Chinese Group Deploying Largest Floating Wind Turbine Platform

A floating wind turbine platform developed by Mingyang Group is now sited at a Chinese offshore wind farm. OceanX, at present the world’s largest single capacity technology of its type, is supporting the 505-MW Yangjiang Mingyang Quingzhou IV project near Guangdong, China.

Mingyang on August 19 announced the platform had completed its 191-nautical-mile trip from Guangzhou to the wind farm off the coast of Guangdong Province. The company said the floating wind turbine platform is arranged in a “V” shape, and holds two 8.3-MW offshore wind turbines. The company said the platform is designed to work “in a wide range of sea areas around the world with water depth of more than 35 meters.”

The OceanX impeller reaches 219 meters at its highest point, with a maximum width of about 369 meters in the air. The entire wind turbine platform has a total displacement of 15,000 tonnes, and a towing draft of 5.5 meters. The platform once operational is expected to produce 54 million kWh annually.

Mingyang earlier this month announced it has an agreement to install wind turbines at a project in Brazil, marking its first foray into Latin America. The company is among the Chinese manufacturers driving the global wind turbine market.

High-Tech, High-Performance Materials

Mingyang in a news release wrote, “OceanX advances wind turbine innovation by enhancing core component technology, driving both aesthetic and functional refinement in design and manufacturing,” adding, “Floating foundation is the key component for floating wind turbines in the deep and distant sea. Unlike traditional steel floating foundations, OceanX’s floating foundation consists of three floats, concrete arms and connectors.”

The group said the platform “pioneers the use of ultra-high-performance concrete with a compressive strength exceeding 115 MPa for floating foundation construction, a material four times stronger than standard concrete, significantly enhancing load-bearing capacity. The floating foundation also utilizes a pre-stressed high-strength concrete assembly structure, facilitating modular and batched manufacturing, thereby substantially reducing construction costs.”

Mingyang is using caisson pre-tensioning technology in its precast concrete construction, and has emphasized interface sealing and the precision of the pre-stressing process. The group said there are “1,500 steel strands expertly threaded through the floating body’s arm,” adding that the platform “has meticulously controlled tensioning forces and ensured uniform stress across the end face throughout the construction.”

OceanX’s float design uses layered material to replace traditional steel or hybrid materials; Mingyang said that “lightens the floats and accommodates their curved form. The three streamlined ellipsoidal floats offer reduced wave resistance and enable lateral rotation, providing yawing power. Rigorous testing confirms that the streamlined shape strikes an ideal balance between stability and load-bearing.” The company also said that putting two wind turbines on a single floating platform “can significantly cut down the per-kilowatt cost, as well as reduce the required sea area and operational maintenance expenses.”

Pioneering Architecture

Mingyang said integrating two turbine towers in a “V” configuration is a first for offshore wind platforms. OceanX’s tower, with an elongated elliptical design, maximizes wind exposure along its longer axis, significantly exceeding that on the shorter axis. The company said, “By aligning the tower with the wind direction at an optimal angle, the wind platform’s area is effectively increased, allowing for swifter alignment to the wind and boosting the efficiency of wind energy capture. Additionally, the towers are fitted with a dual-access system for lifts and ladders, ensuring the comfort and safety of personnel during ascent and descent.”

Mingyang also said the technology’s cable-stayed system is the first of its kind. “OeanX has ingeniously harnessed the spatial framework of its tower system, integrating the world’s largest high-stress strand cable-stayed system. A robust network of 13 main and six auxiliary cables efficiently tensions the mainframe, tower, and floating foundation, establishing a stable tensioning mechanism across the wind turbine’s components. This innovative cable-stayed design has redefined the load transfer path of traditional wind turbines. Instead of the tower bearing the full impeller and gravity loads, the system distributes the tower’s gravity load to the tension cables, with the tower now only partially supporting the impeller loads. This strategic redistribution significantly lightens the tower’s load, enabling a streamlined and lightweight structural design.”

Ocean X uses a combination of graded pre-tensioning, multi-dimensional monitoring, and synchronized tensioning in its system, which the company said “ensures that all 13 main cables achieve their individual pre-tensioning specifications.” The group said the cables—which are 200 meters long, with an 18-centimeter diameter—”can be pre-tensioned to a maximum force of 350 tonnes, optimizing the structural integrity and performance of the wind turbine system.”

The two main engines on the V-shaped tower are equipped with parallel impellers, with a sweeping area of more than 52,000 square meters. The impeller blades’ tips are just five meters apart. Mingyang said “this pioneering design optimizes impeller pitch and wind efficiency while leveraging the V-shape of the tower. It ensures impeller safety and enhances both wind capture and structural stability.”

The impellers rotate in opposite directions at startup, which enhances wind speed in the central area. Mingyang said this increases electricity generation from air kinetic energy by 4.29% compared to a single, large turbine with an equivalent swept area.

Single-Point Mooring

OceanX utilizes a downwind design, alleviating tower headroom constraints for the blades, allowing greater movement, and enhancing the unit’s power generation efficiency through flexible and efficient wind energy capture, according to Mingyang. The company said that the platform’s design takes into account the potential of typhoon-force winds.

“In the face of extreme typhoon conditions, floating wind turbines must be designed to withstand 360° typhoon loads from the outset to ensure stability and safety,” said Mingyang. “OceanX employs a single-point mooring system, which allows the platform to adaptively yaw with the typhoon’s direction. This ensures that the wind turbine consistently faces the incoming wind, regardless of the typhoon’s path.”

Mingyang said a 1:10 scale prototype of the OceanX dual-rotor floating wind turbine platform was launched for testing purposes in Lake Quarry, Germany, in April 2020. By October of that year, it had completed a two-month offshore operation in the Baltic Sea, enduring tests equivalent to 72m/s winds and 30-meter waves, and earned a feasibility certificate from DNV, a global energy research and certification group.

—Darrell Proctor is senior editor for POWER (@POWERmagazine).