Helical Savonius Rotor Research Articles

Numerical and experimental investigation for helical savonius rotor performance improvement using novel blade shapes

Wind energy is extensively invested as a renewable and clean energy source. Savonius wind rotor, as an energy converter, has the merit of being appropriate for specific applications. The current paper centers on the performance enhancement of a helical Savonius wind rotor through the blade shape modification. The basic objective is to assess and compare, numerically and experimentally, the performance of two rotors with novel blade shapes named delta bladed and two-stage delta bladed shapes in relation to a helical Savonius rotor. Numerical study was conducted using Ansys Fluent software. 3-D unsteady simulations were carried out through the use of the SST k-ω turbulence model based on the finite volume method solver. Aerodynamic flow and performance characteristics were investigated. Static and dynamic experimental tests were undertaken on a wind tunnel. An improvement in Cp by 22.58 % and 29.5 % for the two-stage delta bladed rotor and 19.35 % and 16.4 % for the delta bladed rotor over the helical Savonius rotor was recorded, respectively, numerically and experimentally. In addition, the self-starting ability as well as the aerodynamic flow characteristics of the helical rotor were enhanced with the novel blade shapes.

Investigation of The Effect of Phase Angle on The Aerodynamic Performance of Three-Bladed Helical Savonius Wind Turbines Using Computational Fluid Dynamics Method

In this study, the effect of the phase angle of the semicircular blades between the stages on the aerodynamic performance of the three-blade, double-stage helical Savonius wind turbines (HSWT), which are vertical axis wind turbines, was examined by the computational fluid dynamics (CFD) method. In the Savonius wind turbine system, the drag force effect provides the most significant contribution to aerodynamic performance. Performance improvements that can affect drag force can provide significant advantages. For this purpose, three-bladed double-stage helical Savonius rotors with eccentricity L/H=1/2 and phase angles of the semicircular blades between the stages Ɵ=0°, 45° and 90° were designed. Solidworks R2018 is used for designs and ANSYS-Fluent 18.1 programs are used for analysis. The turbine with L/H=1/2 and Ɵ=90° was produced on a 3D printer and tested experimentally. Experiments were carried out in the T-490 air tunnel. The results obtained were used as a reference for numerical analysis and the ideal turbine model was tried to be determined. 10 different air velocities ranging between 3.83-20.35 m/s were used in the numerical analysis. As a result, an 11.64% increase in the drag force was observed by changing the phase angle from 0° to 45° in HSWT 1/2s. By changing the phase angle from 0° to 45° in HSWT 1/2s, a 10.77% rise in the drag coefficient was observed. It has been evaluated that the HSWT efficiency improved with the increment in drag force.

Numerical Investigation on Aerodynamic Performance of Helical Savonius Rotor Inspired by Natural Shapes

There have been extensive studies conducted on Horizontal Axis Wind Turbines (HAWT) at relatively moderate to high wind speed regions. However, such detailed investigations for Vertical Axis Wind Turbines (VAWT), specifically for low wind speed terrains are amply reported. This motivates us to conduct research to explore possibilities in improving performance of VAWT in low wind speed terrains, which is attempted in the present work. This is required due to the fact that most of regions do not have sufficient extractable wind energy due to low speeds. VAWTs can perform at such low wind speed, but are less efficient. Improving efficiency of VAWT will solve the purpose. Hence, the present study is aimed at finding the performance characteristics of VAWT for low Wind speed configurations. Various parameters affecting power generation are investigated. Numerical analyses on various configurations are conducted to study the effects of twist angle, free stream velocity, number of blades. Computational results obtained have been in good agreement with the established results for semi-circular Savonius rotor profile. The results suggest that for low wind speed terrains, there is a need to explore the combination of lift and drag type of profiles, which could be used for the utilization of available wind power. Hence, naturally inspired shapes (profiles) were investigated for the possible solution of combined lift and drag type wind turbines at low speeds. The blade shape for such combined lift and drag type wind turbine were deduced from the available literature. It is well established that the naturally inspired shapes as noted in sea conch follow golden ratio in its contours. The present study provides an insight on the characteristic curves of VAWT for low wind speed terrains, effects of various geometric and flow parameters suitable for low wind speed terrains.

