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The estimation of fatigue in offshore wind turbine is highly relevant, as it can help extend the lifetime of these assets. This article attempts to answer this issue by developing a methodology based on artificial intelligence and data collected by sensors installed in real-world turbines. Good results are obtained and this methodology is further used to learn the value of 8 different sensor setups and employed in a real-world wind farm with 48 wind turbines.

The paper compares two different strategies for wind turbine control when following a power command. Using model-based control design for a 5 MW wind turbine, a comparison in terms of the mechanical loading and the attainable power dynamics is drawn based on simulation studies. Reduced-order models suitable for the integration into an upper-level control design are discussed. The dependence of the turbine behavior on the chosen strategy is illustrated and analyzed.

The gearbox is one of the main contributors to the overall cost of wind energy and it is acknowledged that we still do not fully understand its loading. The study presented in this paper develops a new alternative method to measure input rotor torque in wind turbine gearboxes, overcoming the drawbacks related to measuring on a rotating shaft. The method presented in this paper could make measuring gearbox torque more cost-effective, which would facilitate its adoption in serial wind turbines.

Wind farms are becoming larger and larger and they are shaping up as one of the main drivers towards full green energy transition. Because of their massive proliferation, more and more attention is nowadays focused on optimally design these power plants. We propose an optimization framework in order to contribute for further cost reductions, by simultaneoysly desining the wind turbines and cable layout. We show the capability of the framework to improve designs compared to the classic approach.

Hybrid solar and wind plant layout optimization is a difficult, complex problem. In this paper, we propose a parameterized approach to wind and solar hybrid power plant layout optimization that greatly reduces problem dimensionality while guaranteeing that the generated layouts have a desirable regular structure. We demonstrate that this layout method that generates high-performance, regular layouts which respect hard constraints (e.g. placement restrictions).

Using highly accurate simulations within a design cycle is prohibitively computationally expensive. We implement and present a multifidelity optimization method and showcase its efficacy using three different case studies. We examine aerodynamic blade design, turbine controls tuning, and a wind plant layout problem. In each case, the multifidelity method finds an optimal design that performs better than those obtained using simplified models, but with less cost than high-fidelity optimization.

In controls co-design, whose methods often rely on linearized models of the physics, the physical structure and controller are designed and optimized concurrently, so, it is important to understand how changes to the physical design affect the linearized system. This work summarizes efforts done to understand the impact of design parameter variations in the physical system (mass, stiffness, geometry, etc.) on the linearized system.

In this paper, we assess whether hub-height turbulence can easily be quantified from either other hub-height variables or ground-level measurements in complex terrain. We find a large variability across the three considered locations when trying to model hub-height turbulence intensity and turbulence kinetic energy. Our results highlight the nonlinear and complex nature of atmospheric turbulence, so that more powerful techniques should instead be recommended to model hub-height turbulence.

The damping of an offshore wind turbine is a difficult physical quantity to predict, although it plays a major role in a cost-effective turbine design. This paper presents a review of all approaches that can be used for damping estimation directly from operational wind turbine data. As each use case is different, a novel suitability table is presented to enable the user to choose the most appropriate approach for the given availability and characteristics of measurement data.

Dynamic inflow denotes the unsteady aerodynamic response to fast changes in rotor loading and leads to load overshoots. We performed a pitch step experiment with the MoWiTO 1.8 in the large wind tunnel of ForWind – University of Oldenburg. We measured axial and tangential inductions with a recent method with a 2D-LDA system and performed load and wake measurements. These radius resolved measurements allow for new insights into the dynamic inflow phenomenon.

Active Wake Control (AWC) is a strategy for operating wind farms in a cooperative manner to maximize the overall power production. The state-of-the-art approach optimizes AWC for static wind conditions, which is sub-optimal in real-life due to the continuous variations of the wind resource and the very slow dynamics of the yaw system that controls the rotor direction. This work develops dynamic robust AWC that considers realistic operating conditions including variabilities and uncertainties.

Wake steering is a wind farm control strategy in which upstream wind turbines are misaligned with the wind to deflect their low-velocity wakes away from downstream turbines, increasing overall power production. Here, we present results from a two-turbine wake steering experiment at a commercial wind plant. By analyzing the wind speed dependence of wake steering, we find that the energy gained tends to increase for higher wind speeds because of both the wind conditions and turbine operation.

The paper describes in detail the design of a scaled wind turbine, for studying wakes and wake control applications in the known, controllable and repeatable conditions of a wind tunnel. The scaled model is characterized by conducting experiments in two wind tunnels, in different conditions, using different measurement equipment. Results are also compared to predictions obtained with models of various fidelity. The analysis indicates that the model fully satisfies the initial requirements.

