Vertical Axis Wind Turbine Blade Research Articles

Optimal Design of Anti-Icing Blunt Trailing-Edge Wind Wheel for H-Type Vertical Axis Wind Turbine Under Operating Conditions

Abstract A novel optimization method is developed for the design of an anti-icing blunt trailing-edge wind wheel of H-type vertical axis wind turbine (VAWT) based on the quasi-steady-state icing. The parametric expression of the airfoil is given using the mean camber and thickness functions, the blunt trailing-edge is constructed by the rotation and zoom of coordinates, and then through the aerodynamic design theory, the geometry control equations of the blunt trailing-edge wind wheel are established. The icing process using Solution and Icing modules is repeated at equal interval azimuths to obtain the ice on the wind wheel per revolution. The optimization model is solved using particle swarm optimization (PSO) algorithm integrated with computational fluid dynamics (CFD) method to maximize the wind energy utilization in both ice-free and icing conditions. Significant improvements are realized for flow and aerodynamic characteristics, confirming that the optimization method provides important guidance for an anti-icing design of VAWT blades.

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.

Vertical Axis Wind Turbine for Low Wind Speed Environment: Effect of Scoop Harmony Blade

The wind condition in Malaysia is in the low-speed category with an average speed of 1 ms-1 to 4 ms-1. Effect of ground level relies significantly on the wind speed distribution. Despite these conditions, it is less suitable for the development of horizontal wind turbine as an energy source. The obvious weakness is the lack ability to self-start and predict the wind direction thus affects the energy efficiency output. To overcome this problem, improvement of the vertical axis wind turbine design is observed to be the solution in replacing horizontal axis wind turbine. Hence, this study is to investigate a suitable type of vertical axis wind turbine blade design for the best performance RPM output in a low-speed wind environment. The investigation was conducted in a Longwin LW-9300R subsonic wind tunnel at 0 ms-1 to 10 ms-1 wind speed condition from three wind turbine blades specified as Solid Harmony, Scoop Harmony and Conventional Savonius blade with angle of 90º, 135º and 180º to determine the highest RPM productivity. Result shows that Scoop Harmony blade delivers the highest RPM blade output while Savonius 180º is seen to have the highest self-start blade achieved at 64 rpm at 1 ms-1 wind speed. However, Solid Harmony shows an acceptable range TSR of 0.5 with difference of 23% lower than Scoop Harmony. This shows that both Scoop Harmony has a higher performance RPM but Solid Harmony still has the potential design to be applied at low-speed condition due to its low TSR output.

Simulation Study of the Effect of Wind Speed and Material Type on the Mechanical Properties of Vertical Axis Wind Turbine Blades

Wind energy is a clean and fast-growing renewable energy source that can be harnessed using wind turbines. In a Vertical Axis Wind Turbine (VAWT), turbine blades are a crucial factor, and their fiasco leads to wind turbine failure. However, references to VAWT blade structural analysis are very limited. Therefore, the study was carried out to determine the material with the lowest degree of deformation without structural failure. The finding could be used as a recommendation in the material selection of Savonius type vertical axis wind turbine blades. The study used materials such as aluminum, stainless steel, and fiberglass. The analysis was carried out by simulating using ANSYS software. Computational Fluid Dynamics (CFD) was used for determining the loading by providing speed variations at 3 m/s, 4 m/s, 5 m/s, and 6 m/s. The Finite Element Analysis (FEA) method was applied to analyze the structure, which shows the results of total deformation, equivalent stress, and safety factor. The total deformation results from the aluminum blades showed values of 109.55 mm, 190.73 mm, 299.25 mm, and 425.39 mm. The safety factor values of 4.4049, 2.5166, 1.5647, and 1.1348 revealed that it was also technically safe. Aluminum material can be recommended to be used in the manufacture of Savonius type vertical axis wind turbine blades because of its low price, lightweight, corrosion resistance, and sufficient durability, as revealed from the results of total deformation and safety factor values.