Investigation of a helical Savonius turbine with a deflector system

The growing demand for renewable energy sources to meet electricity needs has underscored the importance of exploring new resources of renewable energy. Among the various alternatives, Helical Savonius rotors have emerged as one of the most widely used technologies for small-scale hydropower generation. Numerous studies have been conducted to investigate these types of rotors, particularly to enhance their power output. Despite existing research, there is still a need for modifications and proposals for new configurations of Savonius rotors. This paper presents a numerical study of a Savonius rotor equipped with a new design of a deflector. The results indicate that the highest power coefficient achieved is 0.1247 at a tip-speed ratio of 0.7 in the absence of a deflector system. The geometric parameters of the deflector are varied to identify the configuration that generates the highest power output. With the implementation of an optimal configuration for the new deflector system, the maximum power coefficient is improved to 0.168 at a tip-speed ratio of 0.7. Otherwise, the maximum power coefficient could be enhanced by 34% compared to the same configuration without a deflector. This significant improvement highlights the potential of the proposed design system.

Numerical Investigation of Hybrid Savonius-Darrieus Vertical Axis Wind Turbine at Low Wind Speeds

The need for electricity on the Earth is increasing day by day, and this requires building more electric power plants where most of the power plants cause CO2 emission which would increase the global warming. Using wind energy as one type of renewable energies, would contribute to reduce the global warming. In countries such as Malaysia where the average annual wind speed is 2-2.5 m/s using wind energy is a challenge because of the low wind speed. However, using a hybrid Savonius-Darrieus vertical axis wind turbine in low wind speed areas, the performance of the wind turbine may increase, and the starting rotation speed will decrease. This research aims at a comprehensive study on a hybrid Savonius-Darrieus wind turbine with helical Savonius rotor combined with helical and straight bladed Darrieus rotor. In this research, a base model with the name of Model Base was generated and two models with new configurations were generated in SOLIDWORKS. A numerical studies and simulation were conducted on these three designs using Ansys Fluent to identify the more suitable combination for low wind speed areas. Based on the obtained result hybrid Savonius-Darrieus with helical Savonius rotor and helical Darrieus rotor were found to be the most suitable combination because of their stable aerodynamic performance throughout a full rotation. Best performance for these models was found to be at 0.45 TRS with maximum torque and power coefficients of 0.68 and 0.306 respectively.

A comprehensive review on design and development analysis and blade material selection of helical Savonius rotor

The helical Savonius rotor (HSR) is used as green energy generation. The accurate design of HSR is essential before installing any wind farm in a region. It has been widely employed that positive static torque coefficients of helical Savonius rotor are higher compared to conventional semicircular rotor stated by several researchers. The reason is behind that the formation of secondary vortex of fluid. It is leading by vertical vortex flow, which passes over the curve surface and creates drag force. Still now, various design have been proposed to meet peak power output through optimum geometry parameters like blade profile design, aspect ratio and overlap ratio. The selection of blade material is also the influencing parameter to improve the starting torque of the rotor. In this regards present paper is aim to study the details experimental, numerical, and analytical review on HSR and selection of blade material with minimum production cost.

Design of type-2 fuzzy logic controller in a smart home energy management system with a combination of renewable energy and an electric vehicle

Home energy management is one of the most important parts of a smart home that manages the efficient use of energy in the smart home. This paper aims to design two type-2 fuzzy logic controllers in the demand-side energy management system. For this purpose, a combination of renewable energy sources, such as fuel cells, photovoltaic solar panels, vertical axis wind turbines with a helical savonius rotor, and an electric vehicle and energy storage system along with an external grid are utilized to supply the electricity usage of home appliances in a smart home. By using the proposed method, higher quality, more economical, and environmentally friendly energy can be accomplished. To this end, the outputs of the proposed controllers are defined to make appropriate decisions about the generated energy, how to supply energy for own consumption, and controllable loads. The number and distribution of membership functions of type-2 fuzzy logic controllers are selected according to the measured real input data over a year in Tehran, Iran. To demonstrate the effectiveness of the proposed method it is simulated by MATLAB/Simulink software, which indicates that the proposed system causes the smart home to receive 49.186 kWh less electricity energy from the grid to supply daily power for home appliances and therefore can weekly consume approximately 343.95 kWh less electricity energy from the grid. it is shown that after applying the proposed strategy, electricity costs were reduced by 71.5%, and the peak-to-average ratio was reduced by 64.6%.

