Savonius Hydrokinetic Turbine Research Articles

Performance investigation of self-adjusting blades turbine through experimental study

In the quest for renewable energy sources and sustainable development, hydrokinetic energy available in marine currents, river currents, water flows and man-made canals should be harnessed. This is particularly true for rural and remote areas, which have access to water but often have poor electricity. The vertical axis current turbine, which is a key hydrokinetic technology, has been greatly improved over the last few years. It has numerous advantages, including independency of flow direction, design simplicity, quiet operation, no required yaw mechanism and low cost. The Savonius hydrokinetic turbine is one of the most important drag-type configurations of a vertical axis current turbine. However, it suffers from negative torque, negative drag force on the returning blades, low efficiency and difficulty interfacing with a generator. This paper proposes a novel drag-based vertical axis current turbine using arms and self-adjusting blades. This novel design was developed based on the framework of a Savonius hydrokinetic turbine. In an effort to decrease the hydrodynamic resistance of the returning blades and increase the total output torque of the turbine, this study aims to investigate the performance characteristics of a novel vertical axis current turbine (hereinafter referred to as “self-adjusting blade turbine”). Experimental tests were conducted in the Universiti Teknologi Malaysia (UTM) at low speed currents to assess the performance characteristics of three configurations of a fixed blade turbine and a self-adjusting blade turbine. The force acting on one blade of the self-adjusting turbine was analysed in detail. The results showed that the arm length and blade angle affected the performance of turbine, and that there was 30.7% increase in performance for the self-adjusting blade turbine compared to the fixed blade turbine.

Performance estimation of Savonius wind and Savonius hydrokinetic turbines under identical power input

In the context of energy crisis, extensive depletion of fossil fuel, and climate change, the vertical-axis Savonius-type wind or hydrokinetic turbines appear to be promising candidates to extract energy from wind or free-flowing water because of their superior self-starting capability and design simplicity. The present investigation focuses on comparative analysis between Savonius wind turbines (SWTs) and Savonius hydrokinetic turbines (SHTs) at the same input power. To accomplish this, two configurations are considered, viz., 2-bladed and 3-bladed turbine designs having semicircular blade profiles. Experimental studies revealed that the SWTs operate in a slightly wider range of tip-speed ratios than the SHTs. It is also observed that, like SHTs, 2-bladed SWTs result in an improved (47%) peak power coefficient (CPmax) than 3-bladed SWTs. In line with this, the computational studies, conducted to complement the experimental analysis, showed the superiority of 2-bladed SWTs over the 3-bladed SWTs. Both experimental and computational analyses reveal that the SHTs and SWTs show identical drag and lift characteristics for given kinetic energy of the inlet fluid stream.

Parametric analysis of model Savonius hydrokinetic turbines through experimental and computational investigations

The drag-based Savonius hydrokinetic turbine (SHT) has an enormous potential for small-scale power generation from free-flowing water and it can be deployed especially at sites remote from existing electricity grids. These turbines can be installed in waves, tides, ocean currents, natural flow of water in rivers, manmade channels and irrigation canals to produce power. The performance of a SHT are highly influenced by its design parameters such as blade profile, number of blades, overlap ratio and aspect ratio. Although, over a period of nine dacade since its invention, serveral studies have been carried out, however, no particular concencus on the optimum design of SHT is arrived. In view of this, in the present investigation, as attempt has been made to parametrically evaluate the performance of the SHT through experimental and computational fluid dynamics (CFD) analysis. The SHT under investigation has been developed in-house. Initially, a comparison of performance between two- and three-bladed SHT with conventional semicircular blades has been carried out experimentally where their maximum power coefficients are found to be 0.28 and 0.17, respectively at their corresponding tip-speed ratios of 0.84 and 0.67. Further experiments with a two-bladed SHT turbine with elliptical blades have shown its inferior performance as compared to the two-bladed semicircular SHT. The reason behind the enhanced performance of the two-bladed semicircular SHT is then analyzed through two-dimensional CFD simulations. Finally, the experiments are conducted at various immersion levels, where the performances of the SHTs are found to degrade with a decrease in immersion. However, the two-bladed semicircular SHT maintains to have a better performance than the others.

