bluuebunny/crossref_metadata_2025_split huggingface dataset:
Residual uncertainty in processed line-of-sight returns from nacelle-mounted lidar due to spectral artifacts
Authors: Brown Kenneth , Herges Thomas 
Published: September 2020

Abstract
An uncertainty quantification technique for nacelle-mounted lidar is developed that extends conventional error analyses to precisely account for residual uncertainty due to observed non-ideal features in processed Doppler lidar spectra. The technique is applied after quality assurance/quality control (QAQC) processing to quantify residual error, both bias and random, from solid-body interference, shot noise, and any additional uncertainty introduced to the data from the QAQC process itself. The approach follows from the one-time construction of a high-dimensional parametric database of synthetic lidar spectra and subsequent processing with an existing QAQC technique. A model of the correspondence between the spectral shape and the associated residual errors due to non-ideal features is then developed for quantities of interest (QOIs) including the geometric median and spectral standard deviation of line-of-sight velocity. The model is preliminarily implemented within a neural network framework that is then applied in post-processing to sample returns from a DTU SpinnerLidar. The initial analysis uncovers the effects of specific sources of uncertainty in the context of both individual spectra and full-field maps of the measurement domain. The technique is described in terms of application to continuous wave (CW) lidar, though it is also relevant to pulsed lidar.
Structural Analysis of a Small Wind Turbine Blade Subjected to Gyroscopic Load
Authors: da Costa M S P , Clausen P D 
Published: September 2020

Abstract
A study was conducted to investigate the structural response of a composite constructed small wind turbine blade subjected to gyroscopic load using finite element analysis. An Aerogenesis 5 kW small wind turbine blade was used as a case study. As part of this study, a high-fidelity finite element model of the 2.5 m long composite blade was built, and the accuracy of its predictions validated against experimental data. The blade model was loaded using a comprehensive method for applying gyroscopic load to finite element models of small-scale blades. The predicted results show gyroscopic loading causes the blade to deflect in both the flap-wise and lead-lag directions and induce reasonably high strains in the composite blade structure. The direction of the gyroscopic loading is a function of the direction of turbine yaw as well as the blade position as it rotates, therefore gyroscopic loading can both exacerbate and reduce the effects of aerodynamic loading acting on the blade.
Computational aeroacoustic prediction of trailing edge noise for small wind turbines
Authors: Zilstra Alison , Johnson David A 
Published: September 2020

Abstract
The study of aeroacoustic noise generated by small wind turbines is important to increase acceptance and implementation of the technology. Small wind turbines have unique challenges due to the low Reynolds number (Re) flow the blades experience, which introduces a potential for tonal noise. Computational aeroacoustics can be applied during the design stage of the turbine blades to improve acoustic performance. This work aims to validate a fully analytical aeroacoustic model by analyzing a SD 7037 blade segment at static angles of attack, with comparison to experimental flow and acoustic data. The Ffowcs-Williams and Hawkings (FW-H) acoustic model is used in combination with Large Eddy Simulation (LES). The following simulation parameters were examined: mesh quality, mesh density, inlet turbulence and spanwise boundary condition. These parameters change the boundary layer (BL) transition process and the formation of the laminar separation bubble on the suction side of the blade segment, both of which impact the aeroacoustic noise prediction. It was found that improvement in mesh quality and density on the surface of the blade segment resulted in improved BL simulation and tonal noise prediction. Alteration of the inlet turbulence and spanwise boundary condition did not have as large of an effect.
Performance analysis of a hybrid vertical axis wind turbine through CFD for distributed generation in rural areas of Peru
Authors: Nuñez-Quispe Johan Joseph , Nuñez-Quispe Aaron Alfredo , Cedamanos-Cuenca Roger Omar 
Published: September 2020

