bluuebunny/crossref_metadata_2025 huggingface dataset:
Wind Turbine Main Bearing Failure Prediction using a Hybrid Neural Network
Authors: Bermúdez Karen , Ortiz-Holguin Eduardo , Tutivén Christian , Vidal Yolanda , Benalcázar-Parra Carlos
Published: June 2022

Energy is necessary for economic growth and improved well-being, but it poses a great challenge to be generated without increasing costs and avoiding pollution. A viable option is wind energy because it is a clean and renewable. However, continuous monitoring and maintenance of wind turbines is required for the further development of wind farms. Main bearing failures were identified by the European Academy of Wind Energy as a critical issue in terms of increasing the availability and reliability of wind turbines. In this work, it is proposed a hybrid neural network for main bearing failure prognosis. This network consists of a two-dimensional convolutional neural network (to extract spatial-temporal characteristics from the data) sequentially connected with a long short-term memory network (to learn sequence patterns) to predict the slow-speed shaft temperature (the closest temperature to the main bearing). The mean square error between its real measurement and its prediction gives a failure indicator. When it is greater than a defined threshold, then an alarm is triggered and gives the maintenance staff time to check the component. The advantage of this strategy is that it does not need faulty data to be trained, since it is based on a normality model, that is, it is trained with a single class of data (healthy) and does not require incurring high costs per acquisition of new sensors since SCADA data is used (which comes in all industrial size turbine). The results show that the use of a hybrid network can identify failures around four months before a fatal failure occurs.
Deep Neural Network Hard Parameter Multi-Task Learning for Condition Monitoring of an Offshore Wind Turbine
Authors: Black Innes Murdo , Cevasco Debora , Kolios Athanasios
Published: June 2022

Breaking the curse of small datasets in machine learning is but one of the major challenges that cause several real-life prediction problems. In offshore wind application, for instance, this issue presents when monitoring an asset in an attempt to reduce its infant mortality failures. Another challenge could emerge when reducing the number of sensors installed in order to limit the investment in monitoring systems. To tackle these issues, the aim of this article is to investigate the impact of small data-set on conventional machine learning methods, and to outline the improvement achievable by the implementation of transfer learning approach. It provides a solution to mitigate this issue by applying a hard parameter multi-task learning approach to the supervisory control and data acquisition data from an operational wind turbine, allowing for smaller datasets to efficiently predict the status of the gearbox’s vibration data. Two experiments are carried out in this paper. The first is to envisage the possibility of using hard parameter transfer on the operational data from two wind turbines. The second is to compare the results of this model to the findings from a conventional deep neural network model trained on the data from a single turbine.
Wake state estimation of downwind turbines using recurrent neural networks for inverse dynamics modelling
Authors: Farrell W , Herges T , Maniaci D , Brown K
Published: June 2022

Presented in this work is a novel approach to estimate absolute lateral wake center position on the rotor plane of a waked turbine using turbine load and operating state information. The approach formulates the estimation of the absolute lateral wake position as an inverse dynamics problem and utilizes a recurrent neural network to model the inverse mapping between the wake center position and select turbine output channels. The technique is validated on experimental data collected from experiments at the Scaled Wind Farm Technology (SWiFT) facility and numerical simulations of the site in the wind farm simulator FAST.Farm. Estimator performance and analysis of optimal conditions for estimation are discussed.
Investigating the impact of atmospheric conditions on wake-steering performance at a commercial wind plant
Authors: Simley Eric , Debnath Mithu , Fleming Paul
Published: June 2022

Wake steering is a wind farm control strategy in which upstream wind turbines are misaligned with the wind to deflect their wakes away from downstream turbines, thereby increasing net energy production. But research suggests that the effectiveness of wake steering strongly depends on atmospheric conditions such as stability. In this paper, we investigate results from a two-turbine wake-steering experiment at a commercial wind plant to assess the impact of stability and five other atmospheric variables on wake-steering performance. Specifically, for different atmospheric condition bins we compare the ability of the controller to achieve the intended yaw offsets, the power gain from wake steering, and the reduction in wake losses. Further, we analyze wake-steering performance as a function of wind speed to eliminate the confounding impact of different wind speed distributions in different atmospheric conditions. Overall, we find that wind direction standard deviation is the best predictor of wake-steering performance, followed by turbulence intensity and turbulent kinetic energy. The results suggest the importance of adapting wake-steering control strategies to different atmospheric conditions.
Impact of calibrated soil-monopile-interaction model on resonance frequencies
Authors: Sastre Jurado C , Stuyts B , Weijtjens W , Devriendt C
Published: June 2022

Offshore wind turbines (OWTs) are sensitive, dynamic structures that require accurate estimation of the natural frequency of the support structure. This requires an integrated analysis of the wind turbine structure, including a realistic representation of the foundation response. This paper studies how the natural frequency analysis is influenced by the soil-monopile interaction model following the PISA guidance. A case study of an instrumented OWT at a Belgian offshore wind farm is presented. Comparing results between the calculated and monitored natural frequencies clearly demonstrates that a realistic representation of the foundation stiffness is crucial for accurate calculation of the OWT dynamics. The integrated analysis of the OWT based on the calibrated foundation model yields very accurate results.
The effect of damage position on Operational Modal Analysis of wind turbine blades for SHM
Authors: Ernst R , Lauridsen P , Klein C , Buffetti B
Published: June 2022

