Vertical Axis Wind Turbine Blade Research Articles

Vertical axis wind turbine operation in icing conditions: A review study

Vertical Axis Wind Turbine (VAWT) can be a promising solution for electricity production in remote ice prone territories of high north, where good wind resources are available, but icing is a challenge that can affect its optimum operation. A lot of research has been made to study the icing effects on the conventional horizontal axis wind turbines, but the literature about vertical axis wind turbines operating in icing conditions is still scarce, despite the importance of this topic. This paper presents a review study about existing knowledge of VAWT operation in icing condition. Focus has been made in better understanding of ice accretion physics along VAWT blades and methods to detect and mitigate icing effects.

PIV measurements over a double bladed Darrieus-type vertical axis wind turbine: A validation benchmark

Vertical axis wind turbines (VAWTs) are very attractive for in-home power generation since they can be adopted even at low wind speeds and highly variable wind direction. Even if significant experimental research activity has been carried out to improve VAWTs performance, the ability to accurately reproduce flow field characteristics around turbine blades by CFD (computational fluid dynamics) techniques represents a powerful approach to further enhance wind turbines performance. Thanks to CFD, in fact, it is possible to reproduce flow characteristics with a detail level impossible to achieve by experiments. Nevertheless, in order to appropriately analyze the flow structure by CFD application, an accurate validation is essential, and high-quality measurements of some main flow characteristics are required. In recent publications the authors investigated, both experimentally and numerically, the performance of an innovative double bladed Darrieus-type VAWT, with the aim to define an optimal configuration also focusing on self-starting ability of the prototype by employing CFD technique. Nevertheless, comparison between experiments and numerical results was made only in terms of power and torque coefficients. To overcome such limitation, in this paper the authors propose an experimental benchmark case for CFD results validation, describing detailed flow field in correspondence of one pair of blades of the innovative Darrieus-type VAWT in static conditions. Measurements were performed employing Particle Image Velocimetry (PIV) technique on a scaled model of the turbine blades realized by 3D printing. An uncertainty analysis was also performed which showed a high accuracy of the obtained experimental results. The measurements of the main flow characteristics (bi-dimensional velocity components) were then used for a test case CFD validation of two different turbulence models.

Design and Manufacturing Method of GFRP Blades for Vertical Axis Wind Turbine

Today, environmental protection and the rational use of natural resources have become growing challenges. One of these aspects is energy producing with less impact on the environment. For some applications the small wind turbines can be a solution. In this paper are presented some aspects regarding the design and manufacturing technology of 500 W vertical axis wind turbine blades. The turbine will be installed in the urban environment so that requirements regarding rotor aesthetics and noise level will be considered. The optimal geometric parameters of the turbine rotor were determined by specialized MathCAD and elaborated in 3D modelling software. For the blades the NACA 0018 airfoil was used with the chord length of 110 mm and is constant throughout the length of the blade. The blades are helical and are 1800 mm long. To estimate the aerodynamic performance of the turbine rotor, a computational fluid dynamics model was developed using ANSYS CFX finite element analysis software. The authors proposed a new method for rapid prototyping of blades using fused deposition modelling procedure. In order to increase the mechanical properties, the blades were covered with several layers of glass-fibres reinforced polymer. Estimation the blade strength to operating loads was performed using Ansys Workbench software. The modelling of the composite material architecture on the blade surface was performed using the special ANSYS Composite PrepPost module. Several simulations were performed with different number of layers and stacking sequences. In order to prevent rotor over engineering the maximum rotation speed of 400 min−1 was accepted (equivalent to ≍12 m/s wind speed). Simulation of the blade strength to operating loads indicate values of around 40 MPa for shear stress (50% less than failure shear stress) and around 80 MPa principal stress (60% less than failure tensile stress). The maximum blade deformations of 3 – 4 mm shows that the blade is stiff enough at imposed operation conditions. For the blade manufacturing, based on the numerical analysis results, the configuration of the strength structure composed of 5 layers of GFRP was selected, which forms a total blade weight of 1895g.