Abstract
Currently, in the developing countries of Latin America there is a great deficiency in the transmission of energy. In Peru, being a developing country, there are many rural areas and indigenous and peasant communities that do not yet have access to electricity due to the difficult access or cost of installing transmission lines in their location. Therefore, the present work will briefly evaluate the current situation of the country and, from that, will formulate a solution based on the development of distributed generation systems using small wind turbines. For this purpose, this paper will develop the preliminary performance analysis of a hybrid vertical axis wind turbine (VAWT) by using the computational fluid dynamics (CFD), for this, the data of the wind resource of Cajamarca, a province in Peru, will be used for this analysis because in this province there is a great wind resource. Even a short aerodynamic and efficiency study was carried out in order to characterize its behaviour with different air flows as they are found in many rural sectors of Peru.
An efficient approach to explore the solution space of a wind turbine rotor design process
Authors: Bortolotti Pietro , Dixon Kristian , Gaertner Evan , Rotondo Megan , Barter Garrett 
Published: September 2020

Abstract
This study proposes a novel approach to explore the solution space of a wind turbine rotor design process. The goal is to offer to blade designers the possibility to select an optimal rotor for given market conditions, assessing trade-offs and alternatives in a matter of minutes. The design process consists of sequential aerodynamic-structural optimizations, where the two loops are linked via a blade-loading parameter that can be varied by the user. A design study is performed starting from the IEA Wind Task 37 land-based reference wind turbine. The solution space is characterized for rotor diameters in the range of 130–160 m, rated generator power values in the range of 3.0–6.0 MW, and tip-speed ratios in the range of 7.5–12.5. Results are discussed highlighting optimal design decisions and trade-offs.
Benchmarking different fidelities in wind turbine aerodynamics under yaw
Authors: Muñoz-Simón A , Palacios R , Wynn A 
Published: September 2020

Abstract
This paper analyses the aerodynamics of wind turbines under yaw with different modelling fidelities (BEM, BEM with skewed wake model, UVLM and LES-AL). First of all, models are compared in a zero-yaw case to demonstrate their accuracy in prediction of out-of-plane loads and the discrepancy of UVLM in the in-plane loads due to the lack of viscous drag. Secondly, the yaw aerodynamics are described through the advancing/retreating and skewed wake effects, which are appropriately captured by UVLM and LES-AL and lead to an incorrect prediction of the location of maximum and minimum loading along a revolution by BEM. Further, when a skew-wake model is included in BEM, it predicts the correct locations but exhibits overly large loading variations. These predictions are consistent for all yaw angles studied (γ = 10° − 30°). All solvers predict similar decrease of root-bending moments, rotor power and thrust coefficients up to a yaw angle of 10°. However, at larger yaw angles, BEM overpredicts this decrease of coefficients with the yaw angle due to the unsuccessful performance of yaw corrections as opposed to UVLM that inherently accounts for three-dimensional effects. This study demonstrates the need to use computational models that can account for three-dimensional effects in the computation of aerodynamic loads for yaw angles above 10°.
Design Optimization of 10MW Downwind Turbines with Flexible Blades and Comparison with Upwind Turbines
Authors: Namura Nobuo , Shinozaki Yosuke 
Published: September 2020

AbstractDownwind turbines can adopt light and flexible blades because of limited risk of tower-strike. We investigate superiority of a downwind configuration in large-scale wind turbines with high extreme wind speed through comparison of optimized 10 MW downwind and upwind turbines. Blades and towers of these turbines are optimized to minimize their levelized cost of energy (LCoE) with steady state aero-structural analyses considering tower shadow and potential flow effects on power production and fatigue damage. Comparison shows that the optimized downwind turbines have an advantage in LCoE due to their lighter and more flexible blades than the upwind turbines with conventional prebend of 6 [m]. This advantage is derived from smaller thrust force, lighter rotor-nacelle-assembly, and a small distance between a tower axis and center of gravity of the rotor-nacelle-assembly. The upwind turbine requires 11 [m] prebend to obtain the comparable LCoE to the downwind turbine.
Co-optimization of the shape, orientation and layout of offshore wind farms
Authors: Feng Ju , Shen Wen Zhong 
Published: September 2020