Operational Modal Analysis (OMA) is an attractive technology for Structural Health Monitoring (SHM) for wind turbine blades as it covers the entire blade with very limited instrumentation. This work points out some caveats inherent in this technology that must be taken care of for successful implementation. In particular, we discuss how the location of damage affects the detection performance. Additionally, measurements of OMA of MW scale wind turbine generator blades are reported. These recordings show that the measurement uncertainty varies within different mode-types, mode-numbers and external conditions. We present tools to the practitioner with which the best modes for damages of certain types and positions can be selected and blind spots on the blade can be estimated. In R&D, validation of OMA type SHM often means inflicting damages at arbitrary positions on a test blade. The results imply that this needs to be augmented with numerical analysis to ensure proper coverage of the critical details in the blade. Finally, incorporating learning’s from field measurements, we discuss strategies to improve resolution for small damages and bring more transparency regarding the detection limits for this monitoring technique.
Automatic detection and correction of aerodynamic and inertial rotor imbalances in wind turbine rotors
Authors: Bertelè M. , Bottasso C.L.
Published: June 2022

In this work, a novel rotor rebalancing algorithm is tested in a simulation environment to evaluate its performance when facing both aerodynamic and inertial imbalances. The algorithm, starting from a generic measurement collected on the wind turbine fixed frame, is capable of remotely minimizing once per revolution vibrations, avoiding the need for on-site inspections, and without requiring detailed information about the machine. Indeed, once access to the pitch system is granted, this algorithm simply iteratively computes the pitch angle that needs to be applied to each individual blade in order to rebalance the rotor.

Several turbulent time histories, with changing mean inflows, were simulated with the goal of testing the proposed method in realistic field conditions. Overall, the algorithm proved capable of significantly reducing the desired once per revolution vibrations in 3 to 4 iterations, irrespective of the imbalance root cause, its severity and its location. The method also appeared quite robust, showing that the found rebalanced configurations guarantee reduced vibrations no matter the machine operating point.
FLORIDyn - A dynamic and flexible framework for real-time wind farm control
Authors: Becker M , Allaerts D , van Wingerden J W
Published: June 2022

This paper presents a new framework of the FLOw Redirection and Induction Dynamics (FLORIDyn) model. It is able to dynamically simulate the wake behaviour in wind farms under heterogeneous and changing environmental conditions at a low computational cost. The novelty of this work is the improved segregation of wake dynamics and wake influence: the framework creates Observation Points (OPs) at each turbine, which propagate wind field states and turbine states downstream and follow the wind direction of the free stream velocity. These observation points cover the dynamic aspects of the simulation. The OPs, along with the stored states, are now used to derive so-called Temporary Wind Farms (TWF), which approximate the effective intra-farm wind conditions at a given location. Within these TWF, the flow conditions are homogeneous and steady state. This way, arbitrary wake models can be used to calculate the farm influence on the location. The FLORIDyn framework also provides interfaces to flow field estimators, which is tested with an effective wind speed estimator. A nine turbine case is used to highlight the quality and performance of the simulation result. Compared to its predecessor, the new FLORIDyn framework decreases the computational cost by one to two orders of magnitude, which makes it a promising candidate for real-time model predictive dynamic wind farm control.
Serial-Refine Method for Fast Wake-Steering Yaw Optimization
Authors: Fleming Paul A. , Stanley Andrew P. J. , Bay Christopher J. , King Jennifer , Simley Eric , Doekemeijer Bart M. , Mudafort Rafael
Published: June 2022

In this paper we present the Serial-Refine method for quickly finding the optimal yaw angles in wake steering. The method optimizes turbine angles serially from upstream to downstream using a small number of candidate angles. The presented results show that Serial-Refine finds solutions that are at least as good as former conventional optimization approaches but that require much less computation time.
Aeroservoelastic stability of a floating wind turbine
Authors: Vanelli T , Rinker J , Zalkind D S
Published: June 2022

The problem of negative damping undermines the aeroservoelastic stability of floating offshore wind turbines. The negative damping problem is most prevalent around rated wind speed, where the sensitivity of thrust to wind speed is the largest. This paper investigates the implementation of peak shaving, a controller feature that limits the rated thrust by pitching the blades before rated wind speed is reached. Two controller designs are investigated: a de-tuned controller and a nacelle-feedback controller. A time-domain metric is defined, inspired by Lyapunov theory, in order to compute and assess the stability of floating offshore wind turbines. The model of the International Energy Agency 15-MW reference wind turbine mounted on the University of Maine VolturnUS-S floater is simulated in HAWC2 with the National Renewable Energy Laboratory reference open-source controller. Peak shaving is applied to the two controller designs and stability is assessed. According to the chosen metric, peak shaving does not improve the stability of the system. This is due to the trade-off between loads and error tracking: although the loads and displacements in the fore-aft direction of the turbine are reduced, the rotor-speed tracking is poorer, which increases the shaft torsion fatigue load.
A novel Nonlinear Model Predictive Controller for Power Maximization on Floating Offshore Wind Turbines
Authors: Pustina Luca , Biral Francesco , Serafini Jacopo
Published: June 2022

