Savonius Rotor Research Articles

Effect of waves on leading edge of modified Savonius rotor blades

The blade profile of the Savonius hydrokinetic turbine has a significant effect on the performance of the rotor. Many previous numerical and experimental research suggested different blade profiles. In the present work, a similar recommended blade profile selected, and two different configurations were namely, i. sharp edge outside and ii. sharp edge inside. The results were compared with the conventional rotor. The investigation concludes that a sharp edge outside delivers better performance than a sharp edge inside and traditional rotor. The best configuration was further tested for different wave amplitudes, i.e. P/λ. The waves on the blades further enhance the performance of the rotor. Compared to a previously proposed design, the present modified configuration indicated a 31% improvement in power coefficient and a 37% improvement compared to the conventional design.

Recent Advancement in Savonius Wind Turbine- A Review

In the steps to save our earth from global warming every nation focused on their own way to promote green energy among which the Savonius vertical axis wind turbine is one of the excellent viable solutions for scavenging wind energy in a downtown background, due to distinctive characteristics such as compactness, self-starting ability at light wind, minimum noise level, with relatively reasonable price and simple assembly. However, the traditional Savonius Wind Turbines with semicircular blades has a proportionately low power coefficient together with a high negative torque produced by the returning blade is a crucial disadvantage of this rotor. This work focuses on reviewing and giving an overview on the form of the wings of Savonius Vertical Axis Wind Turbine. This paper also aims to give a run through of the several augmentation approaches used in Savonius rotor over the last four decades. In this paper, a brief on all possible segments and parts of the machine is given after a brief analysis and research on each topic.

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.

ON THE SELF-STARTING COMPARATIVE PERFORMANCE EVALUATION OF DARRIEUS AND HYBRID HYDROKINETIC ROTOR

Darrieus rotor is a promising technology for hydrokinetic and wind energy harvesting applications. However, the Darrieus rotor suffers from the problem of poor starting performance. The present research highlights solutions to improve the poor starting performance of the Darrieus rotor by introducing the hybrid rotor. Further, a comparative performance evaluation of conventional vertical axis Darrieus and hybrid rotors has been investigated numerically. The most widely used S-series S-1046 hydrofoil has been utilized by hybrid and Darrieus rotors. Further, two semicircular blades are used for the Savonius part of the hybrid rotor. The size of the Savonius part is optimized to obtain maximum performance from the hybrid rotor. Analyzing the flow field distributions across the turbine vicinity has highlighted various possible reasons. The study results have demonstrated that the hybrid rotor yields an exceptional increment of about 159.41% in the torque coefficient under low tip speed ratio (TSR) regimes (during initial starting) compared to the Darrieus rotor. However, due to the Savonius rotor's presence, the hybrid rotor's maximum power coefficient is reduced slightly compared to the maximum operating point of the Darrieus rotor. Further, the hybrid rotor yields a wider operating range than the single maximum operating point by the Darrieus rotor. The present investigations will assist the designers in selecting the site-specific hydrokinetic technology suitable for efficient and optimum use of hydrokinetic potential.

CFD Analysis of The Stage-Ratio Factor on Savonius Wind Turbine Performance to Optimize Clean-Energy Conversion

In Indonesia, 50% of electrical energy is supplied by coal via electric steam power plants, with the remaining 14% supplied by new renewable energy sources. This phenomena demonstrates a significant divergence in the utilization of fossil energy sources against new renewable energy sources. The impact of fossil energy sources is the occurrence of global warming and non-renewable energy sources, a transition process to clean energy produced from renewable energy is required. Hydro, wind, and bioenergy are all possible renewable energy sources in Indonesia. The potential for converting wind energy into electrical energy in Indonesia is relatively large, at 159 GW. The rotor in the wind turbine is one of the primary components that plays a part in reversing the kinetic energy of the fluid into electrical power. Savonius is a simple rotor that can be used to generate power from wind on a small scale. Savonius' merits are its basic structure and ability to function at low wind speeds. This study was carried out on a Stage-ratio variation on a two-stage Savonius rotor with a Phase Shift-Angle of 30˚. The boundary condition is steady-state, and the turbulence type employed in modeling is SST. The goal of this research is to provide an optimal design for the Savonius Wind turbine as a design consideration in local-scale wind energy management, as well as to contribute to the attainment of the SDGs by 2030 through clean energy. Optimal design for Savonius with a PSA of 30˚ was produced Cpmax 0.29 with Stage-ratio 2:1.

