Wind Turbine Model Research Articles

Aerodynamic model comparison for an X-shaped vertical-axis wind turbine

Abstract. This article presents a comparison study of different aerodynamic models for an X-shaped vertical-axis wind turbine and offers insight into the 3D aerodynamics of this rotor at fixed pitch offsets. The study compares six different numerical models: a double-multiple streamtube (DMS) model, a 2D actuator cylinder (2DAC) model, an inviscid free vortex wake model (from CACTUS), a free vortex wake model with turbulent vorticity (from QBlade), a blade-resolved unsteady Reynolds-averaged Navier–Stokes (URANS) model, and a lattice Boltzmann method (from PowerFLOW). All models, except URANS and PowerFLOW use the same blade element characteristics other than the number of blade elements. This comparison covers the present rotor configuration for several tip-speed ratios and fixed blade pitch offsets without unsteady corrections, except for the URANS and PowerFLOW which cover a single case. The results show that DMS and 2DAC models are inaccurate – especially at highly loaded conditions, are unable to predict the downwind blade vortex interaction, and do not capture the vertical/axial induction this rotor exhibits. The vortex models are consistent with each other, and the differences when compared against the URANS and PowerFLOW mostly arise due to the unsteady and flow curvature effects. Furthermore, the influence of vertical induction is very prominent for this rotor, and this effect becomes more significant with fixed pitch offsets where the flow at the blade root is considerably altered.

Aerodynamic interference caused by wake effects of repowered wind farms on the annual energy production in neighboring wind farms

Worldwide, wind farms are updated due to technological advances and the end of life from different aspects: social, environmental, technical, and economical. In Brazil, by 2030, around 50 wind farms will reach the age of 20 years of operation, representing more than 600 wind turbines and a total power of around 1,000 MW. This study aims to develop a technical and economic analysis of the unaddressed topic of interference of repowering in neighboring wind farms by analyzing four wind farms in Brazil. Technical analysis of the wake is based on NOJ and BastanKhah models using the software PyWake, which is also employed to calculate the energy production of wind farms. Three wind turbine models with different hub heights and rated power were also considered. Results showed that the repowered wind turbine characteristics, micrositing, and distance between wind farms greatly influence the energy production of neighboring wind farms. The energy deficit in the existing wind farms varied from 433 MWh to 5391 MWh, indicating that, although repowering is a viable solution for wind farms reaching their end-of-life, careful technical analysis regarding the micrositing and wind turbine model should be considered to mitigate energy losses in neighboring existing wind farms.

Numerical validation of the dynamic aerodynamic similarity criterion for floating offshore wind turbines under equivalent pitch motions

Floating offshore wind turbines, as large equipment for deep-sea wind energy utilization, must be carefully studied for their aerodynamic performances under platform motions. In experiments, the model wind turbine designed by the traditional thrust coefficient similarity is usually insufficient for unsteady aerodynamic reproductions of the prototype wind turbine. In this paper, a dynamic aerodynamic similarity criterion based on the mapping of the optimal tip speed ratio is introduced for wind tunnel model tests, and a model wind turbine is designed using the NREL 5-MW prototype wind turbine. In this case, to avoid the over-height model tower aroused in pitch motions, a method of equivalent surge motions instead of pitch motions is proposed and validated for feasibility. Then dynamic aerodynamic similarities under different pitch amplitudes and frequencies are validated by the Unsteady Blade Element Momentum theory. Results indicate that temporal and spatial characteristics and hysteresis effects of thrust and power coefficients all maintain better similarity with those of the prototype wind turbine than those of the model wind turbine designed by the traditional criterion. This paper provides a criterion with equivalent pitch motions for unsteady aerodynamic studies in wind tunnel model tests, especially the high-fidelity Hardware/Software-In-the-Loop test.

Modeling Wind Turbines to Assess Impact of Offshore Wind Farms on Maritime X- and S-band Radars

This article discusses several aspects related to modeling the impact of offshore wind farms on maritime radar systems operating in the X and S bands. The first part of the paper focuses on theoretical models and analyses, taking into account radio shadowing and false radar echoes. Additionally, the issue of spatial modeling of wind turbines, with diffraction phenomena considered, is reviewed with the help of suitable propagation models. By relaying on a software-based implementation of the proposed model, the authors carried out a detailed simulation of the impact of wind turbines on radar systems operating in the X and S bands. The results of these simulations are presented and discussed in the second part of the article.

