Unsteady analysis on the instantaneous forces and moment arms acting on a novel Savonius-style wind turbine

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

CFD performance enhancement of a low cut-in speed current Vertical Tidal Turbine through the nested hybridization of Savonius and Darrieus

The blade profiles and blade shapes of vertical-axis Savonius wind turbine rotors have undergone a series of changes over the past three decades. Wind turbine aerodynamicists have carried out numerous computational and experimental research to arrive at a suitable rotor blade design configuration so as to harvest maximum energy from the available wind. In most of the studies, the geometric and aerodynamic aspects of the rotor blade design have been reported. Interestingly enough, a couple of review papers got published in the area of Savonius rotors during the last one decade. However, there is not a single piece of literature that gives a comprehensive and a systematic review of Savonius rotor blade profiles and shapes. This paper aims to collate all the research findings related to these blade profiles/shapes and makes an attempt to highlight their features together with future recommendations.

Evolution and Progress in the Development of Savonius Wind Turbine Rotor Blades Profiles and Shapes

Performance evaluation of vent-augmented elliptical-bladed savonius rotors by numerical simulation and wind tunnel experiments

The Savonius-style wind turbine, a class of vertical axis wind turbines, can be a viable option for small scale off-grid electricity generation in the context of renewable energy applications. A better self-starting capability at low wind speeds is one of the major advantages of this turbine. However, as reported in open literature, the power coefficient of the conventional design is found to be inferior as compared to its counterparts. In this regard, a new blade design has been developed. In the present investigation, the aerodynamic performance of this newly designed turbine is assessed under an oriented jet. This is affected by installing deflectors upstream of the turbine blades. The intention of this study is to maximize the utilization of wind energy at the exhaust systems of several practical applications. Experiments are carried out in a low speed wind tunnel at a wind speed of 6.2 m/s. The gradual loads applied to the turbine, and the corresponding rotational speeds are recorded. Power and torque coefficients are calculated at various mechanical loads. Further, all the estimated data are corrected by a suitable correction factor to account for the wind tunnel blockage effects. The results obtained are compared with the experimental data of modified Bach and conventional designs. The results have shown a significant improvement in the performance of newly designed Savonius-style wind turbine under the concentrated and oriented jet.Copyright © 2014 by ASME

Aerodynamic Performance Evaluation of a Novel Savonius-Style Wind Turbine Under an Oriented Jet

Although considerable progress has already been achieved in the design of wind turbines, the available technical designs are not yet adequate to develop a reliable wind energy converter especially meant for small-scale applications. The Savonius-style wind turbine appears to be particularly promising for the small-scale applications because of its design simplicity, good starting ability, insensitivity to wind directions, relatively low operating speed, low cost and easy installation. However, its efficiency is reported to be inferior as compared to other wind turbines. Aiming for that, a number of investigations have been carried out to increase the performance of this turbine with various blade shapes. In the recent past, investigations with different blade geometries show that an elliptic-bladed turbine has the potential to harness wind energy more efficiently. In view of this, the present study attempts to assess the performance of an elliptic-bladed Savonius-style wind turbine using 2D unsteady simulations. The SST k-ω turbulence model is used to simulate the airflow over the turbine blades. The power and torque coefficients are calculated at rotating conditions, and the results obtained are validated with the wind tunnel experimental data. Both the computational and experimental studies indicate a better performance with the elliptical blades. Further, the present analysis also demonstrates improved flow characteristics of the elliptic-bladed turbine over the conventional semi-circular design.Copyright © 2014 by ASME

Unsteady Flow Analysis Around an Elliptic-Bladed Savonius-Style Wind Turbine

\n Over the last few decades, the vertical-axis wind turbines (VAWTs) have undergone intensive research mainly due to their design simplicity and independency of wind direction. The drag-based Savonius wind rotor exhibits a better starting capability, whereas the lift-based Darrieus wind rotor achieves higher efficiency over a wider operating range. Thus, in order to capitalize on their advantages, both the rotors are mounted on the same axis to form a hybrid/combined system. In this review paper, an attempt has been made to collect and analyze the past research studies in the field of hybrid wind rotors. An optimization route has also been suggested for the design of such a hybrid wind rotor to ensure that the design complexity is minimized, and at the same time, both the Savonius and the Darrieus rotors are utilized to their fullest potential. In this regard, a few important parameters are identified whose effects on the hybrid rotor performance must be investigated in future studies. Suggestions and direction of research are presented keeping in mind the improvement of the technology.

Hybrid/Combined Darrieus–Savonius Wind Turbines: Erstwhile Development and Future Prognosis

With the rising fossil-fuel prices, energy scarcity and climate-change, renewable energy plays an important role in producing local, clean and inexhaustible energy source to supply world rising demand for electricity. The selection of suitable wind turbine plays a vital role for urban power generation where wind is characterised by unsteadiness and turbulence. Thus, blade aerodynamics of wind turbine has a significant effect on turbine efficiency.In this study, the aerodynamic aspect of a straight bladed Darrieus turbine is numerically analyzed. Two dimensional numerical modelling and simulation of unsteady flow through the rotor blades (NACA 0018) of the turbine is performed using ANSYS FLUENT 14.5. The unsteady Reynolds averaged Navier-Stokes (RANS) equation is used to demonstrate the effects on the performance of two dimensional Darrieus turbine blade. The Shear Stress Transport (SST) k-ω model has been adopted for the turbulence closure. For the proposed analysis, the flow field characteristics are investigated at different azimuthal angle and tip speed ratio. Further, the parametric quantities such as solidity, number of blades and blade thickness have being investigated for a uniform free stream velocity of 6 m/s. The effect of laminar boundary layer separation on performance of the Darrieus turbine has also been taken into account during the study of flow physics around the blade. The results obtained are compared with the reported experimental and computational data.Copyright © 2015 by ASME

Prasenjit Mukherjee

Papers

Aerodynamic Performance Evaluation of a Novel Savonius-Style Wind Turbine Under an Oriented Jet

Unsteady Flow Analysis Around an Elliptic-Bladed Savonius-Style Wind Turbine

Hybrid/Combined Darrieus–Savonius Wind Turbines: Erstwhile Development and Future Prognosis

Performance Prediction of Darrieus Turbine Through Numerical Analysis