Nonlinear Structural Vibration of Multi-Megawatt Vertical Axis Wind Turbine Blades-Part 1: Derivation of Motion Equations

Replacing fossil fuels with renewable energy is one of the important means to improve energy scarcity and environmental protection, and is of great significance for achieving sustainable development of human society. Vertical axis wind turbine (VAWT) is one of the key equipment for applying green energy — wind energy. During the operation of VAWT, its blades not only have to withstand periodic aerodynamic loads, but also suffer from centrifugal force effects and the Coriolis force effect caused by coupling with multi-dimensional deformation. The complex stress situation makes the blades susceptible to damage, resulting in structural resonance and instability of aeroelastic stability. This paper applies the Euler beam model and Hamilton principle to establish a nonlinear structural vibration motion equation for large-span vertical axis wind turbine blades with fully coupled four-dimensional deformation (i.e. lateral bending deformation, chord bending deformation, axial torsion deformation, and axial tensile deformation), and retains the nonlinear term of the motion equation to the third-order infinitesimal. Separating the motion equation into equilibrium equation and dynamic equation, it can be seen that the displacement of equilibrium state caused by the centrifugal force of the rigid body exists in the form of a coefficient in the dynamic equation, which will have an impact on the dynamic characteristics. This modeling work can provide a research foundation for exploring the dynamic characteristics and aeroelastic stability of VAWT blades in the future.

Blade strain analysis from field measurements on a vertical axis wind turbine

In this paper, the 10 kW WindQuest Vertical Axis Wind Turbine (VAWT) has been instrumented by strain gauges during its trials in the Ifremer in situ test site of Brest to study the effects of the structural dynamic response of the blades under operating conditions. Static and dynamic effects have been investigated as a function of the rotational speed when the rotor operates under stable wind conditions. The analysis segregates the influence of the gravitational, inertial, and aerodynamic loading components on the flapwise bending stress of the blades. The study of the cyclic variations on the blade strain at different Tip-Speed Ratios leads to the identification of the dynamic stall effect on the unsteady loads, while the spectral analysis describes the system eigenfrequencies excited by the interaction of the wind and the structure's motion. The results provide useful data to validate numerical models for VAWT blades with similar design and evaluate the structural fatigue.

On the estimation of the angle of attack for vertical axis wind turbines

Purpose This paper aims to investigate the problem of estimating the angle of attack (AoA) and relative velocity for vertical axis wind turbine (VAWT) blades from computational fluid dynamics data. Design/methodology/approach Two methods are implemented as function objects within the OpenFOAM framework for estimating the blade’s AoA and relative velocity. For the numerical analysis of the flow around and through the VAWT, 2 D unsteady Reynolds-averaged Navier–Stokes (URANS) simulations are carried out and validated against experimental data. Findings To gain a better understanding of the complex flow features encountered by VAWT blades, the determination of the AoA is crucial. Relying on the geometrically-derived AoA may lead to wrong conclusions about blade aerodynamics. Practical implications This study can lead to the development of more robust optimization techniques for enhancing the variable-pitch control mechanism of VAWT blades and improving low-order models based on the blade element momentum theory. Originality/value Assessment of the reliability of AoA and relative velocity estimation methods for VAWT’ blades at low-Reynolds numbers using URANS turbulence models in the context of dynamic stall and blade–vortex interactions.

Investigation of bamboo-based vertical axis wind turbine blade under static loading