Dynamic response analysis of a semi-submersible floating wind turbine based on different coupling methods

This article compares and analyzes the overall performance of offshore floating wind turbines using fully coupled and semi-coupled methods considering aerodynamic loads, as well as decoupled methods without considering aerodynamic loads. The aim is to study the impact of different coupling methods on the dynamic response of floating wind turbines and provide a reference for selecting more convenient calculation methods for the preliminary design of floating wind turbines. Based on the open-source software OpenFAST and the commercial hydrodynamic software AQWA, the OC4-DeepCwind semi-submersible offshore floating wind turbine foundation and the NREL 5 MW reference wind turbine model are selected as the research objects. The natural period of the floating structure is validated, and then the power generation and shutdown conditions of the floating wind turbine are selected as the calculation conditions. The motion responses of the floating structure and mooring tension of the floating wind turbine are calculated in the time domain, and the calculation results are statistically analyzed. The research results show that the decoupled analysis method without considering aerodynamic loads significantly underestimates the dynamic response of the floating wind turbine, and the semi-coupled method is more conservative than the fully coupled method. Therefore, in the absence of conditions for fully coupled analysis, the semi-coupled method can be used as a substitute analysis method in the preliminary design stage.

Evaluation of Weibull parameters for wind energy analysis in the eastern region of the Kingdom of Morocco

This document delves into evaluating wind power potential within Morocco’s Oriental region, encompassing an extensive study of 23 locations over 43 years. The analysis was conducted using the advanced MERRA2 data reanalysis system coupled with MATLAB software. Our comprehensive study aims to map the wind energy capabilities across these sites. We employed eight distinct algorithms to adapt the Weibull distribution for the wind speed data. Additionally, the research includes an analysis of the wind rose and assesses the Capacity Factor ([Formula: see text]) to determine the most efficient periods for wind energy production. Our findings highlight that sites S4, S7, and S11 create an ideal geographic formation for wind farm placement. Within this formation, site S8, boasting a ([Formula: see text]) of 36.97%, emerges as a critical location, especially when paired with the EWT DW54 500 wind turbine model. This investigation opens new avenues for advancing wind energy in the region.

Review of different vertical axis wind turbine modeling methods

Wind energy can be used as an inexhaustible option for human consumption. Wind turbines offer a promising solution for off-grid areas. Darrieus turbine is one of the types of turbines that can be more efficient than other types if it is used by knowing its characteristics. The complex dynamic mechanism of the flow around the machine has led to its aerodynamic optimization problems remaining complex. This article reviews the applied methods in modeling vertical axis turbines and implicitly shows the turbine operation by presenting the results of these methods. Knowing these methods is important because each has its advantages and disadvantages and should be selected depending on the purpose of the research. One of the problems with Darrieus turbines is their poor start-up, which has been little researched so far. Finally, a suitable method that can model the start-up is introduced.

Resolvent-based motion-to-wake modelling of wind turbine wakes under dynamic rotor motion

We propose a linearized deterministic model for predicting coherent structures in the wake of a floating offshore wind turbine subject to platform motions. The model's motion-to-wake predictive capability is achieved through two building blocks: a motion-to-forcing (M2F) part and a forcing-to-wake (F2W) part. The M2F model provides a unified framework to parameterize the effects of arbitrary floating wind turbine motions as unsteady loads of a fixed actuator disk, requiring only the radial distribution of the aerodynamics force coefficient on the blade as input. The F2W model is derived based on a bi-global resolvent model obtained from the linearized Navier–Stokes equations, using the time-averaged wake of a fixed wind turbine as input. In addition to its capability of predicting sensitive frequency ranges, the model excels linear stability analysis by providing spatial modes of the wake response in a motion-specific and phase-resolved manner. The model successfully predicts the wake pulsing mode induced by surge, as well as the similarity and difference of the wake meandering modes caused by sway and yaw. Large-eddy simulations under different inflow turbulence intensities (TIs) and length scales are further conducted to analyse the wake meandering triggered by the simultaneous excitation of free-stream turbulence and sway motion. The results show distinct frequency signatures for the wake dynamics induced by ambient turbulence and sway motion. The inflow TI is found to have a stabilizing effect on the wake, reducing the motion-induced wake responses. Such a stabilizing effect is captured satisfactorily with the proposed model, provided that the effective viscosity is calibrated properly using the data from the fixed turbine wake under the corresponding turbulent inflow.

