Vertical Axis Wind Turbine Research Articles

Aerodynamic techniques to mitigate the 3D loss in the power coefficient of vertical axis wind turbines

The three-dimensional tip loss effect is a critical phenomenon affecting the performance of vertical-axis wind turbines. The vortices on the blades become more complex with the turbine rotation, most notable at the tips, leading to three-dimensional aerodynamic losses and decreasing the turbine power coefficient. Therefore, mitigating the aerodynamic losses at the tips could improve the technological development of these devices. However, the numerical methods to analyze the tip vortices in VAWTs have a high computational cost, and experimental data to verify them is limited. In this study, three passive flow control techniques that mitigate the three-dimensional effects of a vertical axis wind turbine Darrieus H-type have been investigated experimentally in a wind tunnel to quantify their impact on the power coefficient and validate the theoretical results found in the literature. The tested passive flow control aerodynamic designs of the blade tips consist of leading-edge serration, anhedral, and endplate techniques. The results of this work include the experimental power coefficient curves as a function of the tip speed ratio for a two-blade VAWT model without any modification and with the three passive control techniques. The experimental process characterizes the VAWT techniques in a range of Tip Speed Ratios between 0.37 and 3.1. Our results indicate that the leading-edge serration, anhedral, and endplate techniques effectively mitigate the three-dimensional losses, increasing the power coefficient by 7.1%, 14.3%, and 25%, respectively, compared to the reference model. The endplate model exhibited the best Cp improvement. However, it could cause the highest bending on the blade tips of the three tested techniques.

Aerodynamic performance and wake development of NACA 0018 airfoil with serrated gurney flaps

Improving the aerodynamic performance of the airfoil is important for optimising the rotor efficiency of the vertical axis wind turbines. As a simple passive control method, the Gurney flap is widely used to improve the aerodynamic performance of airfoils. In this paper, we study the impact of applying a novel serrated gurney flap with different heights on the NACA 0018 airfoil. An improved delayed detached eddy simulation method is adopted to investigate the lift-enhancing mechanism of the serrated gurney flap and the evolution of the downstream vortex system. The results show that the serrated gurney flap can effectively increase the airfoil lift coefficient and the lift-to-drag ratio. The improvement of the serrated gurney flap on the aerodynamic performance of the airfoil is more pronounced at moderate angles of attack. Further analysis of the downstream wake shows that a pair of vortices wraps over both sides of the airfoil and rotates perpendicular to the wake flow, which is produced by the columnar vortex upstream of the flap. These vortices mixed with the wake and accelerated the dissipation of the separated vortex on the suction surface of the airfoil.

Experimental study on rooftop flow field of building based on the operation of vertical-axis wind turbines

Vertical-axis wind turbines (VAWTs) demonstrate good adaptability for harnessing wind energy on the building rooftops. However, knowledge gaps still exist in the understanding of the wind resources on the rooftop, the operation of VAWTs, and its effect on the wind field. To add new knowledge on this subject, the operation of wind turbines modeled by the NACA0018 airfoil on the rooftop of a building is experimentally studied via wind tunnel. The results indicate that flow above the rooftop of building shows an obvious speed reduction due to the blunt body effect of the turbines, and the turbulence intensities are dramatically enhanced. The different tip-speed ratios, wind directions, and installation locations of wind turbine have significant effect on flow field on the roof. Due to the flow characteristics above the rooftop, the power spectral density of the fluctuating wind speed exhibits high energy below the top position of the VAWT on the rooftop. Additionally, the wind profiles and probability distribution of the wake of VAWTs on the rooftop are analyzed and mathematically fitted for quantifying wind field characteristics rooftop turbines on the roof. For the VAWTs investigated in this study, the impacts of the operation of VAWTs on the wind field are non-negligible on the roof of building. The findings of this study will provide valuable insights for the optimal placement of VAWTs and utilization of wind energy on the rooftops.