An accurate prediction of loads and power of an offshore wind turbine is needed for an optimal design. However, such predictions are typically performed with engineering models that contain many inaccuracies and uncertainties. In this paper we have proposed a systematic approach to quantify and calibrate these uncertainties based on two experimental datasets. The calibrated models are much closer to the experimental data, and are equipped with an estimate of the uncertainty in the predictions.

This paper presents the state-of-the-art technologies and development trends of wind turbine drivetrains – the energy conversion systems transferring the kinetic energy of the wind to electrical energy – in different stages of their life cycle: design, manufacturing, installation, operation, lifetime extension, decommissioning, and recycling. The main aim of this article is to review the drivetrain technology development as well as to identify future challenges and research gaps.

Winds decelerate upstream of a wind plant as turbines obstruct and extract energy from the flow. This effect is known as wind plant blockage. We assess how atmospheric stability modifies the upstream wind plant blockage. We find stronger stability amplifies this effect. We also explore different approaches to quantifying blockage from field-like observations. We find different methodologies may induce errors of the same order of magnitude as the blockage-induced velocity deficits.

This work presents a comprehensive aerodynamic design study of a large scale 5MW VAWT using a vortex based aerodynamic model named CACTUS. Impact of various important design parameters like rotor solidity, number of blades and rotor aspect ratio on loading and power have been analyzed. VAWTs typically suffer from large variation in cyclic loads and they are subjected to high parked loads, which are addressed in this study.

The impact of atmospheric stability on wind energy is widely demonstrated, so we have to know how to characterize it. This work based on a meteorological mast located in a complex terrain, compares and evaluates different instrument set-ups and methodologies for stability characterization. The methods are examined considering their theoretical background, implementation complexity, instrumentation requirements, and practical use in connection with wind energy applications.

In this manuscript, a numerical case study has been presented regarding ice detection and wind resource assessment in ice prone cold regions. Three years SCADA data from a wind park in Arctic region is used for this study. T19IceLossMethod based statistical analysis and Computational Fluid Dynamics (CFD) based numerical simulations are carried out for icing events classification and wind resource assessment, as well as estimation of resultant Annual Energy Production (AEP).

In this paper, a new energy system for the conversion of far-offshore wind energy into methanol is proposed, and the cost of energy is estimated. Results show (i) that this system could produce approximately 70,000 tonnes of methanol per annum at a cost comparable to that of methanol produced by offshore wind farms in the long term.

Wind turbine blade misalignments were measured. About 38 % of the turbines measured have been operating outside the accepted misalignment range. This research quantifies the effect of the measured misalignment on the turbine lifetime by means of simulations. The lifetimes of the main frame at the tower top and the tower base were affected most by a blade misalignment. To avoid a lifetime reduction, blade misalignments should be identified and corrected as early as possible during the lifetime.

The airflow through a wind turbine must expand as it goes through the blades for them to extract energy from the wind. Expansion has not been properly incorporated in wind turbine aerodynamics. We show that the conventional equation for wind turbine thrust becomes inaccurate when the expansion is maximized to achieve maximum power, and expansion reduces power by around 6  %. We formulate equations for the disturbance of the external flow and show that this is maximized at the rotor plane.

This paper illustrates two sensor placement optimisation techniques designed for damage detection while taking into account temperature effects. A case study of a glider wing shows that, compared to the normalised method using the temperature label, the linear method that did not require temperature labels provided features that were less sensitive to damage. However, it is cheaper and more convenient to extract temperature-robust features in practical engineering.

The length of rotor blades of land-based wind turbines is currently constrained by logistics constraints. Turbine manufacturers currently propose segmented solutions to overcome these limits, but blade joints come with extra masses and costs. This work investigates an alternative solution, namely the design of ultra-flexible blades that can be transported on rail via controlled bending. The results show that this is a promising pathway to further increase the size of land-based wind turbines.

Via 11 years of measurements, we made a statistical ensemble of wind speed ramps, in terms of acceleration, mean speed, and shear. Constrained turbulence and large-eddy simulations were coupled to an aero-elastic model, for each ensemble member. Ramp acceleration was found to dominate the maxima of thrust-associated loads, with a ramp-induced increase of 45–50 % plus ~3 % per 0.1 m s⁻² of bulk ramp acceleration magnitude. The LES indicate that the ramps (and such loads) persist through the farm.