CFD Calculations of Average Flow Parameters around the Rotor of a Savonius Wind Turbine

The geometry of a conventional two-bladed Savonius rotor was used in this study based on a report available in the literature. A two-dimensional rotor model consisting of two buckets and an overlap ratio of 0.1 was prepared. The unsteady Reynolds averaged Navier-Stokes (URANS) equations and the eddy-viscosity turbulence model SST k-ω were employed in order to solve the fluid motion equations numerically. Instantaneous velocities and pressures were calculated at defined points around the rotor and then averaged. The research shows that the operating rotor significantly modifies the flow on the downwind part of the rotor and in the wake, but the impact of the tip speed ratio on the average velocity distribution is small. This parameter has a much greater influence on the characteristics of the aerodynamic moment and the distribution of static pressure in the wake. In the upwind part of the rotor, the average velocity parallel to the direction of undisturbed flow is 29% lower than in the downwind part.

Elliptical Bladed Savonius Rotor for Wind Energy: Efficacy of RANS Modeling for Flow Characteristics

Abstract Wind energy is a key contributor to renewable energy production. Vertical axis wind turbine (VAWT) of Savonius type is advantageous in places of small-scale power production and low wind speed regions. It is a VAWT of the drag-based type. The disadvantage of a Savonius rotor is its low efficiency due to the generation of negative torque on the returning blade. To reduce the negative torque, the performance parameters of a Savonius rotor need to be optimized. The shear-stress transport variant of k–ω turbulence model is used in the current study to compute 2D unsteady Reynolds-averaged Navier–Stokes calculations for an ellipse shape blade Savonius rotor to capture its aerodynamic behavior. The flow complexities, such as vortex generation and circulation, are analyzed for four different azimuthal angles 0deg, 45deg, 90deg, and 135deg for a tip speed ratio (TSR) of 0.8. A rise in CD to 1.0 at TSR equal to 0.9 indicates an adverse pressure gradient region on the forward-moving blade. The circulation studied in the present paper could be of practical importance in situations involving an array of Savonius rotors to find an optimum rotor position and rotational direction as in the case of horizontal axis wind turbine (HAWT).

Power Performance Analysis Based on Savonius Wind Turbine Blade Design and Layout Optimization through Rotor Wake Flow Analysis

Savonius vertical axis wind turbines have simple structures, can self-start in environments with low wind speed and strong turbulence intensity, and can be installed at low costs. Therefore, installation is possible in urban centers with low wind speeds, which may contribute to the construction of a decentralized power system. Savonius wind turbines are operated by drag force, with the blades moving in the same direction as the flow current providing the thrust force and those moving in the opposite direction of the wind being rotated by the drag force. In this study, the Savonius wind turbine design was examined to develop a stable wind turbine for use in urban centers at low wind speeds. The Savonius rotor design variables (aspect and overlap ratios) and blade forms (semi-circular, Bach, and elliptical type) were examined using computational fluid dynamics analysis. Moreover, a rotor capable of providing the target output was designed and maximum rotor efficiency of 18% was realized. Further, changes to the flow corresponding with various turbine layouts were analyzed to determine the arrangement that would maximize turbine performance. The results showed that the maximum efficiency of the turbines was in the 17–19% range and without significant variation.

How to Increase Savonius Power Coefficient: Ducted Rotor Performance with Different Overlap Ratios

The use of ducted configuration to increase the efficiency of wind turbine rotors is gaining wide attention in the scientific community. Specifically for mini and micro rotors in urban environment applications this solution demonstrated to be very attractive. The possibility to overcome the Betz limit for power coefficient was widely demonstrated in ducted horizontal axis wind turbines. However, very few studies have dealt with ducted Savonius rotor despite these rotors represented an efficient solution for urban environment thanks to their simplicity, their cheapness and the low cut in velocity in highly turbulent conditions as well. Furthermore, the ducted Savonius concept, might be applicable to oscillating water column wave energy devices, thanks to its self-rectifying capability and simplicity. For these reasons, the authors carried out an experimental campaign to verify the impact of ducting the Savonius rotor, thus leading the way for a possible exploitation of this configuration in many practical applications. Specifically, The present paper deals with a study of ducted Savonius type air turbine performance. In particular, turbine performance was studied as a function of turbine overlap ratio. Four overlap ratios were tested: 0, 1/6, 1/3 and 1/2. A specific experimental setup was built to test ducted turbine, while bare turbine performance was measured using a wind tunnel. All tests were performed at fixed air velocity: 5 m/s. On the basis of the results, it is possible to state that ducted turbine performance is higher than bare turbine performance, at all tip speed ratios and for all overlap ratios. The optimal turbine overlap ratio is equal of 1/3.

