Haiying Sun

Floating offshore wind turbines (FOWTs) suffer from continuous platform motions due to ocean environmental loads, which induces dynamic wake characteristics and affects the power performance of downstream turbines. Understanding these impacts is crucial for wind farm efficiency improvement. This study investigates the middle-to-far wake characteristics of a FOWT under harmonic surge motion, a significant degree of freedom with substantial aerodynamic consequences. By applying the Dynamic Wake Meandering (DWM) model in FAST.Farm, the wake velocity recovery, turbulence intensity (TI), and wake center positions of the NREL 5 MW wind turbine are analyzed at downstream distances of 5D, 7D, and 9D. The study systematically studies the effects of surge amplitude and frequency on these factors. The results indicate that larger surge amplitudes can lead to a pronounced increase in TI and shifting of the wake center and higher surge frequencies can promote wake recovery but have a diminishing effect on TI and velocity fluctuations in the far-wake region (≥7D). Under a typical surge motion of 8 m amplitude and 0.125 Hz frequency, the TI at 7D increases to 3.90%, and wake velocity recovery improves by 21% compared with the fixed-bottom case. Substantially, increased amplitude and frequency of the upstream turbine can lead to a higher mean power output for the downstream turbine but also introduce more significant power fluctuations. This work provides quantitative insights into the physical mechanisms of the impact of surge motion on FOWT wake evolution and its consequences for wind farm performance, which provides valuable guidance for the layout optimization of floating offshore wind farms.

Floating offshore wind turbines (FOWTs) have become a promising solution for harnessing wind energy in deeper seas. However, the complex interplay between FOWT layout, mooring line patterns, and wake effects significantly influences the overall performance of a floating offshore wind farm (FOWF). This paper proposes a novel optimization methodology that integrates mooring line constraints into the FOWF layout optimization process. The wake-induced power deficit is considered, whereas the vortices are neglected. The new method considers the constraint areas for each FOWT, which are defined based on both mooring line buffer zones and wind turbine buffer zones. By defining constraint areas, the optimization process ensures that FOWTs are optimally positioned while avoiding interference and collisions. By carefully considering the buffer zones, the power potential of FOWFs with three-line, four-line, and six-line mooring configurations can be improved by 122%, 100%, and 78%, respectively. Then, a genetic algorithm is employed to optimize the FOWT positions and mooring line angles simultaneously. The effectiveness of the proposed method is demonstrated through a case study in Guangdong, resulting in a significant 5% increase in power output potential compared to conventional approaches. This research contributes to the advancement of FOWT layout optimization and provides valuable insights for the design and deployment of future FOWFs.

In order to make full use of the potential of wind resources in a specific offshore area, this paper proposes a new method to simultaneously optimize the number, hub height and layout of a wind farm. The wind farm is subdivided by grids, and the intersection points are set as the potential wind turbine positions. The method adopts a genetic algorithm and encodes wind farm parameters into chromosomes in binary form. The length of chromosomes is decided by the number of potential positions and the hub heights to be selected. The optimization process includes selection, crossover, and mutation, while the efficiency of wind farm is set as the optimization objective. The proposed method is validated by three benchmark cases. It has proven to be effective in deciding the number of turbines and improving the efficiency of the wind farm. Another advantage of the proposed method is that it can be widely applied to wind farms of any shape. A case study applying the new method to an irregularly shaped wind farm in Hong Kong is demonstrated. By comparing the results with the original regularly shaped wind farm, the new method can improve power generation by 6.28%. Therefore, the proposed model is a supportive tool for designing the best number, hub heights and positions of wind turbines.