Bamboo fiber composites are recyclable, low cost, high strength, and biodegradable compared to synthetic composites. Fiber-reinforced polymer composites such as glass and carbon fibers are extensively used as wind turbine blades followed by a major challenge of recycling and waste disposal etc. The present work investigates the suitability of bamboo-epoxy composite for vertical-axis wind turbine blades. The NACA 0015 and NACA 4415 blade profile has been chosen for study. The static structural analysis of blades is performed using various cross-ply and angle-ply layups. Results demonstrated that layup [45°/90°/0°/-45°]S obtained the minimum values of stress and deflection. The effect of shear webs is also analyzed. It is observed that the blade with two shear webs showed the minimum values of stress and deflection. The unidirectional strength of the composite material is also compared with the maximum design stress and found under acceptable limits. Additionally, the stress and deflection of the bamboo composite blades are compared with conventional blade materials. The stress and deflection on the non-symmetric bamboo-epoxy composite blade with double shear webs are obtained as 15.84 MPa and 4.45 mm which is observed to be decreased by 70.98% (stress) and 1.11% (deflection) respectively in comparison with glass-epoxy blade. Through the structural analysis, it is recommended that the designed blade with natural bamboo composite is acceptable for structural safety.

Energy Generation by Advanced Various Renewable Technology

Aim of this project is to production of electric energy using variable renewable technology, which is to be provided for the daily purpose. About 50% of the electricity used in India is generated by thermal power plants, which release a lot of toxic pollutants into the air and have a lot of negative environmental effects. Due to the high demand for electricity and the rising costs of coal and fuels, it has recently been noticed that there is an electricity crisis or shortage in India and other nations following the pandemic era. Since India is a nation that is constantly developing, there is a rising need for electricity. After all, coal is a type of fossil fuel whose supply will eventually run out, necessitating a shift to renewable technology. Over the road dividers, a vertical-axis wind turbine (VAWT) is being installed. As the car moves along the road, wind turbulence becomes trapped in the VAWT's blades, causing them to rotate and produce electricity. Additionally, we mount the solar panel over the VAWT, which generates electricity as well. When we apply this concept, a small hydroelectric power plant is built if there are nearby water bodies, such as ponds, rivers, dams, and water treatment facilities. A large amount of electricity can be generated by combining three renewable energy sources. It helps you reduce pollution in the atmosphere, earn carbon credits, and make energy generation economical. In our study, we found that about 0.5–1 KW of electricity can be generated in an hour, depending on the availability of wind turbulence and light intensity. This technology is capable of supplying electricity to one home

Blade Structure Analysis of 2 MW V-Shaped Vertical Axis Wind Turbine Using Numerical Simulation

The intensive research on large-scale Vertical Axis Wind Turbine (VAWT) couldprovide an alternative to Horizontal Axis Wind Turbine (HAWT) in offshore deployment for the future. Regarding this fact, this article develops a conceptual design of the VAWT blade structure and analyzes its feasibility using numerical simulation. The blade structure is designed for 2 MW Darrieus type V- shaped VAWT. The blade is tapered, 90m long, and inclined at 35° to the vertical axis. Initially, the blade design is tested for ultimate strength test according to IEC 61400-01 standard using aluminum alloy and homogenized composite material. In doing so, maximum aerodynamic loading on the blade is calculated after steady state 3-D RANS CFD simulation of the blade in ANSYS Fluent. The Finite Element Method (FEM) model of the blade is created using shell element in ANSYS Static Structural with structured meshing strategy, and tested with the aerodynamic load using the one-way Fluid-Structure Interaction (FSI) technique, to obtain mesh independent solution. The impact of the using 2, 3, and 4 number of shear webs is then analyzed on the selected mesh model of the blade. Finally, a four-shear web model of the blade is tested under extreme conditions. The thickness of the blade surface and shear web are varied to test maximum deflection at the tip, and maximum allowable strain of the blade. After obtaining the required blade structure, the deformation, maximum equivalent stress, and maximum equivalent strain for the blade are studied at rotation Tip Speed Ratio (TSR) of 5 under aerodynamic and gravitational loading, using both materials. The study showed significant deflection at the tip of the blade for the tower-less V-VAWT blade, suggesting an alternative support mechanism for the blade. Also, the study concluded that better structural robustness is achieved while using a composite material instead of an aluminum alloy. This article provides basis to study structural behavior of the novel V-VAWT blades and contribute to continuing research on obtaining optimized blade structure for such turbine.

