Three-bladed Horizontal Axis Wind Turbine Research Articles

Robust and intelligent power control for three-bladed horizontal axis wind turbine system using a real wind profile of the northern Morocco

In this work, a robust and intelligent control approach is developed for three-bladed horizontal axis variable-speed wind turbine (VSWT) operating under real climatic conditions (whether the WT is onshore or offshore). Below the rated power, the main purpose of the controller is to optimize the extraction of energy from wind and ensure the full exploitation of the installation, all while minimizing mechanical stress in the system in the presence of uncertainties and external disturbances. In order to achieve optimized wind energy capture without chattering problems or oscillatory phenomena, this study proposes combining the Integral Sliding Mode Control (ISMC) with an artificial neural network technique such as the Radial Basis Function (RBF) to enhance controller performances. Additionally, the RBF neural network (RBFNN) approach is implemented to estimate the wind turbine (WT) model uncertain part, allowing the use of a lower switching gain to achieve faster convergence and avoid steady-state error. Thus, by means of Lyapunov theory, the stability of the system with this controller can be demonstrated. Simulation results of the proposed Neural Network Integral Sliding Mode Control (NN-ISMC) controller are compared with the usual SMC and the standard ISMC. The comparative analysis indicate a superior efficiency of the developed control strategy in terms of decreasing tracking error and eliminating chattering behavior. Moreover, this approach provides a faster transient system response and higher robustness in presence of uncertainties compared to the other controllers.

Aerodynamic characterisation of a thrust-scaled IEA 15 MW wind turbine model: experimental insights using PIV data

Abstract. This study presents results from a wind tunnel experiment on a three-bladed horizontal axis wind turbine. The model turbine is a scaled-down version of the IEA 15 MW reference wind turbine, preserving the non-dimensional thrust distribution along the blade. Flow fields were captured around the blade at multiple radial locations using particle image velocimetry. In addition to these flow fields, this comprehensive dataset contains spanwise distributions of bound circulation, inflow conditions and blade forces derived from the velocity field. As such, the three blades' aerodynamics are fully characterised. It is demonstrated that the lift coefficient measured along the span agrees well with the lift polar of the airfoil used in the blade design, thereby validating the experimental approach. This research provides a valuable public experimental dataset for validating low- to high-fidelity numerical models simulating state-of-the-art wind turbines. Furthermore, this article establishes the aerodynamic properties of the newly developed model wind turbine, creating a baseline for future wind tunnel experiments using this model.

Numerical Study of a Small Horizontal-Axis Wind Turbine Aerodynamics Operating at Low Wind Speed

The present work aims to study the aerodynamic characteristics of a newly designed three-bladed horizontal-axis wind turbine (HAWT) using the Computational Fluid Dynamic (CFD) method. The blade geometry is designed using an improved Blade Element Momentum (BEM) method to be similar in size to the Ampair300 wind turbine. The shear stress transport (SST) transition turbulence model closure is utilized to solve the steady state three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations. The Ansys Fluent CFD solver is used to solve the problem. Then, a comparison between the two turbines’ operating conditions is conducted by monitoring the pressure coefficient, pressure contours and velocity vectors at five different radial positions. The analysis of the Tip Speed Ratio (TSR) effects on the turbine efficiency and on the flow behavior on the blade and in the near wake is carried out. For 8 m/s wind speed, the optimum pitch angle is also investigated, and the results are prepared against each TSR.

A cost-effective algorithm for the co-simulation of unsteady and non-linear aeroelastic phenomena

