Numerical and Experimental Study on Performance Enhancement of Savonius and Bio-Inspired Darrieus Type Vertical Axis Wind Turbines | Shiv Nadar University

Numerical and Experimental Study on Performance Enhancement of Savonius and Bio-Inspired Darrieus Type Vertical Axis Wind Turbines

Wind is one of the most abundant sources of clean and renewable energy available to us. This energy is tapped with the help of different types of turbines, which can be grouped into two categories depending upon the orientation of their axis of rotation. These two types are horizontal axis wind turbine (HAWTs) and vertical axis wind turbines (VAWTs). The main difference between the two types of turbines is the ability of VAWTs to work with any wind direction i.e. being Omni-directional as compared to HAWTs. This gives VAWTs an advantage over HAWTs as the latter needs to be oriented in the direction of the wind that requires additional mechanism adding to the costs and chances of failure. Being an Omni-directional turbine, VAWTs can accept wind from any direction and can sustain turbulent and frequent wind direction changes. This makes VAWTs an ideal choice for an urban environment application. Many designs were proposed and tested, and the present day designs are the ones, which are considered as the most effective ones. The purpose of working on VAWTs is that they can be installed close to the ground and need no operating mechanism, can start with minimum wind speed, are cost-effective, environmentally friendly, ideal for areas with high and fluctuating wind patterns, and most importantly they need not be pointed towards the direction of the wind. VAWTs can be further classified into Darrieus type and Savonius type turbines. Savonius type turbine has relatively lower efficiency due to the fact that it experiences negative torque produced by the returning blade, however, it is self-starting and can even work at very low wind speeds. Darrieus type turbines work using the lift forces generated due to the aerofoil geometry of the blade. One of the major reasons for the low performance of Darrieus turbines is the induced drag which is dominated by tip vortices. This study aims at designing highly efficient Savonius and straight bladed Darrieus VAWTs, and to develop an efficient model for both, for small-scale power generation.
Different wingtip devices are tested, numerically and experimentally, to enhance the performance of a Darrieus Turbine. To further augment the performance, an innovative bio-inspired design of the turbine has also been tested. Taking inspiration from nature, tubercles of a whale fin is mimicked onto the blade profile of the Darrieus Turbine. Its performance is then studied, vis-à-vis the baseline configuration. In case of Savonius, the innovative design of a dimpled and ducted rotor has been tested experimentally. Dimples are made on the negative surface of the rotor, and the turbine tested for its performance. The tests on Darrieus rotors are done computationally, as well as experimentally – with forced circulation of air through a fan for the first design, and inside the wind tunnel for the second design. The Savonius rotor is tested only experimentally inside the wind tunnel. For all the design changes, the rotors have yielded better performance with higher efficiency.

Mechanical Engineering
Student Name: 
Nishant Mishra
Faculty Advisor: