bluuebunny/crossref_metadata_2025 huggingface dataset:
Small Wind Power (SWP) as a Renewable Energy Source in Morocco
Authors: Tenghiri Lhoussaine , Zair Rachid , Koubida Sallem , Bentamy Anas
Published: September 2020

This paper has two main objectives: (1) to identify the causes behind the low penetration of SWP in Morocco, and (2) to study the design of a horizontal axis wind turbine for domestic applications in the Moroccan context by following the design requirements of the international standard of small wind turbines IEC 61400-2. The three most relevant barriers in Morocco are found to be in this order: a) the regulatory barrier, b) the technical barrier and, c) the financial and market barriers. Further, a proposed design of a 11 kW SWT power that would be the most in demand helps in identifying clearly the technical barrier. Within the list of components of this typical design, locally manufactured components are limited to the rotor, the main shaft, the nacelle cover and frame as well as the tower and the foundation. The total cost associated to these components is very low compared to the other imported components in the wind turbine assembly. The constraint of designing a 11kW SWT’s economic viability can therefore only be fully satisfied if all components are locally produced.
Probabilistic Design Space Mapping: Application to Airfoil Design for HAWT
Authors: Mazza P. , Pereira R. , De Oliveira G.
Published: September 2020

This work presents an airfoil probabilistic design methodology for wind energy applications, using an analytical approach to estimate the angle-of-attack fluctuations produced by non-uniformities in the incoming wind field. The contemplated wind speed perturbations include wind shear, yaw misalignment and atmospheric turbulence, and several combinations of the perturbation sources are considered. A probabilistic design space mapping is carried out to evaluate which wind conditions occur more often in practice and how likely each specific combination of perturbation sources is to occur, for both an onshore and offshore scenario. The proposed probabilistic method and specifically the level of angle-of-attack fluctuations is verified by employing the aero-elastic simulation tool FAST for each case. Finally, the probabilistic approach is used to design airfoils sections employing the genetic multi-objective airfoil optimization tool Optiflow, where the probability of angle of attack fluctuations for a given scenario is used to prescribe the operational angle of attack range over which the airfoil performance is relevant. Results of the airfoil optimization for a 24% thick section are presented, illustrating the trends in foil geometry and aerodynamic performance for three different possible optimization objective functions.
Wind farm layout optimization with special attention on noise radiation
Authors: Cao Jiufa , Zhu Weijun , Shen Wenzhong , Sun Zhenye
Published: September 2020

This work presents a new wind farm layout design methodology that calculates the noise radiation using an advanced sound propagation model. Firstly, the wake velocity in wind farm is calculated via an improved engineering wake model. Then, the aero-acoustic noise source of wind turbine is obtained using the BPM method. To simulate the noise level at far field, the basis of propagation model is built on the parabolic wave equation (PE) method. The cost of energy for wind farm is assessed via an engineering model. Finally, based on the genetic algorithm (GA) optimization method, and taking the noise radiation level into account, a new wind farm layout design methodology is developed to solve a trade-off between cost and noise for wind farm.
Combined wind turbine design and wind farm layout optimisation under wind resource uncertainty
Authors: Swamy S Krishna , Szklarz S , Fonseca R M , Bulder B H
Published: September 2020

Applications of the wind farm layout optimisation problem focus on optimally positioning a certain number of turbines within a wind farm so that annual energy production (AEP) is maximised. This study addresses an earlier stage in the wind farm development process. Instead of optimising the individual positions of a certain number of turbines of a selected model, the control variables in the optimisation are rotor diameter of a wind turbine of fixed nominal power, number of turbines in a wind farm of fixed area and orientation angle of turbines in the farm. In addition to AEP, this study considers capital and operational expenses of a wind farm to calculate the levelized cost of energy (LCoE), which is the objective function. Given the stage of development addressed, it is also essential that uncertainty is considered; here the focus is on the impact of wind resource uncertainty. The optimisation is performed with a recently developed state-of-the-art stochastic gradient based method (StoSAG) which has shown in different domains to be computationally efficient and accurate when dealing with optimisation problems under uncertainty. Our results show non-trivial optimal designs with LCoE reductions of ∼0.5% compared to the most optimal solution from a sensitivity analysis.
Global sensitivity analysis of model uncertainty in aeroelastic wind turbine models
Authors: Kumar P. , Sanderse B. , Boorsma K. , Caboni M.
Published: September 2020

A framework is presented for performing global sensitivity analysis of model parameters associated with the Blade Element Momentum (BEM) models. Sobol indices based on adaptive sparse polynomial expansions are used as a measure of global sensitivities. The sensitivity analysis workflow is developed using the uncertainty quantification toolbox UQLab that is integrated with TNO’s Aero-Module aeroelastic code. Uncertainties in chord, twist, and lift- and drag-coefficients have been parametrized through the use of NURBS curves. Sensitivity studies are performed on the NM80 wind turbine model from the DanAero project, for a case with 19 uncertainties in both model and geometry. The combination of parametrization and sparse adaptive polynomial chaos yields a new efficient framework for global sensitivity analysis of aeroelastic wind turbine models, paving the way to effective model calibration.
Wind farm layout optimization with load constraints using surrogate modelling
Authors: Riva Riccardo , Liew Jaime , Friis-Møller Mikkel , Dimitrov Nikolay , Barlas Emre , Réthoré Pierre-Elouan , Beržonskis Arvydas
Published: September 2020

Minimizing the cost of energy of a wind farm is a difficult task, which involves reducing the wake effects while satisfying several constraints. Due to its multidisciplinary nature, this problem is usually solved through numerical optimisers. TOPFARM is one of these tools, and in this paper, we have added to it a constraint on the fatigue loads. The efficiency of the implementation is guaranteed by an extensive use of gradients and load surrogate models. The paper is concluded by showing some case studies.
Power Maximization and Fatigue-Load Mitigation in a Wind-turbine Array by Active Yaw Control: an LES Study
Authors: Lin Mou , Porté-Agel Fernando
Published: September 2020

In this study, we perform a multi-objective parametric study for an array of three miniature wind turbines subjected to active yaw control (AYC), with the objectives of maximizing the power and minimizing the fatigue loads. Using the time series extracted from large-eddy simulation (LES), we compute the mean power and the yaw-moment damage equivalent load (DEL) at every point of a finite decision space spanned by the yaw angles of the first two turbines. The mean power outputs simulated with LES are compared with those measured in the wind tunnel, and a good agreement is found between the two. The Pareto front of different yaw configurations is extracted in the objective space of AYC and the Pareto-optimal strategies are identified in the decision space. We find that most of the Pareto-optimal strategies share the characteristic of moderately decremental yaw angles. We also find that the strategies with a small yaw angle for the first wind turbine are inefficient since they incur significant increases in fatigue while only achieving marginal power gains. The results indicate that the decision space of algorithms searching for optimal AYC strategies can be significantly reduced a priori with the consideration of load mitigation in the optimization.
Optimization of Wind Farm Design for Objectives Beyond LCOE
Authors: Dykes Katherine
Published: September 2020

For wind farms that participate actively in electricity markets versus receiving a fixed kiloWatt-hour payment, design and operational objectives must go beyond the levelized cost of energy (LCOE) to account for system value and profitability of the farm over its lifetime. This work introduces ”beyond LCOE” objectives for farm design and illustrates their impact in a multi-objective optimization case study for LCOE and value-based objectives. The case study shows that the best designs from an LCOE perspective are not those that have the highest value and vice versa. Thus, designing wind farms in the future will require new optimization approaches to address the broader system and market context to ensure overall profitability of the project.
Innovative rail transport of a supersized land-based wind turbine blade
Authors: Carron William Scott , Bortolotti Pietro
Published: September 2020

Wind turbine blade logistic providers are being challenged with escalating costs and routing complexities as one-piece blade approach lengths of 75 m in various regions of the U.S. land-based market. New lower cost solutions are needed to enable further reductions in the levelized cost of energy (LCOE) and continued market expansion. In this paper, a novel method of using existing U.S. rail infrastructure to deploy 100-m, one-piece blades to U.S. land-based wind sites is numerically investigated. The study removes the constraint that blades must be kept rigid during transport, and it allows bending to keep blades within a clearance profile while navigating horizontal and vertical curvatures. Novel system optimization and blade design processes consider blade structural constraints and rail logistic constraints in parallel to develop a highly flexible, rail-transportable blade. Results indicate maximum deployment potential in the Interior region of the United States and limited deployment potential in other regions. The study concludes that innovative rail transportation solutions combined with advanced rotor technologies can provide a feasible alternative to segmentation and support continued LCOE reductions in the U.S. land-based wind energy market.
Generalised grid requirements minimizing the actuator line angle-of-attack error
Authors: Forsting AR Meyer , Troldborg N
Published: September 2020

The actuator line (AL) is a lifting line (LL) representation of aerodynamic surfaces in computational fluid dynamics (CFD) applications. The AL blade forces are computed from 2D airfoil polars and the CFD velocity vector extracted at the line position, as the self-induction at the very centre of the bound vortex should, following vortex theory, be nil. Yet, this is not the case in CFD, which leads to errors in the angle-of-attack computation. We derive an expression for the error in the lift force from vortex considerations and show it to be a function of chord, the smearing length scale used in distributing the AL forces over the numerical domain and the number of grid cells per smearing length scale. Thereby demonstrating that the required number of grid cells-contrary to current belief-needs to grow faster than the inverse of the smearing length scale refinement to maintain the error level. We additionally show that the error can be large for the commonly used ratio of 2 grid cells per length scale, especially if the latter is relatively small with respect to the rotor radius. Ultimately, the recommendation is to always run with the largest smearing length scale possible for the specific application in conjunction with a smearing correction, as this minimizes the error in the blade forces whilst reducing the computational resources required.
Practical Considerations on Wind Turbine Blade Leading Edge Erosion Modelling and its Impact on Performance and Loads
Authors: Papi F , Ferrara G , Bianchini A
Published: September 2020

