Conventional Savonius Rotor Research Articles

Enhancing Savonius Rotor Performance with Zigzag in Concave Surface-CFD Investigation

Savonius, a type of vertical-axis wind turbine (VAWT), is suitable as an appropriate small-scale energy conversion apparatus for regions with relatively low wind speeds, such as Indonesia; however, it exhibits sub-optimal efficiency. One potential approach to improving the efficiency of Savonius turbines is to increase the drag force on the concave surface of the blades. In this case, the dissimilarity in the forces experienced by the two blades can be increased, resulting in a corresponding increase in torque. This investigation aims to assess and compare the power coefficient (Cp), torque and drag coefficient (Cd) of the conventional Savonius rotor with the zigzag pattern implemented in the middle area of the concave surface of the blades at low wind speeds. The efficiency can be achieved by implementing the k-ω shear stress transfer (SST) turbulent model and 3D computational fluid dynamics simulation at tip speed ratio (λ) 0.4-1 with a velocity inlet of 4, 5, and 6 m/s. The study results show that using the zigzag pattern on the concave surface led to an 18.8% boosted in Cp of at λ = 0.8 and an inlet velocity (U) = 5 m/s compared to the standard Savonius rotor model. In this case, the efficiency of the Savonius wind turbine may be enhanced by incorporating a zigzag pattern in the middle of the concave surface of the Savonius rotor.

Evaluation of a Savonius wind turbine in the vicinity of a circular cross-sectional building

Today's urban areas are filled with tall buildings that require significant energy. To enable the implementation of small-scale wind turbines for dispersed electricity generation in cities, it is crucial to evaluate their performance in close proximity to buildings. This study aims to assess the performance of conventional Savonius rotors near a circular cross-sectional building for the first time. The performance of a Savonius wind rotor is being studied at different installation angles (30°, 45°, 60°, and 90°) with a constant non-dimensional gap space (S/D) of 2.0 between the rotor center and building envelope under a constant free-wind speed of 6 m/s. Two possible wind rotor rotation scenarios, inward and outward, are thoroughly tested and studied. Computations are carried out for tip speed ratios (TSR) of 0.4, 0.8, and 1.2. The obtained results are successfully validated for both the Savonius rotor in the free-wind flow (without a building) and a circular cross-sectional building (without a wind rotor) as well. The results show that installing a Savonius rotor at angles of 60° and 90° provides the maximum power coefficient based on the TSR. In contrast, placing the rotor at 30° reduces its performance even more than the reference case. For optimal rotor angles, inward rotation is preferred over outward rotation regardless of the TSR. Finally, there are improvements of 208.72 %–439.95 % compared to the reference case for 60° and 90° under inward rotation.

Optimization of Savonius rotor blade performance using Taguchi method: Experimental and 3D-CFD approach

The Savonius hydrokinetic turbine (HKT) is both cost-effective and reliable, providing clean energy with minimum environmental impact. The efficiency of the Savonius rotor can be improved by modifying the blade profile to increase the effective torque. However, past research works reported that modifying the blade profile is quite challenging due to small Cp improvement and design constraint. Therefore, the present study proposes a newly developed blade profile blueprint, akin to parameterizable designs such as the modified Bach and Benesh profiles but offering more shape versatility. This new blueprint is optimized with a systematic design of experiment (DOE) using a 3D computational fluid dynamics (CFD) simulation to maximize the Cp. The best design is determined statistically using the Taguchi method and analysis of variance (ANOVA). The optimized rotor profile enhances Cp by approximately 10.9 % compared to the conventional Savonius rotor at the optimal TSR (best Cp = 0.159) and 16.7 % improvement at a higher TSR value of 0.9 (Cp = 0.158). Moreover, the optimized rotor outperforms the Fibonacci rotor (Fibonacci blade profile) by 27 % in terms of efficiency. A thorough CFD analysis suggests that the optimized blade profile has a greater lift generated at the convex side of the advancing blade due to its streamlined shape, which delays the flow separation further up to the root of the blade. The confirmation test (experiment) is also performed to verify the Cp improvement of the optimized rotor, and the results herein concluded that the present CFD prediction is accurate and consistent with the experimental values.

