Vertical-axis Turbine Research Articles

Numerical and experimental analyses of the performance of a vertical axis turbine with controllable-blades for ocean current energy

Phasing out high-carbon-emission fossil fuels and using renewable energy have become a global consensus for mitigating climate change. For the application of renewable energy, this study proposes a high-efficiency controllable-blade vertical axis turbine, which has six blades and a cam plate, for ocean current power generation. A novel design for the turbine using cam to control the opening and closing of blades to enhance the performance of vertical axis turbines. The design feature of the drag-type blade is to be active or open quickly in downstream. The effective area of the blade under thrust is increased to enhance the performance. On the other hand, the blade is designed to be inactive or close quickly in upstream and the drag of blade in upstream can be reduced. A commercial software, ANSYS FLUENT is used to simulate the performance of the vertical turbine. The streamline, velocity, and pressure around the turbines are then obtained. The power coefficients and torques are evaluated at various angular velocities and tip speed ratios and are validated by experimental results. The maximum power coefficient of the proposed turbine occurs at an angular velocity ratio of 4 with quick opening of blades and is higher than that of 3, 5, or 6 by 3.4 %, 2.7 %, or 7.4 %, respectively. In addition, performance comparisons among controllable-blade vertical axis turbine, fixed-blade vertical axis turbine, and Savonius turbine are made. The results show that the maximum power coefficient of the presented controllable-blade vertical axis turbine is 143 % and 103 % higher than that of the fixed-blade vertical axis turbine and Savonius turbine at V = 1 m/s, respectively.

Numerical comparison and efficiency analysis of three vertical axis turbine of H-Darrieus type

Hydropower is an important source of energy in Latin America. Many countries in the region, including Brazil, Peru, Colombia, and Chile, rely heavily on hydropower plants to meet their energy needs. However, there are also challenges related to the use of hydropower in the region, such as the construction of dams that can have negative impacts on ecosystems and local communities. A new alternative is the production of energy through hydrokinetic turbines because they are a clean and renewable energy source that does not emit greenhouse gases. In addition, its production is predictable and can be generated in a variety of environments, from coasts to rivers and canals. Within the hydrokinetic turbines are the H-Darrieus turbines although they are still under development, they are seen as an important opportunity to diversify the energy matrix and reduce dependence on fossil fuels. The main purpose of this study is to determine and compare the efficiency of three Darrieus H-type vertical axis hydrokinetic turbines numerically. The turbines were configured with different solidities. The NACA 0018 profile was used for the turbine design. The study was carried out using the ANSYS® Fluent 2022R2 software, two-dimensional (2D) simulations set up constant operating conditions. Rotation speed variations have been set between 21 and 74 RPM with 10 rpm increments. Furthermore, the General Richardson extrapolation method is used for the analysis of mesh convergence, monitoring the turbine power coefficient as a convergence parameter. The numerical results show that the turbine H-Darrieus with a solidity of 1.0, a wider operating range, and lower power and torque coefficient. At low TRS, the largest solidity provided the best efficiency and the greatest self-starting capability, but it also had the smallest operating range

The Design and Analysis of a Novel Vertical Axis Small Water Turbine Generator for Installation in Drainage Lines

The objective of this study was to determine the mechanical power efficiency of a novel vertical-axis small water turbine generator for installation in drainage lines. A 3D model was created to evaluate the performance of each design. The system was designed, analysed, and calculated for the most suitable geometries of the water inlet, drainage lines, main structure, and water turbine wheels using computational fluid dynamics software. The diameter of the water turbine wheel in the numerical model was 48 mm. The control volume technique was used in the numerical simulation method, and the k-epsilon turbulence model was employed to find the computational results. For the Computational Fluid Dynamics (CFD), the appropriate mash element for each model section was generated for numerical simulation, which showed that the torque from the water turbine modelling varied depending on the time domains and was related to speed relative to the developed force. The maximum torque and maximum power that a vertical-axis small water turbine for installation in a drainage line could generate at a maximum flow rate of 0.0030 m3/s were 0.55 N.m and 26.84 watts, respectively. Similarly, calculations with mathematical equations, found that the maximum mechanical power value after calculating the rate of loss within the pipe system was 12.95 watts. The forces generated by the speed and pressure of the fluid can then be applied to the structure of the water turbine wheel. The vertical-axis small water turbine for installation in a drainage line was analysed under its self-weight by applying a gravitational acceleration of 9.81 m/s2 in Solidworks Simulation software version 2022. The numerical simulations that resulted from this research could be used to further develop prototypes for small water turbines generating commercial electricity.

