Vertical Axis Wind Turbine Rotor Research Articles

Triple Rotor Vertical Axis Wind Turbine for Low Wind Speed Range Energy Generation

A new triple rotor vertical axis wind turbine (VAWT) is presented to produce electricity efficiently in light winds. Rotors are designed to consume less consistent energy when moving to boost efficiency. The turbine comprises numerous adjustable dual blades, a frame component adjacent to the hub, and a revolving hub in the centre. Each blade has a serrated part and is joined to a frame component. The rotor shaft connects the hub and frame sections mechanically and can spin along its longitudinal axis. A connector also allows rotational movement by connecting multiple rotor components. The movement of the turbine is efficiently transferred to the generator using a magnetically propelled mechanism linked to the turbine.

Fluid dynamic design of a vertical axis wind turbine rotor under low wind speed

The design of the rotor geometry of a vertical axis wind turbine (VAWT) type H, for power generation at low wind speeds, is presented. The computational simulation allowed us to establish that the NACA 0018 profile offers a better ratio of lift and drag coefficients in contrast to NACA 0021 and NACA 0025, so this geometry was selected as the working profile. Then, to generate a power of 30W, the dimensions of the airfoil chord, the radius, and the rotor's height were found from the blade tip speed ratio (TSR) values and the power coefficient. The results obtained indicate that the appropriate dimensions of the rotor at low-speed conditions are, a diameter of 2 m, a height of 2.16 m, and several blades of 3, for a rotation speed of 9 rad/s. Finally, an agreement was found between the angular velocity calculated theoretically, for the proposed rotor dimensions, and that obtained from the ANSYS-CFD simulation.

Method to Predict Outputs of Two-Dimensional VAWT Rotors by Using Wake Model Mimicking the CFD-Created Flow Field

Recently, wind farms consisting of clusters of closely spaced vertical-axis wind turbines (VAWTs) have attracted the interest of many people. In this study, a method using a wake model to predict the flow field and the output power of each rotor in a VAWT cluster is proposed. The method uses the information obtained by the preliminary computational fluid dynamics (CFD) targeting an isolated single two-dimensional (2D) VAWT rotor and a few layouts of the paired 2D rotors. In the method, the resultant rotor and flow conditions are determined so as to satisfy the momentum balance in the main wind direction. The pressure loss of the control volume (CV) is given by an interaction model which modifies the prepared information on a single rotor case and assumes the dependence on the inter-rotor distance and the induced velocity. The interaction model consists of four equations depending on the typical four-type layouts of selected two rotors. To obtain the appropriate circulation of each rotor, the searching range of the circulation is limited according to the distribution of other rotors around the rotor at issue. The method can predict the rotor powers in a 2D-VAWT cluster including a few rotors in an incomparably shorter time than the CFD analysis using a dynamic model.

Vertical-axis wind-turbine farm design: Impact of rotor setting and relative arrangement on aerodynamic performance of double rotor arrays

The impact of rotor setting and relative arrangement on the individual and overall power performance and aerodynamics of double rotor vertical axis wind turbine (VAWT) arrays is investigated. Eight rotor settings are considered: two relative rotational directions (co-rotating, CO, and counter-rotating, CN), two relative positionings (downstream turbine positioned in the leeward, LW, and windward, WW, of the upstream rotor), and two phase lags (Δθ = 0° and 180°). For each of the eight rotor settings, 63 different relative arrangements are considered resulting in 504 unique cases. The arrangements are considered within 1.25d≤R≤ 10d (d = rotor diameter) and 0° ≤Φ≤ 90°, where R and Φ are relative distance and angle of the rotors, respectively. Unsteady Reynolds-Averaged Navier–Stokes (URANS) CFD simulations, validated with experimental data, are employed. The results show that the power performance of the array is significantly influenced by the relative rotational direction and positioning, ∼8% in power coefficient (CP), while it is marginally dependent on relative phase lag. The different performance of the studied arrays is because of different parts of the downstream turbine revolution being affected by the wake of the upstream turbine and dissimilar strength/width of the shear layer created in the two rotors’ wake overlap. The preferred rotational direction for WW arrays is co-rotating while for LW arrays counter-rotating is favored. For the same arrangement, counter-rotating turbines with LW relative positioning have the highest CP due to their downstream turbine blade moving along the flow direction in the wake overlap region resulting in little energy dissipation and weak shear layer. In contrast, counter-rotating arrays with WW relative positioning have the lowest CP, because the downstream turbine blade moves against the flow in the wake overlap region, resulting in extensive velocity deficit and a thick, strong shear layer.

