THE OPTIMAL SPACING BETWEEN PRIMARY AND SECONDARY ROTORS OF A COUNTER-ROTATING WIND TURBINE

by Hisham Al Mahrizi

Submitted : Fall 2018

Wind energy is an important resource and alternative to the fossil fuels. It provides clean and renewable energy, making it more appealing for clean environment. When a traditional wind turbine with a single rotor system on one side is used for energy conversion, only a part of the available energy is converted. Usually, the turbines are made larger for more power production. This increase in size introduces further problems such as large bearing frictions, noise and even loss of aesthetic. Besides, the amount of power extracted from the wind cannot exceed 59% of the available energy in the wind. In practice, the energy contained within the wake behind the rotor can still be exploited further. This can be achieved by attaching another set of blades on the rear side of the hub. If these rotors are of the same diameters, the amount of energy extraction increases from 59% to 64%. In this project, contra-rotating wind turbine with rotors of different diameters shall be used.

A contra-rotating wind turbine (CRWT) is a wind turbine with two sets of rotors attached on opposite sides of the hub, and separated by a particular appropriate distance. Given the direction of rotation of the wake behind the first rotor, the second set of blades should rotate in a direction opposite to that of the first set. This will enable efficient extraction of energy from the wake. This project will involve selection of proper materials for the blades, focus on the angle of attack of the blades and determine the proper distance between the two sets of blades. The final assembly shall be tested experimentally, besides computational fluid dynamics, to ascertain its performance.

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