Abstracted/indexed

Floating wind is the key technology to harvest the abundant wind energy resource of deep waters. This research introduces a new way of controlling the wind turbine to better deal with the action of waves. The turbine is made aware of the incoming waves and the information is exploited to enhance power production.

Wind turbines extract momentum from atmospheric flow and convert that to electricity. This study explores recovery processes in wind farms that replenish the momentum so that wind farms can continue to function. Experiments with a numerical model show that momentum transport by turbulent eddies from above the wind turbines is the major contributor to recovery except for strong wind conditions and high wind turbine density where horizontal advection can also play a major role.

This paper introduces the numerical models of two 15MW Floating Offshore Wind Turbines (FOWTs) WindCrete and Activefloat. WindCrete is a spar floating platform designed by Universitat Politècnica de Catalunya, while the Activefloat is a semi-submersible platform designed by Esteyco. The floaters are designed within the Horizon 2020 project COREWIND. Afterwards, the responses of both models to wind and second order waves are analyzed with an emphasis on the effect of second order waves.

This study investigates systematic, seasonal biases in the long-term correction of short-term wind measurements (< 1 year). Two popular Measure-Correlate-Predict (MCP) methods yield remarkably different results. Six reanalysis data sets serve as long-term data. Besides experimental results, theoretical findings are presented which link the mechanics of the methods and the properties of the reanalysis data sets to the observations. Finally, recommendations for wind park planners are derived.

We carry out a probabilistic calibration of the Dynamic Wake Meandering (DWM) model using high spatial and temporal resolution nacelle-based lidar measurements of the wake flow field. The experimental data were collected as part of the Small Wind Farm Technology (SWiFT) experiment in Texas. The analysis includes both the velocity deficit, wake-added turbulence, and wake meandering features under various inflow wind and atmospheric stability conditions.

Active trailing edge flaps can potentially enable further increases in wind turbine sizes without the disproportionate increase in loads, thus reducing the cost of wind energy even further. Extreme loads and critical deflections of the turbine blade are design driving issues that can effectively be reduced by flaps. This paper considers the flap hinge moment as an input sensor for a flap controller that reduces extreme loads and critical deflections of the blade in turbulent wind conditions.

When ice forms on wind turbine blades, the smooth surface of the blade becomes rough which changes its aerodynamic performance. So, it is very important to know how to simulate this rough surface since most CFD simulations depend on assuming a smooth surface. This article compares different mathematical models specialized in simulating rough surfaces with results of real ice profiles. The study presents the most accurate model and recommends using it in future airflow simulation of iced blades.

Offshore wind turbines are huge, with rotor blades soon to extend up to nearly 300 meters. Accurate modeling of winds across these heights is crucial for accurate estimates of energy production. However, we lack sufficient observations at these heights but have plenty of near-surface observations. Here we show that a basic machine learning model can provide very accurate estimates of winds in this area, and much better than conventional techniques.

The objective of the paper is to develop a data-driven output constrained individual pitch control approach, which will not only mitigate the blade loads but also reduce the pitch activities. This will lead to an economically viable load control strategy. The proposed control strategy shows promising results of load reduction in the wake-rotor overlapping and turbulent wind conditions.

Wind farms operate in the atmospheric boundary layer and their performance is strongly dependent on the atmospheric conditions. We propose a simple model of the atmospheric boundary layer that can be used as an inflow model for wind farm simulations for isolating a number of atmospheric effects, namely, the change of wind direction with height and atmospheric boundary layer depth. In addition, the simple model is shown to be consistent with two similarity theories.

We investigate the ability of a community-open weather model to simulate the turbulent atmosphere by comparison with measurements from a 250-m mast at a flat site in Denmark. We found that within three main atmospheric stability regimes, idealized simulations reproduce closely the characteristics of the observations with regards to the mean wind, direction, turbulent fluxes, and turbulence spectra. Our work provides foundation for the use of the weather model in multiscale real time simulations.

Lidar-assisted control (LAC) is used to redesign the rotor and tower of three turbines, differing in terms of wind class, size and power rating. The load reductions enabled by LAC are used to save mass, increase hub height or extend lifetime. The first two strategies yield reductions in the cost of energy only for the tower of the largest machine, while more interesting benefits are obtained for lifetime extension.

There are two ways to perform maintenance of a multicomponent system: a corrective maintenance, replace a broken component by a new one, and a preventive maintenance (PM), when some components are replaced in a planned manner before they break down. This article proposes a mathematical model for finding an optimal time to perform the next PM activity and selecting the components which should be replaced. The model is fast to solve, it can be used as a key module in a maintenance scheduling app.

This study investigates aero-elasticity of wind turbines present in the turbulent and chaotic wind flow of the lower atmosphere, using fluid-structure interaction simulations. This method combines structural response computations with high fidelity modelling of the turbulent wind flow. This, using a novel turbulence model which combines the capabilities of large eddy simulations for atmospheric flows with improved delayed detached eddy simulations for the separated flow near the rotor.

This analysis validates the DWM model based on loads and power production measured at an onshore wind farm. Special focus is given to the performance of a version of the DWM model that was previously recalibrated with a lidar system at the site. The results of the recalibrated wake model agree very well with the measurements. Furthermore, lidar measurements of the wind speed deficit and the wake meandering are incorporated in the DWM model definition in order to decrease the uncertainties.

Detailed numerical simulations of turbines in atmospheric conditions are challenging with regard to its computational demand. We coupled an atmospheric flow model and a turbine model in order to deliver extensive details about the flow and the turbine response within reasonable computational time. A comparison to measurement data was performed and showed a very good agreement. The efficiency of the tool enables applications such as load calculation in wind farms or during low level jet events.