Development of a multi rotor floating offshore system based on vertical axis wind turbines

Abstract The upscaling of wind turbines results in fewer units per installed MW reducing infrastructure and maintenance costs of offshore wind farms. Multi rotor systems (MRS), comprising many wind turbine rotors on a single support structure, are potentially a means to maximize the upscaling benefit in achieving larger unit capacities than is feasible or economic with the conventional, 3-bladed horizontal axis wind turbine (HAWT). The MRS has an inherent upscaling advantage which, for a system with many rotors compared to a single rotor, reduces the total weight and cost of rotor-nacelle assemblies by a large factor. An innovative MRS design is presented based on vertical axis wind turbine (VAWT) rotors of the 2-bladed, H-type. Many disadvantages of VAWT design compared to HAWT in a single rotor system (reduced power performance and higher drive train torque, for example) are resolved in the MRS configuration. In addition, reduced component number and simpler components is advantageous for reliability and O&M cost. This MRS concept has many synergies arising from the choice of VAWT rotors. Results comprise a high-level evaluation of system characteristics and the first stage of more detailed investigation of aerodynamics of the high aspect ratio VAWT.

Centrifugal controller of rotation frequency for vertical axis wind turbines

The market for small vertical axis wind turbines (VAWTs) continues to grow rapidly, filling up especially the low wind potential locations. Since the Saudi Government has announced to install 9 GW of wind power by 2032, this ambitious plan could be at least partially improved by the small wind turbines, taking into account the low annual mean wind speed on the most Kingdom of Saudi Arabia territory.However, the safety and durability of most commercially available VAWTs have not been adequately addressed with respect to the turbine over speed in high wind speed conditions.The presented research gives a methodology for calculating a cost-effective dynamic braking controller, based on a centrifugal mechanical activation spring-load mechanism with a pendulum. The analysis is focused on a small two-tier 3 kW Darrieus VAWT, where a mechanically activated friction brake is deployed as the turbine rotational speed approaches a red line. The proposed method makes a small turbine absolutely safe on any available wind speed and/or during accidental electric load switch off. The analysis was made for a typically high continental wind speed of 25 m/s.The paper presents the calculation model in VisSim software. Controller parameters were developed as the result of the research conducted on a functional turbine of the specific size in the model. The experiments covered two different cases: with a relatively low spring stiffness coefficient (400 N/m), showing the periodical oscillations of a controller pendulum on the cut-out speed and a high spring stiffness coefficient (4000 N/m), which the VAWT rotor can be surely braked at.The paper is intended to provide the mathematical basis for the scientific analysis, as well as providing practical implementation information to engineers building similar turbines, including Savonius, Darrieus, H-Darrieus, helix shape, V-type, and any other types of rotating rotors. The estimated capacity utilization factor (CUF) of any VAWTs, when using the proposed centrifugal mechanical controller, can be increased twice to 82% for on-land small VAWTs.

Numerical Simulation and Wind Tunnel Investigation on Static Characteristics of VAWT Rotor Starter with Lift-Drag Combined Structure

In order to get rid of the impact of the global financial crisis and actively respond to global climate change, it has become a common choice for global economic development to develop clean energy such as wind energy, improve energy efficiency and reduce greenhouse gas emissions. With the advantages of simple structure, unnecessary facing the wind direction, and unique appearance, the vertical axis wind turbine (VAWT) attracts extensive attention in the field of small and medium wind turbines. The lift-type VAWT exhibits outstanding aerodynamic characteristics at a high tip speed ratio, while the starting characteristics are generally undesirable at a low wind speed; thus, how to improve the starting characteristics of the lift-type VAWT has always been an important issue. In this paper, a lift-drag combined starter (LDCS) suitable for lift-type VAWT was proposed to optimize the starting characteristics of lift-type VAWT. With semi-elliptical drag blades and lift blades equipped on the middle and rear part outside the starter, the structure is characterized by lift-drag combination, weakening the adverse effect of the starter with semi-elliptical drag blades alone on the output performance of the original lift-type VAWT and improving the characteristics of the lift-drag combined VAWT. The static characteristic is one of the important starting characteristics of the wind turbine. The rapid development of computational fluid dynamics has laid a solid material foundation for VAWT. Thus the static characteristics of the LDCS with different numbers of blades were investigated by conducting numerical simulation and wind tunnel tests. The results demonstrated that the static torque coefficient of LDCS increased significantly with the increased incoming wind speed. The average value of the static torque coefficient also increased significantly. This study can provide guidelines for the research of lift-drag combined wind turbines.

