Presentations

Abstract

Keywords: Gravity waves, blockage, turbine interactions, wind farm clusters, wakes, atmospheric boundary layer, low-level jets. Abstract (max 500 words) Offshore wind farms and their neighbours are increasing in size and scope. Not only this, the size of future turbine rotor diameters (220m+) opens up a set of risks with respect to farm-atmosphere interactions that can not be captured by legacy turbine interaction (wake and blockage) models. The proximity between the turbine rotors to the top and the marine boundary layer is reducing and, in some cases, turbines are large enough to break through the surface layer under some conditions. The turbine's /farm's effect on the atmosphere, its static and dynamic stability responses and, crucially complex interactions between them, all play a role in the farm-/cluster-wide power distributions and ultimately can drive biases in AEP that are hard to capture. In order to obtain the predictive power needed to capture these effects and de-risk AEP pre-construction, more advanced modelling is needed. Higher-order models such is RANS-CFD are able to in a single simulation: * Model mixing layer characteristics and therefore surface stability effects * Stable free atmosphere effects such as gravity waves * Entrainment between the two and interactions that govern wake recovery and power distribution * Viscous and inviscid effects such as wakes and blocakge respectively in a full-coupled manner that can impact atmospheric mixing and response Access to high-order modelling is not commonplace, however the need for it is increasing in order to, at the very least, guide reduced order rapid model developments. This presentation will focus one an aspect of atmospheric response, gravity waves, the total effects of which are hard to quantify on AEP. The need for inclusion of appropriate physics and the proper implementation of the atmospheric boundary layer will be explored. Examples will be provided for wind farm / turbine sizes typical of operational wind farms will be compared to those of future turbines to model any non-linearities that might appear for larger turbines. Novel methods will be used to try and separate the gravity wave response and isolate the specific impact on farm power, and ultimately and indication of the level of risk future wind farms are exposed to will be evaluated. Delegates will see how to effectively use high-fidelity models to start to de-risk complex phenomena, what the pre-requisites for robust modelling are and how these efforts can materialise into better understanding of wind farm AEP predictions. Moreover, they will understand the impact of gravity waves on wind farm power distributions and where shortcomings in legacy models could expose the industry. References [1] Stipa, S., Ahmed Khan, M., Allaerts, D., and Brinkerhoff, J.: An LES Model for Wind Farm-Induced Atmospheric Gravity Wave Effects Inside Conventionally Neutral Boundary Layers, Wind Energ. Sci. Discuss. [preprint], https://doi.org/10.5194/wes-2023-171, in review, 2024.