February 10, 2021, Eize de Vries

The record-breaking 236-meter rotor and 15MW rating combine proven offshore experience with the latest EnVentus onshore technology. Eize de Vries Learn more

Vestas today (February 10) launched the world's first 15MW single-rotor turbine with a rotor size of 236 meters, setting a new standard. The Danish company's goal is to install the V236-15.0MW prototype in the summer of 2022, and then mass-produce it in 2024.

The announcement was made after a comprehensive acquisition of a former offshore joint venture with Mitsubishi Heavy Industries (MHI). However, even in the Mitsubishi Heavy Industries Vestas era (2014-2020), the joint venture's turbine development activities depend on Vestas.

The new giant was developed for strong wind IEC I/S/T conditions, including the typhoon prone market (IEC T), which aims to "strike a balance between output performance and the number of turbines required at the project level", according to Vesta Si's statement. The next-generation offshore platform is based on the proven technical solutions of the 9MW offshore platform and the EnVentus onshore platform.

According to Vestas Chief Technology Officer Anders Nielsen, this huge expansion step utilizes the experience of more than 1,200 turbines installed and operating in offshore environments, including more than 370 units of the V164 series currently in operation. There will be more than 560 unit years at the end of the month. This offshore experience is combined with the company's most advanced turbine technology and applied to the EnVentus onshore platform launched in 2019.

The unique visual appearance of the V236-15.0MW nacelle shows a raised central section, flanked by two horizontal side "compartments" and a nacelle-wide rear compartment, with a passive cooling device on top.

Christian Gjerløv, head of offshore turbine development at Vestas, explained what is hidden "under the hood": "The space in each side compartment is equipped with an upgraded, modular and expandable power converter unit. This unit was originally developed for the EnVentus platform.

"The dual converter solution is an example of our strategy to create the best platform synergy by porting modular medium-speed (6.0MW) EnVentus onshore technology to this new offshore platform, and vice versa, including In the manufacturing footprint. What is also new is that the liquid-immersed 66kV transformer is already a standard accessory of the V164/V174 series and has now been upgraded and installed on the previous main casting."

Gjerløv explained that placing these key electrical and power electronic components close to the center of the tower can create a vibration-friendly operating environment, while helping to make the design structure efficient and quality optimized. The result is a more compact and shorter cabin, including the helicopter lift deck and hub, which is still 28 meters long. If required, these subassemblies can be disassembled for transportation. The cabin is 11 meters high and 9 meters wide.

According to Vestas, V236-15.0 provides a capacity factor of more than 60% under high wind (close to 10m/s) IEC I conditions. Therefore, compared with the V174-9.5MW reference turbine, it can increase the annual power generation (AEP) of a single turbine by up to 65% to about 80GWh. The AEP of the reference-level 900MW wind farm has increased by 5%, and the required turbines, foundations, and related internal array internal wiring have been reduced by 34. The company said these factors together provide huge benefits for a stronger business case, including a significant reduction in the level of energy cost (LCoE).

Vestas said that compared to the V174-9.5MW reference turbine (above), the V236-15.0MW can increase annual power generation by up to 65%

The turbine is equipped with the latest Vestas "System 8000" control system-hardware and software related-for the first time launched with the EnVentus platform. Like EnVentus, the enhanced hydraulic independent pitch control system is load-based. It has a battery backup system to support key functions, such as upwind and yaw control in the event of a simultaneous grid failure under typhoon conditions.

The V236 (pictured below) will be equipped with a record-breaking 115.5-meter-long, internally designed structural shell-shaped blades based on the latest slender blade technology and airfoil introduced for the EnVentus platform in terms of structure and aerodynamics. Gjerløv says that each huge blade incorporates structural reinforcement materials and prefabricated carbon inserts integrated in the upper and lower shells.

"The main design driver is competitive quality; the appropriate and optimal use of expensive carbon for optimal operation and life cycle performance, and the retention of the one-piece blade design from the perspective of manufacturing, transportation and installation," he explained road. "The new feature of Vestas and this turbine model is that the rated tip speed has been increased from 90m/s (standard values ​​for V164 and V174, and common values ​​for offshore wind power) to 104m/s."

He went on to explain that the 16% increase in blade tip speed was achieved by integrating the corrosion-resistant leading edge shell into the laminate of the blade. The solution is specially designed and verified for offshore applications, and its reliability performance has been tested and confirmed for a long time on the V164 turbine under representative conditions.