Increasingly flexible structures force engineers and scientists to improve simulation capabilities incorporating an adequate description of non-linear phenomena. Furthermore, many critical operating conditions of aeronautical and civil structures are associated with unsteady phenomena, which makes it necessary to tackle this kind of problems. A critical aspect to be analyzed is the stability of the system: the determination of, not only the critical flutter speed, but also the post-critical behavior, is fundamental to guarantee the safety of designs and determine mitigation strategies. In this work, a numerical technique that allows simulating the non-linear and unsteady behavior of highly flexible structures immersed in a fluid at high Reynolds numbers is presented. This problem is addressed using a co-simulation approach, coupling the Unsteady Vortex Lattice Method (as the aerodynamic model) with the Finite Element Method using non-linear beams and rigid bodies (as the structural dynamics model). The coupling is achieved through a weak interaction algorithm. The resulting method has a very good compromise between versatility and computational cost, and is not restricted to periodic motions or linear equations of motion. Nonlinearity is included through the possibility to represent large displacements and rotations of the structure, a visco-elastic material behavior, and a nonlinear relation between the aerodynamic loads and the incidence of the incoming flow. The domains considered in the submodels and the temporal and spatial discretizations used for each one are essentially different; the interaction process must take into account these aspects. The computational implementation is carried out by combining a general-purpose structural dynamics code with an aerodynamic tool oriented to the analysis of three-bladed horizontal axis wind turbines. Examples to validate the code and show the potential of the proposed method are presented in the Results section.

On wind turbine loading induced by non-uniform approaching flow at high Reynolds numbers

Influences of non-uniform incoming flow on the wind turbines blades forces and root bending moments (RBMs) are not fully understood. To advance our current understanding, numerical studies of a three-bladed horizontal axis wind turbine with cylinders placed in front of it to produce non-uniform flow approaching the turbine with different non-uniformity levels have been carried out to examine the variations of blade and rotor loading due to the non-uniform incoming flow. The phase-averaged predicted blade forces reveal that the blade tangential force, in-plane RBM, and power coefficient are much more sensitive to the upstream streamwise velocity variations and are much more strongly affected than the blade axial force, out-of-plane RBM, and thrust coefficient. It also shows that for non-uniform incoming flows the blade axial force to the blade tangential force ratio fluctuates significantly during one rotor revolution, resulting in large variations of the blade elastic torsion and that the total blade force (magnitude and direction) undergoes a non-linear change in the circumferential and radial directions, which will likely lead to the reduction in the turbine operational life significantly, especially for long lightweight blades of large size wind turbines. This study also shows different behaviors of the blade forces along the blade span under non-uniform upstream flows in terms of the amplitudes and standard deviations of their oscillations. For the blade tangential force, λ and σ increase monotonously along the blade span up to near the blade tip, whereas those of the blade axial force increase up to approximately 0.6 blade span and show an opposite trend behind that.

Wake Structure in Yawed Approaching Flows for an Axial-Flow Wind Turbine

Abstract Effects of yawed wind turbines on the wake structure are not fully understood. To obtain a better understanding, numerical studies of a small-scale three-bladed horizontal axis wind turbine at tip speed ratio (TSR) = 6.7 with yaw angles of zero, 15 deg, 30 deg, and 45 deg have been carried out to investigate the wake characteristics of the turbine in the near- and farwake. A hybrid approach coupling large eddy simulation (LES) with actuator line modeling (ALM) has been employed in the present study. The predicted results confirm the previous finding that the turbine wake is asymmetric under yawed approaching flows and the wake is inclined to the direction where the rotor is yawed. The present work further demonstrates that at high yaw angles the main wake may be divided into two smaller parallel wakes further downstream that are not symmetric suggesting a dependency on the turbine rotation direction. This study quantitatively explains how the nonuniform variations of radial velocity components at the turbine plane caused by the yawed flows result in the wake deflection and intersection of hub and blade tip vortices further downstream which leads to the wake splitting at high yaw angles.