Reducing the Levelized Cost of Energy is the main objective of wind turbine industry, in particular for the emerging sector of floating offshore turbines. In this work, a novel Economic Nonlinear Model Predictive Control (ENMPC) strategy is developed to maximize the power production of floating offshore wind turbines. The control problem is solved through an indirect method, which achieves the computational efficiency required to apply it in real world cases. A non-linear Reduced Order Model of the floating turbine predicts aerodynamic power, generator temperature and platform motions inside the controller. A set of constraints, including a bound on the generator temperature, the thrust and platform velocities are imposed. Simulations using the open-source engineering tool OpenFAST on the 5MW NREL wind turbine supported by the OC3 spar buoy platform [1] are performed to validate the turbine model and then to assess the controller performances in realistic wind and sea state conditions. With respect to the standard controller, a 4.3% increase of generated power in rated conditions is achieved with a more stable generator temperature.
A comprehensive code-to-code comparison study with the modified IEA15MW-UMaine Floating Wind Turbine for H2020 HIPERWIND project
Authors: Kim Taeseong , Natarajan Anand , Lovera Anaïs , Julan Emricka , Peyrard Christophe , Capaldo Matteo , Huwart Guillaume , Bozonnet Pauline , Guiton Martin
Published: June 2022

An extensive code-to-code comparison among DIEGO, DLW and HAWC2 has been performed on a floating wind turbine (modified version of UMaine floater with IEAWIND 15MW wind turbine). In total, 10 cases are compared, and a few key results of this comparison are reported in this paper. From the comparisons, it is clearly seen that the results predicted by the three codes are generally agreed well despite some differences in specific degrees of freedom like roll, sway and yaw for the extreme load case, which requires additional investigations.
Efficient multibody modeling of offshore wind turbines with flexible substructures
Authors: Steinacker Heiner , Lemmer Frank , Raach Steffen , Schlipf David , Cheng Po Wen
Published: June 2022

Offshore wind turbines, especially floating wind turbines, are often simulated assuming rigid substructures to obtain computationally efficient simulation models for preliminary parameter variation studies. This causes large errors in the determination of coupled natural frequencies and internal loads, particularly with increasing turbine sizes. Finite Element models for flexible substructures were developed by several researchers, often resulting in a high simulation effort. In this paper, a modally reduced Finite Element model, precomputed by the SubDyn module of OpenFAST, is directly included in the generalized Equation of Motion of the Simplified Low Order Wind turbine model SLOW. The approach was tested with the DTU10MW reference wind turbine mounted on a flexible monopile. It shows a high agreement with the former beam-based Multibody System in the calculated coupled natural frequencies and steady state results both for the linear and nonlinear model. A basis has been established to integrate flexible bodies of any shape even into computational efficient Multibody Systems of reduced order, such as SLOW, without coupling of two modules as in OpenFAST. This might improve numerical stability due to unified equations of motion.
Parametrisation Scheme for Multidisciplinary Design Analysis and Optimisation of a Floating Offshore Wind Turbine Substructure – OC3 5MW Case Study
Authors: Ojo Adebayo , Collu Maurizio , Coraddu Andrea
Published: June 2022

The development of novel energy technologies is considered imperative in the provision of solutions to meet an increasing global demand for clean energy. Floating Offshore Wind Turbine (FOWT) is one of the emerging technologies to exploit the vast wind resources available in deeper waters. To lower the levelized cost of energy (LCOE) or optimise the performance response associated with a FOWT system, a detailed understanding of the different disciplines (Aero-Hydro-Servo-Elastic) within the system and the relationship between the FOWT system and the dynamics of the marine environment is required. This requires an efficient Multidisciplinary Design, Analysis and Optimisation (MDAO) framework for FOWT systems to reduce the capital cost and increase dynamic performance. A key component of any MDAO framework is the shape parameterisation scheme, as it enables the modelling of a large array of platform designs with different geometric shapes using limited number of parameters. This work focuses on the B-Spline parameterisation modelling technique of OC3 spar-buoy and the use pattern search optimization algorithm to select the optimal design variants. The parametrisation technique is implemented in an analysis framework, where a B-spline library from Sesam GeniE is used to model each design representation, and a potential flow frequency domain analysis solver (HydroD/Wadam) is used for the hydrodynamic analysis. Validation of the selected designs within the design space is conducted with a benchmark NREL5MW spar-buoy hydrodynamic response results in literature with the hydrodynamic response of the frequency domain modelling approach using Sesam GeniE and HydroD/Wadam. This analysis process shows a high accuracy in response results between the OC3 spar-buoy in literature and the OC3 spar-buoy model design using B-Spline parametrization technique. Key performance metrics like the cost of materials and root mean square (RMS) of the nacelle acceleration also show improvement with the design variants compared to estimation from OC3 design in literature.
Validation of CFD determined hydrodynamic coefficients for a semisubmersible floating offshore wind turbine
Authors: Ramesh Reddy Likhitha , Milano Daniel , Walker John , Viré Axelle
Published: June 2022

