Wind farm model helps study a blade-pitch approach to minimizing fatigue damage and power loss

For wind farms at sea, the wake created by upstream wind turbines can significantly reduce power generation by downstream turbines. These upstream wakes can also increase fatigue of the downstream turbines’ critical components, which could result in expensive equipment failure. Researchers studying these turbulent wakes in offshore wind plants have moved from individual turbine models to array models to investigate potential mitigation strategies for wind turbine wakes.

Research in the Journal of Renewable and Sustainable Energy details large-eddy simulations of an offshore power generation array of four wind turbines fixed to a platform. The simulations test pitch control strategies for load mitigation of the critical components within the downstream wind turbines to ensure that they can operate for the designed service lifetime and still deliver sufficient power.

Demonstrations with the large-eddy simulations showed that a wind direction of 22.5° yielded the largest load fluctuations for the array model. While turbine power production improved at this wind angle, the damage equivalent loads (DEL) for the downstream turbines were nearly twice that of the upstream turbines, which can significantly increase the likelihood of premature blade failure.

To alleviate fatigue on the downstream turbine components, the researchers applied their blade pitch approach to the model. By reducing the blade pitch for downstream turbines in the model by -5° at a mean wind speed of 8 meters per second, they were able to greatly reduce DEL without a large reduction in power production. Increasing wind speed in the large-eddy simulations to 11.7 meters per second required an additional reduction in blade pitch angle to equate downstream turbines’ DEL to that of the upstream turbines, which further decreased overall power production.

Source: “Large-eddy simulation of offshore wind plants and fatigue load mitigation via pitch control strategies,” by Sang Lee, Kyong-hwan Kim, Kangsu Lee, Sewan Park, and Keyyong Hong, Journal of Renewable and Sustainable Energy (2018). The article can be accessed at https://doi.org/10.1063/1.5022400 .