Meeting future world energy needs while addressing climatic changes has led to greater strain on conventional power sources. One of the viable sustainable energy sources is wind. But the installation large scale wind farms has a potential impact on the climatic conditions, hence a decentralized small scale wind turbines is a sustainable option. This paper presents review of on different types of small scale wind turbines i.e., horizontal axis and vertical axis wind turbines. The performance, blade design, control and manufacturing of horizontal axis wind turbines were reviewed. Vertical axis wind turbines were categorized based on experimental and numerical studies. Also, the positioning of wind turbines and aero-acoustic aspects were presented. Additionally, lessons learnt from various studies/countries on actual installation of small wind turbines were presented.

A review on small scale wind turbines

This paper presents a review on the performance of Savonius wind turbines. This type of turbine is unusual and its application for obtaining useful energy from air stream is an alternative to the use of conventional wind turbines. Simple construction, high start up and full operation moment, wind acceptance from any direction, low noise and angular velocity in operation, reducing wear on moving parts, are some advantages of using this type of machine. Over the years, numerous adaptations for this device were proposed. The variety of possible configurations of the rotor is another advantage in using such machine. Each different arrangement of Savonius rotor affects its performance. Savonius rotor performance is affected by operational conditions, geometric and air flow parameters. The range of reported values for maximum averaged power coefficient includes values around 0.05–0.30 for most settings. Performance gains of up to 50% for tip speed ratio of maximum averaged power coefficient are also reported with the use of stators. Present article aims to gather relevant information about Savonius turbines, bringing a discussion about their performance. It is intended to provide useful knowledge for future studies.

A review on the performance of Savonius wind turbines

Optimum design configuration of Savonius rotor through wind tunnel experiments

Optimal blade shape of a modified Savonius turbine using an obstacle shielding the returning blade

Performance tests on helical Savonius rotors

On the performance analysis of Savonius rotor with twisted blades

Accessories, such as end plates, deflecting plates, shielding and guide vanes, may increase the power of a Savonius rotor, but make the system structurally complex. In such cases, the rotor can develop a relatively large torque at small rotational speeds and is cheap to build, however it harnesses only a small fraction of the incident wind energy. Another proposition for increasing specific output is to place non-return valves inside the concave side of the blades. Such methods have been studied experimentally with a twisted-blade Thus, improving a Savonius rotor's, energy capture. This new concept has been named as the 'Valve-Aided Twisted Savonius'rotor. Tests were conducted in a low-speed wind tunnel to evaluate performance. This mechanism is found to be independent of flow direction, and shows potential for large machines.

Valve-Aided Twisted Savonius Rotor

The fluid flow over a Savonius wind turbine rotor has been analyzed by using a multi-physics simulation program. The analysis accounts for fully flow simulation, the effect of rotation on flowfield in, around and far behind the turbine rotor. The aim of this investigation is to study the evolution of fluid contours and the velocity circulation. The flow distribution at various rotor tip speed ratios was studied at an air velocity of 10 m/s. Results obtained from the investigation have been discussed and analyzed.

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M. Jaya Rajkumar

Papers

On the performance analysis of Savonius rotor with twisted blades

Valve-Aided Twisted Savonius Rotor

Simulation of Flow Around and Behind a Savonius Rotor