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This paper investigates the opportunities and limits of two additional devices that improve the aerodynamic performance of wind turbine rotor blades. The objective of attaching these relatively small add-ons is the optimization of the annual energy production over a time period of at least 20 years by mitigating the effects of typical wear-out effects, such as the surface erosion of rotor blades. Hence, the study is a contribution to the reliable and long-term generation of renewable energy.

A brief summary of current regulations and recommendations for the serviceability limit state dimensioning of offshore monopile foundations in sand supporting wind turbines is given. Results from small scale model experiments are presented, discussed and compared to the findings of other research groups to contribute to a better understanding of the complex processes associated with the cyclic load-bearing behavior of piles and to the development of improved calculation approaches.

In this work, we study parks of large-scale airborne wind energy systems using a virtual flight simulator. The virtual flight simulator combines numerical techniques from flow simulation and kite control. Using advanced control algorithms, the systems can operate efficiently in the park despite turbulent flow conditions. For the three configurations considered in the study, we observe significant wake effects reducing the power yield of the parks.

Like young children without help, wind turbines are bad at sharing. Those that are first in line (most upstream) take all the fresh air leaving little for those downstream. This research shows how turbines can operate to share the wind resource better and what parameters are most important for optimizing this technique. Results indicate that power gains of 10 % can be achieved if upstream turbines are operated differently, which may help operators produce more wind power.

Distinct zonations with its own fauna and flora were observed. Algae and blue mussels dominated the structures from the surface down to 20 m, with tube building fan worms and plumose anemones as the main colonisers found below. The park is in its “intermediate” stage and moving towards the “apex” stage, with anemones covering most of the structures. The study was conducted to investigate if a floating wind park has the same fauna and zonations observed on traditional non-floating wind parks.

The article delineates a novel procedure to use 10-minute measurement statistics with few known parameters of the wind turbine to determine the long-term fatigue damage probability and compares this with theoretically expected levels to provide an indicator of structural reliability and remaining life. The results are validated with load measurements from a wind turbine inside an offshore wind farm.

Numerical weather prediction models are used to predict how wind turbines will interact with the atmosphere. Here, we characterize the uncertainty associated with the choice of turbulence parameterization on modeled wakes. We find that simulated wind speed deficits in turbine wakes can be significantly sensitive to the choice of turbulence parameterization. As such, predictions of future generated power are also sensitive to turbulence parameterization choice.

The small wind community relies on simplified wind models and energy production simulation tools to obtain energy generation expectations. We gathered actual wind speed and turbine production data across the U.S. to test the accuracy of models and tools for small wind turbines. This study provides small wind installers and owners with the error metrics and sources of error associated with using models and tools to make performance estimates, empowering them to adjust expectations accordingly.

This work presents a shape optimization framework based on computational fluid dynamics. The design framework is used to optimize wind turbine blade tips for maximum power increase while avoiding that extra loading is incurred. The final results are shown to align well with a related literature. The resulting tip shape, could be mounted on already installed wind turbines as a sleeve-like solution, or be conceived as part of a modular blade with tips designed for site-specific conditions.

Based on the IEC standards, a limited number of simulations is sufficient to calculate the extreme and fatigue loads on a wind turbine. However, this means inaccuracy in the output statistics. This paper aims to build a surrogate model on BEM aerodynamic model simulations output employing non-intrusive Polynomial Chaos Expansion. The surrogate model is then used in a large number of Monte Carlo simulations to provide an accurate statistical estimate of the loads.

This work introduces the FLOW Estimation and Rose Superposition (FLOWERS) wind turbine wake model. This model analytically integrates the wake over wind directions to provide a time-averaged flow field. This new formulation is used to perform layout optimization. The FLOWERS model provides a smooth flow field over an entire wind plant at fraction of the computational cost of the standard numerical integration approach.

This publication presents methods to improve the awareness and control of material fatigue for wind turbines. This is achieved by enhancing a sophisticated control algorithm, which utilizes wind prediction information from a laser measurement device. The simulation results indicate that the novel algorithm significantly improves the economic performance of a wind turbine. This benefit is particularly high for situations where the prediction quality is low or the prediction time frame is short.