Abstract
Previous studies on wind farm design optimization usually assume that the wind farm boundary is fixed. However, due to the uneven distribution of energy for different wind directions, the wind farm boundary, which determines the possible shape and orientation of the wind farm, can have large influences on the wind farm’s energy production. Towards an overall design optimization, the shape and orientation of wind farm should also be considered as part of the design variables. To tackle this problem, we formulate a co-optimization problem of the wind farm’s shape, orientation and layout to maximize AEP under several realistic constraints. As an initial effort, we limit the wind farm boundary to parallelogram shapes. A two-stage optimization method is then proposed to solve the co-optimization problem. The case study on the Horns Rev 1 offshore wind farm demonstrates the importance of choosing proper shape and orientation and the effectiveness of the proposed optimization method.
Distributed Aerodynamic Control using Active Trailing-Edge Flaps for Large Wind Turbines
Authors: Feil Roland , Abbas Nikhar , Bortolotti Pietro , Johnson Nick , Mertz Ben 
Published: September 2020

Abstract
This work presents a numerical framework to investigate distributed aerodynamic control devices for application in large wind turbines. Tool capabilities were extended to facilitate multiple aerodynamic polar tables. The airfoil aerodynamics characteristics were automatically determined, and blade-pitch, generator-torque, and trailing-edge-flap controllers were tuned in-the-loop according to a specific blade design. This automated workflow allows analysis and optimization of trailing-edge flaps, enabling codesign studies. Results targeted reductions of root-flap-bending moment derivatives. The applied trailing-edge-flap control reduced the standard deviation of root-flap-bending moments by more than 6% and benefit related parameters, e.g., reduce blade-tip deflections, by up to 8%. Because of varying thrust distributions along the blade span, different flap designs have nonlinear characteristics in terms of the control objective and show best performance when located at the radial position with maximum thrust. In general, larger flaps provide a greater influence to reduce the target control objective.
Optimization of floating wind turbine support structures using frequency-domain analysis and analytical gradients
Authors: Dou Suguang , Pegalajar-Jurado Antonio , Wang Shaofeng , Bredmose Henrik , Stolpe Mathias 
Published: September 2020

Abstract
A framework for conceptual optimal design of floating wind turbine support structures including mooring system is proposed. A four degree-of-freedom frequency-domain model is used for the dynamic response of the floating wind turbine subjected to wind and wave loads. The framework allows for integrated design optimization involving the geometrical properties of the floater and the mooring system and inclusion of long realizations of multiple load cases in the analysis. Analytical design sensitivities of the governing frequency-domain equations and the design requirements are developed. This ensures that modern numerical optimization methods can efficiently be used to solve the design problem. The framework is applied to sizing optimization of a spar-buoy floater including the mooring system. The inclusion of dynamic constraints in the design optimization is demonstrated. The optimization provides designs accurately satisfying optimality conditions in minutes.
IEA Wind Task 32 and Task 37: Optimizing Wind Turbines with Lidar-Assisted Control Using Systems Engineering
Authors: Simley Eric , Bortolotti Pietro , Scholbrock Andrew , Schlipf David , Dykes Katherine 
Published: September 2020

Abstract
Lidar-assisted control is a promising technology for reducing the levelized cost of energy from wind turbines, but quantifying its impact at the overall system level requires sophisticated systems engineering analysis and optimization frameworks. The joint workshop on Optimizing Wind Turbines with Lidar-Assisted Control Using Systems Engineering was held by the International Energy Agency Wind Task 32 (Lidar) and Task 37 (Systems Engineering) in October 2019 to address this challenge. This paper summarizes the outcome of the workshop and presents a road map for further research. The most promising applications of lidar-assisted control identified at the workshop and discussed here include 1) increasing annual energy production, 2) decreasing capital expenditure costs by reducing design loads, 3) extending turbine lifetime by reducing operating loads, and 4) enabling wind turbine class upgrades. For each application, we review the state of the art and highlight remaining research needs. Finally, we discuss strategies for addressing these research needs by conducting high-fidelity systems engineering optimizations.
Design optimization of a wind turbine blade under non-linear transient loads using analytic gradients
Authors: Iori Jenna 
Published: September 2020