Laboratory tests of blade radius variation on vertical shaft savonius turbine performance

Wind turbines are one of the machines that are currently still used to convert wind kinetic energy so that they can be used by humans such as to drive pumps in agriculture and produce electrical energy. Savonius turbine is a vertical axis turbine that is currently widely used as an electrical energy generator, this wind turbine is a type of drag type wind turbine that has a simple design that is in the form of a semicircular curved blade side. Therefore, the author is interested in researching the resulting performance including turbine rotational speed, power generated, and wind turbine efficiency against the variation of the blade radius. The method used is experimental, the stages of this research are in the form of literature studies, making savonius turbines, testing savonius turbines with variations in blade radius as well as data retrieval, data processing, and analysis. Based on the data obtained, the rotating speed of the turbine is influenced by variations in the radius of the blade. The larger the blade radius, the smaller the turbine rotational speed. The maximum turbine rotation speed at blade radius 63 is 173 rpm, while at blade radius, 88 is 118 rpm and at blade radius 113 is 115 rpm. So the highest turbine rotating speed at a radius of 63.

The Benefit Using a Circular Flow Disturbance on the Darrieus Turbine Performance

Darrieus is a vertical-axis type turbine with difficulty rotating at low current velocity. Adding a circular flow disturbance in front of the Darrieus turbine can improve the self-start capability. This study has aimed to improve the turbine's performance by identifying the configuration and diameter ratio of flow disturbance. Numerical modelling in transient conditions has been done by using Computational Fluid Dynamics (CFD) software with a sliding mesh technique. There are four diameter ratios ds/D 0.1, 0.3, 0.5, and 0.7 and three variations of cylinder position. Each combination variation has been simulated at current velocity of 0.3, 0.4, 0.5, and 0.6 m/s. As a result, depending on where the cylinder installation is located, the circular flow disturbance has an effect that might hinder or enhance the performance of the turbine. The best result is at the flow disturbance position of -60o with a diameter ratio of ds/D 0.5 at TSR 1.43. The maximum coefficient of power (Cp) value has increased by 38%. Furthermore, at overall current velocities with a range of 0.3–0.6 m/s, the average Cp has increased of 30% with the best diameter ratio usage of ds/D 0.5.

Aerodynamic Characterization of Darrieus Turbines during Self-Start at different Azimuthal Quadrants

One key technology to extract kinetic energy from wind and water is the vertical-axis turbines. However, these flows and currents often fluctuate, forcing the turbine rotors to operate in transient modes. To improve rotor performance, the transient aerodynamic characteristics across the four quadrants of the rotor sweep must be well-understood. We address this need by simulating the transient process of a 3-bladed Darrieus turbine rotor during self-start using the dedicated turbine aerodynamics software QBlade. The simulated transient evolution of the rotor compares well against the experimental and computational-fluid-dynamics data from previous studies. When the rotor self-starts within its first three cycles, its torque is contributed differently from each of the four quadrants. Respectively, its windward and upwind quadrant positively contributes by up to 43% and 326% each to the overall torque, and the leeward and downwind quadrant negatively reduces by up to -346% and -85% each from the overall torque. However, upon reaching steady state, these roles change where the positive torques are contributed by the upwind and leeward quadrants by up to 120% and 10%, respectively, while the negative torques are caused by the downwind and windward quadrants by up to -18% and -13%, respectively. Insights into these rotor dynamics can be later used to propose newer rotor designs or operations to improve the transient performance of the turbine