Marine operations represent a significant proportion of costs involved in the installation, operation, maintenance and decommissioning phases of a floating wind farm. The floating wind industry is reaching array-scale deployments and it is very important to optimize the various marine operations involved in each of these phases. This paper analyses the various challenges in the path and opportunities for encountering them by the transfer of technical know-how from similar offshore sectors.

This study analyses two logistical strategies (a service operation vessel and an offshore maintenance base) that could be used for floating wind farms that cannot be reached by crew transfer vessels. The results of this work showed that having one service operation vessel is a preferable strategy if costs and energy availability are taken into consideration. This work also shows how the selection of weather data and wave limits of vessels affects the results.

The research article presents the results of a study of highly resolved numerical simulations of a wind energy test site in complex terrain that is currently under construction in the Swabian Alps in Southern Germany. The numerical results emphasised the importance of considering orography, vegetation, and thermal stratification in numerical simulations to resolve the wind field decently. In this way, the effects on loads, power, and wake of the wind turbine can also be predicted well.

In this study, we propose a new method to detect sea breeze events from the WRF simulation. Our results suggest that the proposed detection method can identify the three different types of sea breezes in the model simulation. In addition, the coastal impact, seasonal distribution and offshore wind potential associated with each type of sea breeze differ significantly. This highlights the importance of identifying the correct type of sea breeze in numerical weather/wind energy forecasting.

In wind plants, turbines can be yawed to steer their wakes away from downstream turbines and achieve an increase in plant power. The yaw angles become expensive to solve for in large farms. This paper presents a new method to solve for the optimal turbine yaw angles in a wind plant. The yaw angles are defined as Boolean variables – each turbine is either yawed or nonyawed. With this formulation, most of the gains from wake steering can be reached with a large reduction in computational expense.

The power performance of a wind turbine is often tested with the turbine standing in a row of several wind turbines, as it is assumed that the performance is not affected by the neighboring turbines. We test this assumption with both simulations and measurements, and we show that the power performance can be either enhanced or lowered by the neighboring wind turbines. Consequently, we also show how power performance testing might be biased when performed on a row of several wind turbines.

Wind turbines extract kinetic energy from the flow to create electricity. This induces a wake of reduced wind speed downstream of a turbine and consequently downstream of a wind farm. Different types of numerical models have been developed to calculate this effect. In this study, we compare models of different complexity, together with measurements over two wind farms. We find that higher fidelity models perform better and the considered rapid models cannot fully capture the wake effect.

To get more insights into the influence of the urban terrain flow on the performance of the rooftop mounted two-bladed Darrieus vertical axis wind turbine, scale resolving simulations are performed for a generic wind turbine in realistic terrain under turbulent conditions. It is found that the turbulence and skewed nature of the flow near rooftop locations has a positive impact on the performance of the wind turbine.

This paper compares different vortex identification methods to evaluate their suitability to study the tip vortices of a wind turbine. The assessment is done through experimental data from the wake of a wind turbine model. Results show comparability in some aspects as well as significant differences, providing evidence to justify further comparisons. Therefore, this study proves that the selection of the most suitable postprocessing methods of tip vortex data is pivotal to ensure robust results.

This work provides an accessible introduction to elastohydrodynamic lubrication theory as a precursor to analysis of lubrication in a wind turbine main-bearing. Fundamental concepts, derivations and formulas are presented, followed by the more advanced topics of: starvation, dynamic EHL effects, surface roughness interactions and grease lubrication.

This paper is the second in a two-part study on lubrication in wind turbine main-bearings. Investigations are conducted concerning lubrication in the double-row spherical roller main-bearing of a 1.5 MW wind turbine. This includes consideration of effects relating to starvation, grease thickener interactions and possible dynamic EHL effects. Results predict that the modelled main-bearing would be expected to operate under mixed lubrication conditions for a non-negligible proportion of its life.