Numerical simulation of the inlet channel geometry influence in the torque generated at the gravitation water vortex turbine

The gravitational water vortex turbine is presented as an alternative for electric power generation for both low head and water flow conditions, additionally it is easy and low cost to implement and maintenance. However, the experimentally reported efficiencies motivate the scientific community to develop new geometries in order to improve its performance. First, it is not clear how the efficiency of the turbine is obtained and second, not all studies report it. The turbine is mainly made up of a tank, the rotor and the electric generator. The geometry of the tank is important because it stabilizes the fluid and in this component that the generation of the vortex is induced, which determines, added to other factors like tank geometry and runner, the global efficiency of the turbine. The primary purpose of this study is to compare numerically the torque generated at six (6) geometrical configurations of the basin inlet channel for Gravitational Vortex Turbine (GVT) with a Savonius rotor. The study was developed in ANSYS® CFX, where a transient state VOF model was configured with a BSL K − ω turbulence model and a discretization a discretization of the control volume made in the ICEM module. The highest torque was 0.553 Nm at 25 rpm for the trapezoidal curved inlet channel geometry, increasing the efficiency respect to the conventional Square inlet channel of the 2.73 %. The increase of tangential velocity contributes positively to the vortex generation, and consequently, an increase in torque is obtained. On the other hand, the design of the rotor considerably affects the performance of the GVT, where it may or may not take advantage of the kinetic energy of the vortex

Peningkatan Kinerja Rotor Savonius Dengan Mengembangkan Sudu Baru Berbasis Airfoil

<p><em>The development of new and renewable energy is currently a top priority for the international community, as energy needs continue to increase while fossil fuels are running low. The Savonius rotor turbine is one of the most widely used turbines but has low efficiency. This study aims to improve the performance of the Savonius turbine by developing a new blade based on airfoil which is simulated in CFD. There are 2 blade models to be simulated, namely the RD-1 model and the RD-2 model, then the simulation results are compared with the conventional blade. The results of the study can be said that the new airfoil-based blade can improve the performance of the Savonius turbine, the increase occurs in the TSR value which is better than the conventional blade. The highest Cp is 0.148 on the RD-2 model blade with a maximum TSR of 0.8</em></p>

Estimation of power performances and flow characteristics for a Savonius rotor by vortex particle method

AbstractThis study investigates the implementation of the vortex particle method (VPM) with the goal of efficiently and accurately estimating the power performances and flow characteristics for a Savonius rotor. The accuracy and efficiency of simulation methods are critical for the reliable design of Savonius rotors. Among various approaches, VPM is chosen because it can be flexibly incorporated with self‐correction techniques, and the distribution of bound vortex particles can effectively represent complex geometries. In this work, a double‐trailing‐edge‐wake‐modeling vortex particle method (DTVPM) is presented to extend the working range of VPM for dealing with large rotating amplitudes and high tip speed ratios (TSRs). DTVPM addresses asymmetrical torque predictions for a Savonius rotor without gap width. However, DTVPM performs poorly at high TSRs due to the absence of viscous effects near the surface. To capture complex wake structures, such as reverse flow structures, the viscous correction for tip vortices is suggested. The current research focuses on the implementation and validation of DTVPM for predicting torque coefficients and wake patterns, as well as comparisons to OpenFOAM results. Two‐dimensional and incompressible flow is estimated at = 0.2–1.2. For the studied cases, a maximum power coefficient is obtained at , consistent with published experimental data. In addition, the process of trailing‐edge vortices generation and detachment is captured by DTVPM. The comparison results between OpenFOAM and DTVPM show that DTVPM allows to efficiently simulate a Savonius rotor without any empirical parameters. DTVPM will help to improve existing engineering models for wind energy fields.