Wind turbines operate in all sorts of weather conditions around the globe, exploiting installation sites with high power production potential. These machines operate within the atmospheric boundary layer and are therefore subject to impacts with rain, hail dust particles and insects, often leading to rapid blade deterioration and performance drops. This wok aims to explore different ways of modelling wind turbine blade leading edge erosion with a medium-fidelity approach and to show how different models impact performance and loads. This provides a quick way of evaluating the effects of blade deterioration. A 2D airfoil erosion model is developed and lift and drag coefficients are calculated with Computational Fluid Dynamics (CFD). An aero-servo-elastic model of the DTU 10MW Reference Wind Turbine (RWT) is then used to evaluate the impacts of the models on performance. Differences in airfoil performance are discussed as well as differences in the turbine’s power coefficient and fatigue loading levels.
Off-axis loading in rotor blade fatigue tests with elliptical biaxial resonant excitation
Authors: Melcher David , Petersen Enno , Neßlinger Sebastian
Published: September 2020

In their lifetime of 20-25 years, wind turbine rotor blades are subjected to high-cycle fatigue. Hence, new rotor blade designs need to undergo cyclic fatigue tests to show that they fulfill the reliability requirements. For these tests, a blade prototype is loaded consecutively in its flapwise and lead-lag directions, which does not represent the actual loading in the field very well. This applies especially for the off-axis load directions of the blade, i.e., the load directions between flapwise and lead-lag directions. By combining the two consecutive tests into one biaxial test, these loads can be improved. Exciting both directions at the same time also generates loads in the off-axis directions.

This work investigates the loading of a biaxial fatigue test using elliptical biaxial resonant excitation. By changing the phase angle of the elliptical excitation, the loading of the blade can be altered to better represent the operational conditions of the blade.
Consolidated results of the laboratory and full scale field validation of an active flap system
Authors: Gonzalez A. Gomez , Enevoldsen P. , Barlas T.K. , Madsen H.Aa , Olsen A. S.
Published: September 2020

This article presents the consolidated results of a comprehensive validation campaign of a pneumatic active flap system (AFS) developed within the scope of the Induflap2 project [1] in a collaboration effort between Siemens Gamesa Renewable Energy A/S (SGRE), the Technical University of Denmark (DTU), and Rehau GmbH. The validation results presented herein include wind tunnel measurements, measurements in a rotating test rig under free atmospheric conditions, as well as the validation at full scale on a 4MW wind turbine with 130m rotor diameter (SWT-4.0-130). This article is of a summarizing character and the reader is referred to further literature where applicable. During the course of the project, several revisions of the AFS were developed and tested at different levels of fidelity. Along with the different variations of the AFS, the impact of variations of the geometric and material related design parameters were studied. Two of the latest revisions of the AFS were tested at full scale on a wind turbine. The measurements presented herein focus solely on the latest revision of the AFS (internally referred to as the FT008rev10 concept). The different tests and measurements were performed in the period from 2016 to 2019. During the full scale measurements, a wind speed dependent load impact between 5% and 10% was measured for the blade root flapwise bending moments, demonstrating thus a large potential for turbine loading adjustments to perform active load control on modern wind turbines.
Experimental Demonstration of Thrust Vectoring with a Vertical Axis Wind Turbine using Normal Load Measurements
Authors: Leblanc Bruce , Ferreira Carlos
Published: September 2020

The aerodynamic loading of a vertical axis wind turbine varies with the azimuth position of the blades. The thrust of the VAWT can be computed as a decomposition of the normal force on each of the blades. By varying the blade loading as a function of turbine azimuth, it is possible to vary the direction of the average thrust of the turbine. An experiment is performed using an active pitch controlled H-VAWT turbine in the Open Jet Facility at TU Delft demonstrating the ability to actively vary the rotor aerodynamic loading and as a result the average thrust vector. By applying a sinusoidal pitch actuation with phase offsets, a directional change in the average thrust vector of over 78° was demonstrated.
Comparison of 3D aerodynamic models for vertical-axis wind turbines: H-rotor and Φ-rotor
Authors: Tavernier D. De , Sakib M. , Griffith T. , Pirrung G. , Paulsen U. , Madsen H. , Keijer W. , Ferreira C.
Published: September 2020