The hydrodynamic characteristics are crucial for accurately analysing floating offshore wind systems. In this paper, the added mass and damping coefficients of a semisubmersible floater are examined around the natural periods of the surge, heave, and pitch motion, using computational fluid dynamics (CFD). The OpenFOAM CFD setup is validated against experimental measurements from the free decay tests, and the same setup is used to determine the hydrodynamic coefficients of the platform subjected to forced motions with different amplitudes and periods. The added mass and quadratic damping coefficients obtained from forced oscillations are consistent with the free decay results. Moreover, the added mass coefficients obtained by CFD is significantly higher than the estimations of the potential flow theory: around 10% larger for surge and 22% larger for heave. The damping is almost independent of the frequency while it varies with the motion amplitude. The deviations in the CFD results from the potential flow theory are due to the viscous effects. Besides, viscous damping is dependent on the drag coefficient specified in the Morison’s equation.
Cost-based mooring designs and a parametric study of bridles for a 15 MW spar-type floating offshore wind turbine
Authors: Pan Qi , Cheng Po Wen
Published: June 2022

This paper highlights a cost-based design method for feasible and cost-effective mooring configurations. A parametric study of mooring designs considering bridle impact is performed for a 15 MW spar-type floating offshore wind turbine (FOWT). This site-specific FOWT is based on the preliminary model from EU funded H2020 Project COREWIND. Without running numerical simulations, the cost-based design method generates 1443 mooring configurations with normalized costs ranging from 1.00 to 1.667. Six configurations with the lowest normalized costs are selected for OpenFAST simulations. The ultimate test results verify the structural strength of mooring configurations. Bridle designs cause significant impact on the ultimate mooring tensions and floater motions in surge, sway and yaw, which is clearly influenced by the mass ratio of a bridle to a mooring line. When the mass ratio decreases from 13% to 5%, peak mooring tensions increase by up to 17%. The influence of bridle designs on mooring tension fatigue is less prominent and the effect of mass ratio on mooring fatigue varies with wind speed. Near the rated wind speed, deviations in mooring fatigue loads are within 5% for all six configurations. This cost-based method promotes feasible and economical mooring designs. The parametric study of bridle designs provides solid support for optimal mooring designs of spar-type FOWTs.
A six degree-of-freedom set-up for wind tunnel testing of floating wind turbines
Authors: Messmer Thomas , Brigden Charles , Peinke Joachim , Hölling Michael
Published: June 2022

In this paper we present a six-degree-of-freedom (DoF) experimental set-up for wind tunnel testing of floating offshore wind turbines (FOWTs). The system is composed of a 6-DoF Stewart platform that can be used to mimic realistically the motions of a floating turbine at laboratory scale. The platform is specifically made for the Model Wind Turbine Oldenburg 0.6 (MoWiTO 0.6). First, the methodology followed to design the system as well as the scaling issues are depicted. Then, the characterisation of the platform is presented. Finally, limitations of the set-up are discussed.
An engineering modification to the blade element momentum method for floating wind turbines
Authors: Mancini Simone , Boorsma Koen , Caboni Marco , Hermans Koen , Savenije Feike
Published: June 2022

The design of next-generation offshore wind rotors for floating applications carries large uncertainties that make it harder to bring costs down. A significant share of this uncertainty is associated with the use of Blade Element Momentum (BEM) methods to run aeroelastic design and loadcase calculations, because the assumptions underlying the momentum theory are violated by the floater motion. This work presents an engineering method for BEM that allows to model generic floater motions and improves the aerodynamic modelling of floating wind turbines. The new model overcomes the challenge of estimating the apparent wind caused by the platform motion in a simple way, which proves to be very effective for rigid aerodynamic simulations. To verify its impact, BEM results with and without the proposed correction are compared to high-fidelity free vortex wake simulations, imposing the same harmonic motion first to the pitch and then to the yaw degree of freedom of the platform. While little differences are found for the yaw motion, the new floating model clearly improves predictions for the platform pitch case in terms of both aerodynamic loads and induction, finding a very good match with the high-fidelity results. An analysis of the verification data provides new valuable insights on the effect of these motions on aerodynamic loads and performance of a floating wind turbine.
Floating wind turbine control optimization
Authors: Zalkind Daniel , Abbas Nikhar J. , Jasa John , Wright Alan , Fleming Paul
Published: June 2022