KAJIAN TEORITIK PENGARUH GEOMETRI DAN TWIST ANGLE TURBIN HYDROKINETIK SAVONIUS TERHADAP KOEFISIEN DAYA

The use of fossil energy sources for electric power generation tends to increase while the availability of fossil energy is very limited. New renewable energy sources promise solutions for human dependence on fossil energy sources Dependence on fossil energy will have an impact on the high cost of distributing electricity to remote areas. The picohydro power plant using a very simple savonius hydrokinetic turbine is one of the solutions for remote areas. The purpose of this paper is to obtain the optimum design of the blade hydrokinetic savonius with a relatively easy design method. Based on the results of the study, the geometry and design of savonius hydro quatern turbine are able to produce power coefficient (CP) 13.99 with specification of aspect ratio H / D = 1; end plate Do / D = 1,1; turbine diameter (D) = 82 mm and plate thickness 2 mm, number of blade 3 and twist angle (α) 150.

Performance analysis of a single stage modified Savonius hydrokinetic turbine having twisted blades

Savonius hydrokinetic turbine is one of the prominent vertical axis turbines for tapping hydro potential available in flowing streams in rivers or canals. In spite of their simple design, Savonius turbines have the problem of poor performance. This study aims to enhance the performance of turbine through modification in the blade shape. Under the present study, geometrical parameters namely blade arc angle and blade shape factor are considered to modify the blade shape of Savonius hydrokinetic turbine. A commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-ε turbulence model has been used for numerical analysis. Using CFD analysis, blade arc angle and blade shape factor are optimized on the basis of coefficient of power. Fluid flow distributions found around the rotor has also been analyzed and discussed. Based on the present investigation, the maximum power coefficient value of 0.426 is obtained for blade arc angle of 150° and blade shape factor of 0.6 corresponding to TSR value of 0.9 at flow velocity of 2 m/s.

Modeling of flow-induced stress on helical Savonius hydrokinetic turbine with the effect of augmentation technique at different operating conditions

Conventional Savonius rotor experiences negative and high static torque coefficient at several rotor angles. To prevail over this issue Helical Savonius hydrokinetic turbine (HSHKT) twisted with 90° is proposed, which is able to avoid excessive shaking due to hydrodynamic forces on blades. Usually, HSHKT have a low efficiency, Therefore to enhance the performance coefficient of the rotor some augmentation techniques are required to be used. In this study modeling of flow-induced stresses on HSHKT are performed through fluid-structure interaction analysis. The maximum hydraulic load and von-Mises stress on rotor are found as 0.79 Mpa and 145.45 Mpa respectively in case of duct with single deflector augmentation techniques. Computation results show that edge of shaft and joint of end plate and shaft rotor experiences zone of high von-Mises stress which leads to fatigue crack in this area. In consequence to that augmentation techniques creates adverse effect on stability, smooth operation and service life of rotor at the higher free stream velocity, which opposes the fact that the rotor performance is enhanced by employing augmentation techniques in certain conditions. In this study, it is found that the possibility of fatigue crack increases at higher free stream velocity while using augmentation techniques.

Performance analysis of a Savonius hydrokinetic turbine having twisted blades

In the quest for renewable energy sources, kinetic energy available in small water streams, river streams or human-made canals may provide new avenue which can be harnessed by using hydrokinetic turbines. Savonius hydrokinetic turbine is vertical axis turbine having drag based rotor and suitable for a lower flow velocity of the water stream. In order to enhance the efficiency of the turbine, this paper aims to analyze the performance of twisted blade Savonius hydrokinetic turbine. Using CFD analysis, an attempt has been made to optimize blade twist angle of Savonius hydrokinetic turbine. The simulation of a twisted Savonius hydrokinetic turbine having two blades has been carried out to investigate the performance. Commercial unsteady Reynolds-Averaged Navier-Stokes (URANS) solver in conjunction with realizable k-ε turbulence model has been used for numerical analysis. Fluid flow distributions around the rotor have been analyzed and discussed. It has been found that Savonius hydrokinetic turbine having a twist angle of 12.5° yields a maximum coefficient of power as 0.39 corresponding to a TSR value of 0.9 for a given water velocity of 2 m/s.