Since the first commercial projects, the development of vertical-axis wind turbines (VAWTs) has been impeded by the limited understanding and inability to accurately model VAWTs. This paper investigates and compares different aerodynamic modelling techniques for VAWTs in 3D. All considered models are using the same blade-element characteristics but use different descriptions to determine the induced velocity field. The H-and Φ-rotor are studied with various aspect ratios and rotor loadings. Both instantaneous azimuthal parameters as well as integral parameters, such as the thrust and power are investigated. The paper concludes that capturing the 3D effects of VAWTs is challenging and the trends to be expected are not straightforward due to the complex vortex system created by VAWTs. All model assumptions affect the results both at the mid-plane of the rotor as well as at the blade tips.
Direct numerical simulation of transitional boundary layers on a horizontal axis wind turbine blade
Authors: Jing Z , Ducoin A , Braud C
Published: September 2020

In boundary layer flow around rotating machines, a radial (or cross-flow) velocity exists due to Coriolis and centrifugal forces. This velocity component can be of great importance for laminar-turbulent transition. A series of direct numerical simulations (DNS) are performed to study the boundary layer flow transition on a rotating Horizontal Axis Wind Turbine blade. To quantify the effect of blade rotation, results are compared with that from airfoil DNS, where the section is taken from 3D blades and does not rotate. It is shown that the rotation gives rise to a small radial velocity and slightly modifies the shape of unstable waves. However, the transition location and mechanism of 3D blade boundary layer flow resemble 2D flow for the investigated case.
Reduced order models for wind turbine blades with large deflections
Authors: Gözcü Ozan , Dou Suguang
Published: September 2020

Non-intrusive nonlinear reduced order modeling (ROM) techniques have been applied by researchers to obtain computationally cheap and yet accurate structural responses of aircraft panels. However, its application to wind turbine blades is new and challenging due to much larger deflections of wind turbine blades. This study improves a non-intrusive nonlinear ROM method for wind turbine blades going through large deflections. In the nonlinear ROM, the nonlinear stiffness is described by the quadratic and cubic functions, and the secondary motions induced by the primary large deflections are described by the modal derivative vectors in the reduction basis. The non-intrusive nature of the method requires a geometrically nonlinear solver, and HAWC2 is chosen in this study for the computation of nonlinear stiffness terms. Two examples, including a cantilever beam example and the NREL 5MW wind turbine blade model, are used to evaluate the accuracy and computational effectiveness of the nonlinear ROMs. The cantilever beam example shows that the nonlinear ROM can accurately capture the axial displacements due to large deflections reaching 20 % of span length as well as the torsion coupled with flapwise and edgewise motions. The NREL blade example shows that the nonlinear ROM is accurate for the tip displacements more than 5.9 m. Because the size of the nonlinear ROM is much smaller than that of HAWC2 model, a speedup factor of 8.5 for computational time is observed for the NREL blade example.
CFD modeling of the Poul la Cour Tunnel
Authors: Sørensen Niels N. , Olsen A. S. , Bak C. , Gaunaa M. , Beckerlee J.S. , Fischer A. , Mikkelsen R.F. , Ildvedsen S.
Published: September 2020

We analyze the new Danish Poul la Cour Tunnel (PLCT) facility using 2D and 3D Computation Fluid Dynamics simulations, with the aim to address the need for wind tunnel corrections. The assessment of tunnel corrections is based on 2D free simulations representing undisturbed airfoil flow, 2D tunnel configurations and a full 3D tunnel setup using laminar/turbulent Improved Delayed Dettached Eddy Simulations. By comparing lift, drag and pressure distributions and detailled flow patterns, the influence of the 2D and 3D tunnel is evaluated. In the present study a NACA 633-418 airfoil is investigated in the tunnel.
Comparison of loads from HAWC2 and OpenFAST for the IEA Wind 15 MW Reference Wind Turbine
Authors: Rinker Jennifer , Gaertner Evan , Zahle Frederik , Skrzypiński Witold , Abbas Nikhar , Bredmose Henrik , Barter Garrett , Dykes Katherine
Published: September 2020

Reference wind turbines (RWTs) that reflect the state-of-the-art of current wind energy technology are necessary in order to properly evaluate innovative methods in wind turbine design and evaluation. The International Energy Agency (IEA) Wind Technology Collaboration Platform (TCP) Task 37 has recently developed a new RWT geared towards offshore floating-foundation applications: the IEA Wind 15 MW. The model has been implemented in two aeroelastic codes, OpenFAST and HAWC2, based on an underlying common ontology. However, these toolchains result in slightly different structural parameters, and the two codes utilise different structural models. Thus, to increase the utility of the model, it is necessary to compare the aeroelastic responses. This paper compares aeroelastic loads calculated using different fidelities of the blade model in OpenFAST (ElastoDyn and BeamDyn) and HAWC2 (prismatic Timoshenko without torsion and Timoshenko with fully populated stiffness matrix), where both codes use the DTU Basic controller and the same turbulence boxes to reduce discrepancies. The aeroelastic responses to steady wind, step wind and turbulent wind (per IEC 61400-1 wind class IB) are considered. The results indicate a generally good agreement between the loads dominated by aerodynamic thrust and force, especially for the no-torsion blade models. Discrepancies were observed in other load channels, partially due to differences in the asymmetric loading of the rotor and partially due to differing closed-loop dynamics, and they will be the subject of future investigations.
Uncertainty in loads for different constraint patterns in constrained-turbulence generation
Authors: Rinker Jennifer M.
Published: September 2020

