Abstracted/indexed

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.

Modern rotor blade designs depend on detailed numerical models and simulations. Thus, a validated modelling methodology is fundamental for reliable designs. This paper briefly presents a modelling algorithm for rotor blades, its validation against real life full scale blade tests and the respective test data. The hybrid 3D shell/solid finite element model is successfully validated against the conducted classical bending tests in flap-wise and lead-lag direction as well as novel torsion tests.

Light detection and ranging (lidar), has become a valuable technology to assess the wind resource at hub height of modern wind turbines. However, because of their measurement principle, common lidars suffer from errors at orographically complex, i.e. hilly or mountainious sites. This study analyses the impact of the five main influencing factors in a non-dimensional, model-based parameter study.

Floating Offshore Wind Turbines may experience large surge motions which, when faster than the local wind speed, cause rotor-wake interaction. We derive a model which is able to predict the wind speed at the wind turbine, even for large and fast motions and load variations of the wind turbine. The proposed dynamic inflow model includes an adaptation for highly loaded flow and it is accurate and simple enough to be easily implemented in most Blade Element Momentum design models.

This research involves studying the flow around the section of a wind turbine blade albeit at a lower Reynolds number or flow speed using wall-resolved large-eddy simulations, a form of computer simulation that resolves the important scales of the flow. Among the many interesting results, it is shown that the energy entering the boundary layer around the airfoil or section of the blade is proportional to the square of the incoming flow turbulence intensity.

A novel inverse problem-based methodology is developed to estimate the drive train main shaft torsional stiffness and displacement only by acquisition SCADA measurements. It involves Tikhonov regularisation for regularising the measurement data and the collage method for system identification. These estimated quantities can be used to identify the site-specific torsional loads of the main shaft and to quantify the remaining useful life of the main shaft as well as other drive train components.

The publication of the Reference Open-Source Controller (ROSCO) provides a controller and generic controller tuning process to the wind energy research community that can perform comparably or better than existing reference wind turbine controllers and includes features that are consistent with industry standards. Notably, ROSCO provides the first known open-source controller with features that specifically address floating offshore wind turbine control.

Wind turbines are frequently placed in forests. We investigate the potential of using satellites to characterise the land surface for wind flow modelling. Maps of forest properties are generated from satellite data and converted to flow modelling maps. Validation is carried out at ten sites. Using the novel satellite-based maps leads to lower errors of the power density than land cover databases, which demonstrates the value of using satellite-based land cover maps for flow modelling.

A new high-resolution data set (NORA3) is validated for offshore wind power purposes for the North Sea and Norwegian Sea. The purpose of the validation is to ensure that NORA3 can act as a planning tool for future offshore wind power installations in the area of concern. The general conclusion of the validation is that NORA3 is well suited for wind power estimates, but gives slightly conservative estimates on the offshore wind metrics.

In RANS-CFD, e^N-based method showed its superiority over local correlation-based transition models (LCTM) coupled with the SST turbulence model for predicting transition behavior at high-Reynolds number flows (3–15 million). In this study, we evaluated performance of two LCTMs coupled with SA turbulence model. As a result, the SA-based two-equation transition model showed a comparable performance with the e^N-based method and better glide ratio (L / D) predictions than the SST-based model.

Wind farm layout optimization is an essential part of wind farm design. In this paper, we present different methods to determine the number of turbines in a wind farm, as well as their placement. Also in this paper we explore the effect that the objective function has on the wind farm design, and found that wind farm layout is highly sensitive to the objective. The optimal number of turbines can vary greatly, from 15–54 for the cases in this paper, depending on the metric that is optimized.