This paper suggests that the impacts of different turbulence models should be considered as uncertainties while evaluating the benefits of LiDAR assisted control (LAC) in wind turbine design. The value creation of LAC, evaluated using the Kaimal turbulence model, will be diminished if the Mann turbulence model is used instead. In particular, the difference in coherence is more significant for larger rotors.

We use data from the Alpha Ventus offshore wind farm to investigate the effects of inter-farm interactions. We show how measured quantities like turbulence intensity, wind speeds, shear, and turbine structural loading are evolving from the period where the park was operating alone to the period where new farms operate in close proximity. In the directions influenced by the neigboring farms increased turbulence intensity, reduced wind speeds, and increased structural loading is observed.

Curved blade tips can potential have a significant inpact on wind turbine performance and loads. A swept tip shape, optimized for wind turbine applications is tested in a wind tunnel. A range of numerical aerodynamic simualtion tools with various levels of fidelity is compared. It is shown that all numerical tools except for the simplest BEM-based are in good agreement with the measurements, suggesting the required level of model fidelity necessary for the design of such tips.

There is continuous effort to try and improve the aerodynamic performance of wind turbine blades. This work shows that adding a leading-edge slat to wind turbine blades can significantly enhance the aerodynamic performance of wind turbines, even more than with vortex generators (which are commonly used on commercial turbines). The findings are obtained through wind tunnel tests on different airfoil-slat combinations.

- Wind power is a promising power generation technology. - The turbulence model has a definitely great influence on the numerical simulation results of wind turbine blade airfoil. - High velocity and low temperature is better conditions to deliver higher power from the wind turbines.

Wake steering aims to redirect the wake away from a downstream turbine. This study explores the potential of a data-driven model whose equations can be interpreted physically. It estimates wake characteristics from measurable input variables by utilizing a simple linear model. The model shows encouraging results in estimating available power in the far wake, with significant improvements over currently used analytical models in conditions where wake steering is deemed most effective.

The paper presents a new validation campaign of wake steering at a commercial wind farm. The campaign uses fixed yaw offset positions, rather than a table of optimal yaw offsets dependent on wind direction, to enable comparison with engineering models of wake steering. Additionally, by applying the same offset in beneficial and detrimental conditions, we are able to collect important data for assessing second-order wake model predictions.

As wind power becomes more popular, there is a growing demand for accurate power production forecasts. In this paper we investigated different methods to improve wind power forecasts for an offshore location in the Baltic Sea, using both simple and more advanced techniques. The performance of the methods are evaluated for different weather conditions. Smoothing the forecast was found to be the best method in general, but we recommend to select which method to use based on the forecasted weather.

The e-Telltale, a new aerodynamic sensor have been tested in a large wind tunnel in the CSTB. This sensor have been designed to detect the flow separation on wind turbine blades which can cause energy production losses and increased aging of the blades. Theses wind tunnel tests higlighted the good ability of the e-Telltale to detect the flow separation and the influence of the size and location of the e-Telltale on the flow separation detection.

We develop two machine-learning-based approaches to temporally extrapolate uncertainty in hub-height wind speed modeled by a numerical weather prediction model. We test our approaches in the California Outer Continental Shelf, where a significant offshore wind energy development is currently being planned, and we find that both provide accurate results.

This article presents a novel method to improve offshore surface wind speeds estimated by Synthetic Aperture Radar satellites and extrapolate them to higher altitudes. It can provide maps of the offshore extractible wind power up to 200 m and thus complement numerical models, especially in coastal areas. The method uses geometrical parameters of the sensor and parameters related to the atmospheric stability, combining them with machine learning. The final accuracy at 200 m is within 4 %.

Wind turbine wake behavior in hilly terrain depends on various atmospheric conditions. We modeled a wind turbine located on top of a ridge in Portugal during typical nighttime and daytime atmospheric conditions and validated these model results with observational data. During nighttime conditions, the wake deflected downwards following the terrain. During daytime conditions, the wake deflected upwards. These results can provide insight into wind turbine siting and operation in hilly regions.

A model for computing vertical-axis wind turbine farms was developed using computational fluid dynamics open-source software. This model has the potential of evaluating wind farm configurations which can lead to a higher annual energy yield. Such configurations have not been studied thoroughly due to the fact that most analysis tools are computational expensive, this model can be run in personal computers within a matter of minutes or hours depending on the number of turbines.

We perform a validation of the new simulation tool FAST.Farm for the prediction of power output and structural loads in single wake conditions with respect to measurement data from the offshore wind farm alpha ventus. With a new wake-added turbulence functionality added to FAST.Farm, good agreement between simulations and measurements is achieved for the considered quantities. Hereby, we give insights into load characteristics of an offshore wind turbine subjected to single wake conditions.