Life Cycle Assessment of Wind Turbine in Turkey

This article aims to assess life cycle analysis of a wind turbine in Turkey regarding production, transport, construction, operation, and disposal processes in terms of energy and environment. In this context, a 2-MW three-bladed horizontal axis wind turbine has been selected. Two different scenarios have been studied which comprises wind turbines using Al-Conductor and Cu-Conductor cables. Although the cost of Al-Conductor cables is low, their joule losses are higher. The life cycle assessment of a wind turbine includes production, transportation, construction, operation and disposal, and the energy has been generated in its operation time (selected as 20 years). Iron, cast iron, steel, copper, aluminum, and oil have been sent to a recycling facility and the composite materials has been sent for incineration at the end of its life. The energy payback period has been calculated as 10 months in both scenarios and the embodied energy is 2858.2 MWh and 2830.3 MWh for wind turbine using Al-Conductor and Cu-Conductor cable during its lifetime, respectively. Air emission and wastewater production have been calculated to assess environmental impacts (global warming, acidification, eutrophication, etc.) whose consequence provides an evaluation of the life cycle assessment of a wind turbine. For example, global warming is 14.44 and 15.24 g CO2 eq./kWh for wind turbine using Al-Conductor and Cu-Conductor cable, respectively. As a result, the life cycle analysis of the wind turbines has been evaluated and compared regarding two different scenarios according to the definition of ISO 14040 standard throughout its life from production to disposal.

Sustainability Assessment of Wind Farms

Sustainable energy solutions are becoming increasingly popular as the shift away from conventional fuel-based energy solutions continues. Solar, wind, and hydro solutions are the most frequently used renewable energy sources. Modern wind energy solutions are usually constructed using a design of a large three-bladed horizontal axis wind turbine (HAWT). The blades are upwind facing, which helps support the turbine tower against environmental strain and torque ripple produced from the spinning motion of the blades. HAWTs are usually organised into large groups referred to as wind farms. Wind farms are becoming increasingly popular with their ability to adapt to offshore and onshore environments. In both scenarios, wind turbines have a relatively low footprint, with the land underneath still available to be utilised for agricultural and aquacultural purposes. This paper investigates the sustainability of wind farms by surveying a range of papers. The papers will cover the development, construction, and continued operation of wind turbines providing insights into the sustainability issues. Reviewing these papers will allow for an informed revision to the code of sustainability for future implementations of wind farms. The paper concludes with a case study to apply the suggested sustainability code in a contextual scenario and recommendations for the general engineering profession.

A Proper-Orthogonal-Decomposition (POD) Study of the Wake Characteristics behind a Wind Turbine Model

A comprehensive study was performed to analyze turbine wake characteristics by using a Proper-Orthogonal-Decomposition (POD) method to identify the dominant flow features from a comprehensive experimental database. The wake flow characteristics behind a typical three-bladed horizontal-axis wind turbine (HAWT) were measured in a large-scale wind tunnel with a scaled turbine model placed in a typical offshore Atmospheric Boundary Layer (ABL) wind under a neutral stability condition. A high-resolution Particle Image Velocimetry (PIV) system was used to achieve detailed flow field measurements to characterize the turbulent flows and wake vortex structures behind the turbine model. Statistically averaged measurements revealed the presence of the characteristic helical-tip vortex filament along with a unique secondary vortex filament emanating from 60% of the blade span measured from the hub. Both filaments breakup in the near-wake region (~0.6 rotor diameter downstream) to form shear layers, contrary to previous computational and experimental observations in which vortex filaments break up in the far wake. A Proper-Orthogonal-Decomposition (POD) analysis, based on both velocity and vorticity-based formulations, was used to extract the coherent flow structures, predominantly comprised of tip and midspan vortex elements. The reconstructions showed coherence in the flow field prior to the vortex breakup which subsequently degraded in the turbulent shear layer. The accuracy of the POD reconstructions was validated qualitatively by comparing the prediction results between the velocity and vorticity-based formulations as well as the phase-averaged PIV measurement results. This early vortex breakup was attributed to the reduced pitch between consecutive helical turns, the proximity between midspan filaments and blade tips as well as the turbulence intensity of the incoming boundary layer wind.

