest model enhancement of the Nordex Delta4000 platform, which has sold more than 5,000 turbine units at operational and under construction projects since the N149/4.0-4.5 was introduced in 2018.
Multiple portfolio expansions followed, including the N175/6.X flagship model, which saw a low- and medium-wind sites prototype installed in July 2024.
Lightweight rotor
In a recent conversation with Max Jungk, Nordex Group vice-president of global product strategy and sales support, we discussed the main product features of the N169/5.X: a lightweight 169-metre rotor comprising a new hub, pitch bearings and blades.
The 169-metre rotor is one of the largest sizes announced for the US market, which according to Jungk, increases wind farm annual energy production (AEP) for a given installed power capacity by up to 11% compared with the N163/5.X. The rest of the nacelle remains virtually unchanged.
The configuration with matching 5.0–5.5MW flexible ratings offers a favourable 223–245W/m2 specific power range and corresponding high capacity factors.
The turbine comes with a range of towers optimised for the US market, including considerations for rail transport of large main components such as towers and blades, which means that sizes and masses must match rail transport equipment capabilities and constraints.
Jungk highlights that onshore rotor sizes exceeding 170 metres start creating transport bottlenecks, making certain projects unattractive.
A logical alternative to N169/5.X could have been a scaled-down N163/5.X variant with reduced 4.5MW rating, a ‘fictive’ N163/4.5 look-alike configuration that would have brought specifications fully in line with the V163-4.5 MW.
However, reality has shown many times that the scaling down of existing turbine configurations is typically not the best way to create new optimised products.
The main reason for this is that the scaling-down process typically introduces sub-optimisations by creating strength and/or stiffness reserves in places where they are not needed – resulting in higher mass and/or cost as possible negative impacts.
Benefits of evolutionary upscaling
Evolutionary upscaling, on the other hand – for example through fitting a larger rotor, as both the V163-4.5 MW and N169/5.X product developments exemplify – enables the application of extra stiffness and/or strength only in essential places, where it is necessary.
Another distinct benefit of these turbine models and their scaling exercises is that it allows the ‘direct’ reuse of available proven and fully validated components such as enhanced gearboxes or electrical systems from the existing portfolio.
This in turn enables platform modularity and in parallel provides a boost to industrialisation processes.
For the N169/5/X, Nordex chose the proven N163/5.X gearbox but incorporated technology enhancements, especially in ongoing torque density increments, to compensate for the higher input torque of the enlarged N169/5.X rotor.
The combination of transport and logistical challenges with the 5.X gearbox technology boundaries makes the selected 169-metre rotor a sweet spot for the new US turbine, according to Jungk.
Production of the N169/5.X for the US market is scheduled to start in 2026 at the Nordex facility in West Branch, Iowa.
The time lapse between setting and freezing all product specifications is essential for completing rotor and full-system validation before ramp-up, Jungk explains, adding that the use of proven technology to the widest possible extent is another crucial factor.
This is particularly important in markets such as the US, where customers and investors are known for their risk aversion and focus on quality.
The local manufacturing of the N163/5X and N163/6.X turbines for both the US and Canada markets will commence in the first half of 2025, preceding the N169/5.X ramp up.
New OceanX multirotor details
On 11 August, Mingyang shared a picture on social media of its 16.6MW OceanX prototype setting sail on a 700km sea journey to the company’s offshore test site along China’s south-east coast.
Several weeks earlier, I had received a video from a local television programme dedicated to Mingyang and its OceanX milestone achievement, offering interesting additional insights into previously unknown details.
The video’s addressee was aerodyn-engineering director Sönke Siegfriedsen, inventor and IP holder of Nezzy2. He introduced the radical fully integrated concept with an initial rating of 15MW and twin two-bladed 150-metre rotors in June 2017.
The OceanX video begins with the rotor-fitting process in the final assembly stage, with each of the individual 180-metre counter-rotating rotors separately mounted using harbour cranes in single lifts.
