It has been suggested that waste heats or naturally available heat sources can be utilized to produce swirling flow by a design similar to that of split channels which is currently used to initiate fire whirls in laboratories. The new design combines the conventional Savonius wind turbine and split channel mechanisms. Previous computational and preliminary experimental works indicate a performance improvement in the new design (named as swirling Savonius turbine) compared to the conventional Savonius design. In this study, wind tunnel experiments have been carried out to optimize the swirling Savonius turbine geometry in terms of maximum power coefficient by considering several design parameters. The results indicate that the blade overlap ratio, hot air inlet diameter and the condition of the top end plate have significant influence on power and torque coefficients, while a larger aspect ratio and closed top end plate have some favourable effects on the performance. The optimum configuration has been tested in four different wind velocities to determine its influence on the performance, and power coefficients were found to be higher in high wind velocities. The performance comparison of optimum configuration with conventional Savonius rotor showed an increase of 24.12% in the coefficient of power.

Geometrical optimization of a swirling Savonius wind turbine using an open jet wind tunnel

Flow Field and Performance Study of Vertical Axis Savonius Type SST Wind Turbine

This article presents a kind of apologetics for cross-flow wind machines At the beginning, general knowledge and initial stages of development for S-type rotors are described The historical review continues with the stage of reduced interest, followed by the stage of enhanced interest after the oil crisis of 70-ies The main advancements and advantages are conveyed Historical evolution of cross-flow runners is also addressed A brief look on the evolution of coaxial wind and electrical rotors is provided as an introduction to the authors’ approach for advancements: a combination of improvements of the conventional wind rotors and of their coupling to the electricity generators The invented Wind Electric Machine Without Stators is quoted The development of competitive vertical axis wind machines is suggested as an important public task, which has to change the agenda of the wind industry

Evolution of the Advancements in Cross Axis Wind Electric Machines

Wind tunnel experiments were carried out on a geometrically optimal swirling Savonius turbine by varying flow parameters to determine their effects on power and torque coefficients. The optimum geometrical configuration used in this experiment was adopted from an earlier study that features 0.20 blade overlap ratio, 195˚ blade arc angle, and 1.06 rotor aspect ratio of a 320 mm diameter rotor with closed top end plate. The parameters considered in this experimental are the hot air temperature, hot air mass flow rate, hot air inlet diameter of swirl chamber, and the free-stream wind velocity. The results indicate that higher hot air temperature and hot air mass flow rate promotes performance of the turbine while power coefficient reached maximum at a certain hot air inlet diameter. Tests on the optimum geometry at four wind velocities revealed that power coefficients are higher in higher wind velocities.

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Effects of flow parameters on the performance of vertical axis swirling type Savonius wind turbine

When compared with other wind turbines, drag driven vertical axis Savonius wind turbine offers lower power coefficient due to its slow turning speed. However, they have many advantages over others, such as simplicity of manufacturing, ability to operate in any wind direction, and having a good starting torque at low wind speed. They are well suited to be integrated in urban environment as small scale power generating wind mills. 
Waste heats or naturally available heat sources such as geothermal and solar energy can be utilized to produce swirling flow when there is a source of angular momentum. Previous computational work suggests that the performance of Savonius turbine can be improved by providing a hot swirling flow inside the turbine chamber. The swirling flow can be induced by a design similar to that of split channels, which includes one or a few vertical slits, and is currently used to onset fire whirls in the laboratories. 
In the present experimental study, the influence of blade overlap, blade arc angle and the diameter of the hot air inlet hole on the torque and power coefficient have been investigated. The results indicate that the maximum power coefficient for a 258 mm diameter rotor occurs at 28 mm blade overlap, '195°' blade angle and 9 mm diameter of hot air inlet hole.

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Influence of blade overlap and blade angle on the aerodynamic coefficients in vertical axis swirling type Savonius wind turbine

Wind energy is non-polluting and is freely available in many areas and is gaining popularity among researchers. Among wind turbines, Horizontal Axis Wind Turbines (HAWT) are more common compared to Vertical Axis Wind Turbines (VAWT) mainly because of their higher efficiency. However, Savonius turbine of VAWT type has many advantages over others such as simplicity in construction, lower cost of production, constancy of the output power regardless of the wind direction, and good starting torque at low wind speed. It is conceived that the efficiency of the Savonius turbines can be increased using industrial wasted heat primarily due to their structural similarity with the split chambers which are often used to induce fire-whirls in laboratories. This work deals with a basic design of such combined configuration and compares its efficiency with a conventional Savonius turbine. The computational results show that the new design has a higher steady state angular velocity as well as higher coefficient of power than the conventional Savonius turbine.

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S. Al-Atresh

Papers

Numerical investigation of performance of a new type of savonius turbine