Rotational and blockage effects on a wind turbine model based on local blade forces

This paper describes the results of an extended experimental campaign, reporting surface pressure measurement over one of the blades of the Berlin Research Turbine (BeRT), placed in a closed-loop wind tunnel facility. BeRT is a three-bladed horizontal axis wind turbine with a 3m rotor diameter. The focus is, on the one side, on the three-dimensional effects experienced by the rotating blade, in comparison to 2D approaches by means of XFoil simulations and 2D blade section experiments. On the other side, the blockage effects are investigated between the wind turbine model, placed in the wind tunnel where a 40% blockage ratio is produced, and lifting line free vortex wake simulations, where wind tunnel walls are not considered. Additionally, CFD computations are added in the comparison, with simulations of the far-field and with the wind tunnel walls. The turbine model is studied at several operational conditions such as different blade pitch angles and turbine yaw misalignments. Results are presented in terms of local force components derived from the surface pressure measurements. It is shown that rotational augmentation is evident at the blade mid-span location despite the large blockage. Additionally, the blockage is noticed by means of an offset in both normal and tangential local forces conserving trends and features under axial inflow and yaw misalignments. It is found that the offset in forces can be counteracted by pitching the blades.

Modelling and Control of a Small Domestic Wind Turbine

A wind turbine is a machine that converts the kinetic energy of wind into mechanical energy like wind turbines. This mechanical wind power has been used through the ages to pump water or grind grain. Current machines are used to produce wind-type electricity which is consumed locally (isolated sites), or injected into the electricity network (wind turbines connected to the network). In this work, we are only interested in the modelling of a three-bladed horizontal axis wind turbine. All the models were developed by the Matlab/Simulink software, which makes it possible to set up fairly quickly models as well as the associated. The results revealed that the wind profile ranges between 6-7 (m/s), the power coefficient Cp for a pitch angle of =2 has an average value of 0.54 with a relative speed λ value of 6.40, and when the origin of electrical losses is ignored, the electrical power equals the electromagnetic power, and the mechanical speed is stable between (70-80 rd/s).

Validation of a Large-Eddy Simulation Approach for Prediction of the Ground Roughness Influence on Wind Turbine Wakes

The ability of high-fidelity computational fluid mechanics simulation to quantitatively predict the influence of ground roughness on the evolution of the wake of a three-bladed horizontal axis wind turbine model is tested by comparison with wind tunnel measurements. The approach consists of the implicit approximate deconvolution large-eddy simulation formulation of Hickel et al., (2006), that is, for the first time, combined with a wall-stress model for flow over rough surfaces and with the actuator line approach (ALM) for modeling of the rotor. A recycling technique is used for the generation of turbulent inflow that matches shear exponents α=0.16 (medium roughness) and α=0.32 (high roughness) and turbulence level of the reference experiments at hub height. Satisfactory agreement of the spectral content in simulation and experiment is achieved for a grid resolution of 27 cells per rotor radius. Except for minor differences due to neglecting nacelle and tower in the simulation the LES reproduces the shapes of mean flow and Reynolds stress profiles in the wake. The deviations between measurement and simulation are more prominent in a vertical cut plane through the rotor center than in a horizontal cut plane. Simulation and experiment deviate with respect to the roughness influence on the development of the wake width; however, the relative change of the maximum wake deficit and of the vertical wake center position due to changes in ground roughness is reproduced very well.

Characteristics Simulation Method of Megawatt Three-Blade Horizontal Axis Wind Turbine Based on Laboratory Kilowatt Low-Power Motor System

Characteristics Simulation Method of Megawatt Three-Blade Horizontal Axis Wind Turbine Based on Laboratory Kilowatt Low-Power Motor System

The Operation of a Three-Bladed Horizontal Axis Wind Turbine under Hailstorm Conditions—A Computational Study Focused on Aerodynamic Performance