An important benefit of the faster rotating V236 rotor is that this greatly reduces the gearbox input torque, resulting in a more compact design. Gjerløv added that the entire transmission system is functionally upgraded in accordance with the proven EnVentus design principles. This includes retaining a modular main bearing unit to carry the rotor on the front, and a rear interface for the gearbox and generator connection, the same as EnVentus.

V236 integrates many solutions first used on EnVentus land platform

"This transmission system layout was first introduced in 2011 with the medium-speed V164-7.0MW, but this version uses a differently designed differential gearbox with roller bearings. The V236 gearbox has three planetary boost stages, and EnVentus has two to compensate for higher ratings and larger rotors. The rotor speed is inherently reduced. The design layout further achieves a smaller size, especially for the first low-speed gear stage," he said.

Similar to the smaller EnVentus unit, the V236 gearbox has journal bearings in all major locations. Its torque density is 48% higher than the V174-9.5 MW reference gearbox, and the value exceeds 200Nm/kg. The combination of high torque density and the increased tip speed of the V236 provides an overall solution optimized for quality and cost. As before, Vestas cooperated with ZF Wind Power to develop a gearbox and a complete transmission system. However, the transportation logistics of the fully assembled and tested unit has not been determined and may differ from the EnVentus solution because the V236 gearbox is much larger.

Vestas engineers cancelled the low-speed coupling between the main bearing unit and the gearbox deployed in the V164/V174 series to prevent the bending moment caused by the rotor from entering the input side of the gearbox. This expensive transmission system component has been omitted from the EnVentus transmission system, but, according to Gjerløv, a lot of design work is again required to create a structurally stable interface between the main bearing unit and the gearbox.

The internally developed permanent magnet generator is based on the experience of the EnVentus platform and is larger and longer because the rating is increased by 2.5 times. Vestas again avoids the use of rare and expensive rare earth dysprosium. Compared with neodymium, it is characterized by greater price fluctuations and greater supply chain security risks. However, the addition of dysprosium allows the generator to operate at a higher magnet operating temperature, so not adding dysprosium means that the design requires an enhanced thermal control mechanism. Vestas solved this problem by connecting a hermetic, air-cooled PMG product with an air-to-water heat exchanger to a passive roof cooler.

The development of the V236 platform will begin in early 2020, and the prototype is planned for the beginning of the second half of 2022, followed by mass production in 2024. It will enter the market with the main version of the 15MW V236-15.0MW model, as well as a second variant with a derated 13.6MW operating mode, "optimized for the specific considerations of the project."

Chief Technology Officer Nielsen said: "V236-15MW was developed as an industrialized and operational product on a global scale. We believe that it is a competitive product suitable for these conditions, focusing on creating maximum value for our customers.

"We further believe that V236-13.6MW may become an attractive product in the Asian low-wind energy market, or, for example, to meet the specific liberalized power market conditions in California, USA. V174-9.5 will also have opportunities for MW in the future, especially when needed Under the conditions of different product sizes."

The specific rated power of V236-15.0MW is 343W/m2, while the rated power of V236-13.6MW is 311W/m2, and the current flagship product of V174-9.5 MW is 400W/m2. In contrast, GE's upgraded 14MW rated Haliade-X provides 405W/m2, and Siemens Gamesa's upcoming SG 14-222 DD 14MW "standard" model is 362W/m2.

In accordance with the general practices of Vestas and the onshore and offshore wind power industry, the newly launched platform always takes future scalability into consideration. The original V164-7.0MW (331W/m2) platform was launched in 2011, followed by the V164-8.0MW prototype and commercial model (379W/m2), and then again upgraded to V164-9.5MW (450W/m2), and finally V164- 10.0MW (​​473W/m2).

Therefore, further expansion of V236-15.0MW along the same evolutionary development path may produce higher results in the future, such as 17MW V236-17.0MW and 389W/m2.

Nielsen does not want to elaborate on any potential future expansion plans for the new next-generation platform at this stage. But he believes that industry-leading gear drive system solutions consistent with Vestas' onshore variants will enable Vestas to reapply load transfer and management best practices in the best possible way. He said that with its scale and capabilities as a global market leader in onshore wind power, it is also crucial for Vestas to become a technology and market leader in offshore wind power.

"With V236-15.0MW, we have set a new industry benchmark for performance and the full pursuit of industrialization potential. At the same time, we will expand the industrialization of turbine design through a modular approach. Expanding components to achieve continued offshore technology cost reduction is the main driving factor. This approach will make this new Vestas turbine product already very competitive in this year’s offshore tenders, and it will be a key component to reach global offshore market leadership by 2025," he concluded .

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