Abstract

Large offshore wind farms are usually clustered around transmission grids to minimize the expense of transmission and due to space military zones, pipelines and constrains due to other uses such as nature preserves. However, this close proximity can undermine power production in downwind wind farms due to wakes from upwind wind farms. Therefore, the wind energy industry has great interest in determining the spatial dimensions of offshore wind farm wakes to assess the economical potential of planned wind farms. In this work we use wake measurements conducted by a research aircraft to evaluate the performance of a wind farm parameterization (WFP) in a mesoscale model during stably-stratified atmospheric conditions, in which the wake is expected to be the strongest. The observations were conducted on the 10 September 2016 within the project WIPAFF (Wind PArk Far Field) at the North Sea. The observations allow evaluation of both the horizontal and the vertical dimensions of the wake. The model simulates the length and most of the time the spatial dimensions of the wake. Further, we show that the largest potential for improving the performance of theWFP is rooted in an improvement of the background flow. This is due to the fact that the mesoscale model has problems representing the atmospheric boundary layer in the transition between land to open sea.

Abstract

Three-dimensional (3D) ground models enable the visualization of complex subsurface conditions in offshore wind farms, which aid engineers in understanding the spatial morphologies and interrelations of different soil layers. Due to the large areas of offshore wind farms, 3D ground models established solely based on limited geotechnical data (e.g., boreholes and cone penetration tests) might lack the required accuracy. Geophysical data, particularly seismic profile data, is capable of revealing stratigraphic information and can be obtained at a relatively low cost. This study presents a case study in which a 3D ground model for an offshore wind farm located off the Southern China coast is developed through the integration of geotechnical and geophysical data. The wind farm features complex interlayering of silty materials below the soft Holocene marine deposits due to repeated sea level changes during the Quaternary period. This created significant challenges for developing a reliable ground model. In this paper, the challenges that were faced and solutions that were applied in this project are presented and discussed.