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Adaptive Composite Blades for Horizontal Axis Tidal Turbines

Adaptive Composite Blades for Horizontal Axis Tidal Turbines
Adaptive Composite Blades for Horizontal Axis Tidal Turbines
The oceans are a huge resource of untapped energy. There are many marine renewable energy sources however tidal energy has the advantage of being highly predictable. The range of devices for tidal energy extraction is extensive with power being generated either by extracting potential or kinetic energy. Due to environmental concerns regarding potential devices it is thought that a breakthrough will occur in the area of kinetic energy devices, most likely horizontal axis tidal turbines (HATTs). No HATT technology is yet commercial and further research into the field is required to advance the concepts, improve the feasibility of maintenance and make devices more efficient and economic.
The blades of a HATT are the source of energy extraction for the device and are required to operate in a harsh subsea environment for a long (20 year) life cycle with minimal need for maintenance. Choice of an appropriate foil section for the blade is integral. A novel bi-directional section has been developed for use on a HATT and compared to a variable pitch device. The concept of using adaptive composite blades in order to improve energy capture but also decrease design complexity has been considered. Preliminary analysis was undertaken and it suggested that a 2.5% increase in annual energy capture and a 10% decrease in thrust loading could be expected through the use of a bend-twist coupled adaptive HATT blade. An experimental method was developed for the assessment of bend and induced twist in a coupled spar, and the results compared well to numerical analysis with the conclusion that the numerical model is very sensitive to manufacturing accuracy. A design tool for the development of adaptive composite bend-twist coupled HATT blades has been developed. The tool couples finite element analysis, computational fluid dynamics and blade element theory to create optimal blades.
Coupling the passively adaptive bend-twist coupled spar with actively adaptive snap-through asymmetric laminates to create an efficient blade that works optimally in both directions of tidal flow has been considered. A comparison between four arrays of 4 turbines in a staggered grid, one each with standard fixed pitch, bi-directional, passively adaptive and actively adaptive blades illustrated that annual energy capture could be increased by up to 120% with the use of actively adaptive blades when compared to a base fixed bladed rotor
Nicholls-Lee, R.F.
eb65ebff-bdc3-4ea0-8e3d-6f769fc323ed
Nicholls-Lee, R.F.
eb65ebff-bdc3-4ea0-8e3d-6f769fc323ed
Turnock, Stephen
d6442f5c-d9af-4fdb-8406-7c79a92b26ce
Boyd, Stephen
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Nicholls-Lee, R.F. (2011) Adaptive Composite Blades for Horizontal Axis Tidal Turbines. University of Southampton, Fluid Structure Interactions Research Group, Doctoral Thesis, 247pp.

Record type: Thesis (Doctoral)

Abstract

The oceans are a huge resource of untapped energy. There are many marine renewable energy sources however tidal energy has the advantage of being highly predictable. The range of devices for tidal energy extraction is extensive with power being generated either by extracting potential or kinetic energy. Due to environmental concerns regarding potential devices it is thought that a breakthrough will occur in the area of kinetic energy devices, most likely horizontal axis tidal turbines (HATTs). No HATT technology is yet commercial and further research into the field is required to advance the concepts, improve the feasibility of maintenance and make devices more efficient and economic.
The blades of a HATT are the source of energy extraction for the device and are required to operate in a harsh subsea environment for a long (20 year) life cycle with minimal need for maintenance. Choice of an appropriate foil section for the blade is integral. A novel bi-directional section has been developed for use on a HATT and compared to a variable pitch device. The concept of using adaptive composite blades in order to improve energy capture but also decrease design complexity has been considered. Preliminary analysis was undertaken and it suggested that a 2.5% increase in annual energy capture and a 10% decrease in thrust loading could be expected through the use of a bend-twist coupled adaptive HATT blade. An experimental method was developed for the assessment of bend and induced twist in a coupled spar, and the results compared well to numerical analysis with the conclusion that the numerical model is very sensitive to manufacturing accuracy. A design tool for the development of adaptive composite bend-twist coupled HATT blades has been developed. The tool couples finite element analysis, computational fluid dynamics and blade element theory to create optimal blades.
Coupling the passively adaptive bend-twist coupled spar with actively adaptive snap-through asymmetric laminates to create an efficient blade that works optimally in both directions of tidal flow has been considered. A comparison between four arrays of 4 turbines in a staggered grid, one each with standard fixed pitch, bi-directional, passively adaptive and actively adaptive blades illustrated that annual energy capture could be increased by up to 120% with the use of actively adaptive blades when compared to a base fixed bladed rotor

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Final_PhD_Thesis_Rachel_F_Nicholls-Lee.pdf - Accepted Manuscript
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More information

Published date: 31 May 2011
Organisations: University of Southampton, Fluid Structure Interactions Group

Identifiers

Local EPrints ID: 209357
URI: https://eprints.soton.ac.uk/id/eprint/209357
PURE UUID: f0d26fc1-c5d9-4d84-9db4-a32ec1b65fd7
ORCID for Stephen Turnock: ORCID iD orcid.org/0000-0001-6288-0400

Catalogue record

Date deposited: 20 Apr 2012 13:21
Last modified: 06 Jun 2018 13:14

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Contributors

Author: R.F. Nicholls-Lee
Thesis advisor: Stephen Turnock ORCID iD
Thesis advisor: Stephen Boyd

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