Research on Matching Characteristics of Wind Turbine and Generator for Small H-shaped Vertical Axis Wind Turbine

Based on the small H-shaped vertical axis wind wheel model (NACA0016),a CFD wind wheel model was constructed. Based on the principle of movinggrid, the grid division of the CFD wind wheel model is completed by usingGAMBIT software, and the boundary conditions such as the inlet boundaryand the outlet boundary are set reasonably. Then, the turbulence model andthe couple algorithm are used to carry out transient simulation calculations,and finally the aerodynamic parameter curves of the two-dimensional CFDwind wheel model are obtained. Based on this, the matching characteristicsof the wind turbine and generator of the small H-shaped vertical axis windturbine are studied. The research results show as follows: when the incomingwind speeds change in range of (2 m/s, 12 m/s), and the power character-istic curve and torque characteristic curve of the generator wind wheel arerespectively overlap the best power curve and best torque of the generator,the matching characteristics of the small H-shaped vertical axis wind turbinerotor and generator are optimal, which provides reference for carrying outrelated research.

Structural and Aerodynamic Characteristics Analysis of a Small V-shaped Vertical Axis Wind Turbine Rotor

ABSTRACT A detailed comprehensive study of a proposed V-shaped turbine rotor is performed in order to examine its structural and aerodynamic characteristics. The structural analysis section of this work determined the most structurally sound blade geometry from 3 different blade geometries. Using the chosen blade profile, 8 rotor models are developed and are tested numerically. These rotor models are of different configurations, focusing on an inclination angle of 45 and 60 degrees, blade twist angle of 0 and 5 degrees and number of blades. Four rotor models are taken from the initial tests for further study, 3B45D which is a three-bladed rotor with a 45 degree inclination angle, 5B45D which is a five-bladed rotor with a 45 degree inclination angle, 5B45D (5deg) which is a five-bladed rotor with a 45 degree inclination angle and a 5 degree blade twist angle, and 5B60D which is a five-bladed rotor with a 60 degree inclination angle. From the structural study, blade design 2 held the best structural characteristics. The design showed an excellent Von-Mises at 8.8 MPa for static structural and 22.2 MPa for fatigue stress response which is well below the yield strength of ABS Plastic. Both experimental and numerical data have relatively good agreement that is within 15% difference. Overall, maximum power coefficient achieved in this study is about 0.259 numerically and 0.213 experimentally. The best performance is seen by the 3B45D rotor in both static and dynamic study considering experimental and numerical corroboration of results.

Design Of Helical-Blade Rotor Of Vertical Axis Wind Turbine (VAWT)

The vertical axis wind turbine (VAWT) with helical-blade has been developed, manufactured and applied in almost all developed countries. In Indonesia, vertical axis wind turbines are still not widely applied compared to horizontal axis wind turbines. Vertical axis wind turbines with helical-blade are still very rare in Indonesia. Research and development of the vertical axis wind turbine are needed because of its advantages compared to horizontal axis wind turbine. The advantages are: can operate in various wind directions, lower noise due to smaller tip speed ratio (TSR) and for large-scale, mechanical and electrical systems of turbine can be placed on ground. The aim of this research is to design a vertical axis wind turbine rotor with helical-blade that can be applied at low speeds and changing direction wind condition, such as urban wind characteristics. Performance analysis of wind turbine rotor is done by using double-multiple stream-tube (DMS) model approach. This research yields a rotor of vertical axis wind turbine with helical-blade with rotor length and diameter are 2m and 1m respectively, the rotor blade airfoil is DU-06-W-200 with chord length is 0.2m. From analysis, the optimum tip speed ratio of the rotor is 2.6 with a maximum power coefficient is 0.57.

Pitch control of small H-type Darrieus vertical axis wind turbines using advanced gain scheduling techniques

Abstract During sudden wind speed changes, the response time of the wind turbine rotor is essential so that optimum operating condition always governs. As a result, wind turbine rotors especially the blades are the most delicate parts in a fluctuating wind condition posing a challenge for their effective operation. This paper focuses on gain scheduling pitch and MPPT control for a small H-type Darrieus vertical axis wind turbine (VAWT) with respect to the power output. A gain scheduled controller is designed by solving Linear matrix inequalities (LMIs) and used for stability control of the Darrieus VAWT rotor in an urban wind condition. A NACA 0018 airfoil is used to demonstrate the wind speed variations and nonlinear aerodynamic rotor behavior. The Stochastic Differential Equations (SDEs) as a function of a random number are imposed in Simulink using MATLAB R2018b. The proposed gain scheduled controller is found to be stable and achieves better performance under a gusty and turbulent wind condition compared to conventional controllers. The simulations are consistent to published experimental and numerical findings such that the system behaves as closely as possible to the real H-Darrieus turbine.