This paper investigates the effect that adding constraints to turbulence simulations has on the uncertainty of resulting aeroelastic loads. The constrained turbulence is generated using the open-source constrained turbulence generator PyConTurb (“Python Constrained Turbulence”). A selection of constraint patterns were used to mimic the design of a met mast layout; i.e., the number of sonic anemometers and their locations throughout the rotor. A case study is presented to demonstrate in detail the effects of adding constraints before a larger numerical experiment is presented. The results of the numerical experiment indicate that adding constraints is extremely beneficial in reducing the mean absolute error of both operational parameters and loads. The reduction in mean absolute error ranged from 13% to 98%. The error in the extreme values and damage-equivalent loads were not impacted by the added constraints due to lack of gusts in the original signals and the similarity of the power spectra of the constrained and non-constrained signals, respectively.
A DNN surrogate unsteady aerodynamic model for wind turbine loads calculations
Authors: Ananthan Shreyas , Vijayakumar Ganesh , Yellapantula Shashank
Published: September 2020

A recurrent deep-neural network (DNN) surrogate model capable of modeling the unsteady aerodynamic response and dynamic stall behavior of wind turbine blades has been developed and validated for use in engineering design codes. The model is trained using a subset of the oscillating airfoil experiments conducted at the Ohio State University wind tunnel. The predictions from our DNN model show excellent agreement with the measured data and, in all cases, a marked improvement over the state-of-the-art unsteady aerodynamic models. The DNN-based unsteady aerodynamics model was integrated with OpenFAST to perform full-turbine load computations for the NREL-5MW rotor. The largest differences are observed for the inboard stations, particularly in the pitching moment response, when using the new surrogate model compared to the other models available in OpenFAST.
CFD Simulation of Two Tandem Floating Offshore Wind Turbines in Surge Motion
Authors: Rezaeiha Abdolrahim , Micallef Daniel
Published: September 2020

High-fidelity unsteady Reynolds-averaged Navier-Stokes (URANS) CFD simulation is employed to investigate the variations in the power performance of two tandem in-line floating offshore horizontal axis wind turbines for the scenario in which the upstream rotor is oscillating in surge motion and the downstream rotor is positioned in a distance of 3D (D: turbine diameter) and is stationary. The rotors are the NREL-5MW reference turbine. The platform surge period and wave amplitude are 9 s and 1.02 m, respectively. The results are presented for 100 full surge periods. It is found that the surge motion of the upstream rotor results in: (i) sinusoidal fluctuations in the power and thrust coefficients (CP
and C
T) of the upstream rotor with a standard deviation (std) of 9.7% and 5.5%, respectively; (ii) such fluctuations in CP
and CT
are less regular with a std of 4.2% and 2.8% for the downstream rotor, respectively. A low-frequency oscillating mode with a period nearly 10 times the surge period is also observed for the downstream rotor. The mean Cp and Ct of the downstream rotor are 28.9% and 38.5% of the upstream one.
Model-based displacement estimation of wind turbine blades using strain modal data
Authors: Gundlach J , Knebusch J , Govers Y , Haller B
Published: September 2020

For wind turbine rotor blades, the use of strain sensors is preferred over acceleration sensors for the purpose of permanent monitoring. Experimental modal analysis during operation is thus constrained to strain information, yielding strain modal data including strain mode shapes. For follow-up investigations such as aerodynamic load assessment or flutter monitoring it is however advantageous to have this information as displacement mode shapes or as displacements of the blade contour over time. This research applies a generic approach that converts strain mode shapes to displacement mode shapes utilizing an FE shell model as a basis for approximation. The accuracy of the approach is assessed by comparison with experimentally identified high-resolution displacement mode shapes which are acquired with accelerometers and serve as a reference. In the process the conversion procedure is illustrated with the help of strain data that has been obtained using a sensor instrumentation installed for certification testing of the blade. The requirements for successful usage of the employed conversion scheme and its suitability for rotor blade data are discussed.
Advances Toward a Lightweight, Variable Fidelity Wake Simulation Tool
Authors: Saverin Joseph , Marten D , Nayeri N , Paschereit CO
Published: September 2020

A method is presented which aims to bridge the gap between overly simplified momentum-based wake models and overly demanding finite volume models of wind turbine wake evolution. The method has been developed to allow an essentially user-defined resolution of the wake. Beyond this, all dominant field quantities are automatically resolved by the solver including convection velocity, shear stress and turbulence intensity. Two distinct methods of solution are presented which both have strengths and weaknesses, the choice of which model being fidelity and application dependent. Both methods make use of multilevel spatial integration to allow greatly improved computational efficiency. The method is here presented for 2D flow in the symmetry plane of a vertical axis wind turbine as an initial demonstration of the potential of the method.
Development of a fluid structure interaction tool based on an actuator line model
Authors: Spyropoulos Nikos , Prospathopoulos John , Manolas Dimitris , Papadakis George , Riziotis Vasilis A
Published: September 2020