3D CFD Modelling of Performance of a Vertical Axis Turbine

Recently, wind turbine research has switched focus to vertical axis wind turbines due to the extensive research that has been performed on horizontal axis wind turbines and the potential of vertical axis wind turbines in built-up areas. This study aims to analyse the performance of a small-scale hybrid vertical axis wind turbine that can switch from functioning as a Darrieus (lift) turbine to a Savonius (drag) turbine by rotating the blades. The turbine was analysed using 3D computational fluid dynamics (CFD) simulations in ANSYS Fluent as the primary method, and the findings were verified using wind tunnel experiments. During the analysis, design parameters such as the blade length, diameter, and number of blades were varied to determine if the design had room for improvement. It was found that the current design of the turbine has an optimal efficiency of 12.5% in the Darrieus configuration, which was found to increase when the diameter or blade length was increased. The Savonius configuration was found to be more efficient at low tip-speed ratios (<0.14), and its efficiency could be increased by adding more blades. The experiments found similar trends to the simulations; however, the efficiencies obtained were on average a tenfold increase from the simulation. Implementing the changes that increased efficiency leads to an increased wake recovery distance, making it less suitable for use in a wind farm.

Deep Learning-Based Prediction of Unsteady Reynolds-Averaged Navier-Stokes Solutions for Vertical-Axis Turbines

The following study investigates the effectiveness of a deep learning-based method for predicting the flow field and flow-driven rotation of a vertical-axis hydrokinetic turbine operating in previously unseen free-stream velocities. A Convolutional Neural Network (CNN) is trained and tested using the solutions of five two-dimensional (2-D), foil-resolved Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, with free-stream velocities of 1.0, 1.5, 2.0, 2.5, and 3.0 m/s. Based on the boundary conditions of free-stream velocity and rotor position, the flow fields of x-velocity, y-velocity, pressure, and turbulent viscosity are inferred, in addition to the angular velocity of the rotor. Three trained CNN models are developed to evaluate the effects of (1) the dimensions of the training data, and (2) the number of simulations used as training cases. Reducing data dimensions was found to diminish mean relative error in predictions of velocity and turbulent viscosity, while increasing it in predictions of pressure and angular velocity. Increasing the number of training cases from two to three was found to reduce relative error for all predicted unknowns. With the best achieved CNN model, the variables of x-velocity, y-velocity, pressure, turbulent viscosity, and angular velocity were inferred with mean relative errors of 6.93%, 9.82%, 10.7%, 7.48%, and 0.817%, respectively.

On the Regulation of Oscillations of a Galloping-Based Wind Power Harvesting System

Currently, various possibilities for obtaining energy from renewable sources, in particular, flows of water or wind, are intensively investigated. The most widely used wind power harvesters are those where the working element rotates (a propeller or a vertical axis turbine, such as a Darrieus or Savonius rotor). However, the possibility of using the flow-induced oscillations of elastic structures in order to generate energy is now actively considered. One of the types of such oscillations is galloping, i.e. vibrations of bluff bodies in the direction perpendicular to the incident flow. The occurrence of galloping is due to the fact that aerodynamic forces acting on a bluff body, under certain conditions, create a negative damping. In this paper, we consider a mechanical system consisting of three bodies that can move in a direction perpendicular to the flow. One of these bodies is a square prism, and the other two are material points. The bodies are connected in series with each other and with a fixed support by linear elastic springs. A permanent magnet is rigidly connected to the prism. This magnet moves inside an induction coil. As a result, an electric current is generated in the electrical circuit connected to the coil. For such installations, on the one hand, it is required that galloping occurs at the lowest possible flow speed. On the other hand, at high flow speeds, it is necessary to reduce the amplitude of oscillations so that the device would not be damaged. The influence of the system parameters (in particular, the spring stiffness coefficients) on the stability of the equilibrium and on the characteristics of periodic solutions is studied. It is shown that by changing the stiffness of the springs, it is possible to significantly expand the range of flow speeds where the galloping occurs. The amplitudes of oscillations of bodies increase as the flow speed grows. In order to increase the limit flow speed, at which the amplitudes of oscillations start exceeding the maximum permissible value, a regulating algorithm is proposed. Within the framework of this algorithm, the displacement of one of mass points with respect to the prism is locked/unlocked depending on the current flow speed.