Understanding the Aerodynamic Behavior and Energy Conversion Capability of Small Darrieus Vertical Axis Wind Turbines in Turbulent Flows

Small Darrieus vertical-axis wind turbines (VAWTs) have recently been proposed as a possible solution for adoption in the built environment as their performance degrades less in complex and highly-turbulent flows. Some recent analyses have even shown an increase of the power coefficient for the large turbulence intensities and length scales typical of such environments. Starting from these insights, this study presents a combined numerical and experimental analysis aimed at assessing the physical phenomena that take place during the operation of a Darrieus VAWT in turbulent flows. Wind tunnel experiments provided a quantification of the performance variation of a two-blade VAWT rotor for different levels of turbulence intensity and length scale. Furthermore, detailed experiments on an individual airfoil provided an estimation of the aerodynamics at high turbulence levels and low Reynolds numbers. Computational fluid dynamics (CFD) simulations were used to extend the experimental results and to quantify the variation in the energy content of turbulent wind. Finally, the numerical and experimental inputs were synthetized into an engineering simulation tool, which can nicely predict the performance of a VAWT rotor under turbulent conditions.

Investigation of Blade Tip Shape for Improving VAWT Performance

Vertical axis wind turbine (VAWT) is a competitive power generation device due to structural simplicity, wind direction independence, no yaw mechanism required, easier maintenance, and lower noise emission. However, blade tip vortex will be generated at both ends of the blade during the rotation, resulting in torque loss and efficiency reduction. In this paper, computational fluid dynamics is used to study blade tip vortex and its reduction technique of a single-blade VAWT rotor in real scale. By monitoring the force and flow field at different heights of the blade, the influence ranges of tip vortex are obtained. The reduction effect of the bulkhead obtained from the blade profile curve is studied, and the size of the bulkhead is optimized. On the basis of adding the optimal bulkhead, the influence of the supporting strut is also explored. The joint action is obtained by changing the location of the supporting strut. The results show that the top supporting strut-bulkhead structure is the optimal position. The power-extraction efficiency of the rotor with this integrated structure is significantly improved at optimal tip speed ratios (TSRs) and higher TSRs.

Experimental and numerical investigation of twin vertical axis wind turbines with a deflector

In this paper we report on the design and testing of a novel vertical axis wind turbine (VAWT) system. The system consists of two counter-rotating VAWT rotors and a deflector that is placed between the two rotors. The system’s performance is first quantified in wind tunnel experiments and subsequently, three-dimensional computational fluid dynamics (CFD) simulations are performed to complement the experiments and to provide the fluid mechanical details. It is found that the deflector has a significant effect (power-increasing) on the power output of the two rotors, which is related to the rotational direction of the two rotors. With the addition of the deflector, the twin VAWT is able to harness up to 38.6% more wind energy compared with the system without deflector. The analysis of the CFD-produced flow field showed that the increased power output is the result of local acceleration of the fluid and local blockage effect of the deflector. The use of a deflector is found to be a simple and practical approach to improve the performance of twin VAWT system.

An experimental test of the effect of cup diameter on the power performance of novel design HC-type VAWT

Wind energy is one solution to overcome the energy problem in Indonesia. This study aimed to analyze the effect of cup diameter on the power performance of an HC-type vertical axis wind turbine (VAWT). The wind turbine used a combination of an H-type Darrieus wind turbine and a type-C rotor VAWT. The Darrieus HC-rotor wind turbine blade has a height H = 800 mm and diameter D = 800 mm with C-rotor variations on the tip with diameters of 76,2, 101,6, and 152,4 mm. The wind tunnel used an electric motor with a power of 1 HP (740 Watt) and 1400 rpm connected to a fan. The variation of wind speed was set to 2, 3, 4, 5, 6 and 7 m/s. The results showed that: (a) the highest rotation speedal speed was achieved by the HC-rotor diameter of 76,2 on 105 rpm with a wind speed of 7 m/s; (b) the highest value of the coefficient of power (Cp) is achieved by the HC-rotor diameter of 101,6mm (c) the highest value of the coefficient of torque (Ct) is achieved with the HC-rotor diameter of 152,4mm (d) the Darrieus HC-rotor wind turbine is suitable to be used in tropical regions that have low wind speeds. This result provides important information about the effect of the C rotor radius on the performance of HC-rotor Darrieus wind turbine blade vertical axis.