In the present paper the methodology and the procedures for the implicit coupling of an Actuator Line (AL) aerodynamic code with a beam like structural code for the analysis of wind turbine rotors are detailed. Results from benchmark aeroelastic simulations of canonical inflow conditions, comparing the newly developed AL model against a standard Blade Element Momentum (BEM) model are presented in the paper. The two models provide very similar results in simple, uniform inflow, axisymmetric flow cases. The advantages of this newly developed tool emerge when more complex inflow conditions are addressed. In the present paper, besides axial flow conditions, operation under high yaw misalignment is also considered. BEM model accounts for the effect of the wake skewness through the application of an a posteriori engineering correction. Therefore, in this particular non symmetric flow case, deviations between AL and BEM are expected to be higher, especially as yaw misalignment angles increase. In the paper the above differences are assessed and interpreted.
Blade research and demonstration platform
Authors: Haselbach Philipp U. , Zahle Frederik , Berring Peter , Semenov Sergei , Voltá Laura , Roqueta I , Robert Verelst David
Published: September 2020

At DTU Wind Energy, a 12.6 m reference wind turbine rotor blade and the corresponding blade moulds were designed and manufactured. The entire blade design and the related test data will be published according to the FAIR principles. The blade moulds are intended to serve as a blade research and demonstration platform, allowing to realise theoretical concepts and testing these in full-scale on a wind turbine blade and thus enabling a comparison to numerical solutions. In this article, the preliminary blade design progress and process, initial load calculations and a 3D scan of the blade molds are presented.
Investigations of active boundary layer control using DDES
Authors: Rumpf Andreas , Bangga Galih
Published: September 2020

The root area of a wind turbine rotor is usually constructed by very thick airfoils with a relative thickness of more than 35%. An airfoil at that thickness is characterized with strong flow separation. To solve this issue, vortex generators can be used as an active control in order to stabilize the airflow and improve the aerodynamic performance, consequently. Boundary layer control however, investigated employing numerical techniques, strongly depend on the employed method as well as the mesh especially due to a weak vortex conservation in the RANS model. Using the method of Delayed detached eddy simulation (DDES) the solution can benefit from effort-efficient boundary layer modeling as well as LES vortex resolving apart from the surface. The present studies aims to investigate suitable numerical approach mesh dependencies in comparison to experimental data, for application to thick airfoil in future studies.
A comparative study of wake interactions between wind-aligned and yawed wind turbines using LES and actuator line models
Authors: Onel Huseyin C. , Tuncer Ismail H.
Published: September 2020

An LES based OpenFOAM solver is coupled with the actuator line model for the simulation of wind farms and the prediction of power production. The tool developed is validated for wind aligned and yawed tandem wind turbines. Two NREL 5MW turbines in a tandem configuration are considered. The solution parameters are first studied in detail. The development of vortical wakes behind the upstream and the downstream turbines are simulated under uniform and atmospheric boundary layer inflow conditions, and the power productions of the turbines are predicted. The impact of a yawed upstream rotor on its wake deflection and the resulting power production of the tandem configuration are assessed. It is shown that the coupled solver developed is quite successful in capturing the wake deficits and wake deflections, and predicting the power production of tandem wind turbine configurations.
CFD Prediction of Tip Vortex Aging in the Wake of a Multi-MW Wind Turbine
Authors: Cormier Marion , Bühler Manuel , Mauz Moritz , Lutz Thorsten , Bange Jens , Krämer Ewald
Published: September 2020

In the present study, prediction from high-fidelity Computational Fluid Dynamics (CFD) simulations of the tip vortex aging in the near-wake of a multi-MW wind turbine is evaluated and compared to in-situ measurements as well as results of a semi-empirical model. Optimized tip vortex refinement is also introduced to investigate the influence of the grid topology on the vortex evolution. The grid refinement affects only the vortex core size and a reduction of the core radius by a factor of 3.4 was achieved with the chosen parameters. On the refined setup, vortex core sizes and strength are comparable with in-situ Unmanned Aircraft System (UAS) based measurements at 0.5 rotor radius downstream of the wind turbine. A comparison of the aging function with a semi-empirical vortex helix model shows a good agreement with the refined CFD results, but the core size predicted by the model is smaller than in simulations and experiments.
Method for the generation of stochastic wind fields fitted to measurement data in real-time
Authors: Thomas Philipp , Szyslo Tom
Published: September 2020