Aerodynamic Performance of Vertical and Horizontal Axis Wind Turbines: A Comparison Review

The need for energy and electricity has been increasing globally, and this means more power is required from the power plants. Power plants, however, will then continue harming the earth because of the greenhouse gasses produced while generating energies that contribute to global warming. Using renewable sources to produce clean energies is one of the sustainable methods to deal with such challenges. Wind energy is one of the renewable sources, which is accessible anywhere on earth, creating green energy. Wind turbines are mainly categorized into Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT). This paper firstly presents a general comparison between the HAWTs and VAWTs. Then, it presents mathematical modelling for the aerodynamic factors of HAWT and Darrieus VAWT to assist the researchers to understand some key design aspects of wind turbines, such as lift/drag ratio, tip speed ratio, power coefficient, and torque coefficient. Also, this paper presents a review of the aerodynamic performance of the recent VAWT designs to help researchers to identify and choose the best model among the Savonius and Darrieus rotors for further development or designing a new model at different wind conditions. This comparison review shows that for a large scale HAWT upwind 3 bladed wind turbines are the most optimum. The helical Savonius rotors perform better by having positive torque coefficient at all azimuth angles. Moreover, helical Darrieus was found to produce lesser noise and suitable for conventional areas. hybrid Savonius-Darrieus rotors can solve the self-starting challenge of the VAWTs, and they are suitable at low wind speeds. At last, this review shows some of the recent hybrid Savonius-Darrieus rotors which would help to solve the low efficiency of Savonius rotor and self-starting challenge of Darrieus rotors.

Experimental study of helical savonius rotor profiles with different number of blade

This research is about the savonius wind turbine which was made in the form of a prototype as a simple student learning media. The goal is the students understand the process of converting wind energy into mechanical energy. The turbine model used is helical savonius rotor with U, S, and L profile on three blades and four blades. Tests carried out using wind tunnels. The test results show that helical savonius rotor with three blades provides better performance than four blades. The best turbine power is obtained in the L profile with three blades which is equal to 1, 62 watts. While the best power coefficient is obtained from the S profile with 3 blades with a power coefficient value of 0.122.

Performance Improvement in a Helical Savonius Wind Rotor

Above all vertical axis wind turbines, for their lower cost and independent on wind direction, Savonius rotor takes the advantage to be more suitable for some implementation. Thus, many investigations have been carried out to improve its efficiency. This study emphasizes on the effect of the overlap distance and the blade shape on a helical Savonius wind turbine performance. Assessment methods based on the flow field characterizations, the variation of torque and power coefficient are performed. Thus, transient simulations using the SST k–ω turbulence model are carried out. The numerical model is validated using wind tunnel tests. Results indicate that the non-overlapped helical Savonius rotor highlights higher maximum power coefficient of 0.124 at a tip speed ratio of 0.73 over rotors with overlap distance of 10 mm, 15 mm and 20 mm, respectively. In addition, the delta-bladed rotor improves the performance of the helical Savonius rotor by 14.51%. With the novel blade shape, the maximum power coefficient reaches a value of 0.142 at a tip speed ratio of 0.78. The obtained results present an interesting data that could provide the aerodynamic characteristics of the airflow for the designers and engineers to enhance the efficiency of the helical Savonius turbine.

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.

Experimental Study on Aerodynamic Characteristics of Helical Savonius Rotor with Twist of 180°

Experimental Study on Aerodynamic Characteristics of Helical Savonius Rotor with Twist of 180°

Numerical and experimental study of a helical Savonius wind turbine and a comparison with a two-stage Savonius turbine

In this paper, the aerodynamic performance of a helical Savonius rotor model with 180° twisted blades is investigated numerically and experimentally. It is also performed a comparison of results with a two-stage Savonius with similar parameters. The experimental study is conducted in the aerodynamic tunnel Prof. Debi Pada Sadhu at the Fluid Mechanics Laboratory of UFRGS. Numerical simulations are performed using the Finite Volumes Method performed by the solution of the Reynolds Averaged Navier-Stokes (RANS) using the k-ω SST turbulence model. The static torque, dynamic torque and power coefficients are compared. Results show that the turbine has a positive static torque coefficient for any studied rotor angles. The dynamic torque coefficient of the turbine shows less torque variation along each rotation in comparison with a two-stage turbine, reaching the maximum value for a tip speed ratio (λ) of 0.2 for the experimental and numerical cases. The helical turbine, despite having a more complex manufacturing process than the two-stage turbine, presents stable torque and higher power coefficient. The maximum power coefficient of the rotor is obtained for λ of 0.65 for both cases. The numerical simulations and the experimental results present differences between 2.34% and 12.5% in CT and CP values.