Design and Comparison of Vehicle Mounted Wind Turbines

Electric vehicles (EVs) are gradually taking place of the conventional fossil fuel-based vehicles. However, popularity of EVs is hindered due to longer charging time and lower mileage. To address the mileage issue, in this paper we have proposed to use wind turbines to be mounted on vehicle, so that it can harness the wind energy to charge the batteries while the vehicle is in motion. We have designed two types of wind turbines: horizontal axis and vertical axis turbines and our analysis showed that vertical axis turbines provide better solution in extracting maximum wind power.

Experimental and multiphase modeling of small vertical-axis hydrokinetic turbine with free-surface variations

Vertical-axis hydrokinetic turbines are promising option to harness the low velocity currents. However, limited investigations have been carried out considering the interactions between the turbine rotor and the channel section, including the free-surface. Thus, a vertical-axis turbine model has been designed and manufactured, to be tested in an open channel. Also, a three-dimensional multiphase simulation has been carried out, using the volume of fluid (VOF) model, to capture the air–water interface and to investigate the free-surface variations effects on the turbine output. Experimentally, the turbine model has been characterized under different flow conditions and free-surface levels. The peak power coefficients are found to increase with the upstream velocity. This effect is directly linked to the blockage ratio and the Froude number. A reasonably good match has been found between the experimental and the numerical results. The VOF model is able to simulate the free-surface longitudinal variations, and the effect of the turbine blockage of the channel. The velocity field and the pressure coefficient distribution, around the turbine rotor, have been studied and correlated with the free-surface variations from upstream to downstream of the turbine. Finally, the vortex street generated by the blade–plate interaction has been analyzed.

Energy efficiency enhancement onboard by use an innovative system of turbines integrated to tanker ship hull

The environmental awareness and rising costs of marine fuel led research activities to focus on eliminating the dependence on fossil fuels as a traditional source of energy. Clean and renewable energies, such as hydro energy for instance, could be used onboard to enhance the ship energy efficiency.In this research, a novel type of capturing energy is used. By exploiting the water flow that is​ generated around the ship hull while sailing overseas, and putting turbines to face this flow, the turbines will spin, and consequently generate a useful energy that may be used to cover a part of needed power onboard. An innovative system of array of turbines integrated to the second version of Kriso Very Large Crude Carrier (KVLCC2)’s hull was modeled, and the numerical investigations, using computational fluid dynamics (CFD), were carried out to analyze the effect of this link on the propulsion hull power and the hull resistance. The gross generated power was calculated, then the additional hull resistance converted to resistance power was estimated to find out the net power of the system which could be used later.To calculate the excess resistance added to the hull resistance, the flow simulations were conducted on the hull itself and its resistance was numerically calculated and validated with the experimental calculations found in literature. Also verification & validation were carried out on the turbines before their integration to the hull to assure their computerized three-dimensional 3D model design. Using the characteristics of KVLCC2 hull in this study, with the attachment of an array of 10 spherical vertical axis turbines to each side of the hull. An excess net power of about 15%–17% of the required effective power of the ship was obtained. Thus, the study presents a new solution for utilizing the renewable hydro-power onboard which limits the great dependence of the fossil fuel.