The excitation of the wind turbine by the wind represents one of the main sources of excitation for the components of the wind turbine. The resulting structural loads can be measured relatively easily. The measurement of wind excitation, however, is much more complex. Even with the latest measuring equipment, such as LiDAR, the spatially and temporally high-resolution wind measurement required for the validation of the load measurement in the time domain can only be realized with a disproportionately high financial outlay and is thus unsuitable for large-scale application in the field. The method presented here shall be able to generate a realistic spatial wind excitation by means of the measured wind information present at each wind turbine, thus enabling model and load validation in the time domain. Furthermore, the method is fast enough to calculate the wind excitation in real time, allowing for application in Hardware-in-Loop or as part of a digital twin of the wind turbine.
On the multi-scale turbulent structure interactions within wind farms
Authors: Liu Huiwen , Zhao Zhenzhou , Chamorro Leonardo P. , Hayat Imran , Jin Yaqing , Zheng Yuan
Published: September 2020

The quantification of the scale-by-scale interaction of multi-wakes and background flow is required to estimate turbines behaviour within wind farms. The paper provides insight on the evolution of multi-scale turbulence of a model wind farm operating in turbulent boundary layer. The wind farm configured with aligned turbines set at streamwise spacing between units of 5 diameters by spanwise spacing of 2.5 diameters, corresponding to an array of 8x3 turbines. Howtwire anemometry was used to acquire high-resolution measurements of streamwise velocity fluctuations at various locations. Experimental results suggest that the contribution of multi-scale turbulence structures to the kinetic energy of the wake is highly dependent on the location inside the wind farm, the evolution is significantly modulated by turbine rotation, wake interactions and outer flow, large scale motions mainly dominate outer and far wakes, while small scales are popular in inner and near wakes.
Multiphysics simulations of the dynamic and wakes of a floating Vertical Axis Wind Turbine
Authors: Balty P , Caprace D-G , Waucquez J , Coquelet M , Chatelain P
Published: September 2020

A framework performing Large Eddy Simulations of the flow past Floating Offshore Vertical Axis Wind Turbines (FOVAWT) mounted on semi-submersible platforms is presented. The simulation tool captures the unsteady flow and the resolved 6-DOF motion of the system. A state-of-the-art vortex particle-mesh method solves the aerodynamics and wakes of the turbines. The hydrodynamic loads are accounted for via the relative form of the Morison’s equations while the mooring lines tension is computed through a lumped-mass model. Realistic conditions are further obtained by introducing a sheared turbulent inflow and erratic waves in a simulation domain that extends ten diameters downstream of the machine. First, analyses of an isolated FOVAWT wake and motion are performed and the impact of prominent environmental phenomena is assessed. In a second step, the interactions of two FOVAWTs throughout their wakes are studied. In general, the incoming wake signature induces larger oscillation of the downstream machine, alters the shape of the wakes and shortened the transition to turbulence.
Wind farm flow reconstruction and prediction from high frequency SCADA Data
Authors: Rott Andreas , Petrović Vlaho , Kühn Martin
Published: September 2020

The flow inside a typical large wind from propagates through the array from turbine to turbine. We present an algorithm that intuitively processes measured values from as much as possible turbines in real-time and uses them to determine a flow reconstruction and minute-scale forecast for the downstream turbines. For the validation we used full-field measurements from the offshore wind farm Global Tech I. The flow reconstruction is compared to the measurements of one turbine, which was excluded from the algorithm and achieved a root mean square error of 0.55 ms−1 for the wind speed estimation. The flow forecasting is tested for three prediction horizons 30s, 60s and 120s. Together with automated error correction to account for calibration errors and wake effects, the flow prediction achieves a root mean square error of 0.52 ms−1 for the 120s-forecast of the wind speed, which beats the persistence forecasting method. The reconstruction allows to analyse the flow in the wind farm, to detect abnormal turbine behaviour and to estimate fatigue loads, and the minute-scale forecasting is a useful tool for predictive wind farm control and estimating the available power of a wind farm, which becomes more and more necessary for grid stability.
Effect of thrust coefficient on the flow blockage effects in closely-spaced spanwise-infinite turbine arrays
Authors: Strickland Jessica M. I. , Stevens Richard J. A. M.
Published: September 2020

The performance of a wind turbine within an array is not necessarily equivalent to the performance of a free-standing turbine because the presence of the neighboring turbines influences the incoming flow. However, insight into these blockage effects is still lacking. Here, we use large eddy simulations to investigate how the blockage effect depends on the turbine thrust coefficient CT
. We consider three main scenarios: a free-standing turbine, a closely-spaced spanwise-infinite row of turbines, and an entire wind farm with a high turbine density. We observe that the power production of turbines in the row increases approximately linearly with

C

T

′

when compared to the production of a free-standing turbine. Here,

C

T

′

=

C
T

/

(
1

−

a
)

2

where a is the induction factor. In contrast, the power output of turbines in the first row of a wind farm decreases approximately linearly with CT
when compared to the production of turbines in a corresponding, solitary row.
The effect of urban tourism on an urban economy (the case of Malang Municipality)
Authors: Nurfitriya I D , Iskandar D A
Published: September 2020