Aerodynamic performance improvement analysis of Savonius Vertical Axis Wind Turbine utilizing plasma excitation flow control

Drag type Savonius Vertical Axis Wind Turbine (VAWT) has the advantages of the low total cost, simple manufacture and maintenance. Although the efficiency is low, it is suitable for residential areas with low wind speed. This article intends to use flow control methods to improve the efficiency of Savonius VAWT. Plasma excitation flow control is a relatively new type of active flow control technology. Therefore, this article uses the User-Defined Function (UDF) in ANSYS Fluent to load the plasma excitation sources on the Savonius VAWT blades. This paper numerically studies the influence of plasma flow control on the aerodynamic performance of a two-blade Savonius VAWT. Firstly, the changes in wind turbine performance under different excitation parameters are analyzed. The research results show that adding plasma exciter at a reasonable position can effectively improve the performance of the wind turbine, and the electric field force distribution in different directions will effect its range of action. Meanwhile, the voltage excitation frequency is also an influencing factor. Secondly, the principle and process of plasma excitation on the Savonius VAWT are analyzed. Finally, the relationship between the power consumed by the plasma and the increased power to drive the wind turbine is analyzed. Besides, the influence of plasma excitation on the overall performance of the wind turbine is summarized.

Aerodynamic Characteristics of a Single Airfoil for Vertical Axis Wind Turbine Blades and Performance Prediction of Wind Turbines

The design of wind turbines requires a deep insight into their complex aerodynamics, such as dynamic stall of a single airfoil and flow vortices. The calculation of the aerodynamic forces on the wind turbine blade at different angles of attack (AOAs) is a fundamental task in the design of the blades. The accurate and efficient calculation of aerodynamic forces (lift and drag) and the prediction of stall of an airfoil are challenging tasks. Computational fluid dynamics (CFD) is able to provide a better understanding of complex flows induced by the rotation of wind turbine blades. A numerical simulation is carried out to determine the aerodynamic characteristics of a single airfoil in a wide range of conditions. Reynolds-averaged Navier–Stokes (RANS) equations and large-eddy simulation (LES) results of flow over a single NACA0012 airfoil are presented in a wide range of AOAs from low lift through stall. Due to the symmetrical nature of airfoils, and also to reduce computational cost, the RANS simulation is performed in the 2D domain. However, the 3D domain is used for the LES calculations with periodical boundary conditions in the spanwise direction. The results obtained are verified and validated against experimental and computational data from previous works. The comparisons of LES and RANS results demonstrate that the RANS model considerably overpredicts the lift and drag of the airfoil at post-stall AOAs because the RANS model is not able to reproduce vorticity diffusion and the formation of the vortex. LES calculations offer good agreement with the experimental measurements.

Development of a wind turbine using 3D printing: A prospection of electric power generation from daily commute by car

The design, construction, and development of micro-turbines using 3D printing has been an important advance in the wind energy field to explore the possibility of offering viable alternative for the electric power generation, reducing the pollution caused by fossil fuels. In this work, a five blade vertical axis wind turbine prototype was tested. The components were designed using CAD and the turbine was manufactured by additive technology in a 3D printer. The material employed for 3D printing was commercial polylactic acid. The mechanical properties of the material used were obtained by tensile tests under the ASTM D-638 standard. On the other hand, a static structural simulation was performed by finite element method. Maximum tensile stress safety factor, maximum principal stresses, and fatigue analyses of the main turbine components were computed. The turbine performance as function of rotational velocity and relative wind velocity was analyzed implementing an experimental set-up.

Analytical Modeling of Modulated Rotating-Blade Noise : the Skipping Rope and the Darrieus Wind Turbine

The present study is about the modulations of the aerodynamic broadband noise heard from slowly rotating rotors with few blades. It is aimed at producing a fast-running prediction tool that could be used to assess the nuisance of Vertical-Axis Wind Turbines (VAWT) in the context of urban installation. The simpler case of a skipping rope that only involves part of the modulation effect is addressed as a first step. The rope is split into segments for which an instantaneous sound-radiation model exists to yield an overall spectrogram. Finally, its time signature is reconstructed by additive synthesis. After inspection of existing databases from oscillatory-airfoil experiments, needs for data representative of the dynamic stall of VAWT blades are seen as the missing block to reconstruct a synthetic spectrogram.

Structural optimization of H-type VAWT blade under fluid-structure interaction conditions

To reduce the errors caused by the rigid body hypothesis in the aerodynamics-structure coupling calculation and improve the structural performance, an optimum structure design with the consideration of the fluid-structure interaction are performed for the H-type vertical axis wind turbine (VAWT) blade. Based on the ANSYS Workbench platform, the geometric model, computational domain and grids of the wind wheel are constructed, the turbulence model, boundary conditions and composite material layers are set up, and the fluid and solid domains are solved in a coupled way. The single-objective structural optimization model in which the thicknesses of glass clothes, foam and gel coat, and the positions of two webs are taken as design variables is solved using the response surface optimization method to minimize the wind wheel mass. The frequencies and vibration modes of original and optimized blades with and without pre-stress and the transient characteristics of wind wheels in different wind speeds are investigated. The results indicate that after the blade optimization, the first-order frequency and critical speed become larger and other frequencies reduce for the static, single pre-stress and multiple pre-stresses states, and the maximum displacement, stress and strain of the wind wheel decrease under rated and extreme wind speeds, confirming significant performance improvements. The research provides useful guidance for the integrated design of structure and aerodynamics of wind turbine blades.