We analyse the non-stationarity in Pearson correlation matrices for high frequency wind turbine data. Applying a hierarchichal k-means clustering to a time series of matrices, we distinguish different states, which exhibit distinct correlation structures. These arise from the turbine control system reacting to the current wind speed. We model boundary wind speeds between the different states. Our method enables accounting for the non-stationarity when predicting or analysing turbine failures.

A typical daytime atmosphere is modelled and used as input for a simulation of the flow around wind turbines. The flow directly behind the turbine is called the "wake" and it is very dependent on the atmospheric conditions. Therefore it is important to be able to simulate in various different atmospheric conditions, but at the same time it is desired to a have a simple model, so that the simulation can be executed fast; this is the purpose of the suggested model.

Uncertainties in initial conditions (ICs) decrease the accuracy of wind speed forecasts. We find that IC uncertainties can alter wind speed through modulating the weather system. IC uncertainties in local thermal gradient and large-scale circulation jointly contribute to wind speed forecast uncertainties. Wind forecast accuracy in the Columbia Basin is confined by initial uncertainties in a few specific regions, providing useful information for more intense measurement and modeling studies.

To get a better understanding of the influence of the terrain flow on the unsteady pressure distributions on the wind turbine surface, a fully resolved turbine was simulated in the complex terrain of Perdigão, Portugal. It was found that the pressure fluctuations at the tower caused by vortex shedding are significantly hampered by the terrain flow, while the pressure fluctuations caused by the blade-tower interaction are hardly changed.

Lidar-assisted control of wind turbines requires a wind field generator capable of simulating wind evolution. Out of this need, we extend the Veer’s method for 3D wind field generation to 4D. We propose a two-step Cholesky decomposition approach. Based on this, we develop a 4D wind field generator – evoTurb coupled with TurbSim and Mann turbulence generator. We further investigate the impacts of the spatial discretization in 4D wind fields on lidar simulations to provide practical suggestions.

An engineering aerodynamic model for non-planar horizontal-axis wind turbines is proposed. The performance of the model is comparable with high-fidelity models, but has similarly low computational cost as currently used low-fidelity models, which does not have such capability to model non-planar rotors. The developed model could be used for an efficient and accurate load calculation of non-planar wind turbines, and eventually be integrated in a design optimization framework.

In the wind energy industry, a digital twin is fast becoming a key instrument for the monitoring of a wind turbine blade's life cycle. Here, our introduced model updating with invertible neural networks provides an efficient and powerful technique to represent the real blade as built. This method is applied to a full finite element beam model of a blade to successfully update material and layup parameters. The advantage over state-of-the-art methods is the established inverse model.

In this work, we present an aerodynamic tool that can model an arbitrary collections of wings, blades, rotors and towers. With these functionalities, the tool can be used to study and design advanced wind energy concepts, such as: horizontal axis wind turbines, vertical axis wind turbines, kites, or multi-rotors. This article describes the key features of the tool and present multiple applications. Field measurements of horizontal and vertical axis wind turbines are used for comparison.

This work presents a method to use low noise IEPE Sensors in the low frequency range down to 0.05 Hz. In order to achieve phase and amplitude accuracy with this type of sensor in the low frequency range, a new calibration procedure for this frequency range was developed. The calibration enables the use of the low-noise IEPE sensors for large structures, such as wind turbines. The calibrated sensors can be used for wind turbine monitoring, such as fatigue monitoring.

In this paper, we have assessed to which extent mesoscale numerical weather prediction models are more accurate than state-of-the-art reanalysis products in characterizing the wind resource at heights of interest for wind energy. The conclusions of our work will be of primary importance to the wind industry for recommending the best data sources for wind resource modeling.

We described a new automated method to separate the wind turbine wake from the undisturbed flow. The method relies on the wind speed distribution in the measured wind field to select one specific threshold value and split the measurements into wake and background points. The purpose of the method is to reduce the amount of data required – the proposed algorithm does not need precise information on the wind speed or direction and can run on the image instead of the measured data.