Darrieus Vertical Axis Wind Turbine Research Articles

Recovery of electrical power from exhaust air—role of vertical axis wind turbine

AbstractThis article explores the potential of regeneration of power from unnatural wind sources with the help of vertical axis wind turbines (VAWT). Researchers are searching for urban as well as industrial wind sources, which can be useful as the natural wind source to obtain electrical energy and utilize it. The wind sources considered here are the exhaust of the cooling or ventilation fans used in buildings, industries, and other places. The Darrieus VAWT extracts wind power from the exhaust air and reduces the power consumption of the concerned electrical drives. These uncommon energy sources have an inherent capability to recover a significant amount of energy without polluting the environment with less payback period. Recovered energy can be suitably converted into electrical energy and may be fed back to the power grid without any pollution, thus minimizing the total energy consumption of the building and reducing the cost operations. A detailed study of experimental models with different types of assembly and turbine models is conducted here with power outputs and operational behaviors on the existing systems. Various parameters and factors for existing and new applications are in detail that show the system has no negative impact on regular operation.

Addressing VAWT Aerodynamic Challenges as the Key to Unlocking Their Potential in the Wind Energy Sector

While the wind turbine industry has been primarily dominated by horizontal-axis wind turbines, the forefront of knowledge of these turbines has revealed significant challenges in various aspects, including manufacturing, structural design, cost, and maintenance. On the other hand, the advantages associated with Darrieus vertical-axis wind turbines (VAWTs) demonstrate significant potential that can address the existing challenges of the wind turbine industry. Current work aims to investigate the practicality of this potential for the wind energy sector. To this end, the benefits of employing Darrieus turbines for domestic and industrial applications, isolated operation, and on/offshore windfarm applications have been explored. It is apparent that Darrieus VAWTs are better suited to a wide range of environments, whether they are deployed in isolation or integrated systems, and whether they are utilized on a small or large scale. Darrieus VAWTs are adaptable to urban unsteady variable wind, are less expensive on large scales, provide higher power density at the windfarm level, and provide stability for offshore platforms. Nevertheless, challenges remain in fully harnessing VAWT potential rooted in their complex aerodynamics. This serves as a primary challenge for VAWTs to address the challenges of the wind turbine industry in line with the 2050 roadmap.

Numerical and experimental investigation of Darrieus vertical axis wind turbines to enhance self-starting at low wind speeds

Wind energy, being renewable, cost-effective, and environmentally friendly, has attracted global attention. However, due to suboptimal performance and limited research, vertical axis wind turbines (VAWTs) lag behind horizontal axis wind turbines (HAWTs) in commercial applications, particularly for large-scale installations. This study aims to improve the self-starting capability of the Darrieus VAWT. While some parameters, such as the number of blades (N) and solidity (σ), have been studied extensively, the airfoil shape has not received as much attention. This study compares the performance of National Advisory Committee for Aeronautics (NACA) airfoils and Selig airfoils at a Reynolds number (Re) of 40,673. The investigation revealed that the NACA0015 airfoil exhibited the highest peak power coefficient (Cp). Further analysis utilizing an advanced double multiple stream tube (DMST) code in MATLAB increased the peak Cp by adjusting the thickness-to-camber ratio (t/c) of the NACA0015 airfoil, resulting in a 12.50 % increase in the maximum achievable Cpat a Re of 40,673. This study compared four modes of VAWT operation, utilizing the NACA0015 airfoil and a modified NACA0015 airfoil for both straight-bladed and embossed-bladed VAWTs. The results showed that the modified NACA0015 airfoil for embossed-bladed VAWTs exhibited the best self-starting capability and rotation at wind velocities of 1 to 9 m s-1. Additionally, the self-starting force required by embossed-bladed VAWTs was lower than that needed by straight-bladed VAWTs due to the ability of the embossed material to enhance airflow attachment to the VAWT and suppress turbulence.