Power enhancement of vertical axis wind turbine using optimum trapped vortex cavity

Vertical Axis Wind Turbine (VAWT) blades experience stall conditions at lower tip speed ratios during rotation, resulting in inefficient power performance. The power performance can be augmented by improving the blade's aerodynamic efficiency using active or/and passive flow control mechanisms. In this research, the power performance of 2-D H-type VAWT is enhanced by employing an optimum cavity on the suction side of the NACA 0018 blade airfoil. The optimum cavity shape was found using the Genetic Algorithm coupled with the Gaussian Process Regression (GPR) model at an airfoil static stall angle of attack in an isolated environment to reduce the computational cost of the optimization process. Two GPR models were employed to predict lift and drag coefficients, while the lift-to-drag ratio was used as an objective function in the optimization algorithm. 80 CFD runs were utilized for initial training and testing of the models, which reduced computational effort by 97% compared to a pure CFD-based optimization approach. The aerodynamic efficiency of the optimum cavity shape predicted by GPR models was also confirmed by CFD simulation, which showed only a 0.5% difference. For an airfoil with an optimum cavity, the aerodynamic efficiency was consistent at lower angles of attack. However, a significant rise of up to 31.8% was observed in the near stall region between 12° to 16° angle of attack in comparison to clean airfoil. The optimum cavity on baseline VAWT blades enhanced power performance by 63.8% at a TSR of 1.5. Moreover, at TSRs of 2, 2.5, 3, and 3.5, the enhancement in power performance was achieved by 34.4%, 22.2%, 16.1%, and 3.2%, respectively. This demonstrates the potential of employing an optimum cavity on the suction side for performance augmentation without applying the suction and a cost-effective solution by conducting optimization in an isolated environment.

Performance enhancement of an H‐Darrieus vertical axis wind turbine via moving surface boundary‐layer control

AbstractThe moving surface boundary‐layer control method (MSBC) is a kind of active flow control methods that overcomes the adverse pressure gradient and suppresses the flow separation by directly energizing the boundary layer near the moving surface. In this study, computational fluid dynamics simulations were performed to investigate the feasibility of using MSBC to improve the aerodynamic performance of a straight‐bladed H‐Darrieus vertical axis wind turbine (VAWT). In doing so, a segment of the original surface of the VAWT blade was then replaced with a moving surface. Influences of different geometric and motion parameters of moving surface, including location, length, velocity ratio, and groove depth on the net power coefficient of VAWT, were systematically studied. Moreover, the sensitivity of different parameters to the net power coefficient of VAWT at the optimal tip speed ratio was analyzed via the orthogonal design method. As a result, the optimal combination of moving surface parameters was able to be determined. The present results show that the maximum net power coefficient of VAWT having blades with partially moving surface can be increased by 22.8% compared with that of the baseline VAWT. In addition, the effectiveness of two active flow control methods, co‐flow jet and moving surface, in improving aerodynamic performance of a VAWT was also compared. It is found that MSBC method has the potential to achieve superior control performance and promote the energy utilization coefficient of the VAWT more effectively by using comparatively less external energy input.

Time scales of dynamic stall development on a vertical-axis wind turbine blade

Vertical-axis wind turbines are excellent candidates to diversify wind energy technology, but their aerodynamic complexity limits industrial deployment. To improve the efficiency and lifespan of vertical-axis wind turbines, we desire data-driven models and control strategies that take into account the timing and duration of subsequent events in the unsteady flow development. Here, we aim to characterise the chain of events that leads to dynamic stall on a vertical-axis wind turbine blade and to quantify the influence of the turbine operation conditions on the duration of the individual flow development stages. We present time-resolved flow and unsteady load measurements of a wind turbine model undergoing dynamic stall for a wide range of tip-speed ratios. Proper orthogonal decomposition is used to identify dominant flow structures and to distinguish six characteristic stall stages: the attached flow, shear-layer growth, vortex formation, upwind stall, downwind stall and flow reattachment stage. The timing and duration of the individual stages are best characterised by the non-dimensional convective time. Dynamic stall stages are also identified based on aerodynamic force measurements. Most of the aerodynamic work is done during the shear-layer growth and the vortex formation stage which underlines the importance of managing dynamic stall on vertical-axis wind turbines.