Hydrodynamic performance enhancement of Savonius hydrokinetic turbine using wedge-shaped triangular deflector in conjunction with circular deflector

Savonius hydrokinetic turbine is a viable technology for producing small-scale hydropower. The present numerical study proposed a novel deflector system to guide the incoming water stream effectively and to improve the hydrodynamic performance of the conventional Savonius turbine rotor. The combined deflector system comprises two deflectors: a newly proposed wedge-shaped triangular deflector and a circular cylindrical deflector. The triangular deflector is placed upstream of the returning blade, and the circular deflector is positioned upstream of the advancing blade. Different configurations of the proposed deflector system are obtained by varying the dimensions and location of the triangular deflector (deflector 1), while the diameter and location of the circular deflector (deflector 2) are fixed in all configurations. Without a deflector system, the Savonius rotor yields a maximum power coefficient equal to 0.248 at a tip speed ratio (TSR) of 0.7. The best configuration of the combined deflector system yields a maximum power coefficient of around 0.432 at a (TSR) value of 1.0. The deflector-augmented Savonius hydrokinetic rotor records a 73.7% increase in the maximum power coefficient (CPmax) compared to the conventional Savonius rotor. Further, the flow contours verify improved flow interaction with turbine blades and enhanced hydrodynamic performance.

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.

Comprehensive influence of the additional inner blades with different configurations on the performance of a Savonius wind turbine

ABSTRACT The effects of adding inner blades to the Bach-type Savonius turbine deserve extensive attention due to its promising improvement of the performance over the conventional turbine. In the present work, the performance improvement is based on comparing the power coefficient of two modified configurations, which produced by installing concentric blade inside the original rotor blade of the conventional Savonius rotor. Numerical simulations are performed for three configurations: the traditional rotor; turbine with the additional inner blades tip parallel to the original turbine blades tip; and turbine with the additional inner blades parallel to the original rotor blades root. Numerical CFD analysis is carried out to study the influence of varying the radius and/or the central angles of the additional inner blades applying ANSYS FLUENT. The considered radius of the additional blades ranges from 0.25 to 0.85 of that of the reference blade whereas the blade central angle varied from 70° to 180°. The acquired numerical results reveal that the performance of the turbine with additional inner blades is increased by 22.39%, 46.27%, and 103.86% when the tip speed ratio equals 0.75, 0.25, and 1.3, respectively.

In the quest of an appropriate turbulence model for analyzing the aerodynamics of a conventional Savonius (S-type) wind rotor

For over two decades, the quest for decentralized electric power generation has stimulated much research interest into the Savonius (or S-type) wind turbine rotors. To enhance their efficiency, the operating parameters have already been examined by various numerical and experimental techniques. While most researchers have focused on using selected turbulence models to arrive at some meaningful conclusions and recommendations, no study analyzing a range of turbulence models in a systematic and comprehensive manner is reported. This study thus aims at conducting 2-D unsteady numerical simulations of a conventional semicircular-bladed Savonius rotor using six different turbulence models, viz., standard k–ε, realizable k–ε, RNG k–ε models, standard k–ω and shear stress transport (SST) k–ω, and transition SST (TSST) turbulence models. The simulations are performed by commercial finite-volume method solver ANSYS Fluent 17.1 at a fixed Reynolds number (Re) of 1.23 × 105 based on the rotor overall diameter. This study demonstrates the prediction capabilities of realizable k–ε, RNG k–ε, SST k–ω, and TSST models more accurately than those of other models. However, due to higher computational cost associated with TSST model, the use of realizable k–ε, RNG k–ε, and SST k–ω models for predicting the aerodynamic performance of other developed and to-be-developed profiles of Savonius rotor is recommended.

The effect of spacing between inner blades on the performance of the Savonius wind turbine

Savonius wind turbine is an interesting type of vertical axis wind turbines (VAWTs) which has a low cost of manufacturing, however, this turbine has a relatively low power output compared to the other types of VAWTs. Further study is required to enhance its performance to match the high demand of the power generation in small-scale applications. The main objective of the current study is to enhance the power output coefficient (Cp) of the conventional Savonius rotor by adding two-inner blades to the geometry. The performance assessment was performed for five different angles of inner blades (100°, 120°, 140°, 160°, and 180°). Moreover, the effect of spacing between inner blades was numerically examined for three values of spacing i.e. 0.02, 0.01, and 0.005 m. The current two-dimensional simulation was performed utilizing the Ansys Fluent solver. The simulation results affirmed that the maximum enhancement to be 32.9% compared to the conventional rotor at TSR equal to 0.7 when the spacing between inner blades is 0.005 m with an inner blades angle of 100°. Moreover, results demonstrated that the Ct max is 0.435 at TSR = 0.4 for the rotor with 160° inner blades and a spacing of 0.005 m.