Insights into the flow dynamics and rotor performance of a Savonius turbine with dynamic venting using controllable flaps

The drag-driven vertical-axis turbines with semicircular rotor blades, commonly known as Savonius turbines, remain potentially beneficial to extract renewable energy from wind and water streams, especially in terms of their practicality to provide low-cost solutions to rural areas. However, they suffer drawbacks due to the negative torques on their returning blades. We propose a novel solution by dynamically venting out these returning blades using controllable flaps, which retained their omnidirectional capability. Results from unsteady numerical simulations showed that the vented rotor attained a maximum average power coefficient (CP) of 0.275 at the tip-speed ratio (symbolized as λ) of 0.9, which was 21.7% better than that on the unvented rotor. Furthermore, the proposed dynamically vented blades produced large improvements in the average torque coefficient (CT), with maximum gains of 38.3% on the returning blade at λ = 0.4 and 24.8% on the full rotor at λ = 1.0, relative to those on the unvented rotor. The controlled dynamic venting was beneficial because it modified the pressure distributions surrounding the returning blade and changed the flow structure downstream of the vented blade that improved the torque on the subsequent blade entering the returning side. Elucidation on the flow dynamics revealed that the flows were vented outward through the flap aperture onto the convex side of the returning blade, rather than inward into its concave side, as initially hypothesized.

Numerical investigation of a two-bladed vertical-axis turbine operating in a confined channel

The energy harvesting performance of a hydrokinetic turbine in a confined channel has been investigated through numerical simulations. It consists of a two-bladed vertical-axis turbine with a NACA0015 profile. Fluid dynamics are reproduced by a 2D numerical model solving the unsteady RANS equations through a finite volume approach in OpenFOAM-v6 . Following a numerical sensitivity analysis, the baseline model has been validated with respect to reference data for an unconfined turbine with similar design. The model has then been employed for assessing the influence of the main design parameters – namely blade-channel gap ε 0 , solidity σ and tip-speed ratio λ – on the performance of the turbine. First, a parametric study on the plane λ × σ revealed that best performance is obtained at high solidity and low tip-speed ratios. In a range of solidities from 0.06 up to 0.48 , the optimal value of tip-speed ratio – which is considerably higher when compared with unconfined turbines – is precisely identified. Finally, the effects of the blade-channel gap ε 0 on the performance of the turbine has been investigated as well. It has been found that ε 0 should be set as small as possible in order to maximise energy harvesting. Moreover, numerical results allowed for estimating a limit value of ε 0 > 9 over which the performance of a turbine operating in a confined channel should match that of an unconfined turbine.

Numerical simulations of a vertical-axis hydrokinetic turbine with different blade-strut configurations under free-surface effects

Numerical simulations of a vertical-axis hydrokinetic turbine with different blade-strut configurations under free-surface effects

Analysis of Wake Turbulence for a Savonius Turbine for Malaysia’s Slow-Moving Current Flow

With Malaysia being surrounded by water bodies, tidal energy could be used for energy extraction. While several turbine designs and technologies have been used for tidal energy extraction, information on the use of vertical-axis tidal turbines (VATTs) for shallow-water applications is scarce. However, implementing horizontal-axis tidal turbines (HATTs) is not feasible due to Malaysian ocean depths. Hence, examining the wake-flow characteristics of VATTs in a shallow water-working environment in Malaysia is essential. The wake turbulence of the Savonius turbine model was compared with that of a hypothetical ‘actuator' cylinder, a VATT representation. Subsequently, the wake turbulences of a Savonius turbine model in static and dynamic simulations were compared to understand the flow distinction. Compared with that exhibited by the hypothetical actuator cylinder of 2.5 m, the hypothetical actuator cylinder of 5 m exhibits greater velocity deceleration. Additionally, the modelled Savonius turbine exhibits significantly more deceleration than that exhibited by the hypothetical actuator cylinder. Finally, the analysis of the static model of the Savonius turbine shows deceleration that is greater than that of the dynamic model.