Double-Multiple Streamtube Analysis of a Flexible Vertical Axis Wind Turbine

Vertical-axis wind turbines (VAWTs) have drawn increased attention for off-grid and off-shore power generation due to inherent advantages over the more popular horizontal-axis wind turbines (HAWTs). Among these advantages are generator locale, omni-directionality and simplistic design. However, one major disadvantage is lower efficiency, which can be alleviated through blade pitching. Since each blade must transit both up- and down-stream each revolution, VAWT blade pitching techniques are not yet commonplace due to increased complexity and cost. Utilizing passively-morphing flexible blades can offer similar results as active pitching, requiring no sensors or actuators, and has shown promise in increasing VAWT performance in select cases. In this study, wind tunnel tests have been conducted with flexible and rigid-bladed NACA 0012 airfoils, in order to provide necessary input data for a Double-Multiple Stream-Tube (DMST) model. The results from this study indicate that a passively-morphing VAWT can achieve a maximum power coefficient (Cp) far exceeding that for a rigid-bladed VAWT CP (18.9% vs. 10%) with reduced normal force fluctuations as much as 6.9%. Operational range of tip-speed ratio also is observed to increase by a maximum of 40.3%.

Optimization of active blade pitching of a vertical axis wind turbine using analytical and CFD based metamodel

This study optimizes the active blade pitching (ABP) motion of a vertical axis wind turbine (VAWT) to increase its power output over a wide range of tip speed ratios (TSRs). The study begins by developing a simplified analytical model to compute the torque output of the VAWT as a function of its ABP. The analytical model is used to generate a preliminary optimal ABP at a single TSR. Next, computational fluid dynamics simulations are employed to develop metamodels of the response of the VAWT. These metamodels are used to determine the final optimal ABP. The optimization procedure is then repeated for different TSRs to determine an optimal ABP as a function of the TSR. The power outputs for the ABP-driven VAWT are compared with those of a fixed blade VAWT at different TSRs. The results indicate a 13% increase in the maximum power output of the VAWT compared to an optimal fixed pitch strategy. The torque outputs of the ABP-driven VAWT are then compared with those of a fixed blade VAWT at low TSRs. The results indicate that ABP would significantly improve the self-starting capability of VAWTs.

Analysis of Structural Vibrations of Vertical Axis Wind Turbine Blades via Hamilton’s Principle — Part 3: Pitch Angle and Equilibrium State

Pitch angle is one of the most important parameters of wind turbine blade. This study is aimed to investigate the effect of the pitch angle on the deformation of a VAWT. Lagrangian mechanics and Euler’s beam theory are used to derive the motion equations of linear structural vibration for straight blade vertical axis wind turbine blade with the pitch angle [Formula: see text]. The complete equations of motion take account of the 4-DOF deformation of flexural–flexural–torsion–extension as well as the material damping. Vibration analysis of generalized displacement about the equilibrium state (GDAES) is carried out with respect to the displacement of the equilibrium state (DOES), which is separated from the motion of vibration. After simplifying the equilibrium equation of 4-DOF into 1-DOF system, the exact solution of displacement [Formula: see text] of the equilibrium state is derived. The correction [Formula: see text] of [Formula: see text] due to the pitch angle and the characteristics of [Formula: see text] with constant linear speed are analyzed. Furthermore, we investigate the coupling effect of lateral bending and axial extension of the blade on [Formula: see text] is analyzed. Finally, the exact solution of [Formula: see text] is verified by the central difference method.

Numerical simulations on static Vertical Axis Wind Turbine blade icing

During the last decade, there was an increased interest in wind turbine icing. Most of the icing studies are related to horizontal axis wind turbine icing (HAWT). Vertical axis wind turbine (VAWT) icing is seldomly reported in the literature. Compared to the HAWT blade VAWT blade operates under various angles of attack. Therefore, ice accretion shapes on static VAWT blade must be considered under different angles of attack. In the present study, a novel approach to predict ice accretion shapes on VAWT is described. Ice accretion shapes are obtained at a range of angles of attack between −25° and 25° using FENSAP-ICE which is the state-of-art icing simulation tool. Moving reference frame (MRF) was used to consider rotating effect on droplet field. The present method helped to draw the following conclusions. Firstly, the whole leading edge is covered by ice. Secondly, in rime ice conditions smooth ice shape is obtained, which does not significantly affect aerodynamic performance. Whereas in glaze ice conditions bumpy ice shapes causing massive flow separation and lift force degradation. Finally, iced VAWT loses up to 60% of power performance due to rime ice conditions. In glaze ice conditions VAWT is unable to produce power.

