This paper takes the Phase II project of the Zhangpu Li’ao offshore wind farm, developed by China Three Gorges Corporation in Fujian Province, as a case study. This project represents one of China’s important large-scale offshore wind power initiatives. It also provides relatively complete public data, making it a suitable real-world engineering example for analyzing turbines, foundations, and offshore construction techniques.

1. Project Scale and Wind Turbine Configuration

The Phase II Zhangpu Li’ao offshore wind farm lies southeast of the Li’ao Peninsula in Zhangpu County, Fujian. It is located more than 30 kilometers off the coastline. The project has a total installed capacity of about 400 MW. It deploys 28 offshore wind turbines of 13 MW or larger, including six 16 MW turbines. The project achieved full-capacity grid connection in June 2024.

The public parameters for the 16 MW turbine include the following. The single-unit rated capacity is 16 MW. The hub height reaches 152 meters. Each blade measures 123 meters in length. The rotor diameter spans 252 meters.

One full rotation of a single turbine generates approximately 34.2 kWh of electricity. Its annual power output exceeds 66 million kWh. For the entire Zhangpu Phase II project, the design annual grid electricity supply exceeds 1.6 billion kWh after full operation. This is expected to save about 500,000 tons of standard coal each year.

2. Offshore Wind Resources and Site Selection

The Zhangpu Li’ao area faces the Taiwan Strait and enjoys abundant offshore wind energy resources. According to public data, the annual average wind speed along this coastal area exceeds 9.4 m/s. The wind power density surpasses 800 W/m². The effective wind occurrence percentage ranges from 82% to 93%.

Compared with onshore wind power, one of the greatest advantages of offshore wind lies in the greater stability of marine wind resources. At the same time, larger turbines can reduce the number of turbine positions required per unit of installed capacity.

However, the offshore environment also introduces completely different engineering challenges. These include typhoons, waves, ocean currents, seawater corrosion, offshore lifting windows, seabed geological conditions, and submarine cable installation.

Therefore, the design difficulty of offshore wind foundations is significantly greater than that of ordinary onshore wind foundations.

3. Offshore Foundation Structure

The foundation system of the Zhangpu Phase II project represents a highly valuable aspect for analysis. The project site lies more than 30 kilometers from the coastline. Public data indicate water depths of about 26 to 50 meters at the site. Current public procurement documents from China Three Gorges Corporation explicitly describe the turbine foundations as offshore pile-jacket foundations.

During construction, the project completed the installation of 116 steel pipe piles for the 28 turbine foundations and the offshore booster station foundation. Public reports also note that the project adopted a four-pile jacket structure. The steel pipe piles are relatively long, and the maximum water depth approaches 50 meters, which imposes high precision requirements for pile driving.

This structure differs markedly from onshore turbine foundations. Onshore turbines rely mainly on large-volume foundations to transfer loads to the ground. In contrast, offshore jackets require a complete load transfer pathway that goes through the following sequence. The load passes from the steel pipe piles to the seabed soil, then to the jacket structure, then to the tower, and finally to the wind turbine.

Therefore, offshore foundation design must consider not only vertical bearing capacity. It must also place significant emphasis on horizontal loads, wave loads, current effects, turbine thrust, cyclic loads, pile fatigue, and seawater corrosion.

4. Extra-Large Rotor and Tower Structure

The 16 MW turbine has a hub height of 152 meters. Each blade reaches 123 meters in length, and the rotor diameter spans 252 meters. For such large rotors, the tower structure must simultaneously meet strength and stiffness requirements. This is especially critical under typhoon conditions, when turbines still experience significant wind loads even after shutdown.

For offshore turbines, extreme load cases are generally more complex than those for ordinary onshore wind turbines. Consequently, structural design must address several key issues.

The first issue is extreme wind loads. The Fujian coast lies in a typhoon-affected region. Extreme wind conditions impose large instantaneous loads on the blades, nacelle, tower, and foundation. The second issue is fatigue loads. Offshore turbines continuously experience cyclic loads from wind, waves, currents, and turbine operation over their service life.

Therefore, fatigue design constitutes an important part of both foundation and tower design. The third issue is corrosion. Offshore steel structures remain in high-humidity, high-salinity environments for extended periods. Engineers must control corrosion risks through protective coatings, material selection, and detailed structural design.

5. Offshore Installation and Construction

The Zhangpu Phase II project presented considerable construction difficulty. One major reason is that the wind farm lies far from land. Public data show that the project center is about 33 kilometers from the shoreline, with water depths ranging from 26 to 42 meters.

Construction required the use of large offshore construction vessels. The project team also needed to schedule work windows according to sea state conditions. Moreover, the project achieved full-capacity grid connection only after completing the installation of all 28 turbines. As a result, the foundation works, tower erection, nacelle placement, and blade lifting required close coordination.

For 16 MW-class turbines, the offshore lifting of 123-meter-long blades poses particular challenges. These include crane vessel capacity, sea state control, wind speed windows, lifting attitude control, and precise blade-to-hub alignment. This clearly demonstrates that construction techniques must advance in parallel with the trend toward larger offshore turbines.

6. Conclusion

The Phase II Zhangpu Li’ao offshore wind farm has a total installed capacity of about 400 MW. It installs 28 offshore turbines of 13 MW or larger, of which six reach 16 MW. The maximum water depth at the site is about 40 meters. The project adopts pile-jacket foundations. It therefore exemplifies the industry trend toward larger-capacity units, deeper-water foundations, and large-scale construction methods in offshore wind power development.