DEVELOPMENT OF AN EFFICIENT HYDROKINETIC TURBINE

Abstract

The growth of civilization has been linked to our ability to capture and use the force of flowing water to our benefit. As lot of potential is available in flowing streams,so natural power available in streams has gained keen interest in electricity production for many years. Energy of waterways is mainly extracted by means of conventional hydropower plants that require some kind of a dam or reservoir. In the past, hydropower has been seen as a viable resource seem to have little effect on the environment as river flow modifications and temperatures cause adverse effects to fish and other marine life. Therefore, the tidal energy systems were adapted for river energy extraction, which have their origins in wind energy extraction technologies. Recent developments have focused on a new technology in which kinetic energy of moving water is extracted, which prove to be more sustainable as this type of extraction do not need a large reservoir or flow modification and the system used for the extraction of kinetic energy of running water is known as hydrokinetic turbine. Under present dissertation work, parametric analysis of straight bladed squirrel cage Darrieus vertical axis hydrokinetic turbine is conducted using the Computational Fluid Dynamics (CFD), k-epsilon realizable model in its unsteady form. By fixing different 2-D parameters like solidity, number of blades, Reynolds number and blade pitch angle (fixed), their effect on the aerodynamic efficiency of the turbine is evaluated in order to determine the power coefficient and torque coefficient of the turbine at different tip speed ratios. Also, effect of angle of attack has been investigated to find the optimum angle for a flow condition. Further with the help of CFD results, a small-scale 15 cm diameter, straight bladed squirrel cage Darrieus hydrokinetic turbine is designed, fabricated and tested in the water channel of Hydraulic Measurement Laboratory of Alternate Hydro Energy Centre, IIT Roorkee. Experiments were also conducted on the turbine to find out the operating parameters of the turbine and then calculations were made to find out the performance parameters. With the help of these parameters, characteristics curves are drawn to represent the performance of the turbine. Based on the experimentation, it has been found that the maximum value of power coefficient and torque coefficient has been obtained as 0.372 and 0.525 respectively, corresponding to a tip speed ratio of 0.709.