This is similar to the mounting of both distinctly shaped nacelles, with the prototype also in floating mode and docked at the assembly quay.
The next section depicts the OceanX operating in a marine environment, highlighting the close inner spacing between the 9-metre rotors and showing the 369-metre total installation width between the outer blade tips.
We have previously described the floater assembly process for the OceanX, but watching it is truly impressive.
It involves the use of multi-wheel self-propelled modular trailers (SPMTs) that move and precisely position each concrete segment and mount it to the three-legged floater structure being assembled step by step.
One of the three steel end modules with a pre-assembled white-yellow buoyancy element is shown in the video being carried atop the SPMT.
Shallow-water mooring system
Hybrid mooring system details – seen briefly in a quick sequence – reveal multiple horizontal cable-guiding structural elements attached to the seabed. This is an unusual solution, which is being deployed perhaps to match the shallow-water mooring challenges of the prototype site, at water depths of just 40 metres.
No further details are given on the full three-dimensional mooring layout comprising both cables and chains.
A Mingyang employee in another video part-climbs the yellow-painted ladder alongside the grey central main tower towards an outer service platform equipped with an access door.
We are not shown how exactly he reaches the ladder – typical boat-landing access would be even more challenging than for fixed-bottom offshore turbines because both the floater and the boat move. I am unaware of whether Mingyang is considering the deployment of stabilised access systems like the one designed by Dutch pioneer Ampelmann.
The person is seen proceeding further inside the central tower and climbing towards the upper-flange tower-mounting area. This is where the two inclined towers meet, and the following sequence shows a TV reporter and the Mingyang employee riding an internal lift together, for the final stretch towards a nacelle.
The bright white droplet-shaped tower internals accommodate an array of power transport cables running downward from each nacelle, towards the inside of the main central tower bottom section incorporating the electrical conversion system.
Having a single electrical system into which both turbines feed in power reduces its complexity. Alternatively, individual nacelle-based electrical systems would increase nacelle mass but reduce power transport loss down-tower. This is only a theoretical comparison with OceanX, as the nacelles of Mingyang’s compact MySE8.3-180 HybridDrive lack the internal space needed to accommodate individual full electrical systems including converter(s), MV-transformer and switchgear.
Helicopter hoisting
Some final shots of the prototype show both men standing atop the nacelle’s helicopter-hoisting platform. I cannot help wondering at what wind speeds and wave heights it would be safe to transfer service crew and tools/equipment to and from the turbines.
During our conversation in June, Mingyang’s chief technology officer and president Qiying Zhang did not explicitly elaborate on the next scaling steps for OceanX but remarked that the current layout could prove to be an ideal optimal size.
In our previous talk two years ago, Nezzy2/OceanX partners Siegfriedsen and Zhang hinted at the introduction of flexible ratings, with the MySE8.3-180 (326W/m2) as a reference.
This would mean reduced ratings for low-wind typhoon-prone markets such as northern China, with typical mean wind speeds of 7.5–8.0m/s, and 10–15% higher ratings for high-wind (export) markets.
The latter could be achieved by reusing the MySE8.3-180 design reserves in parallel with raising the rated tip speed, with power (P) a function of torque (T) and rotational speed (n) – in the formula P = f(T x n).
If OceanX proves to be successfully scalable and Mingyang decides to pursue upscaling, it has multiple portfolio options to choose from, including the latest 18.8–22MW turbine platform with a rotor range of 260 to 292 metres.
Mingyang shared with me these and other specifications in detailed technical documentation on the platform for publication in “uåX˜äŠÊ˜·³Ç’s Turbines of the Year 2023. In August 2024, it completed installation of a prototype with a 292-metre rotor but undisclosed rating.
This new platform represents a major technological switch away from HybridDrive (with aerodyn-engineering’s SCD as a basis) to a new fully integrated layout. With maximised rating and rotor size, this would enable a rating of 44MW and installation width of around 600 metres.
It would also offer higher capacity factors, as larger rotors inherently can entrain higher-energy air from the upper atmospheric layers.
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