Self-starting and performance improvement of a Darrieus type wind turbine using the plasma actuator

Although the popularity of Darrieus-type vertical axis wind turbines is growing for small-scale electricity generation, these turbines have severe challenges in self-starting. This paper proposes a flow control method, namely, the plasma actuator, to solve the self-starting problem besides enhancing the turbine performance. The Darrieus turbine is numerically investigated using a pressure-based finite volume method to solve the unsteady Reynolds-averaged Navier–Stokes and the γ–Reθt transitional model equations. Simulation of the blade rotation is performed using the sliding mesh technique accompanied by the turbine equation of motion to enable the blade rotational degree of freedom. Furthermore, the body forces associated with the plasma actuator are determined by calibrating the Shyy plasma model parameters. The plasma actuator is assessed at both the constant and free rotational speeds. The constant rotational speed results in plasma off condition show negative torque generation for tip speed ratios lower than 1.5, known as the origin of turbine self-starting challenges. The plasma actuator improves the negative torque by 128% in the tip speed ratio of 0.5 and turns it positive. Also, at larger tip speed ratios, it reduces the negative torque generation and enhances the turbine power production by up to 260%. Furthermore, the plasma actuator in free rotational speed improves the tip speed ratio increment by up to 8%, reducing the total time of turbine self-starting.

Aerodynamic performance and starting torque enhancement of small-scale Darrieus type straight-bladed vertical axis wind turbines with J-shaped airfoil

Wind energy is one of the most eminent renewable sources for the generation of power. The increasing enthusiasm toward the advancement of small-scale Darrieus type straight-bladed vertical axis wind turbines (SB-VAWTs) can offer a potential remedy for addressing power shortage and the unpredictability of climate conditions. These particular wind turbines provide distinct advantages over their counterparts due to their linear blade design and uncomplicated structure. However, enhancements are required in their aerodynamic efficiency and self-initiation capabilities. These challenges stem from using traditional straight blade configurations and symmetrical airfoils. By substituting these conventional elements with J-shaped straight blades and along with cambered airfoils, these issues can be effectively overcome. The current study aims to investigate the effect of J-shaped straight blades with a series of cambered airfoils to improve the aerodynamic performance and starting torque of small-scale Darrieus type SB-VAWTs. Therefore, experimental and numerical studies are conducted to analyze the J-shaped airfoil impact with various opening ratios systematically. The J-shaped blade profile is designed by eliminating some portion toward the trailing edge of a conventional airfoil. This analysis demonstrated that the J-shaped blade incorporating a cambered NACA 4418 airfoil outperforms its alternative cambered airfoil designs. The performance of SB-VAWT improves by about 25% by the J-shape of the cambered NACA 4418 airfoil with a 70% opening ratio. Moreover, the use of J-shaped airfoils enhances the self-starting torque of SB-VAWT compared to conventional airfoils.

Conformally Decambered Natural Laminar Flow Blades for Vertical-Axis Wind Turbines

A two-element natural laminar flow airfoil—commonly used on medium-altitude, long-endurance, unmanned air vehicles—was conformally decambered for application on a two-bladed, H-rotor, vertical-axis wind turbine. Blade kinematics were used to determine the virtual camber line, which was then used to conformally map the original profile onto the chord line. Both decambered and original blade profiles were evaluated experimentally using large chord-radius ratios (0.6 and 0.75) that exploited dynamic stall to produce the driving torque. Decambered blades showed substantially greater power and torque coefficients than the original blades, up to 60 and 27%, respectively, which represents the first experimental validation of conformal decambering. Relatively large peak power coefficients of 0.28 were attained, despite maximum chord-based Reynolds numbers being less than 2×105. Depending upon the chord-radius ratio, either light or deep dynamic stall occurred in the second upstream quadrant, and the flap flow remained attached virtually throughout. In contrast, on the original profiles, massive separation was observed on the blades, and the flap flow remained separated due to assumed outer surface flow separation. Future research should consider surface pressure and flowfield measurements, significantly higher Reynolds numbers, and variable intracycle flap deflection mechanisms to optimize performance and minimize unsteady loads.

Vertical Axis Wind Turbine

The key components of a vertical-axis wind turbine (VAWT) are located at the base of the turbine, with the primary rotor shaft aligned transversely to the wind. Because of this arrangement, maintenance and repairs are made easier because the generator and gearbox are located close to the ground. The parts of a vertical axis wind turbine include the blade, shaft, bearing, frame, and blade support. In short, the rotor rotates because of the dynamic pressure exerted by the wind on the blades. Concurrently, the opposing side of the blades encounters aerodynamic hindrance, occasionally referred to as "drag." We experience something similar when we run or cycle: airflow is constantly working against us. Key Words: Turbine, Dynamic pressure, Rotar resistance, Shaft.

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.

