Vertical Axis Wind Turbine Research Articles

Development of a Predictive Model for Evaluation of the Influence of Various Parameters on the Performance of an Oscillating Water Column Device.

Oscillating Water Column (OWC) systems harness wave energy using a partially submerged chamber with an underwater opening. The Savonius turbine, a vertical-axis wind turbine, is well-suited for this purpose due to its efficiency at low speeds and self-starting capability, making it an ideal power take-off (PTO) mechanism in OWC systems. This study tested an OWC device with a Savonius turbine in an air duct to evaluate its performance under varying flow directions and loads. An innovative aspect was assessing the influence of power augmenters (PAs) positioned upstream and downstream of the turbine. The experimental setup included load cells, Pitot tubes, differential pressure sensors and rotational speed sensors. Data obtained were used to calculate pressure differentials across the turbine and torque. The primary goal of using PA is to increase the CP-λ curve area without modifying the turbine geometry, potentially enabling interventions on existing turbines without rotor dismantling. Additionally, another novelty is the implementation of a regression Machine-Learning algorithm based on decision trees to analyze the influence of various features on predicting pressure differences, thereby broadening the scope for further testing beyond physical experimentation.

Numerical study on wake recovery of vertical-axis wind turbines through fixed blade pitch offsets: H vs X rotors

This study assesses the wake recovery mechanism between an H-type Darrieus and an X-type vertical-axis wind turbine, named H-Rotor and X-Rotor respectively for different blade pitch offset configurations. The analysis is conducted in OpenFOAM using the actuator line method to model the turbines to present qualitative (velocity and vorticity contours) and quantitative (available power) studies for three different fixed blade pitch offsets. The results demonstrate that the H-Rotor recovers the wake much faster than the X-Rotor at positive pitch offsets. Overall, applying fixed pitch offsets to VAWT blades helps recover the wake faster than having no blade pitch offset.

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.

Study of the Self-starting Performance of a Vertical-axis Wind Turbine

Study of the Self-starting Performance of a Vertical-axis Wind Turbine

Design and fabrication of a helical vertical axis wind turbine for electricity supply

Design and fabrication of a helical vertical axis wind turbine for electricity supply

Develop an Energy Storage Strategy for Emerging Wind Farms in India Over IoT

Energy is a fundamental component of daily life, essential for performing various tasks. Currently, non-renewable energy sources such as oil, coal, and gas dominate energy consumption. However, these resources are unsustainable and significantly contribute to global warming, posing serious environmental hazards. In contrast, renewable energy sources, including solar, wind, tidal, and biogas, offer sustainable and abundant alternatives to meet energy needs. Among these, wind energy stands out as the purest form of renewable energy, extensively utilized for electricity production due to its minimal environmental impact.Wind energy harnesses the kinetic energy of atmospheric air, converting it into mechanical energy through wind turbines. Both Vertical Axis Wind Turbines (VAWT) and Horizontal Axis Wind Turbines (HAWT) are employed for this conversion. Countries worldwide, including India, recognize the importance of wind energy and adopt it as a primary renewable energy source, primarily due to its cost-effectiveness compared to other renewable options.This research focuses on the design and development of a multi-axis windmill integrated with the Internet of Things (IoT) to enhance efficiency and monitoring capabilities. The proposed system incorporates components such as the Atmega 328 microcontroller, LCD, voltage sensor, IoT module, load, battery, inverter, DC motor, gear ball bearing, and control board. The successful implementation of this system demonstrates the feasibility of an advanced wind energy solution, contributing to a more sustainable and environmentally friendly energy landscape.