As the economy of cities grew at unprecedented rate, urbanites’ changing perceptions of the way they see urban space – the city as an entertainment machine – creates a challenge that becomes the background for this study. Malang urbanized area is chosen as the unit of observation due to its potentials as the site for urban tourism development. New tourism icons and economic activities continue to emerge which begs the question as to why such things exist in Malang. Primary and secondary data are garnered through field observation, in-depth interview and from government policy related to tourism development. Mixed method is employed to reveal the effects of tourism sector development on the economic growth of the city. The findings indicate strong correlation between the two; however, cautionary note should be taken as there are many external factors beyond tourism sector development which affect the economic growth of Malang urban area during the observed period. Culinary activities create direct impact as seen through the increase of locally-owned revenues while thematic neighbourhood tourism development affects the local economy and informal sector.
Spatial patterns of land prices changing around toll gates (Cipali Toll Road case study)
Authors: Fakhruddin A , Nurlambang T , Sumadio W
Published: September 2020

Toll road construction has been carried out and has had an direct and indirect economic impact, which applies to Cipali Toll Road as well. High economic activities, growth of new facilities, and land use changes around this toll road are signs of new economic activities. New economic activity centers have triggered an increase in land prices in the surrounding area. The objective of this study is to determine the land use price changes along the Cipali Toll Road and understand the factors that influence it, namely the economic activity, distance from the toll road gate, land status, and land use. Data were collected by interviewing key informants from formal agencies and the communities as well. Using overlay technic between land price changes and factors that influence it, the result shows that land price changes did not happen in all areas around the toll road in the same way. Changes in land price also vary. The factor that influences land price changes is the distance from the toll road gate. This result was supported by Pearson Product Moment analysis. The conclusion of this study shows that land price changes in areas that have urban characteristics.
Migration and rural development: The impact of remittance
Authors: Hidayati I
Published: September 2020

In Indonesia rural society, remittance sent to families is more economical and routine since it is used to meet the families’ life necessities, education, and health, as well as to support the life necessities of whom are taking care of the family during the migrants are in destination areas. Remittances sent to families in migrants’ homelands are ideally using for production and investment activities. This usage of remittances gives a positive impact on homelands development, especially can be seen clearly in rural areas. This research will consider the relationship of remittance and rural development. The data collected included qualitative data from in-depth interviews and supported by study works of literature. Expectations of this research are remittances from migrants will improve rural development. This research showed that remittance is not only eagerly by migrants’ families, but also giving advantages for their homelands. Improvement of rural economy will strengthen the national economy and development.
Optimization of waste management in developing countries with spatial approaches (Study case: Depok City and Curitiba City)
Authors: Amri S , Soesilo T E B. , Martono D N , Supriatna
Published: September 2020

Waste management is a challenge for city authorities in developing countries especially due to increase of waste. The burden that is incurred on the city budget as a result of the high costs associated with its management and lack of understanding of the diversity of factors that influence the various stages of management. Comparative and descriptive analysis are utilized in this paper to observe the differences that arise at various levels of the administration so that they can be analysed. Data are collected from journal publications starting in 2013-2019. This paper compares how the handling of waste management has used a spatial approach starting from the Asian, Indonesian, and Depok levels. The purpose of this research is to find out what areas of waste management can be solved by spatial approaches, and recommendations for solutions that can be applied to the Depok City based on success story in other countries or regions. The Depok City already has a community-based approach that runs the trash bank. However, the waste bank is still ineffective, despite the low level of waste collection in Depok City. The optimization of waste management in Depok City can be improved its accuracy using spatial approach.
Analysis of groundwater recharge zone using remote sensing method in Bayah Region
Authors: Maghribi A A , Supriatna
Published: September 2020

Groundwater is one of the most important natural resources. Based on population needs, groundwater use meets around 60% for irrigation, industry, drinking water, sanitary facilities, etc. Based on data from the DESDM of Banten Province (2016), the Bayah Sub district area belongs to a small productive aquifer and rare underground water. With the development of in the Bayah region, it will be necessary to have a spatial with environmental insight. One of the important things in determining environmentally planning is by determining groundwater recharge areas in the area. The method used in this study is the Remote Sensing method. Data sources which used here is geological maps, DEMNAS imagery, Landsat-8 imagery, Landsat-5 TM imagery, Bayah rainfall stations. These data are processed using GIS to produce thematic maps such as lithology maps, land cover, lineament density, drainage density, rainfall, slope, and geomorphology. Scoring of all thematic maps is done using the multi-criteria evaluation / analysis method based on the superiority of each thematic map and the data in the thematic map itself on groundwater recharge value. The results of scoring on each thematic map are then overlaid on each thematic map to produce a map of potential groundwater recharge. According to this study the research can conclude that remote sensing and multi criteria evaluation can effectively use for finding groundwater recharge potential by using those 7 thematic maps. The study area mostly has high value groundwater potential recharge (2-3) which is 109,17 km2 and 77% of the study area.