Comprehensive study of vortices interaction and blades height effect in a Darrieus vertical axis wind turbine with J‐type blades

AbstractThere is a growing demand to improve the performance of vertical axis wind turbines to facilitate their commercialization for application in urban areas. This study utilizes a 3D numerical analysis to examine the influence of different vortices generated on turbine efficiency with straight and J‐type blades. The numerical simulation of this study employs the Reynolds‐Averaged Navier–Stokes equations and ‎sliding ‎mesh techniques ‎to more accurately model the rotational motion of blades about the turbine axis in relation to the ‎wind. Comparing the output ‎torque and the flow field at different span‐wise sections, the J‐type blades achieve better ‎performance at mid‐spans where the effect of stall vortices is dominant. Conversely, the lower ‎performance of J‐type blades is seen at tip spans due to stronger tip vortices. Investigations also ‎reveal the criticality of the downwind region on the overall performance at high tip speed ratios. It is observed that by ‎increasing the height, the tip vortices are limited to the tip sections, and stall vortices expand further ‎along the blade. At TSR = 1, the improvement by J‐type blades rises from 10% at a height of 0.8 m to 44% ‎at 3 m. The growth in height at lower wind speeds becomes more beneficial. Compared to the straight blades, the self‐starting ‎generated torque by J‐type blades for heights of 0.8, 1.2, and 1.6 m, are improved by 15.6%, ‎‎26.9%, and 34.7%, respectively. Overall, it is concluded that by increasing the blade height, the superiority ‎of the J‐type blade becomes more noticeable as the blade mainly contributes to suppressing the stall ‎vortices effect where the tip vortices effect is not presented. ‎

Blade Pitch Angle Regulation for H-Type Darrieus Vertical Axis Wind Turbine: A Review

Blade Pitch Angle Regulation for H-Type Darrieus Vertical Axis Wind Turbine: A Review

Effect of baffles on efficiency of darrieus vertical axis wind turbines equipped with J-type blades

This study investigates the effects of incorporating baffles in J-type bladed vertical axis wind turbines. The objectives are to analyze the behavior of vortices and their impact on turbine performance and to explore various locations for placing the baffles along the J-type blades. The 3D numerical simulations of the current study applies the sliding mesh techniques to better model the rotational motion of blades about the turbine axis with respect to the wind. The results show that mounting zero-thickness baffles over the tips of the blades effectively reduces vortex leakage, minimizes tip vortices, and increases the pressure differential across the sides of J-type blades leading to a significant improvement of the turbine performance. At low tip speed ratios (TSRs) of 0.5, 0.75 and 1, in particular, the torque generation in comparison with conventional NACA0021 straight bladed turbines has been improved by up to 49.5 %, 38.2 %, and 28 %, respectively. Considering a wide range of TSRs, on average, the implementation of baffles results in a 17.5 % increase in torque generation. The effect of the baffle thickness on generated vortices and their evolution along the course of flow is also investigated to show how the zero-thickness baffles improves the blade aerodynamics.

Numerical investigation of the effects of increased and mixed chord lengths for a 4-bladed darrieus vertical axis wind turbine

Abstract Increasing amounts of study and research on vertical axis wind turbines (VAWTs) have shown that they are a competitive option in wind energy power generation. However, the VAWT’s primary drawback is low power efficiencies. Although there are several studies on the effects of solidity on Darrieus VAWT performances, few focus on the effect of the aerofoil chord length. Hence, in the present study, 2D numerical simulations are performed to explore the effects of different aerofoil chord lengths on the performance of a Darrieus VAWT. The simulation was first validated with the experimental data from the literature. The studied turbine is a 4-bladed VAWT fitted with NACA0021 blades with an original chord length, c of 85.8 mm and another with an increased chord length of 1.2 c (102.96 mm). Additionally, a modified rotor geometry with mixed chord lengths of c and 1.2 c to improve turbine performance is proposed and investigated. The coefficients of power (C P) and torque (C T) for tip speed ratios (TSRs) between 1.4 and 3.3 for each of the turbines are evaluated and comparatively analysed. All the data was obtained using the computational fluid dynamics (CFD) software ANSYS Fluent in conjunction with the shear stress transport (SST) k−ω turbulence model. The findings show that the turbine with 1.2 c chord length and hence larger solidity outperforms those with smaller chord lengths at low TSRs. However, their performances decrease significantly at TSRs above 2.5, resulting in up to 86.1% lower C P values. The mixed chord lengths case was successful at achieving significantly higher C P values at both TSR ranges with only a decrease of 3.03% in maximum C P at its optimum TSR.

