Layout optimization of offshore wind farm considering spatially inhomogeneous wave loads
Zilong Ti, Deng Xiao Wei
Abstract
Monopile-supported wind turbines are usually placed in a harsh ocean environment and wave load becomes a major consideration in the nearshore wind farm design. Affected by the coastal geography and seabed terrain, the wave field inside a wind farm is usually spatially inhomogeneous and the wave load on each turbine can be greatly different. However, current practice for wind farm layout design is based on a passive strategy in which the layout is determined first, then followed by the wave load calculation and support structure design. Such a passive design strategy does not take inhomogeneous wave loads into consideration and may inappropriately place some turbines into the intense wave load regions, e.g., high wave or breaking wave zones, which is uneconomic and even risky for structural safety. In this paper, a novel coupling approach considering inhomogeneous wave loads on monopile-supported wind turbines in wind farm layout optimization is presented. The main goal is to arrange all turbines in an optimal layout, in which the total wave load of the wind farm is minimized while simultaneously maintaining the favorable AEP (annual energy production). The inhomogeneous wave field is characterized using either an analytical wave model or a numerical wave model. The wind energy production and wave loads are investigated and coupled in the layout optimization. A user-defined knockdown coefficient is employed in the coupling optimization to allow the users to customize the exact tradeoffs between AEP and wave load. The optimization is driven by the Multistart algorithm to efficiently approximate the best layout. It is discovered that the coupling optimization shows apparent benefits in producing satisfactory layouts, in which the total wave loads are significantly reduced by 20.1%-40.5% while maintaining a favorable amount of AEP. The presented coupling approach provides a useful alternative optimization strategy for offshore wind farm layout design to reduce the costs related to wave loads, especially in the harsh sea regions.