Recommendation for strut designs of vertical axis wind turbines: Effects of strut profiles and connecting configurations on the aerodynamic performance

The strut is a necessary support structure that connects the vertical axis wind turbine blade to the rotating shaft and transfers the torque, and is one of the key factors affecting the aerodynamic performance of the wind turbine. However, research on struts is limited and the appropriate strut design remain uncertain. Therefore, in this paper, the struts of a straight-bladed vertical axis wind turbine are investigated by a three-dimensional computational fluid dynamics approach, to find the appropriate strut design parameters that minimize the impact on the aerodynamic performance. Thirty strut profiles with different chord lengths, thicknesses, areas, and streamlined shapes were parametrically created and analyzed, including a novel strut-specific profile proposed in this paper. Furthermore, all strut connecting parameters, such as spanwise and chordwise positions, connecting angle and fairing were investigated. The results show that the power loss of a vertical axis wind turbine has a relatively linear relationship with the dimensionless absolute thickness of the strut within a certain range. The strut chord length is another important influencing factor. Equal chord lengths of the strut and the blade should be avoided as much as possible. The proposed novel olivary strut profile has lower drag characteristics and more favorable geometrical structural properties compared to the most used NACA airfoil. The influence of the spanwise connecting position (within the range around the blade quarter span) is minor. But the chordwise position has a significant effect, and special attention should be paid to avoid the strut maximum thickness position connecting with the blade aerodynamic center, which will result in the greatest performance degradation. Analysis of the connecting angles shows that inclined struts are suitable for small wind turbines. The fairing is effective when the strut chord length is equal to or longer than the blade chord length. With these results, a set of recommended design parameters for vertical axis wind turbine struts is presented.

Analysis of vertical axis wind turbine blade for off-shore applications

In this work, static and dynamic analyses are carried out on VAWT blade using analytical and numerical methods to figure out reasons behind the failure in the blade for off-shore applications arising due to turbulence of wind. The design flaws and different operating conditions play major role in failure of blades. Fatigue life cycles, natural frequencies of blade in different modes and turbine harmonic frequency have been calculated analytically using Goodman’s and vibration analysis theories respectively. In analysis, life cycles, natural frequencies and mode shapes for VAWT blade are studied. Analytical and numerical results have been compared, life cycles and frequencies are determined. The numerical results showed good agreement with theoretical concepts.

Numerical Calculation Method of Spanwise Icing Characteristics and Performance Loss of Three-Dimensional Vertical Axis Wind Turbine Blades

Most icing studies use 2D or quasi-3D models, ignoring the effects of blade span and tip icing. In this paper, a new model for predicting 3D vertical axis wind turbine blades icing by supplementing the blade span is established, the icing characteristics of blades under multiple working conditions are simulated step by step from the time scale, and the unsteady icing laws are compared and analyzed. Ice properties and surface temperature distribution determine the corresponding deicing power. The analysis results show that the unfrozen water film flows in the spanwise direction of the blade, resulting in a smaller icing limit on the pressure surface than the two-dimensional model, which indicates that the chordwise anti-icing structure can be set in a small range. At the same time, the annular ridge ice formed at the end of the blade slows down the reduction rate of the lift-drag ratio of the blade, effectively reducing the influence of the leading edge ice shape on the aerodynamic performance of the blade. Finally, the critical ice melting power density required to reach equilibrium temperature at the leading edge of the blade is reduced by about 11% compared to the trailing edge due to the increased thermal resistance of the gas-to-blade matrix interface by the ice layer.