We present a framework for optimizing the control parameters of floating offshore wind turbines (FOWTs). The framework combines aeroelastic simulations with a systems engineering model and control software. In an example of the optimization framework, we minimize tower damage equivalent loading with generator speed constraints. We also study the effect of thrust-limiting control and quantify the trade off between fatigue loading and energy capture using a set of optimal controller designs. Finally, we optimize the controller of four different FOWT models and compare their dynamic responses. Additional details and other use cases for the framework are presented, which can optimize different control problems and evaluate FOWT designs.
Wind field reconstruction using nacelle based lidar measurements for floating wind turbines
Authors: Gräfe Moritz , Pettas Vasilis , Cheng Po Wen
Published: June 2022

In this work we investigate the influence of floater motions on nacelle based lidar wind speed measurements. The analysis is focused on wind field characteristics which are most relevant for performance analysis, namely rotor effective wind speed, shear and turbulence intensity. A numerical approach, coupling the publicly available in-house lidar simulation framework ViConDAR (Virtual Constrained turbulence and liDAR measurements) with an aeroelastic floating offshore wind turbine simulation is employed. Synthetic turbulent wind fields are generated with the open source turbulence generator TurbSim. The dynamics of the floating offshore wind turbine are simulated in the aeroelastic simulation code OpenFAST. Turbine dynamics and the corresponding synthetic wind field are then passed to the lidar simulation module of ViConDAR, which has been adapted for the consideration of turbine dynamics in all six degrees of freedom to simulate the lidar measurements under influence of motion. The simulation framework is demonstrated in a case study, simulating a lidar system on the nacelle of the IEA 15 MW turbine in combination with the WindCrete floater concept. Two different realistic lidar patterns are investigated under different metocean conditions. Different motion cases are examined individually and combined to evaluate the influence of rotational and translational degrees of freedom. Results show an increase of mean absolute error between lidar estimated and full wind field rotor effective wind speed of 0 to 25% depending on the environmental conditions. Observed overestimation of mean rotor effective wind speed was found to be in the region of up to 1%.
Wind tunnel investigation of the wake-flow response for a floating turbine subjected to surge motion
Authors: Fontanella A. , Zasso A. , Belloli M.
Published: June 2022

Floating wind turbines undergo large translation motions allowed by the high compliancy of the support structure. Large motions affect the rotor aerodynamic response and wake. This paper examines wake measurements of a wind tunnel experiment with a scale model of the DTU 10MW subjected to imposed harmonic surge motion. The effect of surge motion on the wake is detected by means of spectral analysis of velocity data. It is found that when the rotor undergoes surge motion, periodic forcing is introduced into the fluid, which produces a harmonic variation of the wake speed. The velocity perturbation around the rotor is then convected downstream at about the average axial velocity in the wake. The amplitude of the velocity pulsation at 2.3D is radially-dependent, and is correlated to the amplitude of the variation of the normal-force distribution along the blade.
Stability information derived from a floating lidar system using bulk Richardson formulation
Authors: Hatfield Daniel , Gottschall Julia , Bay Hasager Charlotte
Published: June 2022

In this contribution we introduce a Fraunhofer IWES floating lidar system (FLS) equipped with an integrated pulsed lidar device, motion sensors, near-surface atmospheric variable sensors (air temperature, relative humidity and air pressure) and a sea-surface temperature sensor. All measures were compared and validated with the nearby offshore meteorological mast FINO3 in the German North Sea. Atmospheric stability information was derived using the bulk Richardson formulation from the FINO3 station at both 30-m and 100-m as well as at the FLS at a 2-m height. The stability parameter was then extrapolated to the higher heights from the FLS using the mean wind speed measured from the lidar. The FLS was able to recreate the stability conditions calculated at the 30-m height but could not effectively match that of the 100-m calculations. This is mainly attributed to the significant changes with height of the atmospheric variables and their importance in the stability calculations.
Dynamics of two floating wind turbines with shared anchor and mooring lines
Authors: Gözcü Ozan , Kontos Stavros , Bredmose Henrik
Published: June 2022

Floating wind farms present the opportunity to harvest wind resources located in deep water sites. Shared mooring designs can contribute in making floating wind energy more cost-competitive, and it is important to understand the new system dynamics that arise. We are presenting here HAWC2Farm, an extension of HAWC2 that can model multiple wind turbines with shared mooring lines. We apply the new modeling capabilities to simulate two 15 MW floating wind turbines on spar floaters with shared mooring lines. We consider two different sites and we identify and compare the natural frequencies and mode shapes of the shared mooring designs with those of an individual moored turbine. Furthermore, we investigate the influence of design parameters on the systems’ natural frequencies and we show that it is possible for a shared mooring design to achieve similar characteristics as a single turbine design. Finally, we test the response of the shared mooring design in steady wind and regular waves and find that the surge displacement of the upstream turbine and its mooring line loads are considerably larger compared to the single turbine case.
Axial induction control design for a field test at Lillgrund wind farm
Authors: Bossanyi Ervin , Ruisi Renzo , Larsen Gunner Chr. , Pedersen Mads Mølgaard
Published: June 2022