Savonius wind turbines: A review of recent advances in design and performance enhancements

The energy crisis due to a rapid globalization and adverse effects of global warming has led to an increased need for the non-conventional sources of energy. In the recent times, significant research activities are carried out in the renewable energy field, mostly in solar and wind power generation. Wind turbines are categorised into vertical axis wind turbines (VAWT) and horizontal axis wind turbines (HAWT). Savonius rotor (S-type) is a type of VAWT and its function depends on the drag force. It has many advantages of easy installation, simplicity in design, good self-starting capability, low speeds operation and independency of direction of wind. Although, the negative torque produced on the returning blade leads to its low efficiency. Researchers have conducted several investigations to improve the functioning of Savonius rotor for satisfying large-scale energy demands. The parameters affecting the performance, such as, overlap ratio, aspect ratio, tip speed ratio and blade shapes, are improved by undergoing various designs. Several augmentation techniques, such as, end plates, shielding obstacle, guide box tunnel, deflecting plate, curtain plate, quarter blades and nozzles, have been used to enhance the performance of S-type VAWT. With the installation of these augmentation devices, the negative torque acting on the blades was reduced and the starting ability of the rotor was improved. These devices in turn help in increasing the power output as well as the torque coefficient of various rotor configurations. It has been reported in the literature that the coefficient of power of the conventional Savonius rotor lies in the span of 0.12 to 0.18. By using different methods for optimizing its design or installing the augmentation devices, the coefficient of performance can be improved to a value of 0.52. In this article various performance influencing parameters and the power augmentation techniques used for S-type VAWT have been studied and reported studies on these techniques have been reviewed. The article concludes with proposed directions for future research.

Application of Counter Rotating Rotors for Improving Performance of Savonius Turbines

In this paper, a new configuration is proposed for using Savonius rotors by installing two Counter-Rotating Savonius Rotors (CRSR) together. In order to study the aerodynamic performance of the CRSR turbine, 2D unsteady turbulent flow around the CRSR turbine is simulated using commercial CFD software ANSYS-Fluent16.0. Turbulence modeling is done using $$k - \omega$$ SST model. Numerical results demonstrate a considerable improvement in aerodynamic performance of the CRSR turbine in comparison to a single conventional rotor. Effect of the distance between two rotors and different angular positions of two rotors on the CRSR turbine performance is studied. It is shown that the most effective parameter influencing the performance of the CRSR turbine is the distance between the rotors. Numerical results reveal that, locating two rotors in an optimal phase angle (θ = 90) and distance(S = 1.0D0), average power coefficient of the CRSR turbine can be increased to 21%, which indicates a rise of 38% compared to conventional Savonius rotors.

Design and construction of Savonius rotor

Renewable energy sources have been researched for more than a century now. Wind energy; which is often characterized as an unreliable source of energy, is not unreliable if placed at places with smooth wind currents. Savonius rotor as Vertical Axis Wind Turbine (VAWT) can be used as a standalone power generation device because of its low cost, low cut-in speed and the fact that it can accept wind from any direction. S-Rotors when compared to other types of rotors have a lower Power Coefficient but factors like Overlap ratio, Aspect Ratio, Number of Blades and Blade shapes can affect its efficiency. This paper discusses the Design and construction of a Savonius wind turbine by studying how the factors above influence the rotor’s performance. Finally, a Single-stage, Two blade conventional Savonius rotor with an Overlap Ratio of 0.1 and Aspect Ratio of 3.3 has been constructed and discussed below. Studies for choosing the best material have also been conducted and PolyVinyl Chloride (PVC) has been selected to prepare the blades from. According to the study conducted, the voltage output recorded at 5.4 m/s wind speed was 19.1 Volts.

Numerical Investigation of Inner Blade Effects on the Conventional Savonius Rotor with External Overlap

Numerical Investigation of Inner Blade Effects on the Conventional Savonius Rotor with External Overlap

Effect of twist angle on starting capability of a Savonius rotor – CFD analysis

Starting capability is an important feature of any high performance wind turbine. This parameter is usually referred to the rotor static performance. In this paper, the results of CFD analysis on four Savonius rotor designs are presented with the objective of investigating the effect of twist angle on the starting capability. Essentially it is a comparison between a conventional Savonius rotor and three helical rotors with 0°, 90° and 180° twist angle. The proposed methodology was first validated against the published wind tunnel test data. The best parameters were then used to evaluate the static performance of the four Savonius models. It is observed that helical Savonius rotor contributes to positive static torque coefficient for all rotor angles. The rotor with 90° twist angle gives the highest average static torque coefficient of 0.442 followed by 0° twist angle rotor and 180° twist angle with static torque coefficient of 0.434 and 0.385 respectively. This improvement in static torque coefficient will not only contribute to the better starting capability but also to the overall performance of Savonius rotor.

