OWA Industry Report | Why did the floating fan survive Typhoon Capricorn?

Recently, Typhoon "Capricorn" has brought a profound impact on Mulan Bay offshore wind Farm in Wenchang, Hainan. In order to further study the challenges faced by offshore wind turbines against typhoons, Based on the academic article "Typhoon Resistance Analysis of OffshoreWind Turbines:A Review", this paper deeply discusses the wind resistance capability of offshore wind turbines under typhoon conditions and the direction of technical improvement.

Typhoon Resistance Analysis of OffshoreWind Turbines:A Review was published in the international academic journal Atmosphere in 2022. The paper was co-authored by Li Jiawen and other scholars from Dalian Maritime University. This paper aims to study the damage mechanism of typhoon to offshore wind turbines and summarize the current research progress of anti-typhoon design. This paper is not only authoritative in the academic field, but also puts forward important reference opinions for the offshore wind power industry to cope with extreme weather such as typhoons.

title of paper

During Typhoon "Capricorn", a fan broke off in Mulan Bay offshore wind farm in Wenchang, Hainan. Some media pointed out that there were two main reasons: Some fans were installed but not powered up, so they could not yaw to cope with the typhoon; The wind speed of "Capricorn" is up to 62 m/s, far exceeding the maximum wind speed standard that IEC Class I fans can withstand (10 minute average wind speed of 50 m/s). Nevertheless, floating wind turbines in the same typhoon region, such as the "Mingyang Tiancheng" and "Three Gorges Leading", successfully resisted the impact of the typhoon.

The accident revealed the design and technical shortcomings of offshore wind turbines in the face of extreme weather, and the success of floating wind turbines has raised concerns about their ability to withstand typhoons.

1. The influence mechanism of typhoon on wind turbine

The paper points out that typhoon is one of the main natural factors leading to the failure of offshore wind turbines. The extreme wind speed, sharp wind direction changes and strong turbulence brought about by typhoons can put enormous pressure on the blades, towers and foundation systems of wind turbines. These factors work together to greatly increase the structural vulnerability of wind farms. Especially near the eye of the typhoon, the wind speed changes most dramatically, causing wind turbines to be unable to adjust their attitude quickly to respond to the rapidly changing wind direction.

The damage of China's offshore wind farms in typhoons over the years is the same as the original paper

2. Typhoon resistance design of blades

The blades of offshore wind turbines are usually the most vulnerable part. Although the blades can be angled to reduce wind load during strong winds through a variable pitch system, this measure is often not enough to avoid damage completely during extreme typhoons. For example, the article mentioned that Typhoon "Usagi" caused the blades of several fans to break, and one of the key factors was that the wind speed exceeded the design load capacity of the blades.

The paper suggests that blade design needs to be optimized with more accurate aerodynamic analysis tools, especially considering the airflow characteristics and load conditions unique to typhoons. In addition, with the expansion of the scale of the fan, the length of the blade also increases, which greatly increases the degree of deflection of the blade under extreme wind load, so it is necessary to strengthen its bending ability.

A fan of an offshore wind farm damaged by Typhoon Usagi

3. Typhoon resistant design of towers and foundation systems

The paper points out that tower collapse is often one of the main reasons for the failure of typhoon-induced power units. Under the action of strong wind, the tower root will bear huge bending moment and shear force, resulting in buckling and even collapse. For example, during Typhoon Rammasun, several fan towers experienced local buckling and connector failure.

In order to enhance the wind resistance of the tower, the report recommends the use of high-strength materials and thick wall construction to increase the stiffness of the tower. In addition, drastic changes in wind direction and eddy effects near the eye of the typhoon must be considered, which can create additional loads on the tower structure.

The fan tower collapsed due to the typhoon

Compared with fixed wind turbines, floating wind turbines have obvious advantages in dealing with typhoons. The floating fan is stabilized by a floating platform and mooring system, which is better able to adapt to the strong winds and waves of the deep-sea environment. For example, the "Mingyang Tiancheng" and "Three Gorges Guide" successfully withstood the extreme wind speed of 62 meters per second during the typhoon, and their floating platforms can be dynamically adjusted to absorb the impact of wind waves.

The paper points out that floating wind power is the key development direction of anti-typhoon design in the future. Its flexible foundation and intelligent control system can effectively reduce the risk of damage to the unit in extreme weather.

Fixed fan base characteristics

Basic characteristics of floating fan

Through the accident of Typhoon "Capricorn" and the research results of Typhoon Resistance Analysis of OffshoreWind Turbines:A Review, we can draw the following conclusions:

The necessity of design optimization: the wind resistance of current offshore wind turbines, especially fixed wind turbines, needs to be improved in the face of super typhoons. The blades and towers of wind turbines require higher strength designs to withstand the extreme wind loads brought by typhoons.

The future of floating wind power: floating wind turbines show stronger adaptability under extreme weather conditions, and the future development and promotion of floating wind power technology should be increased to improve the safety of wind farms in typhoon-prone areas.

Strengthen the intelligent control system: under extreme typhoon conditions, the yaw and pitch control system of the wind turbine must have sufficient redundancy and reliability to ensure that the unit can respond to changes in wind direction and speed in real time to avoid catastrophic consequences caused by loss of control.

By combining the research results in the paper with the latest events, we can better understand the key points of typhoon resistance design for offshore wind projects and provide effective guidance for future wind farm construction.