Investigation on fixed pitch Darrieus vertical axis wind turbine

Small-scale Darrieus wind turbines have a wide scope in areas that are isolated from the power grid for such small-scale household applications. Applications of wind turbines on house roofs are one potential way to generate electricity from wind energy harvesting in low-wind urban locations. This work studies the aerodynamic behavior of a vertical axis wind turbine based on a MATLAB programming mathematical model. The NACA0021 airfoil profile blade was used in this present research investigation. The turbine was fabricated with dimensions such as chord length, c = 95 mm, blade height, h = 600 mm, and turbine diameter, D = 600 mm. The experimental results of the turbine for air velocity from 1 to 12 ms−1 were used in this paper and compared with analytical results. It has been observed that the fixed-pitch turbine does not start by itself at a low air velocity of 1 to 5 m/s due to a minimum and negative torque.

A comprehensive investigation on Darrieus vertical axis wind turbine performance and self-starting capability improvement by implementing a novel semi-directional airfoil guide vane and rotor solidity

Darrieus vertical axis wind turbine is classified as a lift-based power generation turbomachine. However, it is burdened with the limitations of mid-range efficiency and requiring initial torque for startup. The quest to improve the turbine's performance has focused on enhancing its aerodynamic performance and self-starting ability. One of the most effective approaches is to flow control and injection toward the rotor blades. This computational fluid dynamics research study utilizes a novel geometry known as the “Semi-Directional Airfoil Guide Vane” (SDAGV) to inject airflow smoothly and effectively toward the rotor blades at the upstream section. The investigation found that using a two-passage SDAGV increased rotor efficiency by up to 55% at a tip speed ratio (TSR) of 2.5. The pressure distribution analysis showed that azimuth angles between 90° and 135° significantly impacted the rotor's self-starting ability. Additionally, studying the turbine solidity revealed that a five-bladed rotor with SDAGV had a higher self-starting capability and efficiency than a two-bladed rotor with SDAGV. This was because its power coefficient (Cp) was approximately 160% greater at TSR = 1.4. Due to blade-to-blade interaction, high-solidity turbines from TSR = 2 onwards face performance challenges, which means their efficiency drops in the low-TSR range.

Design of a Floating Vertical Axis Wind Turbine for Wind-Wave Basin Experiments

This paper presents the design and manufacturing of two novel small floating Darrieus vertical axis wind turbines (VAWT) developed for a wind-wave basin test campaign. As with typical designs, the rotor design needed to satisfy the traditional structural safety requirements (such as strain, deflection, resonant-free dynamics) from design standards along with other manufacturing and assembly constraints. In addition, for this particular design, some special conditions are present as the facility (the wind-wave basin itself) and use of existing Floating Offshore-wind and Controls Advanced Laboratory (FOCAL) semi-submersible floating platform (originally designed for HAWT test) imposed an additional set of design requirements including wind speed and size constraints, and specific, target overturning moments and rotor mass. Addressing all these constraints (facility, existing hull, structural safety, and manufacturing) presented a challenging design task in this case, thus the focus of this paper is presenting the design approach and results leading to final designs satisfying all these competing requirements. Using the presented design process, two Darrieus troposkein-shaped vertical axis wind turbines (two-bladed and three-bladed versions) were designed and manufactured, after ensuring compliance with all the design requirements. The presented study can aid researchers interested in developing similar floating turbine test campaigns.