CFD analysis of the effects of multiple semicircular blades on Savonius wind turbine performance

The goal of this work is to simulate and improve the efficiency of an innovative multiple semicircular-bladed Savonius wind turbine, which is identified as belonging to the vertical axis wind turbine (VAWT) category. It is characterized as a low speed turbine that is simpler and cheaper to build than traditional turbines. This makes it appropriate for generating mechanical energy in lower wind speed regions, and it can be coupled with solar panels in urban agglomerations. The objective of this paper is to compare the aerodynamic characteristics and power efficiency of four different geometries of the Savonius wind turbine (two-conventional and two-modified rotors) in order to estimate the most efficient design. The proposed Savonius design comprises multiple semicircular blades added to conventional two- and three-bladed Savonius rotor configurations. The comparison of the efficiency in terms of the torque coefficient (C T ) and power coefficient (C P ) of the new system configurations with the conventional ones finds that the multiple semicircular two-bladed Savonius rotor is more efficient than others. The numerical simulation of the conventional Savonius rotor is developed and validated against experimental and numerical data derived from a literature review. The choice of turbulence model and local or global mesh refinement play essential roles in the accuracy of the numerical simulation results. In this work, we adopted a Shear Stress Transport (SST) model for modelling turbulence, which incorporates the near wall fluctuation capturing capability of the k-w model, and the robust k-ei€ model for modelling the whole numerical domain. An average improvement in the power coefficient of 8.43% for different tip speed ratios (TSRs) is observed for the new configuration compared with the others.

Modified Design of Savonius Wind Turbine Blade for Performance Improvement

In the context of worldwide energetic transition, wind energy shows up as one of the most prominent renewable energy to provide an alternative for the conventional energy source. Therefore, new technologies of a wind turbine are developed, horizontal axis wind turbines have been extensively investigated and evolved. However, the development of vertical axis wind turbines is still an open and area of research, The main objective is to develop a more efficient type of wind turbines able to operate at low wind speeds to take hold maximum wind potential, The Savonius rotor goes with such conditions, however, it faces critical drawbacks, in particular, the low performance in comparison with horizontal axis wind turbines, as well, the blade in return of savonius wind turbine generates a negative torque leading to a decrement of turbine performance. The present work aims to investigate a modified model of the conventional Savonius rotors with a focus on improving the coefficient of power, transient computational fluid dynamics (CFD) simulations are carried out in an effort to perform a validation of numerical results according to experimental data, also to conduct a comparative analysis of both savonius models.

Effect of Capped Vents on Torque Distribution of a Semicircular-Bladed Savonius Wind Rotor

To address the problem of the imminent energy crisis, pollution from fossil fuels, and global warming, it is necessary to incorporate renewable technologies. In that context, the drag-based Savonius wind turbine has tremendous potential to extract wind energy and can be operated as a standalone system at remote areas where the conventional electricity cannot be provided. The present study primarily focuses on the performance evaluation of a conventional semicircular-bladed Savonius rotor with capped vents (CVs) or nozzle chamfered vents. The rotor blades having vent ratios of 7%, 14%, and 21% are tested in a wind tunnel, and subsequently, their performances are compared with a rotor without CVs under identical test conditions. Computational fluid dynamics (CFD) simulations have also been carried out to compliment the surprising experimental results and also to analyze the flow physics around the rotor blades. From the understanding of torque distribution, it has been noticed that the performance of the rotor with CV deteriorates compared with the conventional semicircular-bladed rotor. The vents are found to decrease the positive torque and increase the negative torque by disturbing the pressure distribution of the conventional semicircular-bladed Savonius rotor.

Numerical and Experimental Study on the Savonius Rotor Performance with The Gap Width Variations of Ventilation in Middle Blades

In previous research, the use of ventilation at 15° from the outer end of the blade Savonius was able to increase the efficiency of Savonius windmill. This study aims to determine how the influence of the fixed ventilation on middle of the blade towards a performance of the Savonius windmill. There are one model of the conventional Savonius windmill and three models of the ventilated Savonius windmill that simulated by CFD and tested in the wind tunnels. Simulation variabels used are variations for ventilation width and the rotation angle position of the rotor. Experimental variables were variations for the gap width of ventilation and wind speed. The ventilated Savonius with ventilation position in the middle of the rotor blades turns out to have the average power coefficient (Cp) lower than the conventional Savonius windmill. The wider the gap from the ventilation will further reduce the performance of the ventilated Savonius rotor. In this study, the SV65-10 model produced the worst performance. This power coefficient of the SV65-10 model is 29% lower than a conventional Savonius rotor..