Lillgrund offshore wind farm near Copenhagen has been the subject of a number of research projects. The close turbine spacing makes it an interesting candidate for research into turbine wakes and wind farm control. As part of the EU TotalControl project, an axial induction controller has been designed for field testing at Lillgrund. The controller was designed using steady-state optimisations in DNV’s LongSim code, which predicted a small but significant power gain along with a considerable reduction in fatigue loading. Some simplifications were introduced for ease of practical implementation on this particular site; the controller was initially optimised to improve the power output of one 7-turbine row, with the aim of extending to the whole wind farm if the first test was successful. The expected power gain was confirmed by running realistic, detailed time-domain simulations in LongSim, and independently corroborated using steady-state calculations with DTU’s linear CFD code Fuga. The controller was implemented on site, and a toggle test was initiated on site in late December 2021, with the wind farm controller toggling between controlled and default states every 50 minutes. First results are expected early in 2022.
Life Cycle Environmental Impact of Wind Turbines: What are the Possible Improvement Pathways?
Authors: Guilloré A , Canet H , Bottasso CL
Published: June 2022

This study explores the effect of different technology choices on the life cycle Greenhouse Gases (GHG) emissions of wind turbines. It aims at identifying possible improvement pathways and quantifying potential benefits. First, an automated Life Cycle Assessment (LCA) model is developed and validated against other studies. The breakdown of the resulting Impact Of Energy (IOE) by life stages, components and materials is presented for a selected reference turbine. Sensitivity analyses are conducted on the different hypotheses to model the turbine life cycle. The model is then applied to analyze the potential effect of turbine size, foundation type, tower type, drivetrain technology, carbon-fiber blades and thermoplastic polymer resin for the blades. The tower type (especially wooden tower) and the thermoplastics (allowing to recover materials at the end-of-life) are identified to have the biggest potential to reduce the life cycle environmental impact of wind energy.
Case study on the benefits and risks of green hydrogen production co-location at offshore wind farms
Authors: He Wei , Zheng Yi , You Shi , Strbac Goran , Therkildsen Kasper T. , Olsen Gudmund P. , Howie Aaron , Byklum Eirik , Sharifabadi Kamran T.
Published: June 2022

Abstract Advances in large-scale green hydrogen production (LGHP) create commercial opportunities for enhancing rapid offshore wind farm (OWF) development. This study investigates whether LGHP co-location at OWF sites improves those OWF’s economic outlooks under potential electrical grid capacity bottlenecks towards 2050. Eight cases have been studied using measured annual OWF power production series and cost estimation integrated with offshore engineering experience: i) two base cases: 2 GW OWFs with HVAC and HVDC transmission infrastructure showing that the levelized cost of electricity (LCOE) increases, and ii) six LGHP co-location cases demonstrating that the calculated levelized cost of hydrogen (LCOH) reduces when the LGHP capacity increases from 20% to 50%, and 100% of 2 GW. Furthermore, three economic improvement factors studied are: i) utilizing existing gas pipelines reducing LCOH by 7.5%, ii) hydrogen for offshore customers changing “no-go” projects to “go”, and iii) scaling-up from 2 to 4 GW reduced the LCOH by 17%. This study shows that LGHP co-location is effective at maintaining OWF full production, but has higher risks including i) LGHP co-location safety at OWFs, ii) high costs to cover more operational conditions and iii) running LGHP operations using high, fluctuating OWF power. Further R&D of LGHP co-location are recommended.
A comparison of wind turbine blade parametrization schemes for planform design optimization
Authors: Iori Jenna , McWilliam Michael K.
Published: June 2022

This work compares nodal, spline and interpolation parametrization schemes for wind turbine blade planform design. The comparison is done on a power coefficient maximization problem, where the aerodynamic properties of the blade are computed using the Blade Element Method. The problem is solved using a gradient-based interior-point method with analytic gradients. We show the variation in planform design for each parametrization scheme when the degrees of freedom of the parametrization varies. We compare how the power coefficient converges with increasing degrees of freedom for each scheme. Our results shows that the B´ezier spline, the Piecewise Cubic Hermite Interpolation Polynomial (PCHIP) and Lagrange interpolation schemes present the best grid convergence out of all studied schemes.
An open-source framework for the uncertainty quantification of aeroelastic wind turbine simulation tools
Authors: Verdonck H , Hach O , Polman J D , Braun O , Balzani C , Müller S , Rieke J
Published: June 2022

The uncertainty quantification of aeroelastic wind turbine simulations is an active research topic. This paper presents a dedicated, open-source framework for this purpose. The framework is built around the uncertainpy package, likewise available as open source. Uncertainty quantification is done with a non-intrusive, global and variance-based surrogate model, using PCE (i.e., polynomial chaos expansion). Two methods to handle the uncertain parameter distribution along the blades are presented. The framework is demonstrated on the basis of an aeroelastic stability analysis. A sensitivity analysis is performed on the influence of the flapwise, edgewise and torsional stiffness of the blades on the damping of the most critical mode for both a Bladed linearization and a Bladed time domain simulation. The sensitivities of both models are in excellent agreement and the PCE surrogate models are shown to be accurate approximations of the true models.
Comparison of a mid-fidelity free vortex wake method to a high-fidelity actuator line model large eddy simulation for wind turbine wake simulations
Authors: Houck D R , deVelder N , Kelley C L
Published: June 2022