Wind Velocity Effect on the Aerodynamic and Acoustic Behavior of a Vertical Axis Wind Turbine

In this work we present a numerical study on the effect of wind velocity on the aerodynamic and acoustic behavior of a Savonius-type vertical axis wind turbine (VAWT). The study focuses on the prediction of the torque coefficient for different flow velocities and rotational velocities of the wind turbine. We also present the triggering of the wake zone near the wind turbine blades to see the dynamic effect on the behavior of the wind turbine. The study of the numerical simulation is carried out using a fluent CFD calculation code using the finite volume method for the discretization of the differential equations. The equations governing the flow are solved by the SIMPLE algorithm using two K-epsilon turbulence models.

Relaxation oscillations in the Darie wind power plant model

The article discusses the mathematical model of the Daria small wind power plant. This installation is a type of vertical axis wind turbine named after its inventor, Georges Jean Marie Darrieux. The design consists of a vertically oriented shaft with curved blades or airfoils attached to it, forming a shape similar to an egg whisk. In today’s world, against the backdrop of climate change and steadily increasing energy demand, wind energy acts as a critical pillar of the transition to renewable energy sources. This technology helps reduce carbon emissions and mitigate humanity’s impact on the environment. In this context, wind energy is emerging not only as a means of supplying electricity, but also as a powerful catalyst for building a more sustainable and energy-efficient future. The equation of stationary modes is studied at the value of the external resistance of the dynamic model specified by the simplest equation. Conditions have been found under which relaxation oscillations are observed in the system.

Fatigue-Life Prediction of the Optimized Savonius Vertical-Axis Wind Turbine Composite Blades

Abstract The sustainability of modern human civilization is significantly concerned with enhancing sustainable energy resources. Vertical-Axis Wind Turbines (VAWTs) gained a promising impact on the global energy mix due to their belief in sustainable energy solutions. This paper presents an integrated study of the dynamic performance and fatigue-life characteristics of the optimized Savonius-rotor VAWT composite blades. Furthermore, this paper introduces an experimental validation, numerical modeling, and visualization/verification study of the optimized VAWT composite blades and assesses its impact on the whole performance of the optimized Savonius VAWTs. Four combination levels of the optimal settings of the S-VAWT composite blade configurations are designed, modeled, simulated, and fabricated of Carbon/Glass—Polyester. The modal parameters such as natural frequency, mode shape, and damping factor are investigated using fast Fourier transformer (FFT) analyzer. The numerical finite element models (FEM) are generated to model, visualize, simulate, and predict the dynamic nature and fatigue-life characteristics of the optimal S-VAWT composite blade configurations. A correlation between the experimental and numerical results is established. The study findings highlight the significant impact of VAWT composite blades in enhancing the dynamic performance and fatigue-life characteristics of Savonius VAWTs. Furthermore, a small damage percentage of 2.8% predicted by the finite element analysis (FEA) for the optimal S-VAWT composite blade configuration validated the sustainability of the VAWT composite blade configurations in dynamic loading conditions.

Development and Application of an FSI Model for Floating VAWT by Coupling CFD and FEA

The emerging floating vertical axis wind turbines (VAWTs) are regarded as a preferred solution to overcome the challenges faced by the traditional horizontal type in open-sea environments. Numerous numerical models have been advanced for assessing this novel object. However, current fully coupled models predominantly rely on simplified theories, assuming a linear fluid load and a one-dimensional slender beam structure. Despite computational fluid dynamic and finite element (CFD-FEA) coupling being qualified for high precision, this technology remains limited to the fixed VAWT field. To predict the load and structural response accurately and comprehensively, this study aims to extend CFD-FEA technology to floating VAWTs. First, an aero-hydro-moor-elastic fully coupled model is developed, and this model is validated by comparing it with several model experiments. Subsequently, a full-scale floating straight-bladed VAWT is simulated with the geometry and numerical models introduced. Furthermore, load and structural responses in a typical case are analyzed in both time and frequency domains. Finally, the sensitivity analysis of each structure part in floating VAWTs to environmental parameters is conducted and discussed. The discovery highlights the intricate nature of tower structural response, which incorporates 2-node, 3-node, wind frequency, and wave frequency components. Distinct from blades or floating foundations, which are primarily influenced by a single environmental parameter, the tower response is significantly amplified by the combined effects of wind and waves.