Employing Computational Fluid Dynamics to Derive Beddoes–Leishman Model Airfoil Parameters for Vertical Axis Wind Turbines

AbstractThe blades of a vertical axis wind turbine (VAWT) experience large variations in the angle of attack at low tip-speed ratios and induce blade force oscillation. These unsteady aerodynamic effects must be considered in the VAWT aerodynamic modelling methodology by utilizing a dynamic stall model. The Beddoes–Leishman (B–L) dynamic stall model is a popular method to simulate the unsteady VAWT blade dynamic stall aerodynamics. However, a limitation of the B–L dynamic stall model is the number of the airfoil dependent parameters derived from both steady and unsteady experimental measurements. In this paper, a methodology is described to compute these B–L dynamic stall model airfoil coefficients utilizing a computational fluid dynamics (CFD) model. This method permits the calculation of the blade dynamic stall characteristics over a range of reduced pitch rates by employing a user-defined sliding mesh motion technique. Furthermore, the variation in the blade Reynolds number is accounted for by conducting simulations at the maximum and minimum VAWT envelope operating limits. Aerodynamic blade force experimental measurements are used to compare the predictions from a low-order model with airfoil data extracted CFD and experiments. This approach expands the applicability of the B–L dynamic stall model for large-scale VAWTs.

Performance Analysis of Reinforced Epoxy Functionalized Carbon Nanotubes Composites for Vertical Axis Wind Turbine Blade.

Synthetic materials using epoxy resin and woven Kevlar fiber nanocomposites were fabricated in the presence of functionalized multiwalled carbon nanotubes (F-MWCNTs). Kevlar-reinforced epoxy nanocomposites were designed to manufacture a small blade of vertical axis wind turbines (VAWT). It is important to estimate the deflection of the versatile composite turbine blades to forestall the blades from breakage. This paper investigates the effect of F-MWCNTs on mechanics and deflection of reinforced epoxy composites. The outcomes show that the mixing of F-MWCNTs with epoxy resin using a sonication process has a significant influence on the mechanical properties. Substantial improvement on the deflections was determined based on finite element analysis (FEA). The vortices from the vertical axis wind turbines (VAWTs) blades have a negative impact on power efficiency, since small blades are shown to be effective in reducing tip vortexes within the aerospace field. To support the theoretical movement of the VAWT blade, modeling calculations and analyzes were performed with the ANSYS code package to achieve insight into the sustainability of epoxy nanocomposites for turbine blade applications below aerodynamic, gravitational, and centrifugal loads. The results showed that the addition of F-MWCNTs to epoxy and Kevlar has a significant effect on the bias estimated by finite element analysis. ANSYS analysis results showed lower deflection on the blade using epoxy with an additional of 0.50 wt.% of MWCNTs-COOH at tip speed ratios of 2.1, 2.6, and 3.1.

Flow analysis and optimization of a vertical axis wind turbine blade with a dimple

In this study, the influences of the geometric characteristics of a dimple on the aerodynamic properties of a vertical axis wind turbine are investigated, and its configuration optimization that maximizes the wind turbine's performance is carried out. Three parameters that control the position, size and depth of the dimple are used to parameterize the dimple's configuration and to conduct optimization. With these parameters, when the flows around the wind turbines with various dimples are compared, several meaningful physical phenomena are found. First, a strong association between the position of a dimple and the power coefficient is found where the power coefficient increases as the position of the dimple approaches the trailing edge of the wind turbine blade. Second, high-performance enhancement tends to be achieved when a dimple is small, but this attribution becomes weaker as the dimple moves toward the trailing edge. Furthermore, when the flow of the optimal wind turbine is compared with the one without a dimple, a reduction of the blade wake and delay of the flow separation can be identified. Finally, the shed vortices from the optimal wind turbine blade are weaker and decay faster than the ones shed from the wind turbine without a dimple.