Maximizing wind farm power output with the helix approach: Experimental validation and wake analysis using tomographic particle image velocimetry

AbstractWind farm control can play a key role in reducing the negative impact of wakes on wind turbine power production. The helix approach is a recent innovation in the field of wind farm control, which employs individual blade pitch control to induce a helical velocity profile in a wind turbine wake. This forced meandering of the wake has turned out to be very effective for the recovery of the wake, increasing the power output of downstream turbines by a significant amount. This paper presents a wind tunnel study with two scaled wind turbine models of which the upstream turbine is operated with the helix approach. We used tomographic particle image velocimetry to study the dynamic behavior of the wake under the influence of the helix excitation. The measured flow fields confirm the wake recovery capabilities of the helix approach compared with normal operation. Additional emphasis is put on the effect of the helix approach on the breakdown of blade tip vortices, a process that plays an important role in re‐energizing the wake. Measurements indicate that the breakdown of tip vortices and the resulting destabilization of the wake are enhanced significantly with the helix approach. Finally, turbine measurements show that the helix approach was able to increase the combined power for this particular two‐turbine setup by as much as 15%.

Adaptive blade pitch control method based on an aerodynamic blade oscillator model for vertical axis wind turbines

In recent decades, the high fatigue loads (mainly derived from the blade normal force fluctuation) and low power coefficient at the low tip speed ratio with high incoming wind speeds have greatly hindered the development of vertical axis wind turbines. Regulating the blade's angle of attack using a pitch control method is an effective way to reduce the blade normal force amplitude and improve the power coefficient. This paper proposes an adaptive blade pitch control method based on an aerodynamic blade oscillator model and studies its performance and control mechanism using the computational fluid dynamics method combined with the dynamics of the aerodynamic oscillator. The results show that the pitch control provides positive performance for most parameter configurations with the power coefficient increased by 105% and the blade normal force amplitude reduced by 29.5% for the best parameter configuration; poor performance with one parameter configuration indicates that the virtual pitch center should not be too close to the acting point of the aerodynamic force, otherwise the flow state transformation will make the pitch variation unsatisfactory; with an appropriate parameter configuration, the adaptive pitch control adaptively decreases the pitch angle amplitude with the tip speed ratio increase and provides positive performance for varying tip speed ratios. The research provides a theoretical basis for the application of the adaptive pitch control on vertical axis wind turbines.

Combined MIMO Deep Learning Method for ACOPF with High Wind Power Integration

The higher penetration of renewable energy sources in current and future power grids requires effective optimization models to solve economic dispatch (ED) and optimal power flow (OPF) problems. Data-driven optimization models have shown promising results compared to classical algorithms because they can address complex and computationally demanding problems and obtain the most cost-effective solution for dispatching generators. This study compares the forecast performance of selected data-driven models using the modified IEEE 39 benchmark system with high penetration of wind power generation. The active and reactive power load data of each bus are generated using Monte Carlo simulations, and synthetic wind power data are generated by utilizing a physical wind turbine model and wind speed samples withdrawn from a Weibull distribution. The objective is to design and evaluate an enhanced deep learning approach for the nonlinear, nonconvex alternating current optimal power flow (ACOPF) problem. The study attempts to establish relationships between loads, generators, and bus outcomes, utilizing a multiple-input, multiple-output (MIMO) workflow. Specifically, the study compares the forecast error reduction of convolutional neural networks (CNNs), deep feed-forward neural networks (DFFNNs), combined/hybrid CNN-DFFNN models, and the transfer learning (TL) approach. The results indicate that the proposed combined model outperforms the CNN, hybrid CNN-DFFNN, and TL models by a small margin and the DFFNN by a large margin.