Design And Analysis of Modern Vertical Axis Wind Turbine (VAWT)

With traditional energy sources running low, the world is turning more towards renewable energy, particularly wind power. But current wind turbines have their flaws. Enter the wind turbine tree, a potential solution to these issues. This study looks at various research papers on different wind turbine designs. After analysing them all, it's clear that wind turbine trees with Savonius blades are better than traditional bladed turbines. They take up less space and produce the same amount of power. This paper explores these findings and suggests that wind turbine trees could be the future of wind energy.. Keywords- Renewable Energy, Wind Turbine, wind Turbine Tree, Vertical axis wind turbine (VAWT), Horizontal axis wind turbine (HAWT), Computational fluid Dynamics (CFD).

Numerical Study of Control Rod's Cross-Section Effects on the Aerodynamic Performance of Savonius Vertical Axis Wind Turbine with Various Installation Positions at Suction Side

Numerical Study of Control Rod's Cross-Section Effects on the Aerodynamic Performance of Savonius Vertical Axis Wind Turbine with Various Installation Positions at Suction Side

Computational fluid dynamics study on the efficiency of straight-bladed vertical axis wind turbine

The present study treats numerically the performance of a straight-bladed, vertical axis, Darieus wind turbine. A two-dimensional (2D), Unsteady Reynolds-averaged Navier–Stokes (URANS) simulations were performed out by the solver ANSYS/FLUENT using the sliding mesh method. Four turbulence models, namely the one-equation Spalart– Almaras (SA) model, the two-equation Shear Stress Transport (SST) k-ω, the Transitional Shear Stress Transport (TSST), and the realizable k-ϵ models, with low Reynolds number capabilities, were tested.The dependency of the power curve upon the torque coefficient and the Tip Speed Ratio (TSR) was evaluated under identical conditions to previously published experimental studies. The results suggest that the realizable k-ϵ model outperformed other turbulence models and matched better with the experimental data. Further numerical investigations were performed to determine the conditions for an optimal performance of the VAWT in question.

Numerical Investigations on the Transient Aerodynamic Performance Characterization of a Multibladed Vertical Axis Wind Turbine

The use of vertical axis wind turbines (VAWTs) in urban environments is on the rise due to their relatively smaller size, simpler design, lower manufacturing and maintenance costs, and above all, due to their omnidirectionality. The multibladed drag-based VAWT has been identified as a design configuration with superior aerodynamic performance. Numerous studies have been carried out in order to better understand the complex aerodynamic performance of multibladed VAWTs employing steady-state or quasi-steady numerical methods. The transient aerodynamics associated with a multibladed VAWT, especially the time–history of the power coefficient of each blade, has not been reported in the published literature. This information is important for the identification of individual blade’s orientation when producing negative torque. The current study aims to bridge this gap in the literature through real-time tracking of the rotor blade’s aerodynamic performance characteristics during one complete revolution. Numerical investigations were carried out using advanced computational fluid dynamics (CFD)-based techniques for a tip speed ratio of 0 to 1. The results indicate that transient aerodynamic characterization is 13% more accurate in predicting the power generation from the VAWT. While steady-state performance characterization indicates a negative power coefficient (Cp) at λ = 0.65, transient analysis suggests that this happens at λ = 0.75.

Solidity effects and azimuth angles on flow field aerodynamics and performance of vertical axis wind turbines at low Reynolds number

Solidity is an important parameter in the design, manufacture, and operation concerning energy yield and performance efficiency of VAWTs. This paper examined detailed aerodynamic analysis of solidity effects at constant Re and at low Reynolds numbers, the flow field and forces (lift, drag, and Torque coefficients) aerodynamics at various azimuth positions, and the changes in the performance and the flow field of VAWTs at a wide range of TSR. The simulation of two three-bladed VAWT configurations, σ = 0.26 (C = 0.03 m) and σ = 0.34 C = 0.04 m) over 1.5 ≤ λ ≤ 5.5 tip speed ratios on the CL, CD, CM, and speed were monitored and extracted, and the blades surrounding flow field is plotted from the CFD simulations. Performance (Cp -λ) curves, force hysteresis, and plots of the flow field for the turbines are matched at low λ = 2 5, high λ = 4, and Reynolds number to explain solidity effects on the VAWTs performance and aerodynamics thus providing good insight into the underlying aerodynamics for the differences in power coefficient between the two rotors in detail. This allowed the linking of the performance to the detailed force and flow field aerodynamics at various azimuth angles. It has been shown that the initiation of blade stall and stall vortices shedding started earlier on the σ = 0.26 VAWT than the σ =0.34 VAWT, thus affecting the force attained and ultimately limiting the rotor efficiency of σ = 0.26 compared with the σ =0.34 rotor and provided an improved understanding of solidity phenomenon that will help in the design, production and operation of VAWTs.