Abstract
This work presents and compares two formulations for the co-design optimization of a wind turbine blade under non-linear transient loads: the Nested Analysis and Design (NAND) and the Simultaneous Analysis and Design (SAND) approaches. Analytic sensitivies are used in order to ensure the convergence of the optimization within reasonable computational resources. The two formulations are compared on a mass minimization problem with dynamic constraints, solved with the interior-point method in IPOPT, for a gust input and a turbulent input. Results shows that the NAND and SAND approaches converge towards the same optimum with similar performances. The SAND approach benefits from a simpler design sensitivity analysis and a sparse jacobian of the constraints.
Innovative alternatives for repowering offshore wind farms
Authors: He Wei , Grant Richard J , Baden Victoria , Suntharalingam Jarani 
Published: September 2020

Abstract
To deliver a climate neutral Europe by 2050 there is an unprecedented urgency to decarbonise Europe’s electricity supply. The offshore wind industry is gearing up to this challenge with an increase in the rate at which high generating capacity offshore wind farms (OWFs) are deployed. Innovative repowering integrates early decommissioning and repowering of OWFs by using future large wind turbines (WTs, e.g. 20 MW WT). First-of-its-kind case studies have been presented to quantify the increased power generation capacity and the levelized cost of energy (LCOE) of repowering two OWFs with fixed and floating foundations. The repowering alternatives have been compared with the base case scenario (which involves decommissioning after the design life of 20 years) and the lifetime extension scenario (decommissioning in 25th year). The case studies show that a significant increase in energy output could be coupled with a reduction in the LCOE using the same OWF sites. The capacities of the OWF with fixed and floating foundations have been increased by 2.5 times (317 MW to 800 MW) and 2 times (400 MW to 800 MW) by repowering, respectively. Compared with developing an OWF on a new site, repowering has the potential to significantly accelerate the current installation capacity. Repowering has the potential to provide a competitive alternative to the lifetime extension of OWFs. Furthermore, the OWF with floating foundations has greater LCOE reductions compared with the OWFs with fixed foundations. This study has also provided evidence that enabling technologies and collaboration with other sectors would reduce the environmental impacts and costs of decommissioning of OWFs. This paper has suggested a way forward for research and development to overcome both technological and non-technological barriers to unlock the potential benefits of innovative alternatives of repowering OWFs.
An Unsteady Actuator Line Solver to Enable Adjoint Sensitivity Studies for Wake Steering
Authors: Young Ethan , Allen Jeffery , Bortolotti Pietro , King Ryan , Barter Garrett 
Published: September 2020

AbstractThis study demonstrates the sensitivity of wind turbine wake steering performance to blade design. An actuator line model was implemented within an unsteady adjoint solver that enables efficient execution of gradient-based optimization and sensitivity studies. After first confirming the feasibility of wake steering by controlling actuator line chord profiles and formulating a suitable objective function for wake position, a sensitivity study was conducted to determine the relative importance of chord length as a function of spanwise position on the resulting turbine wake deflection. The results presented here support the idea that blade design choices play a role in wake control. In a larger context, this study demonstrates a computational framework in which turbine and blade designs can be studied at the individual and farm-wide level to enhance wind plant controllability and manage power output.
Uncertainty propagation and sensitivity analysis of an artificial neural network used as wind turbine load surrogate model
Authors: Schröder Laura , Dimitrov Nikolay Krasimirov , Aasted Sørensen John 
Published: September 2020

