Loads assessment of a fixed‐bottom offshore wind farm with wake steering

Abstract

Wake steering via deliberate yaw offset is an emerging wind farm control technique that has the potential to mitigate wake losses and further increase wind farm energy yield. The loads impact of this technique has been studied, but there is limited insight into wind‐farm‐wide impacts of wake steering. Understanding such impacts is crucial to determining the feasibility of using wake steering in commercial wind farms. To that end, this work investigates the impacts of wake steering on the loads of all turbine components across all turbines in a wind farm operating under a broad set of inflow conditions, including inflow velocity, shear exponent, turbulence class, and inflow angle. This was done by performing FAST.Farm simulations of a 12‐turbine wind farm array, excerpted from a larger hypothetical wind farm. The International Energy Agency Wind 15‐MW reference wind turbine was modeled atop a monopile substructure, an open‐source model that closely approximates the properties of similar commercial options. Wake steering was included via yaw offsets that were computed using an offline optimization with the National Renewable Energy Laboratory tool FLORIS. For each inflow case, the 12‐turbine array was simulated with and without wake steering. Results were compared in terms of time‐averaged means, standard deviations, ultimate loads, and damage‐equivalent loads. The findings show that because wake steering is generally applied at rated wind speeds and below, it is unlikely to drive ultimate loads. For fatigue loads, wake steering does increase the overall fatigue accumulation for some load channels, such as blade‐root and shaft bending. This is to be expected when overall power yield increases but may cause the damage accumulation to be more uniform throughout the array. The significance of the added fatigue loading is dependent on how frequent wake steering is utilized in the overall set of inflow conditions across the wind rose.

Measurement-Driven Large-Eddy Simulations of a Diurnal Cycle during a Wake Steering Field Campaign

“…A direct outcome of this work is to enable aeroservoelastic simulations of turbines operating in the observed conditions and validate predictions of wake-steering loads. This is detailed in the companion paper by Shaler et al (2023), which compares the simulated response of turbines T2 and T3 with SCADA signals and available loads measurements.…”

“…A study period was identified based on the availability of both quality controlled lidar wind and loads data (for the study of Shaler et al (2023)). The availability of lidar data was considered essential for this study because the lidar captures more inflow characteristics than point measurements of wind conditions.…”

“…The present paper focuses on turbine performance only, comparing high-fidelity results with an engineering wake model used in wake steering controller design. An assessment of simulated windturbine loads, in comparison with measurements from the field campaign, will be detailed in a companion paper by Shaler et al (2023) that will also include results from a mid-fidelity dynamic wake meandering model.…”

The value of wake steering wind farm control in U.S. energy markets

“…To avoid extreme yaw misalignments, we constrain the lower and upper yaw offset bounds to −25° and +25°, respectively. Note that in practice, further reducing the magnitude of the yaw offset bounds as wind speed increases may be necessary to mitigate higher structural loads caused by yaw misalignment (Damiani et al, 2018;Shaler et al, 2022).…”

Impact of wake steering on loads of downstream wind turbines at an above-rated condition

“…Wake steering has been central to many numerical [2,3,4] and wind tunnel [5,6] studies, leading to commercial field testing [7,8]. The benefits of increased wind farm power due to wake steering usually come at the expense of increased fatigue loads [9].…”