The aim of this study is the aerodynamic degradation of a three-bladed Horizontal Axis Wind Turbine (HAWT) under the influence of a hailstorm. The importance and originality of this study are that it explores the aerodynamic performance of an optimum wind turbine blade during a hailstorm, when hailstones and raindrops are present. The commercial Computational Fluid Dynamics (CFD) code ANSYS Fluent 16.0 was utilized for the simulation. The first step was the calculation of the optimum blade geometry characteristics for a three-bladed rotor, i.e., twist and chord length along the blade, by a user-friendly application. Afterwards, the three-dimensional blade and the flow field domain were designed and meshed appropriately. The rotary motion of the blades was accomplished by the application of the Moving Reference Frame Model and the simulation of hailstorm conditions by the Discrete Phase Model. The SST k–ω turbulence model was also added. The produced power of the wind turbine, operating in various environmental conditions, was estimated and discussed. Contours of pressure, hailstone and raindrop concentration and erosion rate, on both sides of the blade, are presented. Moreover, contours of velocity at various cross sections parallel to the rotor are demonstrated, to understand the effect of hailstorms on the wake behavior. The results suggest that the aerodynamic performance of a HAWT degrades due to impact and breakup of the particles on the blade.

Effect of Rain on the Aerodynamic Performance of a Horizontal Axis Wind Turbine – A Computational Study

This paper analyzes numerically the impact of rainfall on the aerodynamic performance of a three-bladed Horizontal Axis Wind Turbine, with blades constructed by NACA 4418 airfoil. The simulations were conducted by the help of the commercial Computational Fluid Dynamics code, ANSYS Fluent. Firstly, the optimum geometry of the blade was designed with an application based on Blade Element Momentum theory. The Moving Reference Frame Model was applicated to simulate the rotation of the blades and the k-ω shear-stress transport turbulence model was added as well. The simulation of rain was accomplished by the Discrete Phase Model and the Taylor Analogy Breakup model was enabled to simulate droplets breakup. Three different rainfall conditions were studied, corresponding to Liquid Water Contents of 10g/m³, 30g/m³ and 60g/m³. The influence of droplet diameter on the aerodynamic performance of the blade was also examined. The results showed that the aerodynamic performance of the wind turbine is degraded in rain conditions, and the degradation is greater for higher values of Liquid Water Content and for larger diameter of water droplets.

Wind Turbine Trailing Edge Noise: Mitigation of Normal Amplitude Modulation by Individual Blade Pitch Control

This work deals with the elimination or mitigation of amplitude modulation (AM) at any single listener position in the near proximity of a state-of-the-art three-bladed horizontal axis wind turbine by applying individual azimuthal pitch control to the blades. The investigation is restricted to normal AM (NAM) in the close vicinity of the turbine. The effects of the listener position, shear rate of the inflow, and flexibility of the blades are studied. The methodology is model-based: Among others, the fundamental sub-models are the Brooks, Pope and Marcolini airfoil self-noise model, Howe's directivity model for trailing edge sound sources, Rozenberg's convective amplification model for sound sources in motion and an atmospheric damping model. The aeroelastic behaviour of the complete wind turbine is modelled via a multibody approach as encoded in the Horizontal Axis Wind turbine simulation Code 2nd generation (HAWC2) from the Danish Technical University (DTU). The complete model is integrated into an optimisation scheme that seeks an azimuthal pitch control of each blade for minimal modulation depth of the overall sound pressure level at an arbitrarily chosen listener position. The sound prediction model is validated by experimental data from 160 commercial 3.2 MW turbines and the University of Siegen small-scale research wind turbine. As a result, individual blade pitch control as obtained by the optimisation scheme eliminates NAM at any targeted listener position, at the expense of an increase of NAM at other ground locations. Cancelling NAM for a lateral listener position requires the largest amplitude and gradients in the azimuthal pitch control. In case of elastic blades, the required amplitude of the optimised azimuthal pitch control is substantially larger as compared to rigid blades. It is also shown that azimuthal pitch control causes small fluctuations of the axial thrust and aerodynamic power output of the turbine.