Response Surface Optimisation of Vertical Axis Wind Turbine at low wind speeds

The Vertical Axis Wind Turbines (VAWTs) have an increasing global market and this emphasis the need for to improve the performance of VAWTs, especially at relatively low wind speed. This paper utilises the Response Surface methodology to optimise the performance of a VAWT. A three bladed VAWT configuration was considered with a NACA0015 profile. Three significant input parameters were selected including the tip speed ratio, the turbine solidity, and the pitch angle. An extended range of each input parameter was chosen in order to gain a good insight into how these input parameters affect the performance of the VAWT. The high-fidelity Computational Fluid Dynamics (CFD) simulations were carried out for the modelling of the turbine. The use of the Response Surface Optimisation based on Multi-Objective Genetic Algorithm (MOGA) along with the CFD simulations is found to be useful in the selection of the optimal design of VAWT. Moreover, the 3D aspects of the VAWT geometry are investigated and these include the turbine aspect ratio and the effect of the blade tip geometry. The implementation of an optimised winglet at the tip of the turbine blades is found to provide a significant enhancement of the cycle averaged power coefficient, especially at low aspect ratios.

Computational Investigation of Vertical Axis Wind Turbine in Hydrogen Gas Generation Using PEM Electrolysis

Both offshore wind and hydrogen generation are increasingly seen as central to global decarbonization. The objective of current research is to investigate the effect of wind turbine height of Vertical Axis Wind Turbine (VAWT) on hydrogen generation. The numerical investigation of VAWT is conducted using techniques of Computational Fluid Dynamics. The VAWT design is developed in Solidworks design software and CFD analysis is conducted using ANSYS CFX software. The CFD analysis conducted on VAWT aided to determine the torque generated from it at 10m/s wind velocity determining the system impacts and ability of electrolyzer technology to accommodate the varying input from wind turbine. The research findings have shown that height of VAWT blade has significant effect on power generation. The power generation from VAWT increases with increase in blade height. The maximum hydrogen mass is generated for 850mm height wind turbine i.e., 2.09Kg. The external wind flow conditions have significant effect on power generation from VAWT and therefore the effect of varying air flow conditions needs to be investigated.

Effect of upstream deflector utilization on H-Darrieus wind turbine performance: An optimization study

This paper aims to enhance the performance of H-Darrieus Vertical Axis Wind Turbine (VAWT) via introducing upstream deflectors. The impact of this addition has been investigated and discussed through different deflector configurations. The turbine performance before and after adding different wind rotor barriers was compared. A two dimensional, incompressible, transient, and turbulent flow model was built up in order to simulate the air flow around the turbine blades. Model verification and validation were performed through comparing the model solutions using different mesh sizes, time steps, turbulent models, and discretization schemes. Computational Fluid Dynamics (CFD) models were validated to provide novel insights on the effect of the deflectors on the aerodynamic characteristics of a VAWT blades. Results showed that the presence of a single deflector increases the highest value of the moment coefficient of the bare configuration by 24%, either increases the negative torque values, while two defectors increase the maximum value by 22% and the overall average value of the moment coefficient over the optimal range for the tip speed ratio.

The dynamic stall dilemma for vertical-axis wind turbines

Vertical-axis wind turbines (VAWT) are excellent candidates to complement traditional wind turbines and increase the total wind energy capacity. Development of VAWT has been hampered by their low efficiency and structural unreliability, which are related to the occurrence of dynamic stall. Dynamic stall consists of the formation, growth, and shedding of large-scale vortices, followed by massive flow separation. The vortex shedding is detrimental to the turbine's efficiency and causes significant load fluctuations that jeopardise the turbine's structural integrity. We present a comprehensive experimental characterisation of dynamic stall on a VAWT blade including time-resolved load and velocity field measurements. Particular attention is dedicated to the dilemma faced by VAWT to either operate at lower tip-speed ratios to maximise their peak aerodynamic performance but experience dynamic stall, or to avoid dynamic stall at the cost of reducing their peak performance. Based on the results, we map turbine operating conditions to one of three regimes: deep stall, light stall, and no stall. The light stall regime offers VAWT the best compromise in the dynamic stall dilemma as it yields positive tangential forces during the upwind and downwind rotation and reduces load transients by 75% compared to the deep stall regime.