Multi-objective optimization study on the performance of double Darrieus hybrid vertical axis wind turbine based on DOE-RSM and MOPSO-MODM

The Double Darrieus Vertical Axis Wind Turbine (DD-VAWT) effectively enhances wind energy efficiency at low tip speed ratios. In this study, the multi-objective optimization method is constructed for DD-VAWT. The optimization objective is to enhance the power coefficient as well as reduce the maximum instantaneous torque coefficient, while decision variables include the inner ring wind turbine diameter, inner ring wind turbine height, inner ring wind turbine blade airfoil chord length and inner and outer ring wind turbine phase angle. Firstly, the computational fluid hydrodynamics model of DD-VAWT is established and validated by experimental data from the literature. Then, the regression model between critical structural parameters and power coefficients, maximum instantaneous torque coefficients is constructed using response surface analysis. Finally, the multi-objective particle swarm optimization algorithm is used to optimize the objective and the optimal solution is selected from the Pareto frontier solution. This work provides a direction to improve the operating performance of DD-VAWT at low tip speed ratios as well as contributes to energy saving and emission reduction.

Computational fluid dynamics analysis on performance assessment of Darrieus-type vertical axis wind turbine using NACA0016, NACA0019 and NACA0020 airfoil sections

The efficiency of a vertical-axis wind turbine is remarkably less than a horizontal-axis wind turbine and consequently, the most important challenge of the former one is to enhance its aerodynamic performance. An earlier study shows that the selection of an efficient airfoil shape is an important criterion for enhancing the overall performance of a wind turbine. The objective of the present work is to perform the two-dimensional Computational Fluid Dynamics simulation of Darrieus Vertical axis wind turbine using NACA0016, NACA0019 and NACA0020 airfoils which are neither too thick nor too thin. Furthermore, the performance of these three airfoils is compared with two established airfoils, namely NACA0015 and NACA0018. The result reveals that the overall power coefficient of NACA0019 airfoils resulting from the CFD simulation is significantly higher than that of NACA0015. Therefore, the NACA0019 airfoil may be considered one of the effective alternative airfoils for the Darrieus VAWT. Highlights Simulation of vertical axis wind turbine using NACA0016, NACA0019 and NACA0020 airfoils Unsteady URANS studies are carried out to investigate the performance of the airfoils Among the blade profiles studied in this work, NACA 0019 offers superior fluid mechanical performance

A Numerical Study of Blade Geometry Effects in a Vertical-Axes Wind Turbines

Several geometrical elements influence the aerodynamic properties of the Darrieus vertical axis wind turbines (VAWTs). Many extant studies have examined properties, such as solidity, pitching axis position (x/c), length of chord (c), blade quantity (N), diameter (d) of the rotor, and aspect ratio. However, not many have examined the shape of the airfoil (AF), which is a vital property that remains to be thoroughly investigated. Therefore, this present study used computational fluid dynamics (CFD) to investigate many airfoils blade characteristics, such as blade thickness (BT), maximum camber ratio (MCR), MCR location (MCRL), and air speed (AS), to determine their impact on VAWT performance. The results demonstrate a blade thickness BT of 10 to 12%, MCR of 0 to 22%, and MCRL of 24 to 23% yield a comparatively high coefficient of power, adequate optimal blade rotation to airspeed ratio (TSR), broader operational area, and high band efficiency while air velocities of 15 to 10% yield a comparatively higher power coefficient.