Performance study of a Helical Savonius hydrokinetic turbine with a new deflector system design

The use of renewable energy sources has becoming a necessity to generate electricity. Helical Savonius rotors have been preferred for small-scale hydropower generation. Numerous studies were carried out to improve the performance of the Helical Savonius rotor which has not been fully explored. In this paper, an experimental study was carried out to evaluate the performance of a Helical Savonius water rotor in an irrigation channel. In order to enhance the performance of the studied water rotor, a new deflector system design was proposed. Different configurations of the proposed deflector system were tested numerically using the commercial software ANSYS FLUENT 17.0. Without a deflector system, the maximum power coefficient is found to be equal to 0.125 at tip-speed ratio of 0.7. Using the optimal configuration of the new deflector system, the maximum power coefficient reaches 0.14. The utilization of this new design system is predicted to contribute towards a more efficient use of flows in rivers and channels for electricity production in rural areas.

Optimization of the helical Savonius rotor through wind tunnel experiments

In this paper, the authors propose a novel vertical wind turbine named helical Bach rotor. This rotor combines the helical rotor and the Bach rotor. The Bach rotor had a high value of power coefficient Cp; but it had negative values of static torque coefficient. These negative values would prevent the rotor to start on their own at certain rotor angles. Similarly, the helical rotor had a lower value of the power coefficient than the Bach rotor but it could provide positive values of static torque coefficient. Therefore, the combination of these two rotors would produce a helical Bach rotor with a better performance. Hence, this study attempted a new design of the rotor made of resin and glass fiber and tested it in an open wind tunnel. Tests were conducted to evaluate the power coefficient, torque coefficient and static torque coefficient for each rotor. The experimental results indicate that the helical Bach rotor had the highest power coefficient and static torque coefficient compared to the helical rotor. The helical Bach rotor yielded 0.2 power coefficient whereas the helical rotor yielded 0.18 power coefficient.

Aerodynamic performance of helical Savonius wind rotors with 30° and 45° twist angles: Experimental and numerical studies

In this study, the aerodynamic performance of helical Savonius rotors with 30° and 45° twist angles have been investigated experimentally and numerically and compared with the conventional rotor with zero twist. This comparison has been performed at two Reynolds number of 1.50 × 105 and 1.84 × 105 (corresponding to wind velocities of 7.3 and 9 m/s) on Savonius type rotors with an aspect ratio of 1.0. Numerical simulations have been performed using the ANSYS-Fluent commercial software using the sliding-mesh method for considering the rotation of the turbine. The experimental measurements, however, are performed at an open-circuit wind tunnel facility. Results show that the maximum power coefficient of the helical rotors are less than the conventional rotor, in a manner that this coefficient decreases from 0.12 to 0.11, when the conventional rotor is replaced with the helical rotor having 45° twist angle. However, the helical rotors have a more uniform time variations of the torque coefficient. The maximum power coefficient for all the rotors has occurred at the tip speed ratio of 0.7. The good agreement observed between the numerical and experimental results revealed the suitability of the employed numerical scheme for predicting the aerodynamic performance of Savonius-type wind turbines.

Computational model of Savonius turbine

Although vertical axis turbines have long existed, it was not until the beginning of the twentieth century when the Darrieus (1921) and Savonius rotors (1924) appeared; the two most used models nowadays. Savonius rotor was invented by the Finnish engineer Sigurd J Savonius with two half cylinders basic design that rotate around an axis. In this research, four different models of Savonius rotor blades are analyzed, as well as the traditional rotor. The principal aim of this research is to find the best Power Coefficient (Cp) and the best torque coefficient (Cm) for different models. In order to achieve the objective, a CFD computational model was used, with 3D simulations in transient regime. A computational domain was defined as a function of the minimal longitude in the system, and meshing is performed after a mesh size independency analysis. The results show that helical Savonius rotor performs the best in the analyzed operation conditions and improves in ~20% above the other configurations. In addition, 3-blade rotor presents the lowest performance of all the models with a power coefficient Cp of 0.073.