Model development of bond graph based wind turbine

<span>Just recently, wind energy continues to be one of most important renewable energy resources, by cause of its production is ecologically friendly; for that reason, the technology built for the renewable energy production by way of wind turbines takes excessive challenges in the study. Due to several physical domains prevailing in wind turbine, namely aerodynamical, mechanical and electrical, the modeling of wind turbine is problematic; thus, modeling based on physical techniques has a superior reliability in these circumstances. One of these approaches is bond graph modeling that model system evolved from conservation law of both of mass and energy comprising in the structures. This study presents modeling the parts of bond graph-based wind turbine. Then, sub models are connected together to attain the entire model of wind turbine for simulation based on 20-Sim software. The proposed wind turbine is 2.5 kW of variable velocity wind turbine with three blades, gearbox, tower, and doubly-fed induction generator type. The effectiveness of bond graph modeling system on wind turbine has been proven in simulation results.</span>

Novel control strategy for the global model of wind turbine

This paper presents a new nonlinear control for the overall model of a three-blade horizontal axis variable speed wind turbine (VSWT) including mechanical and electrical parts, with the aim of improving its performance and making it more profitable. The proposed control is an extension of the classical sliding mode control (SMC) by converting its sliding surface into a sliding sector. The classical SMC approach is widely used for nonlinear systems due to its stability against parameter variation, it is robustness against modeling uncertainties, its good results against external disturbances, and its ease of implementation in real time. Unfortunately, the SMC has a major drawback related to the chattering phenomenon. This phenomenon is due to the utility of a higher switching gain in the case of large uncertainties, it causes high-frequency oscillations once the sliding regime is reached, and it can cause a loss of accuracy by influencing the input control variables. This is the reason that aims to develop a new control law to eliminate the chattering and to guarantee stability, which is demonstrated by the Lyapunov theory. The effectiveness of the developed control is compared with the SMC and is illustrated by numerical simulations using MATLAB toolboxes.

LSTM Neural Networks Using the SMOTE Algorithm for Wind Turbine Fault Prediction

Abstract This work proposes a method using a long short-term memory neural network as a diagnostic tool to detect wind turbine rotor mass imbalance. The method uses the synthetic minority oversampling technique for data augmentation in an unbalanced dataset. For this purpose, a 1.5 MW three-bladed wind turbine model was simulated at Turbsim, FAST, and Matlab Simulink to generate rotor speed data for different scenarios, simulating different wind speeds and creating a mass imbalance by changing the density of the blades in the software. Features extraction and power spectral density were also used to improve the Neural Network results. The results were compared to nine different classifiers with four different combinations of datasets and demonstrated that the technique is promising for mass imbalance detection.

Performance Analysis of Horizontal Shaft Wind Turbine Through Blade Design Modification

The objective of this study is to investigate the performance of a horizontal shaft wind turbine model with variations in blade shapes. The focus of the research lies in examining the impact of different blade shapes, specifically the curved shape, inverted linear taper, and rectangular shape measuring 8 cm x 20 cm at a 200 tilt angle. The experiments are conducted at various wind speeds: 7, 8, 9, 10, and 11 m/s. The findings reveal that changes in blade shape significantly influence the operation of the horizontal shaft wind turbine. The Brake Horse Power (BHP) reaches its maximum with a rectangular blade shape, achieving 1.1 watts at a wind speed of 11 m/s and a corresponding torque of 0.0221 Nm. Additionally, the highest efficiency is attained with the rectangular blade shape at a wind speed of 7 m/s, reaching 21%.

Wind Tunnel Experiments on Vertical-Axis Wind Turbines with Straight Blades

This paper gives the experimental performances obtained in a wind tunnel for a flexible experimental model of vertical axis wind turbine (VAWT) with straight blades. The effects of blades arrangement in one or two stages, of setting angle and of blade numbers influences on the output performance were analysed. The results showed that the VAWT developed torque at low speeds is greater when the setting angle of blades is greater but the VAWT developed torque at higher speeds is greater when the setting angles of blades is less.

Maximum Power Control of DFIG Based Grid Connected Wind Turbine Generator System

This paper presents a simulation model of variable speed wind turbine with a doubly fed induction generator developed in Matlab/simulink. Vector control of a doubly fed induction generator (DFIG) drive for variable speed wind power generation is described. A slip ring (wound rotor) induction generator with back to back three phase PWM converter between its rotor and the grid forms the electrical system. A vector control scheme for the PWM converters results in independent control of active and reactive power. Line (supply) voltage oriented reference frame has been used to independently control the active and reactive power. Results are provided at the end for sub synchronous and super-synchronous operation of the DFIG.