Analysis of Wake Interaction of Savonius Tidal Turbine in Shallow Water Application

Malaysia highly depends on non-renewable energy sources like fossil fuels to supply the country's growing energy needs. On the other side, the oil and gas industry is facing challenges due to the depletion of fossil fuel supplies. Renewable energy is an alternative to fossil fuels that has been developed as a means of maintaining steady development in Malaysia. This is due to the slow average current speed in the sea around the country. Various renewable energy sources have been researched, with tidal energy garnering the most interest. This study focuses on tidal turbine array configuration for shallow water applications by using a Savonius turbine. The turbine layout is challenging to deploy the tidal array properly, and the wake interaction between the devices must be studied. The multi-row and single-row arrays have been studied using Computational Fluid Dynamics (CFD) simulations. The numerical research using a CFD technique is used to explore the effect of turbine spacing and capacity on the array's wake production. The vertical axis turbine is represented by a hypothetical 'actuator' cylinder and a 'Savonius' disc (VATT). Following the domain configuration, the turbine has been configured to static modes. According to the findings, the VATT model has a faster wake recovery and follows the definition of the distant wake. When working in shallow water, staggered arrays with bigger spacing are recommended since there is a lower chance of wake mixing between the rows.

Rotors of Vertical-Axial Wind Turbines Assembled in Bearings and Aerodynamic Characteristics of a Blade with Unclosed Wing Profile

Abstract In world practice, traditional blades used in high-speed wind turbines, both horizontal-axial and vertical-axial, have a wing-shaped profile. However, for horizontal-axial wind turbines, blades with such a profile have a fairly narrow range of operating values of the angle of attack of the incoming air flow and a low value of the moment of pulling from place. As for vertical-axial wind turbines, the self-starting of the rotor with wing blades is completely absent and additional devices are needed to start the rotor into operation. In order to ensure the self-starting of the rotor and the operation of the wind turbine at high and low wind speeds, a new shape of the blade profile was developed, called non-closed wing profile. The concept of the development is that the blade should have a configuration in which the pulling force is involved at the beginning of the movement, and then, with the establishing of the movement, a lifting force would arise, which acquires a prevailing character in the operating mode. The article presents the results of experimental studies of the aerodynamic characteristics of the developed non-closed wing blades. One of the results obtained is to determine the effect of the thickness of the blade profile on the range of values of subcritical angles of attack of the incoming air flow and the differences between the nature and range of changes in the coefficients of lifting force and pulling force in a traditional wing blade and a blade with a non-closed wing profile. Studies of the rotor model of a vertical-axial wind turbine with non-closed wing blades have confirmed the presence of its self-starting and operability even at low wind speeds.

Advancement of Tidal Current Generation Technology in Recent Years: A Review

Renewable energy provides an effective solution to the problem existing between energy and environmental protection. Tidal energy has great potential as a form of renewable energy. Tidal current generation (TCG) technology is the earliest renewable energy power generation technology. The advancement of science and technology has led to TCG rapidly developing since its emergence in the last century. This paper investigates the development of TCG in recent years based on the key components of TCG systems, both in terms of tidal energy harvesting research and power generation unit research. A summary of tidal energy harvesting is presented, investigating the main tidal energy harvesting units currently available. In addition, research on generators and generator control is summarized. Lastly, a comparison between horizontal and vertical axis turbines is carried out, and predictions are made about the future trends in TCG development. The purpose of this review is to summarize the research status and research methods of key components in tidal energy power generation technology and to provide insight into the research of tidal energy-related technologies.

Development of the reciprocating airflow generator for wave power generator and study on the vertical axis turbine characteristics in reciprocating airflow

AbstractRenewable energy is attracting attention as an alternative to current mainstream power generator sources. One source of renewable energy is wave energy. We devised a simulator for the OWC‐type wave power generator and developed a reciprocating airflow generator is generated reciprocating airflow by using the reciprocating motion of a piston. This piston motion was achieved by converting the rotational motion of the motor into linear motion of the ball screw via gears. Furthermore, we used a vertical axis turbine with arc camber blades and studied on the turbine characteristics. Owing to the reciprocation of the piston, a substantially sinusoidal reciprocating airflow was generated in the measurement section. It was confirmed that a reciprocating airflow speed was generated for all the target values. A load characteristic test of the turbine was conducted. It was confirmed that the maximum turbine output was 1.60 W.