The need for mid-fidelity wind turbine simulations is increasing due to their balance of accuracy and computational efficiency. A common form of mid-fidelity code is the free wake vortex method (FVWM), but these are known to inaccurately represent the far-wake depending on their implementation. Herein, we compare CACTUS, a FVWM code, to Nalu-Wind, an actuator line model large eddy simulation (ALM-LES) code with particular focus on the far wake. Specifically, we compare one CACTUS simulation, which necessarily has steady and uniform inflow, to three Nalu-Wind simulations using a steady and uniform inflow, a low turbulence inflow, and a high turbulence inflow. The comparison reveals interesting parallels between CACTUS and all Nalu-Wind cases, but ultimately demonstrates that CACTUS is not an appropriate tool for the simulation of the far-wake of a wind turbine.
Employing Bayesian Quadrature to Improve Fitting of Surrogate Models to Wind Turbine Loads
Authors: Caterina Clark Anna , Clark Caitlyn E.
Published: June 2022

Stochastic, high-fidelity simulations are increasingly used to estimate wind turbine and plant loads and performance. While these simulations are more accurate, they are prohibitively computationally expensive. Surrogate models can be used to replace direct simulation for lower computational cost; for stochastic surfaces, a Gaussian Process (GP) is appropriate for random variables that follow Gaussian distributions, such as turbine loads and performance.

In this study, we employ an advanced surrogate modeling technique to estimate the loads, reliability, and energy production of wind turbines in a wind plant, based on mid-fidelity aero-elastic simulations. Specifically, we use Bayesian Quadrature (BQ) to produce a training data set that, for a given size, minimizes the variance over the entire domain of a GP surrogate model to estimate rotor torque load on a waked turbine. When applied to a GP that was trained with aero-elastic simulation data, the BQ-enabled algorithm reduced variance—a measure of predictive uncertainty—over the entire GP to < 0.3 with 30 samples. When compared to a uniform sampling approach with the same solution space, the BQ method reduces computational time by 99.88%, or over 590 simulation evaluations.
Assessment of a heterogeneous computing CFD code in wind farm simulations
Authors: López B , Guggeri A , Draper M , Usera G
Published: June 2022

The use of heterogeneous architectures, based on CPU-GPU processors, has led to a significant increase in the performance of parallel computing applications. In recent years, this approach has been implemented in various computational fluid dynamics (CFD) codes to take advantage of the compute capability of the GPU graphics cards. The objective of this work is to assess the performance of a general purpose CFD open-source code in wind energy applications, running in a heterogeneous architecture. To this aim, a numerical wind turbine model was migrated from a CPU-based Fortran program to the CFD code. Several timing tests were performed on a local computing station, while running simulations of well-documented wind tunnel experiments. The results obtained show a significant reduction in computational time and resource required, indicating a great potential of the GPU-accelerated CFD code to be used in large wind farms simulations or in real-time applications.
Towards the development of an advanced wind turbine rotor design tool integrating full CFD and FEM
Authors: Cozzi Lorenzo , Bellucci Juri , Giovannini Matteo , Papi Francesco , Bianchini Alessandro
Published: June 2022

Large, highly flexible wind turbines of the new generation will make designers face un-precedent challenges, mainly connected to their huge dimensions. To tackle these challenges, it is commonly acknowledged that design tools must evolve in the direction of both improving their accuracy and turning into holistic, multiphysics tools. Furthermore, the wind turbine industry is reaching a high level of maturity, and ever more accurate and reliable design tools are required to further optimise these machines. Within this framework, the study shows the development of an integrated platform for blade design integrating 3D CFD flow simulations and 3D-FEM structural analysis. Artificial intelligence techniques are applied to develop an optimization procedure based on the proposed tool. The potential of the new platform has been tested on the well-known test case of the MEXICO rotor, for which an optimization of the blade design has been carried out. Exploring a design space sampled with 2000 CFD and FEM computations, increases in blade torque have been obtained at each of the three tip-speed ratios (TSR) investigated, ranging from 6% at the nominal TSR to 14% at the lowest one, while stresses on the blade are kept almost unaltered.
Multidisciplinary aeroelastic optimization of a 10MW-scale wind turbine rotor targeting to reduced LCoE
Authors: Serafeim G. , Manolas D. , Riziotis V. , Chaviaropoulos P.
Published: June 2022