Wind tunnel tests applied to wind energy management: comparison of measurements in closed-circuit and open-circuit wind tunnels

Power loss, damages overestimation and environmental impacts are the main problems related to wind energy and its planning and management. One of the tools used to analyse and manage this problem is the aerodynamic wind tunnel. In this work wind tunnel tests were performed in two different facilities, an open-circuit wind tunnel and a close-circuit wind tunnel, in order to study the suitability of these features to optimize wind farms layout and power quality and its dependence of the type of tests facility. Experimental results in this work are reported as wind speed and turbulence intensity vertical profiles and flow fields with a simulated ABL with and without the presence of a three-bladed wind turbine model. Results show that mean wind velocity is similar in both tunnels, but turbulence intensity is higher for the open-circuit wind tunnel.

ExaWind: Open‐source CFD for hybrid‐RANS/LES geometry‐resolved wind turbine simulations in atmospheric flows

AbstractPredictive high‐fidelity modeling of wind turbines with computational fluid dynamics, wherein turbine geometry is resolved in an atmospheric boundary layer, is important to understanding complex flow accounting for design strategies and operational phenomena such as blade erosion, pitch‐control, stall/vortex‐induced vibrations, and aftermarket add‐ons. The biggest challenge with high‐fidelity modeling is the realization of numerical algorithms that can capture the relevant physics in detail through effective use of high‐performance computing. For modern supercomputers, that means relying on GPUs for acceleration. In this paper, we present ExaWind, a GPU‐enabled open‐source incompressible‐flow hybrid‐computational fluid dynamics framework, comprising the near‐body unstructured grid solver Nalu‐Wind, and the off‐body block‐structured‐grid solver AMR‐Wind, which are coupled using the Topology Independent Overset Grid Assembler. Turbine simulations employ either a pure Reynolds‐averaged Navier–Stokes turbulence model or hybrid turbulence modeling wherein Reynolds‐averaged Navier–Stokes is used for near‐body flow and large eddy simulation is used for off‐body flow. Being two‐way coupled through overset grids, the two solvers enable simulation of flows across a huge range of length scales, for example, 10 orders of magnitude going from O(μm) boundary layers along the blades to O(10 km) across a wind farm. In this paper, we describe the numerical algorithms for geometry‐resolved turbine simulations in atmospheric boundary layers using ExaWind. We present verification studies using canonical flow problems. Validation studies are presented using megawatt‐scale turbines established in literature. Additionally presented are demonstration simulations of a small wind farm under atmospheric inflow with different stability states.

Effect of tip speed ratio on coherent dynamics in the near wake of a model wind turbine

The near wake of a small-scale wind turbine is investigated using particle image velocimetry experiments at different tip speed ratios ( $\lambda$ ). The wind turbine model had a nacelle and a tower mimicking real-scale wind turbines. The near wake is found to be dominated by multiple coherent structures, including the tip vortices, distinct vortex sheddings from the nacelle and tower, and wake meandering. The merging of the tip vortices is found to be strongly dependent on $\lambda$ . A convective length scale ( $L_c$ ) related to the pitch of the tip vortices is defined that is shown to be a better length scale than turbine diameter ( $D$ ) to demarcate the near wake from the far wake. The tower induced strong vertical asymmetry in the flow by destabilising the tip vortices and promoting mixing in the lower (below the nacelle) plane. The nacelle's shedding is found to be important in ‘seeding’ wake meandering, which, although not potent, exists close to the nacelle, and it becomes important only after a certain distance downstream ( $x>3L_c$ ). A link between the ‘effective porosity’ of the turbine and $\lambda$ is established, and the strength and frequency of wake meandering are found to be dependent on $\lambda$ . In fact, a decreasing trend of wake meandering frequency with $\lambda$ is observed, similar to vortex shedding from a porous plate at varying porosity. Such similarity upholds the notion of wake meandering being a global instability of the turbine, which can be considered as a ‘porous’ bluff body of diameter $D$ .