Experimental Analysis of a 20° Twist Helical Savonius Rotor at Different Overlap Conditions

Wind power is a major source of sustainable energy and can be harvested using both horizontal and vertical axis wind turbines. Vertical axis wind turbines (VAWTs) accrue more popularity due to its self-starting characteristics and Omni directional in nature. Out of which Savonius rotor is the most popular drag-based VAWT which is having lower efficiencies but having good self-starting characteristics. In order to improve the performance, helix in the tip of the blade is targeted which reduces the negative torque coefficient of the rotor thereby could improve the performance of the rotor. Therefore, in this paper the power coefficients of a two-bucket helical Savonius rotor at different overlap ratios (from 0.0% to 19.76%) with helix twist angle of 20° are investigated experimentally. The investigations mainly concentrate to find out the optimum overlap ratio which is responsible for generation of maximum aerodynamic power. It is seen from the results that the power coefficient of the rotor increases with the increase in overlap ratio up to a certain limit, and further increase of the same decreases the power coefficients. The maximum power coefficient Cp of 0.289 is obtained at an optimum overlap ratio of 12.76 %.

PERFORMANCE ANALYSIS OF A HELICAL SAVONIUS ROTOR WITHOUT SHAFT AT 45° TWIST ANGLE USING CFD

Helical Savonius rotor exhibits better performance characteristics at all the rotor angles compared to conventional Savonius rotor. However studies related to the performance measurement and flow physics of such rotor are very scarce. Keeping this in view, in this paper, a three dimensional Computational Fluid Dynamics analysis using commercial Fluent 6.2 software was done to predict the performance of a two-bucket helical Savonius rotor without shaft and with end plates in a complete cycle of rotation. A two-bucket helical Savonius rotor having height of 60 cm and diameter of 17 cm with 45° bucket twist angle was designed using Gambit. The buckets were connected at the top and bottom circular end plates, which are 1.1 times the rotor diameter. The k-ε turbulence model with second order upwind discretization scheme was adopted with standard wall condition. Power coefficients (Cp) and torque coefficients (Ct) at different tip speed ratios were evaluated at different rotor angles. From the investigation, it was observed that power coefficient increased with increase of tip speed ratio up to an optimum limit, but then decreased even further tip speed ratio was increased. Further investigation was done on the variations of Cp & Ct in a complete cycle of rotation from 0° to 360° in a step of 45° rotor corresponding to the optimum tip speed ratio. The value of Cp at all the rotor angles is positive. Moreover, velocity magnitude contours were analyzed for each rotor angle and it could be concluded that high aerodynamic torque and power can be expected when the rotor is positioned at 45º & 90º with respect to incoming flow.

PERFORMANCE ANALYSIS OF A HELICAL SAVONIUS ROTOR WITHOUT SHAFT AT 45° TWIST ANGLE USING CFD

Helical Savonius rotor exhibits better performance characteristics at all the rotor angles compared to conventional Savonius rotor. However studies related to the performance measurement and flow physics of such rotor are very scarce. Keeping this in view, in this paper, a three dimensional Computational Fluid Dynamics analysis using commercial Fluent 6.2 software was done to predict the performance of a two-bucket helical Savonius rotor without shaft and with end plates in a complete cycle of rotation. A two-bucket helical Savonius rotor having height of 60 cm and diameter of 17 cm with 45° bucket twist angle was designed using Gambit. The buckets were connected at the top and bottom circular end plates, which are 1.1 times the rotor diameter. The k-ε turbulence model with second order upwind discretization scheme was adopted with standard wall condition. Power coefficients (Cp) and torque coefficients (Ct) at different tip speed ratios were evaluated at different rotor angles. From the investigation, it was observed that power coefficient increased with increase of tip speed ratio up to an optimum limit, but then decreased even further tip speed ratio was increased. Further investigation was done on the variations of Cp & Ct in a complete cycle of rotation from 0° to 360° in a step of 45° rotor corresponding to the optimum tip speed ratio. The value of Cp at all the rotor angles is positive. Moreover, velocity magnitude contours were analyzed for each rotor angle and it could be concluded that high aerodynamic torque and power can be expected when the rotor is positioned at 45º & 90º with respect to incoming flow.