Numerical investigation of performance and flow patterns of a modified Savonius hydraulic rotor

The Savonius hydraulic turbine is effective in harnessing the energy carried by flowing water. The advantages of the Savonius hydraulic turbine, such as simple in structure and good start-up characteristics, have been acknowledged. Nevertheless, the lack of a detailed investigation of the flows around the Savonius hydraulic rotor hampers the technical advancement of the Savonius hydraulic turbine. Here, a modified Savonius hydraulic rotor based on conventional Savonius rotors was designed to investigate the performance and flow characteristics of the Savonius hydraulic rotor. Computational fluid dynamics techniques were used. The influence of the rotor blade geometry and the tip speed ratio was considered. The results indicate that the ratio of the length of the straight edge to the radius of the circular arc of the blade has an important impact on the performance of the Savonius hydraulic rotor. The maximum power coefficient of the rotor with such a ratio of 0.81 is 58% higher than the rotor with the ratio of 0.46. The tip speed ratio corresponding to the maximum power coefficient is related to the ratio. Comparative analysis of the velocity and pressure distributions for different rotor setting angles was conducted to describe the interaction between the flow medium and the rotor. The torque coefficient of the rotor depends considerably on the area and position of high upstream pressure; meanwhile, downstream vortices impose a negative effect on the rotation of the rotor. The results provide a sound support for the optimal design of the Savonius hydraulic turbine.

Four Decades of Research Into the Augmentation Techniques of Savonius Wind Turbine Rotor

The design and development of wind turbines is increasing throughout the world to offer electricity without paying much to the global warming. The Savonius wind turbine rotor, or simply the Savonius rotor, is a drag-based device that has a relatively low efficiency. A high negative torque produced by the returning blade is a major drawback of this rotor. Despite having a low efficiency, its design simplicity, low cost, easy installation, good starting ability, relatively low operating speed, and independency to wind direction are its main rewards. With the goal of improving its power coefficient (CP), a considerable amount of investigation has been reported in the past few decades, where various design modifications are made by altering the influencing parameters. Concurrently, various augmentation techniques have also been used to improve the rotor performance. Such augmenters reduce the negative torque and improve the self-starting capability while maintaining a high rotational speed of the rotor. The CP of the conventional Savonius rotors lie in the range of 0.12–0.18, however, with the use of augmenters, it can reach up to 0.52 with added design complexity. This paper attempts to give an overview of the various augmentation techniques used in Savonius rotor over the last four decades. Some of the key findings with the use of these techniques have been addressed and makes an attempt to highlight the future direction of research.

A numerical and experimental study of a new Savonius wind rotor adaptation based on product design requirements

This paper presents the numerical-experimental study carried out on a new rotor adapted from a Savonius rotor. Aesthetic, ergonomic and functional requirements have been incorporated into it in order to be part of sustainable consumer products. The new rotor consists of a parametric model adaptable to the dimensions and geometry of the products which it will be part of. A set of translation, symmetry, rotation and scaling operations have been applied to the bucket sections of the Savonius rotor by means of transforming the initial cylindrical buckets into topological surfaces with an organic shape. The new modified Savonius rotor and the conventional Savonius with the same Aspect Ratio have been tested in an open jet wind tunnel in order to verify the influence level of product design parameters on rotor performance, in terms of power coefficient, torque coefficient and mechanical power generated. Experimental tests have been carried out for Reynolds values in the range of [3.430 · 104 and 1.419 · 105]. A numerical analysis using an incompressible unsteady Reynolds average Navier Stockes model has been validated by means of the experimental results. Experimental and numerical results coincide with a 3.5% error. The behavior of the turbine has been analyzed by varying the angle of rotation for the sections of its buckets. Using a rotation angle of 45° the power coefficient values improve by 32% compared to the values obtained using an angle of 0°. The rotor has been dimensioned for its application in a patented consumer product of small dimensions and requirements of lateral accessibility to its interior. Under these limited conditions the rotor meets the small-scale energy requirements of the product. The new rotor is designed as an aid to the energy consumption of the product in which it is incorporated, maintaining the advantages of a conventional Savonius rotor as self-starting, easy manufacture and maintenance, obtaining at the same time a product that sells better, is more able to integrate into its environment and is customizable for the consumer.