Evolving a Bio-Inspired Blade Shape of the Drag-based Vertical-axis Wind Rotor Derived from Orange Sea-pen (Ptilosarcus Gurneyi)

Abstract Inspired by the polyp leaf of the Orange sea-pen (Ptilosarcus gurneyi), a novel blade shape of the Savonius vertical-axis wind rotor is developed. The similarities between the aerodynamic and the hydrodynamic aspects of the Savonius rotor blade profile and the sea-pen leaf are reviewed, and an appropriate analogy is thereby established. The shape of the sea-pen leaf is then extracted to fabricate the rotor blades. The performance of this sea-pen bladed rotor is evaluated in a low-speed subsonic wind tunnel at different wind velocities. The two-dimensional (2D) numerical analysis is also performed to support the experimental findings and to study the influence of blade shape on the pressure and the torque distributions of the rotor. The novel sea-pen bladed rotor, having lesser material requirements, is seen to demonstrate higher performance than that of the conventional semicircular bladed rotor in the tested range of low tip-speed ratio.

The role of wake splitter deflector on performance enhancement of Savonius wind turbine

The Savonius drag-type wind turbine suffers from poor efficiency due to the adverse negative torques on the returning blades when they rotate against incoming flows. It was proven that using a suitable deflector system has the potential to improve wind turbine efficiency. However, as previously identified in studies, the common drawback of using a flat deflector is the strong wake zone behind it. The present study aims to improve the overall performance of a drag-type wind turbine by using a cylinder deflector with a wake splitter plate to manage and mitigate the detrimental effect of the wake zone behind the deflector. The wake control and suppressing vortex shedding downstream of a circular cylinder have been divided into active and passive flow control techniques. Amid the latter control methods, the adoption of splitter plates has proven to be highly effective for wake control and suppressing vortex shedding behind the cylinder. Unlike previous studies, a cylinder deflector with the wake splitter plate will be utilized instead of the conventional deflectors to improve the efficiency of the wind turbine by disturbing the wake zone downstream of the deflector. To obtain a more efficient configuration, the effect of the variations of the wake splitter length (Ls/D), attachment angle (θwsp), and the count of wake splitters on the outputs such as generated torque coefficient (Cm), power coefficient (CP), and wake zone on the performance of the Savonius rotor were investigated via Computational Fluid Dynamics simulation. The results revealed that cylinder deflectors with the wake splitter increased the Savonius rotor's performance the most for almost all Tip Speed Ratios (TSRs). The average Cm and CP raised considerably up to 15% using a deflector with two wake splitters at TSR = 0.6 compared to the case without deflectors.

Performance Investigation of Vertical Axis Wind Turbine with Savonius Rotor using Computational Fluid Dynamics (CFD)

The quest of clean and sustainable energy has grown rapidly all over the world in the recent years. Among the renewable energy resources available, wind energy is considered one of the reliable, environmentally friendly, green and fastest-growing source of electricity generation. This generation is accomplished through wind turbines. However, the efficiency of these wind turbines is still very limited and unsatisfactory. The primary goal of this study is to evaluate the performance of a Savonius rotor wind turbine in terms of aerodynamic characteristics, including torque, torque coefficient, and power coefficient. The design of Savonius wind turbine blades is varied and its effects is observed. The simulation models are developed using a modeling software known as Solidworks 2021 and then generated into Ansys Design Modeler 2021 R1 to define the fluid domain. In total, three distinct turbine blades are modelled while varying the diameter and height of the rotor. The simulation study is performed using FLUENT 2021 R21. A constant wind speed value of 9.2 m/s has been used throughout the simulation. The simulation was carried out using a transient time flow with a constant upstream wind speed. The results have shown that the power coefficient of all models increases with TSR and the highest efficiency is consensually obtained at almost a unity (0.9) TSR. Comparing the performance of all models, Model 2 generates the highest power coefficient followed by Model 3 and Model 1, respectively. In terms of power, torque and torque coefficient, nearly similar conclusion is drawn.

A review on comparative study of Savonius wind turbine rotor performance parameters.

One approach for reducing the level of environmental contamination threats around the world is to use renewable energy-harvesting equipment. Wind is a potential environmental resource that has become a desirable aspect of urban use due to advances in wind turbine design technology. Other variants have been developed based on the classic vertical-axis Savonius rotor model, which, according to experimental test findings and computational calculations, show higher operational characteristics performance. Generated power and shaft torque operational results are obtained by providing specific rotor blade shapes in these models, one of the most common designs, among small-scale rotor which uses a drag-based vertical axis whereas Savonius turbines having large-scale rotors not developed yet. This kind of rotor has the advantages of being simple to design, affordable, performing well at low speeds, and turns to flow direction independently. However, it was discovered that the Savonius rotor suffers through high quantity of negative torques created by the returning blade after a number of examinations into its performance. Many studies on various rotor types have been conducted to resolve the Savonius turbine's performance constraints. The research showed and analyzed the difficulties and modification in design parameters of rotor, as well as their major impact on rotor performance.