Flow analysis and sensitivity study of vertical-axis wind turbine under variable pitching

The general frame of the present study falls under the umbrella of ongoing research and innovation in wind energy technology to improve the efficiency and reliability of vertical-axis wind turbines (VAWTs) in terms of design and control. While blade pitching is foreseen as a solution to minimize boundary layer separation and maximize the lift force during the entire cyclic blade operation (effectively enhancing the performances of VAWTs), conclusive research on active blade pitching mechanisms in low wind speed regions is limited because of the 3D complex aerodynamic around VAWT blades. The paper reports a holistic study on active blade pitching solutions to enhance the performance of H-rotor Darrieus VAWTs for different turbine design parameters, i.e., geometrical (different number and airfoil thickness, and solidity) under several operational conditions (Reynolds number (Re), and tip speed ratio (TSR)). In this study, a variable blade pitching technique, adapted for periodic variation of the angle of attack, is incorporated in a high-fidelity two-dimensional VAWTs transient Computational Fluid Dynamics (CFD) model to eliminate the dead band of small-scale wind turbines operating at low wind speed regions and increase the performance coefficient Cp at different TSRs. Sliding mesh and remeshing to capture the blade pitching are used to manage the rotor rotation. The CFD model is validated against experimental data from the literature. The results indicate that the local widening of the angle of attack (AoA) for each NACA0015 airfoil produces a Cp of 0.44, which represents 81% enhancement in the Cp at TSR of 1.5. Moreover, the study shows that increasing the number of blades or extending the blade chord length can eliminate the dead band of wind turbines. Furthermore, the maximum possible torque for 3- and 4-bladed rotor designs is achieved using the variable pitching mechanism.

Numerical Investigation on J‐Shaped Straight‐Bladed Darrieus Vertical Axis Wind Turbines Equipped with Gurney Flaps

This study provides a numerical investigation about J‐shaped straight‐bladed Darrieus vertical axis wind turbines equipped with outboard, inboard, and two‐sided Gurney flap (GF). The performance of the turbines is examined for different GF heights and tip speed ratios (TSRs). The aerodynamic analysis is carried out using power curves, vorticity field, and pressure field surrounding the wind turbine. The results indicate that employing the inboard GF effectively enhances the turbine’s performance by harnessing the drag force in the desired direction and postponing the flow separation up to 14° of azimuth angle. The inboard GF with a height of 0.75% chord length exhibits the best performance among the GFs, showing an increase in output power at higher TSRs up to 12.35%. Conversely, the use of outboard and two‐sided GFs of any height cannot improve the turbine efficiency.

Improvement in the performance of Darrieus vertical axis wind turbine using J-type airfoil shape

Improvement in the performance of Darrieus vertical axis wind turbine using J-type airfoil shape

Novel CFD and DMST Dual Method Parametric Study and Optimization of A Darrieus Vertical Axis Wind Turbine

The deteriorating effects of greenhouse gases resulting from the use of fossil fuels have led to increased public attention to renewable energy sources, with wind energy being a particularly favored option. This prompted the development of various wind turbine types' efficiency. This study intends to explore the influence of key design parameters consisting of the number of blades, blade chord length, helical angle, and J-shaped blade on the performance and self-starting ability of a Darrieus VAWT. Furthermore, implementing an efficient optimization model to obtain maximum power based on the numerical findings. To achieve this, two different numerical modeling approaches, namely Computational Fluid Dynamics (CFD) and Double Multi-Streamtube (DMST), have been applied. The results indicated that employing a higher blade number and chord length enhances the starting capability of the turbine. Moreover, increasing the helical angle to 60° reduces the generated torque fluctuations. Inspired by the design of the Savonius turbine, the implementation of a J-shaped airfoil boosted the Cp at low TSR. Finally, the Kriging optimization method has been employed to optimize the design parameters explored through CFD analysis. The outcomes showed that the optimum configuration of the examined Darrieus VAWT comprises a 3-bladed rotor with a blade chord length of 0.04 m and helical angle of 0° and a J-shaped blade length ratio of 0.68. This configuration yields an 10% increase in efficiency at the optimum TSR.