Abstract
Recent studies have shown the advantage of replacing aeroelastic simulations with regression models based on Artificial Neural Networks (ANNs), which can be used as surrogate models for fast and efficient wind turbine load assessments. Once trained on a high-fidelity load simulation database covering a broad range of conditions, the surrogate model can be applied to predict loads for any site with wind climate falling within the range covered by the database. The aim of this study is to quantify the uncertainty propagation through such an ANN and to analyse how much the selected input variables influence the variance of the fatigue blade load estimations by means of a global sensitivity analysis. Results confirm that the selected ANN architecture seems suitable for this task resulting in small output uncertainties. Furthermore, the sensitivity analysis shows that the turbulence is mainly responsible for the blade load estimation, followed by the wind shear and the wind speed. The contributions of the turbulence length scale, turbulence anisotropy factor and wind veer angle are comparatively low. Comparing three different methods for sensitivity analysis shows that the partial derivative algorithm, Sobol variance decomposition and Shapley effect result in similar sensitivity measures.
Comparison of a Direct Drive Wind Turbine with and without LSS-Coupling Regarding Air Gap Displacement
Authors: Baseer A , He Y , Schelenz R , Kari A , Roscher B , Jacobs G 
Published: September 2020

Abstract
Wind turbines (WT) are highly coupled and complex systems. The dynamic interaction between various components is especially pronounced for multi megawatt wind tur-bines. As a result, the design process is generally split into several phases. [3]
The first step consists of creating a global aero-elastic model that includes essential dynamics of structural components using the minimum possible number of degrees of freedom (DOFs), with the most important simplifications concerning the drivetrain and rotor nacelle assembly. This approach is not suitable to analyse the generator air gap of a direct drive wind turbine. In this paper a more detailed simulation model is depicted, which calculates realistic deformation of the wind turbine and in particular the displacement between the generator-rotor and generator-stator. For these analysis a detailed multibody simulation (MBS) model of a generic direct drive WT is set up and used to analyse the generator air gap [3].
Several concepts of a direct drive WT are available on the market. One of them includes a coupling between the hub and generator-rotor to decouple the input wind loads from the generator and thus to decrease the impact on the generator air gap deflection [5]. The aim of this paper is to compare such a concept with a conventional concept without coupling.
Acceleration of vortex-particle simulations using a pseudo-particle method
Authors: Thönnißen F , Fritz E K , Schröder W 
Published: September 2020

Abstract
Vortex methods like vortex-lattice or vortex-panel methods are particularly promising to enhance the industrial aerodynamic design process of modern wind turbines. However, despite their advantages over low order methods, like the blade-element-momentum theory, vortex methods share an essential disadvantage. Their computational cost rapidly increases, which is due to their n-body problem characteristics. To overcome this issue, a method that neither relies on multipole expansions nor on a multi-grid approach is presented. Based on the aerodynamic simulation of the MEXICO rotor, it is shown that the proposed vortex pseudo-particle method (VPPM) is able to reduce the computational cost related to the n-body problem of vortex methods to O(n × log(n)). However, its application is not only advantageous in terms of the reduction of the computational cost. Since vortex-and pseudo-particles share the same properties, the VPPM’s implementation is quite simple compared to that of fast multipole methods. Furthermore, no method specific boundary-conditions need to be imposed as in the case of multi-grid methods. Therefore, the presented pseudo-particle approach is an attractive alternative to fast multipole or multi-grid methods.
Impact of manufacture-induced blade shape distortion on turbine loads and energy yield
Authors: Rosemeier M , Saathoff M 
Published: September 2020

AbstractA blade shape distortion develops during the manufacturing process. The distortion is defined as the difference between the target blade shape as per the design and the shape under operational temperatures. This initial distortion varies under operational temperatures due to the different thermal coefficients of expansion of the various blade materials. The resulting manufacture-induced distortion and operational temperatures affect the twist angle, the cross-sectional shape, and the sweep of the blade. Young’s modulus of the blade’s raw materials, i.e., the matrix of the fiber-reinforced polymers and the adhesive material, changes during the manufacturing process, complicating the determination of the distortion. This work calculates the shape distortion for a reference temperature on the basis of a thermal stress analysis using a full 3D finite element blade model. It performs an aero-elastic load simulation for two models: one with the target blade shape and one with the distorted shape. The simulation reveals that the turbine with the distorted shape has an energy yield which is 0.5% lower and a lifetime extension of additional 4. 4 years.