Techno-economic evaluation and comparison of the optimal PV/Wind and grid hybrid system with horizontal and vertical axis wind turbines

Applications for alternative energy sources range from very small scale to large scale grid-coupled hybrid energy systems. In addition, hybrid energy systems are safer to generate power and cheaper to produce than single-source energy systems. The main goal of this study is to determine whether renewable energy hybrid system with horizontal axis wind turbine (HAWT) or vertical axis wind turbine (VAWT) is more efficient and cost effective in terms of energy, economics, and environmental performance. The use of the Multi Objective Genetic Algorithm (MOGA) in MATLAB software for the sizing of hybrid sustainable energy system with wind turbine (horizontal and vertical axis), solar photovoltaic, and grid connection is evaluated in this study. The results revealed that the cost of energy, NPC and system total cost for the case where HRES consists of HAWT is $0.02 /kWh, $85,905, and $332,240, respectively, while for the case when VAWT is used, these values are $0.06 /kWh, $129,932 and $502,511, respectively. The renewable fraction and CO2 emission saving are 80.5% and 73.2% for cases 1 and 2, respectively. The use of renewable energy sources will spread more widely and there will be less air pollution as a result of less reliance on grid electricity. The findings from both situations show that adopting HAWTS-based HRESs is more cost effective and efficient for electrifying rural areas. This study paves the way for researchers to focus on types of wind turbines while designing HRESs.

Enhancing Savonius Rotor Performance With Zigzag Surface Investigated at Drag Force, Pressure, and Flow Visualization Analysis

Savonius, a type of vertical-axis wind turbine, is a small-scale energy conversion device suitable for low wind speeds, such as those characteristic of Indonesian wind speeds, yet has low efficiency. Savonius is a drag-type turbine. Drag force on the surface is affected by roughness or wavyness. The purpose of this study is to analyze the impact of applying wavy (zigzag) variations to the concave surface of Savonius blades on their performance. This was achieved by the use of 3D computational fluid dynamics simulation at TSR 0.6 with a velocity inlet of 5 m/s. The model was semicircular, zigzag on the concave surface on semicircular with t = 0.75, t = 0.25, and t = 1 mm. The result of this study's CD maximum is 1,817 at the zigzag model with t = 1 and CD avrg =1.24. The average drag coefficient increased by 14 percent compared to the conventional semicircular rotor. The maximum Cp value is also found at t = 1 mm, which is 0.315. The power coefficient increased by 29 percent compared to the conventional semicircular rotor. The total pressure on the blade shows the highest model with t = 1 mm at the same angle of attack (α = 30). Zigzag on the concave surface affects blade pressure, which improves the performance of the Savonius rotor.

Recent Progress in Design and Performance Analysis of Vertical-Axis Wind Turbines—A Comprehensive Review

Vertical-axis wind turbines (VAWTs) are receiving more and more attention as they involve simple design, cope better with turbulence, and are insensitive to wind direction, which has a huge impact on their cost since a yaw mechanism is not needed. However, VAWTs still suffer from low conversion efficiency. As a result, tremendous efforts are being exerted to improve their efficiency, which mainly focus on two methods, regardless of whether the study is a CFD simulation, a field test, or a lab test experiment. An active approach involves modification of the rotor itself, such as the blade design, the angle, the trailing and leading edges, the inner blades, the chord thickness, the contra-rotating rotor, etc., while the second approach involves passive techniques where the flow is directed to optimally face the downwind rotor by mounting guiding vanes such as a diffuser or other shapes at the upwind position of the rotor. Among all the techniques undertaken, the counter-rotating wind turbine (CRWT) rotor technique seems to be the most effective, with an output comparable to that of horizontal-axis wind turbines (HAWTs), while the Savonius rotor has received more attention compared to other VAWT designs. Apart from technological issues, it has also been suggested that geographical issues, such as proper site siting of a wind turbine rotor at a particular location where a uniform flow can be guaranteed, are of paramount importance to ensure an effective conversion capacity of wind turbines. Thus, this study has successfully highlighted the latest improvements in augmentation methods and has established a solid foundation for future research aimed at improving the efficiency of VAWTs.