Experimental Investigations on the Performance Characteristics of a Modified Four Bladed Savonius Hydro-Kinetic Turbine

Torque variation along the angular positions of the rotor blade and lower efficiency are the main drawbacks of Savonius turbine. To overcome these problems several attempts have been made by the researchers in the recent past. In this work, an attempt has been made to increase the torque along the angular positions where the torque is low, by placing a set of additional blades called secondary blades in front of the concave side of main rotor blades. These secondary blades are interacting with the flowing fluid when the main blades are not in action. The performance of the modified Savonius turbine is compared with the conventional single blade 0 overlap and 0.2 overlap Savonius turbines, by carrying out the experiments in the open irrigation canal of size 42 cm x 45 cm. Results shows that, the efficiency is improved from 16 % to 19% and the torque values increased along the angular positions of 90°, 120°, 270°, 300°, 330°. From the observations, it has also been noted that, the modified four bladed Savonius turbine rotates smoothly in comparison with the conventional Savonius. The negative torque a common problem in conventional Savonius is also effectively eliminated in the modified design.

Influence of overlap ratio and aspect ratio on the performance of Savonius hydrokinetic turbine

A strong contender for the utilization of the hydropower sources is Savonius turbine because of its good starting characteristics and simplicity in fabrication. The aim of the present work is to study the effect of overlap ratio and aspect ratio on the performance of a Savonius turbine for hydrodynamic application. The findings would be useful to decide design parameters of a Savonius hydrokinetic turbine. This study is conducted in three open channels namely small laboratory channel with depth of water 270 mm, large laboratory channel with depth of water 480 mm and a real life irrigation canal with depth of water 900 mm. Influence of endplates is studied to establish the significance of their presence on rotor performance. Maximum coefficient of power is observed for an overlap ratio of around 0.11 for Savonius turbines with aspect ratio less than 0.6. For a given overlap ratio, the increasing trend of the coefficient of power is observed with the increase in the aspect ratio. However, for aspect ratios greater than 1.8, the coefficient of power becomes nearly stagnant. Copyright © 2016 John Wiley & Sons, Ltd.

Numerical investigation of hydraulic load and stress induced in Savonius hydrokinetic turbine with the effects of augmentation techniques through fluid-structure interaction analysis

The objective of the present study is to estimate hydraulic load, induced stress and factor of safety of the Savonius hydrokinetic turbine when operating under free stream velocity of 0.3 m/s to 4 m/s at rotor angle 0° to 360°. Hydraulic load evaluated from CFD analysis, whereas the induced stress computed from FEM analysis based on the computed hydraulic load through CFD in ANSYS 14. The effects of deflector and duct augmentation technique on the hydraulic load and induced stress have also been investigated. The maximum hydraulic load and von-Mises stress on rotor are found as 0.57 Mpa and 153.41 Mpa respectively in case of duct with single deflector augmentation techniques at rotor angle 0°, 180° and 360° at 4 m/s free stream velocity. In Savonius rotor with augmentation techniques, at higher free stream velocity the factor of safety reached very low, somewhat equal or less than minimum specified limit of failure. Computation results show that front area of shaft rotor from inlet side experiences zone of high von-Mises stress and has minimum factor of safety that leads to chances of fatigue crack, when applied for a free stream velocity greater than 2 m/s.

Experimental Investigations on the Performance Characteristics of a Modified Four Bladed Savonius Hydro-Kinetic Turbine

Experimental Investigations on the Performance Characteristics of a Modified Four Bladed Savonius Hydro-Kinetic Turbine

A Simulation Study of Flow and Pressure Distribution Patterns in and around of Tandem Blade Rotor of Savonius (TBS) Hydrokinetic Turbine Model

Abstrac t—Th e performance of hydrokinetic turbines of Savonius using a Tandem Blade Savonius (TBS) rotor was studied. These were three types of TBS: Overlap (Type I), Symmetrically (Type II) and Convergence (Type III). Through a comprehensive bibliographical research, it is possible to identify the influenced parameters, and to show that the optimum efficiency of the Savonius rotor can be particularly improved their partition space between blade and tandem. This simulation shows the way of the flow characteristic and pressure distribution pattern in and around of the blade swept area. The results show that the convergence TBS (Type III) have a higher gap pressure between upstream and downstream, or they have best performance than other types.