Mechanisms of power augmentation in two side-by-side vertical axis wind turbines

Using two-dimensional computational fluid dynamics (CFD) simulations, this study examines the physical mechanisms of performance improvement in a double rotor vertical axis wind turbine (VAWT) as compared to a single rotor VAWT. It was found that the primary mechanism for the approximately 10% improvement in power coefficient (CP) for the double rotor VAWT was a reduction in the bypass flow that passes around the outside of the single rotor VAWT. The single rotor VAWT is shown to cause greater than 54% of the incoming flow to bypass around the outside of the VAWT. By placing a second rotor in the system, the cross-stream flow that would normally exist to one side is suppressed due to the opposing cross-stream flow from the second rotor. The collision of cross-stream velocities results in a high pressure field upstream of the rotors. This high pressure field re-directs more flow through the rotors, reducing the total bypass down to below 51%. This reduction in total bypass is solely due to the reduction in bypass on the interior of the double rotor system as the exterior side actually experiences an increase in bypass of about 83%.

Performance Improvements for a Vertical Axis Wind Turbine by Means of Gurney Flap

Abstract A numerical study was carried out to investigate the effects of a Gurney flap (GF) on the aerodynamics performance of the NACA 00 aerofoil and an associated three-blade rotor of a H-type Darrieus wind turbine. The flow fields around a single aerofoil and the vertical axis wind turbine (VAWT) rotor are studied using unsteady Reynolds-averaged Navier–Stokes equations (URANS). The height of GF ranges from 1% to 5% of the aerofoil chord length. The results show that the GF can increase the lift and lift-to-drag ratio of the aerofoil as associated with the generation of additional vortices near the aerofoil trailing edge. As a result, adding a GF can significantly improve the power coefficient of the VAWT at low tip speed ratio (TSR), where it typically gives low power production. The causing mechanism is discussed in detail, pointing to flow separation and dynamic stall delay.

FEA Assisted Design and Structural Research on Vertical Axis Wind Turbine Rotor

The scope of the project is to perform finite element analysis of the Vertical axis wind turbine rotor assembly.Blade, arm, connectors and strings assembly of rotor are considered for analysis and to study the static behaviour at the different loading conditions. Total vertical load of 132 kg self-weight is acting downward direction to the structure. Considered that rotor will be rotating at maximum speed (RPM) aerodynamic load with self weight conditions. Due to higher angular velocity (154 RPM) blades will be subjected to great centrifugal force. Along with the centrifugal load rotor also will get subjected to fluctuating aero dynamic loads. In analysis it is considered as the rotor in stationary position and subjected to the maximum drag force at 52 (m/s) wind velocity at azimuth value of 90˚. SOLID92 is used for the 3-D modelling of solid structures. The maximum stress value obtained from the analysis is 183.1 N/mm2 for the loading and boundary conditions.

Design, manufacturing and validation of a vertical-axis wind turbine setup for wind tunnel tests

The potential of vertical-axis wind turbines (VAWTs) for specific applications (floating off-shore or urban installations) has been reconsidered in recent years. This renewed interest has led to an increasing number of experimental studies on VAWTs. A challenge of experimental work is correctly interpreting experimental results but just as important is the design of the experimental setup. The objective of the present study is to elaborate on the complete development process of a VAWT wind tunnel test setup, from design to aerodynamic interpretation. The effect of the design choices and structural characteristics of the setup can be traced in the measured torque. The influence of structural dynamics of an experimental setup are proven to influence unsteady measurements significantly through the analysis of the spectral content of the measured torque. An extensive modal analysis of the VAWT rotor allows to link modal vibrations to their contaminating effect on the measured torque. In addition, the dynamics of the sensors and setup are found to be important contributions to the contamination of dynamic measurements. To interpret unsteady torque measurements, the complete experimental setup needs to be dynamically characterised.

CFD analysis for the performance of micro-vortex generator on aerofoil and vertical axis turbine

A numerical study was performed to investigate the effects of Microvortex Generators (MVGs) on the aerodynamic performance of the NACA 0018 airfoil and an H-type Darrieus wind turbine. MVGs can delay stall, which may occur for a sustained duration during turbine operation. The flow fields around a single airfoil and the Vertical Axis Wind Turbine (VAWT) rotor are investigated. The purpose of the present work is to determine the best configuration of MVGs. In total, eight different configurations are studied. The results show that MVGs have significantly enhanced the lift of the airfoil near the stall and improve the stall margin. The improved airfoil design with MVGs installed at 20% chord length and 16° to the inlet flow with a rectangle shape has the maximum lift and stall angle. In addition, adding MVGs of the same configuration can significantly improve the power coefficient of the VAWT at a high tip speed ratio, where it typically gives low power production. The flow separation is suppressed in the azimuth angle ranging from 120° to 135°, where the power output increase is observed showing a potential impact for VAWT design.