Investigation of the effect of critical structural parameters on the aerodynamic performance of the double darrieus vertical axis wind turbine

Double Darrieus Vertical Axis Wind Turbine (DD-VAWT) can efficiently capture wind energy at low tip speed ratios. In this work, the laws governing the effects of critical structural parameters, such as diameter of inner ring wind turbine, height of inner ring wind turbine, inner ring wind turbine blade airfoil chord length, and phase angle of inner and outer ring wind turbine, on the power performance and aerodynamic load are investigated. The power coefficient increases from 0.1670 to 0.2403 when the diameter of the inner ring wind turbine decreases from 1600 mm to 400 mm. The power coefficient increases from 0.1755 to 0.2135 when the height of the inner ring wind turbine increases from 600 mm to 1200 mm. The power coefficient increases from 0.1773 to 0.2135 when the chord length of the inner ring wind turbine blade airfoils increases from 0.15 m to 0.3 m. The power coefficient decreases from 0.2135 to 0.1976 when the phase angle of the inner and outer wind turbine is increased from 0° to 135°. Finally, based on Taguchi's experiments and grey correlation analysis, it is known that the most influential weight on the power coefficient and the maximum instantaneous torque coefficient is the airfoil chord length of the inner ring wind turbine blades, and the least is the phase angle of the inner and outer ring wind turbines. This work provides a reference for enhancing the DD-VAWT's performance.

Intracycle RPM control for vertical axis wind turbines

AbstractThe wind energy market is currently dominated by horizontal axis wind turbines (HAWTs); however, vertical axis wind turbines (VAWTs) are emerging as a design alternative, especially for deep‐water offshore siting due to their low center of gravity, ease of access to drivetrain components, and overall simplicity. Due to the absence of a pitch mechanism in large‐scale Darrieus VAWTs, stall control has often been used to manage power and loads. Introducing a pitching mechanism in H‐type VAWTs has been studied, but this diminishes the mechanical simplicity advantage, and the use of a pitching mechanism in a large‐scale Darrieus‐type VAWT is not practical. This work examines an innovative, alternative method to control the rotor dynamics of a large‐scale 5 MW VAWT to maximize power while constraining loads without introducing any new or complex mechanical elements. This control strategy is termed intracycle revolution per minute (RPM) control, where the rotational speed of the turbine is allowed to vary in an optimal fashion with the azimuthal location of blades as opposed to typical constant RPM operation. An optimization framework is formulated for an open‐loop optimal control problem and solved to maximize power subject to constraints on aerodynamic design loads. Results are presented to demonstrate the benefits and the performance limits of intracycle RPM control for large‐scale 5 MW Darrieus VAWTs, namely, (1) power production (quantified in terms of AEP) that can be increased subject to baseline load limits and (2) opportunities to significantly increase AEP or decrease loads via intracycle RPM control that are examined for both two‐bladed and three‐bladed VAWTs.

Leading Edge Radius Effects on VAWT Performance

Numerous studies have been conducted to investigate effect of blade geometry of vertical axis wind turbine performance. Most of the evaluations have focused on the airfoil series and airfoil geometry parameters such as thickness and camber of the airfoil. Few studies have examined the effect of other blade geometry parameters on the vertical axis wind turbine performance. In the present study, the effect of geometric change in leading-edge radius (LER) of a vertical axis wind turbine performance has been numerically studied. Hence, modified NACA 0021 airfoil profiles were created using the geometric method (CST). Then, the flow behavior around a Darrieus vertical axis wind turbine was simulated under the influence of the reduction and set-up coefficients of the leading-edge radius at a constant wind speed of 9 m/s and a tip speed ratio of 1.5 to 3.5 using the computational fluid dynamics. Additionally, the effects of the examined parameter (leading-edge radius) on fluid flow and aerodynamic performance coefficients, including the coefficients of power and torque, were investigated. The results indicated that the leading-edge radius affected the near wake flow of the turbine, and the optimization of leading-edge radius parameter controls the dynamic stall and reduces the formation of a vortex. Finally, the optimization of LER revealed that at 20% reduction in the LER the performance of the turbine at tip speed ratio of 1.5 was increased by more than 50%. This reinforces the self-starting capability of a Darrieus wind turbine.