Blockchain-Driven Demand Response System for Resilient and Sustainable MicroGrids Integrating Wind Energy Conversion Systems

This study introduces the B-DDR system, leveraging blockchain technology for real-time, decentralized energy management in MicroGrids. By integrating Vertical Axis Wind Turbines (VAWTs), including a novel H-Darius VAWT-PMSG model with magnetic levitation and aerodynamic considerations, the proposed approach addresses challenges in optimizing energy supply and demand. Blockchain smart contracts facilitate peer-to-peer energy trading among WECS owners and users, promoting efficient renewable energy utilization. The system, analyzed through optimization models, demonstrates a notable reduction in peak demand rate from 40% to 15%, an improvement in energy efficiency from 7% to 12%, and a remarkable 92% increase in utilization efficiency. With a transaction speed of 5s during outages, the B-DDR system proves its capability to enhance MicroGrids, ensuring a robust, efficient, and sustainable energy environment. The incorporation of H-Darius VAWT-based PMSGs and blockchain technology enables precise demand response, achieving effective grid energy state equilibrium while minimizing losses. The self-executing agreements, monitored by H-Darius-PMSG nodes, provide real-time tracking and balancing, addressing the dynamic challenges posed by fluctuating demand requirements in a decentralized and efficient manner.

Performance Rating and Flow Analysis of an Experimental Airborne Drag-Type VAWT Employing Rotating Mesh

This paper presents the results of a performance analysis conducted on an experimental airborne vertical axis wind turbine (VAWT), specifically focusing on the MAGENN Air Rotor System (MARS) project. During its development phase, the company claimed that MARS could generate a power output of 100 kW under wind velocities of 12 m/s. However, no further information or numerical models supporting this claim were found in the literature. Extending our prior conference work, the main objective of our study is to assess the accuracy of the stated rated power output and to develop a comprehensive numerical model to analyze the airflow dynamics around this unique airborne rotor configuration. The innovative design of the solid model, resembling yacht sails, was developed using images in the related web pages and literature, announcing the power coefficient (Cp) as 0.21. In this study, results cover 12 m/s wind and flat terrain wind velocities (3, 5, 6, and 9 m/s) with varying rotational velocities. Through meticulous calculations for the atypical blade design, optimal rotational velocities and an expected Tip Speed Ratio (TSR) of around 1.0 were determined. Introducing the Centroid Speed Ratio (CSR), which is the ratio of the sail blade centroid and the superficial wind velocities for varied wind speeds, the findings indicate an average power generation potential of 90 kW at 1.4 rad/s for 12 m/s and approximately 16 kW at a 300 m altitude for a 6 m/s wind velocity.

Optimization of VAWT installation with spatial and temporal complexity considerations

The constant need for fuel to meet the commercial sector’s ever-increasing demand has driven researchers to discover and optimize renewable energy resources, paving the way for sustainable production of reliable and clean energy resources. The goal of the current work is to close the gap in process parameter optimization needed to convert wind energy wake from traffic on highways into electrical energy utilizing vertical-axis wind turbines (VAWTs). The energy output from the VAWT is analyzed to investigate how it is impacted by the variations in multiple parameter settings. Using the central composite design (CCD), a three-level four-factor array was used to investigate the following parameters: VAWT vertical distance (VD) and horizontal distance (HD) as continuous parameters, while road side (S) and location (L) of VAWT as categorical parameters. To find the most important parameter, response surface methodology (RSM) optimization and an analysis of variance (ANOVA) test are performed. L accounts for 66.67% of the total variable, with S coming in second with 51.80%. Using the best results from RSM and ANOVA, a confirmation test is run, and the results show yields of 88.75% ± 0.05% and 87.5% ± 0.05%, respectively. Therefore, RSM and ANOVA can be utilized equally for optimization at the same VAWT design. Lastly, the findings of the economic and environmental evaluation demonstrate that, in comparison to the basic settings, VAWT operating at optimal settings can save up to 180% and 200% more energy and reduce carbon emissions, respectively.