PERFORMANCE EVALUATION OF TIDAL STREAM TURBINE USING COMPUTATIONAL FLUID DYNAMICS

Abstract

Research for development of marine and tidal current energy, has seen noticeable growth in the recent past. The horizontal-axis tidal stream turbine is one of the most technologically and economically viable one for harnessing tidal kinetic energy. The oceans are a reserve of untapped potential of energy. and among such sources, tidal stream energy is a predictable form of energy with high energy density. There are examples of large-scale marine current turbines rated at more than 1 MW deployed around the world. In this prospect, the industry and the academic research have shown positive growth of interest in horizontal axis tidal stream turbines, as reflected in the literature review in this dissertation. Unlike conventional hydropower and tidal barrage installations, water current turbines lie in the open flow and can generate power from the flow of sea water, with negligible environmental impact. These turbines find a much wider range of sites than those available for conventional tidal power generation. Through this work, recent developments in current turbine design are reviewed and potential advantages of ducted or 'diffuser-augmented" current turbines are explored. Ducted turbines are not subjected to the so-called Betz limit, which defines an upper limit of 59.3% of the incident kinetic energy that can be converted to shaft power by a single actuator disk turbine in open flow. It is foreseeable that this particular field will continue to develop at an increasing pace and a growing number of countries will start to look into the feasibility of tapping renewable tidal energy. Taking the opportunity to explore this upcoming and promising scheme of energy generation, this report explores the development in the field of horizontal axis tidal stream turbines with emphasis on ducted turbines. The main purpose of this report is to present the design and performance evaluation of alaboratory scale ducted horizontal axis tidal stream turbine through Computational Fluid Dynamics. Analysis is also exercised to investigate the performance of the airfoil section used in the turbine. The duct, turbine and the combination are modelled in CAD applications and performance evaluation is done through flow simulation package FLUENT available under ANSYS v14 with the objective to find an optimized geometrical configuration of the duct for best performance. A new turbine is designed to suit to the ducted flow conditions and the outcome is compared to the previous results obtained in the literature for similar open turbine.