Prediction of power generation of two 30 kW Horizontal Axis Wind Turbines with Gaussian model

In order to improve the total efficiency of power generation in a wind farm, this paper investigated the effect of different operating conditions of the upstream wind turbine on the power of the downstream wind turbine by Gaussian wake model. A three-bladed Horizontal Axis Wind Turbine with the generator capacity of 30 kW was used. Firstly, Gaussian model for evaluating the wake flow was developed, which fit well with experiment data. Then, the influence of the operating condition of the upstream turbine on the downstream turbine performance was estimated by calculating the energy amount resulted from the velocity deficit of the wake. Finally, the effect of the installation position of the downstream wind turbine was analyzed. In consequence, the total power coefficient Ptotal of the wind turbines was relatively higher when the upstream turbine was at tip speed ratio λ = 6.4 and pitch angle β = 2° among different test conditions. Meanwhile, the Ptotal showed the maximum value when the downstream turbine was installed at the streamwise location x/D = 2.0 and lateral offset location y/R = 1.5 when the inflow turbulence intensity is 0.22≤TIref ≤ 0.35. This paper provided a better guidance for optimizing the wind turbine layout and improving the total power output of the entire wind farm.

On wind turbine power fluctuations induced by large-scale motions

Our current understanding on the dynamic interaction between large-scale motions in the approaching turbulent flow and wind turbine power is very limited. To address this, numerical studies of a small-scale three-bladed horizontal axis wind turbine with cylinders placed in front of it to produce energetic coherent structures of varying scale relative to the turbine size have been carried out to examine the temporary variations of the turbine power. The predicted spectra reveal a strong interaction between large-scale turbulent motions generated by cylinders and the instantaneous turbine power. More specifically, it shows how the large dominant turbulent scales of incoming flow affect the spectral characteristics of turbine power, i.e, determining the level and trend of the turbine power spectrum. Comparisons reveal that there are two critical frequencies recognisable in the turbine power spectrum: the first one, close to the turbine rotational frequency, above which the coupling of upstream flow and turbine power disappears; the second one, identified for the first time and related to the dominant large-scale motions which dictate the level and trend of the turbine power spectrum. This study also shows that the strong scale-to-scale interaction between the upstream flow and turbine power reported previously does not appear at high Reynolds numbers.

Development of a three-bladed horizontal axis wind turbine with active control by using a programmable logic controller

For the increasing the physical efficiency, useful life and avoid accidents in wind turbines, it is very useful to implement a pitch control on the blades that help as an aerodynamic brake and orientation in the base to follow the wind direction. The main goal of this paper was to develop a digital controller on the wind turbine blades that allows to keep the constant angular velocity and monitor the orientation of the wind. A computer-aided design software was developed for allowing the aerodynamic analysis by using Solid Works® software based on a flow simulation tool. On the other hand, a MATLAB model was created employing Simulink tool and the Simscape toolbox with typical data from a 2MW wind turbine whereas the electrical and mechanical dynamics and control feedback were calculated having as input parameters the wind direction and speed. Consequently, a prototype was designed in 3D which was implemented to make the different tests. For lab experimentation, a fuzzy control algorithm was developed in structured control language and then implemented using the S7-1200 PLC. The trials with programmable logic controller and the fuzzy algorithm were satisfactory, which could be a basis for the optimization of the performance of a three-bladed horizontal axis wind turbine.

Characterization of the wake behind a horizontal-axis wind turbine (HAWT) at very high Reynolds numbers

The wake of a three-bladed horizontal axis wind turbine was studied at aerodynamic conditions similar to what is experienced by commercially available turbines. Field relevant Reynolds numbers and tip speed ratios were obtained through the use of a high-pressure wind tunnel, at relatively low velocities. Measurements of the streamwise velocity were acquired through the use of the novel nano-scale thermal anemometry probe (NSTAP), which yields very high spatial and temporal resolution, enabling unattenuated turbulence measurements. Profiles of the mean velocity and turbulent fluctuations are presented, as they demonstrate important features of the wake development, such as wake recovery and tip vortex evolution. One dimensional energy spectra are also presented to provide details on the dominant flow features present in the wake. Reynolds number invariance is shown for mean velocity deficit and streamwise variance profiles for all downstream positions presented. Downstream evolution of streamwise variance profiles provides insight to the dynamic interactions between the tip and root vortex, such as their eventual coalescence. Spectral analysis show that the near wake flow-structures are dominated by the tip vortex, but that other larger structures are present as well, which may be related to the wake meandering phenomenon.