Design and Development of Vertical Axis Wind Turbine with Inverter

Design and Development of Vertical Axis Wind Turbine with Inverter

Numerical study on aerodynamic performance improvement and efficiency enhancement of the savonius vertical axis wind turbine with semi-directional airfoil guide vane

The growth of greenhouse gases increased the need for wind energy resource. Savonius vertical axis wind turbines (VAWT) have high potential as a turbomachine. Optimization methods such as flow injection on the rotor suction side to flow control on buckets developed as Savonius VAWTs operating range and efficiency are lower than other VAWTs. In this study, the semi-directional airfoil guide vane (SDAGV) was introduced to improve the aerodynamic performance and increase the efficiency of Savonius VAWT. The results indicate that the vane installation at the lower upstream of the rotor yields a power coefficient (Cp) of 0.12, representing a 140% growth compared to a single Savonius rotor. Furthermore, this installation extended the operating range of the turbine from a tip speed ratio (TSR) of 0.51–0.8. According to the results, it was found that more passages could improve efficiency. Five types of symmetrical airfoil profiles were evaluated for the guide vane. The NACA0010 airfoil profile, which has lower thickness than the others, obtained 7% higher efficiency than the base case consisting of NACA0012. Also, the optimal stagger angle for configurations NACA0021, NACA0018 was found to be 45°, and for NACA0010 and NACA0012 was determined to be 30°, respectively.

Gauging Centrifugal Instabilities in Compressible Free-Shear Layers via Nonlinear Boundary Region Equations

Curved free shear layers emerge in many engineering problems involving complex flow geometries, such as the flow over a backward-facing step, flows with wall injection in a boundary layer, the flow inside side-dump combustors, or wakes generated by vertical axis wind turbines, among others. Previous studies involving centrifugal instabilities have mainly focused on wall-flows where Taylor instabilities between two rotating concentric cylinders or Görtler vortices in boundary layers are generated. Curved free shear layer flows, however, have not received sufficient attention, especially in the nonlinear regime. The present work investigates the development of centrifugal instabilities in a curved free shear layer flow in the nonlinear compressible regime. The compressible Navier–Stokes equations are reduced to the nonlinear boundary region equations (BREs) in a high Reynolds number asymptotic framework, wherein the streamwise wavelength of the disturbances is assumed to be much larger than the spanwise and wall-normal counterparts. We study the effect of the freestream Mach number M∞, the shear layer thickness δ, the amplitude of the incoming disturbance A, and the relative velocity difference across the shear layer ΔV on the development of these centrifugal instabilities. Our parametric study shows that, among other things, the kinetic energy of the curved shear layer flow increases with increasing ΔV and A decreases with increasing delta. It was also found that increasing the disturbance amplitude of the incoming disturbance leads to significant growth in the mushroom-like structure’s amplitude and renders the secondary instability structures more prominent, indicating increased mixing for all Mach numbers under consideration.

Decarbonizing airport using solar and wind farm: A case of Biratnagar, Nepal

Airports strive for a greener energy transition to minimize their carbon footprint and greenhouse gas emissions. The installation of solar or wind turbines is gaining significance among stakeholders working in sustainable airports. This study focuses on developing Biratnagar airport as a completely greener airport by identifying suitable sites for installing Solar and wind farms within the premises without compromising on safety aspects, including glare occurrence and environmental and electrical safety. PVSYST V6.8.7 and HOMER V2.81 software are used to simulate the performance of PV and wind turbine power plants. Three sizes of Vertical axis wind turbines (VAWT) of EOLO 15 kW, Tree tree-shaped wind Turbine (TSWT) 58.5 kW and TSWT 585 kW have been used for the Simulation. A sensitivity analysis of various parameters, including interest rates, wind speed, and wind turbine types, has been carried out to study the cost of energy generation in grid-connected mode. According to the study, a 157 kWp solar PV power plant is sufficient for Biratnagar Airport to become Nepal's first fully green-powered airport. The project's Levelized Cost of Electricity (LCOE) equals 0.141 $/kWh if wind energy is used to supply part of the electricity with the annual wind electricity production of 23,184 kWh. The combined 15 kW wind turbine-grid scenario is superior to the grid scenario for wind speeds of more than nine m/s and interest rates of less than 10 %. These findings increase airport authorities' and stakeholders' confidence in the investment in greener airports.

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.