Performance investigation of a Savonius rotor by varying the blade arc angles

Wind energy is a promising source of renewable energy due to its availability. Savonius turbine is a vertical axis wind turbine that converts kinetic energy from the wind to mechanical energy. The current research investigates the performance of the conventional Savonius turbine by varying the position of the endpoints based on varying the blade arc angle. In addition, the outer blade arc angle of a modified configuration, which generated by varying the gap ratio, is also investigated. The ANSYS-Fluent package is used to perform the numerical simulation of the turbine to solve the equations of the unsteady Reynolds Averaged Navier–Stokes (RANS). The flow characteristics through the turbine are resolved by using the SST k-ω turbulence model. The numerical result of the conventional configuration is validated by using previous numerical and experimental research works. The current investigation proved that varying the outer and inner blade arc angles to 160° and 20° enhanced the maximum power coefficient by 4.5% and 12.9%, respectively. Furthermore, the maximum power coefficient of the modified Savonius rotor at a gap ratio of 0.1333 and an outer blade angle of 180° increased by 13.6% compared to the conventional profile.

Performance analysis of Savonius hydrokinetic turbine using ‘C’ shaped Deflector

ABSTRACT Nonrenewable energy sources are limited and harmful to the environment. The use of a Savonius rotor to harness one of the renewable energy sources, hydrokinetic energy, is investigated in this study. The power output of the Savonius rotor is low; therefore, a ‘C’ shaped deflector was employed on the rotor’s upstream side to boost power output. The experimental analysis was done to find the best position for the ‘C’ shaped deflector in this work. The experiments were conducted in two stages: keeping the X-coordinate fixed and varying Y-coordinates. After getting maximum power output for Y-coordinate, the X-coordinate was optimized. The results show an increase in rotor power output by 23% and a decrease in the power coefficient for the best deflector position.

Performance enhancement of low speed current savonius tidal turbines through adding semi-cylindrical deflectors

Qeshm channel between the Persian Gulf and Oman Sea with a maximum tidal current velocity of about 2 m/s is unsuitable for installing conventional tidal turbines. This study aims to introduce a new turbine with semi-cylinder deflectors, which is added to a Savonius tidal turbine to make feasible power extraction from this low-speed tidal current. For this purpose, Computational Fluid Dynamics analysis is done on the Savonius turbine with 2,3, and 4 blades in two cases (with and without deflectors). The results show an increase in power coefficient (CP) to 0.38 at an optimum TSR of 0.68 for two-blade Savonius Rotor by implementing semi-cylinder deflectors. In comparison, the maximum CP is 0.14 for a two-blade Savonius rotor without deflectors. Power coefficient decreases by increasing the number of blades in rotors with obstacles. CP has an upward trend by increasing the speed of water flow in the absence of deflectors. However, CP has an upward trend till 1.5 m/s current speed and after that has a downward trend in rotors with deflectors. As a general result, the Savonius turbine with semi-cylinder deflectors is very consistent with the conditions of the Qeshm channel, in which the tidal current speed is always fewer than 2 m/s.

Effect of the Phase-Shift Angle on the vertical axis Savonius wind turbine performance as a renewable-energy harvesting instrument

Wind energy is the third-largest renewable energy source after hydro and solar energy, so it has great potential in increasing renewable energy as a percentage of national energy. However, wind energy installation is only at 0.25% of the existing potential; so, it still needs to be developed. One of the development efforts is to optimize the wind turbine rotor design. Savonius rotors are among the most popular rotors to convert wind energy into electrical energy. The Savonius turbine is a simple structure, easy to modify to upgrade Savonius performance, and can be operated at low velocity. Phase-shift angles of 0°, 30°, 60°, and 90° were utilized in this study on a two-stage Savonius wind turbine. This study was carried out using Solver CFX utilizing the Computational Fluid Dynamic technique on the ANSYS Student version software. An SST (shear stress transport) turbulence model with steady-state turbulence was used. The purpose of this study was to assess the influence of PSA on the performance of the Savonius two-stage turbine. Factorial design analysis was used in conjunction with the CFD approach. The results indicated that PSA influenced the Savonius turbine’s performance, with 30° being the optimal PSA. Simultaneously, the Cpmax may be obtained using 0.29. The factorial design study with two components revealed that the Phase-Shift Angle had a considerable effect on rotor performance, and the two factors (TSR and PSA) had an interaction.