Vertical-Axis Wind Turbine Blade-Shape Optimization Using a Genetic Algorithm and Direct-Forcing Immersed Boundary Method

The aim of this study was to prove that an optimization method combining genetic algorithms with a direct-forcing immersed boundary method as a distinguished numerical method could improve the performance of vertical-axis wind turbine blades. The proposed direct-force immersed boundary (DFIB) flow solver was tested using the benchmark laminar flow problems (lid-driven flow, flow over a stationary cylinder, and vortex-induced vibration of the circular cylinder). Two cases were analyzed, one of a stationary airfoil and another of a rotating airfoil in a vertical-axis wind turbine. The analysis was carried out using two-dimensional flow simulations in a laminar flow regime. A NACA 0012 airfoil was used as the original airfoil cross section of the vertical-axis wind turbine. The proposed method successfully simulated the moving blade in the flow field, and the results revealed that the optimized wind turbine blade designed using the proposed method had an efficiency improvement of 5.61% compared to the original airfoil.

Numerical investigation of the effect of triangle strut in vertical axis wind turbine (VAWT)

Strut is used in vertical axis wind turbine (VAWT) to restraint the framework. In this study, struts are analyzed to show the pressure losses in VAWT. ANSYS computational fluid dynamics (CFD) software is used to investigate triangle strut in VAWT. This study aims to show a CFD simulation of struts, which affects the aerodynamic of VAWT. In CFD software, the aerodynamic of VAWT can be analyzed in terms of pressure losses in the struts. The simulation method starts by making a struts model, then meshing and setting up ANSYS's boundary conditions. The last iteration runs in ANSYS until convergence. Our results show the percentage of pressure losses with the variation of the angle of wind 0°, 20°, 40°, and 60° are 0.67 %, 0.52 %, 0.48 %, and 0.52 %. The effect of triangle strut in VAWT did not affect the wind flow to the VAWT blade. The results also indicated that the triangle strut could be applied in the multi-stage of VAWT system.

An investigation on the aerodynamic performance of a co-axial contra-rotating vertical-axis wind turbine

In this study, a conceptual co-axial contra-rotating vertical axis wind turbine (CR-VAWT) is conceived by splitting the single conventional vertical axis wind turbine (C-VAWT) blade length into two equal lengths forming two rotors separated by a small distance about the same axis of rotation. The available literature lacks much systematic investigation to find the best possible numerical setting and to extract an in-depth understanding of dominant factors limiting the aerodynamic performance of the CR-VAWT using CFD, constitutes the primary focus for the present study. Results from the CFD were compared with the analytical model formulated using FAST along with literature results. The power output of the CR-VAWT agrees well in the low wind speed and variation increases gradually as the wind speed increases compared to C-VAWT, however, the thrust is in good agreement at all wind speeds. The wake velocity directly behind the C-VAWT and CR-VAWT follows the general trend but differences were noticed to a distance accordingly, with the wind speed. The power performance reduces gradually with increasing speed for a fixed blade pitch angle. The present adopted concept of CR-VAWT are found to have negligible aerodynamic torque and side-side force action at the tower base.

Structural Design and Stress Analysis of a Helical Vertical Axis Wind Turbine Blade

In this study, a Computational Fluid Dynamics (CFD) model is designed to investigate the structural analysis of a helical Vertical Axis Wind Turbine (VAWT) blade which is using National Advisory Committee for Aeronautics (NACA) 0018 airfoil and numerical calculations are conducted by using Comsol Multiphysics. The main objective of this study is to determine that the strength of the turbine blade against bending caused by increased wind speeds is sufficient for the selected turbine blade material. This paper presents also an investigation of the effects of different wind speeds on the structure of a helical VAWT blade that is fixed to the support arm which is attached to the VAWT’s main shaft. In this study, a turbine blade which is placed in an air flow field is subjected to approaching strong wind with different velocities. The model solves for the flow around the blade and the structural displacement due to the fluid load. This investigation consists of two main parts: Solving for the fluid flow around the turbine blade with a free stream velocities of 1, 3, 5, 7, and 9 m/s, and Studying the deformation of the turbine blade caused by the fluid load. The risk of failure according to the von Mises criterion for the ductile materials such as aluminum is also investigated.

Chicamocha canyon wind energy potential and VAWT airfoil selection through CFD modeling

The use of vertical axis wind turbines (VAWT) in Colombia could tackle the energy distribution difficulties as large parts of the territory are not connected to the electrical grid. The present research experimentally determines the wind resource available of a rural place known as Chicamocha’s canyon and selects the airfoil for a VAWT blade through CFD modeling. By using the mean wind speed of the location, the performance of the NACA0018 and DU06W200 airfoils is evaluated in terms of the lift and drag coefficients through a 2D CFD modeling using OpenFOAM and the “Spalart-Allmaras fv3” turbulence model. It is found feasible the use of wind energy at the location where the mean year density power is 485 [W/m2], and the DU06W200 airfoil is suggested for constructing the blades of a VAWT, as its aerodynamic efficiency (cl/cd) overcomes by 14% the commonly used NACA0018.