In the present paper, multidisciplinary optimization (MDAO) is applied with the aim to reduce the levelized cost of energy (LCoE) of the DTU-10MW Reference Wind Turbine (RWT) rotor. As application paradigm, the widely applied in the literature passive load control method of Bend Twist Coupling (BTC) is considered. The integrated optimization framework combines in a common loop, rotor aerodynamic and full wind turbine structural elasto-dynamic analyses, aiming at determining the optimum rotor diameter, the planform of the blade in terms of twist and chord distributions, the offset ply angle for BTC and the inner structure of the blade with cost function directly the LCoE. It is based on an in-house servo-aero-elastic analysis tool for determining the ultimate loads along the span of the blades and the power yield, whereas a cross-sectional analysis tool is employed for acquiring structural properties of the modified blade and stresses distributions over the blade sections. A cost model of the overall wind turbine is implemented by combining existing in the literature models and open data. The new rotor design is found to have a reduced LCoE by 0.71% and to produce 2.4% higher energy annually due to its increased by 3.7% diameter.
Unsteady aerodynamic modelling for dual-rotor wind turbines with lifting surface method and free wake model
Authors: Chen Jiajia , Yin Fanfu , Li Xinkai , Ye Zhaoliang , Tang Wei , Shen Xin , Guo Xiaojiang
Published: June 2022

A time-marching aerodynamic model for dual-rotor wind turbines (DRWT) is presented with the lifting surface method and free wake model. The performance of a reference DRWT by two axial connected NREL 5MW wind turbines is calculated to verify the algorithm. The output converges with remarkable oscillation. Free wakes swell under the coupling effect. The accumulated power of DRWT outranges single-rotor wind turbine (SRWT) by a limited extent under certain operating conditions. The front rotor (FR) produces the major portion of the power, especially for low inflow velocity. The unsteadiness of performance and spanwise load is further investigated, and the result shows that the power output of the rear rotor (RR) undergoes greater fluctuation than FR. The rotor-rotor induction strengthens both the rotors’ performance before they align and weakens it when they rotate away. The additional disturbance caused by FR’s tip vortices acts negatively on RR’s torque by upwashing the blade tip.
Experimental proof-of-concept of an energy ship propelled by a Flettner rotor
Authors: Elie B , Bognet B , Boileau T , Weber M , Gilloteaux J-C , Babarit A
Published: June 2022

The energy ship is a new concept for offshore wind energy capture. It consists of a wind-propelled ship that generates electricity using water turbines attached underneath its hull. Since it is not grid-connected, the generated energy is stored aboard the ship (for instance, using batteries or through conversion to hydrogen using an electrolyser). This concept has received little attention until today. In this paper, a proof-of-concept of an energy ship propelled by a Flettner rotor is presented. The experimental results are compared to numerical simulations. A very good agreement is obtained, which validates previous numerical simulations that indicate that a full-scale energy ship equipped with Flettner rotors can lead to positive net energy production.
Multi-Timescale Wind-Based Hybrid Energy Systems
Authors: Stanley Andrew P. J. , King Jennifer , Barker Aaron , Guittet Darice , Hamilton William , Bay Christopher , Fleming Paul , Sinner Michael
Published: June 2022

This paper focuses on the design of wind-based hybrid power plants that operate at different timescales ranging from seconds to days. Traditionally, renewable power plants have been designed to maximize the amount of energy produced. As the energy system transitions to higher amounts of renewables, hybrid power plants may be asked to provide baseload or peaking plant services that have been traditionally been serviced by coal and natural gas power plants. This paper demonstrates that considering these types of plants and their corresponding objects, that operate at different timescales, result in different solutions and should be considered in the design phase of hybrid power plant development.
Optimal Planning of Co-Located Wind Energy and Hydrogen Plants: A Techno-Economic Analysis
Authors: Li Honglin , Rahman Jubeyer , Zhang Jie
Published: June 2022

Green hydrogen produced using renewable electricity could play an important role in a clean energy future. This paper seeks to analyze the techno-economic performance of integrated wind and hydrogen systems under different conditions. A co-located wind and hydrogen hybrid system is optimized to reduce the total system cost. We have adopted and improved a state-of-the-art techno-economic tool REopt, developed by the National Renewable Energy Laboratory (NREL), for optimal planning of the integrate energy system (IES). In addition to wind and electrolyzer components, we have also considered battery energy storage, hydrogen tank, and hydrogen fuel cell in the IES. The results show that (i) adding electrolyzers to the grid-connected wind energy system could reduce the total system cost by approximately 8.9%, and (ii) adding electrolyzers, hydrogen tank, and hydrogen fuel cells could reduce the total system cost by approximately 30%.
Atmospheric Irrigation with Wind Turbines
Authors: Jauch C , Emeis S
Published: June 2022

In this paper, atmospheric irrigation with wind turbines is proposed. This technology addresses the problem of water scarcity by enhancing the natural water circuit in the atmosphere with wind turbines. There are three different operating modes conceivable for this technology. In two of these the wind turbines interact with the ground in their near wake. The third operating mode is the one which is discussed in this paper, and it aims at transporting water potentially over long distances. The basic working principle, the utilized physical phenomena and the basic design of the technology are introduced. The equations governing the hydraulic and the hydrological effects are presented. The goal of this paper is to quantify the necessary power and the necessary amount of water when wind turbines humidify a certain volume of air in the atmosphere. For this purpose, the power and water demand are assessed, both in a generalized manner and for a realistic scenario. It is concluded that the proposed system can achieve the objective in most wind speed conditions. However, the required amount of water is substantial. Therefore, an alternative source of fresh water has to be found when the system is used on a comparably large scale.