The University of Southampton
University of Southampton Institutional Repository

Performance quantification of marine current energy converters in constrained flow fields

Performance quantification of marine current energy converters in constrained flow fields
Performance quantification of marine current energy converters in constrained flow fields
The Marine Current Energy Converter (MCEC) industry is currently at a stage where early farms are being designed. These farms will provide an indication of the commercial viability of the technology to future investors. Only limited full-scale device data is available in order to inform designers of performance, due to only small numbers of o shore deployments. Smaller-scale laboratory testing can provide greater understanding of device performance and loading. Understanding device performance and loading are important as they will impact on projects finances by affecting energy yield and allowing extreme loading to be designed for to avoid unplanned maintenance. The loading of MCEC devices in constrained flow fields is currently not well understood at either full or laboratory-scale.

The aim of this study is to investigate the influence of constrained flow fields on MCEC device loading and wake development. The results will inform: the limits of current analytical MCEC performance models, the calibration of empirical wake models, and the limits of existing computational fluid dynamic array models. The findings will therefore aid the development of design tools used in MCEC device modelling. This work presents the results from a series of small-scale laboratory static porous disk experiments in which the changes in loading and wake structure of a single device are characterised with variation in channel properties such as: area blockage ratio, Froude number and channel aspect ratio. Dual-array devices are also studied with the effects of device spacing and channel geometry upon wake formation and device loading characterised.

Thrust coefficient is shown to be a function of Froude number, area blockage ratio and channel aspect ratio; with each non-dimensional parameter contributing significantly to differences in loading. Despite differences in thrust coefficient with changes in channel aspect ratio it is shown that one-dimensional linear momentum actuator disk theory models are capable of accounting for these differences. Wake velocity profile, wake expansion, transition point from near to far wake and wake recovery are shown to be different in the vertical and horizontal planes in some channels geometries. Variation in channel geometry, i.e. the proximity of bounding surfaces, is shown to have an effect on these parameters indicating that it may be possible to calibrate semi-empirical wake models to predict wake development in either flows of constrained geometry or within array deployments. Device spacing in a dual-array is also shown to affect wake structure and device loading. The relationships between these two parameters are shown to be a function of device diameter/water depth ratio.
University of Southampton
Keogh, Bradley
b698d61e-30f2-483a-bd87-41368c08f708
Keogh, Bradley
b698d61e-30f2-483a-bd87-41368c08f708
Bahaj, Abubakr
a64074cc-2b6e-43df-adac-a8437e7f1b37

(2016) Performance quantification of marine current energy converters in constrained flow fields. University of Southampton, Faculty of Engineering and the Environment, Doctoral Thesis, 201pp.

Record type: Thesis (Doctoral)

Abstract

The Marine Current Energy Converter (MCEC) industry is currently at a stage where early farms are being designed. These farms will provide an indication of the commercial viability of the technology to future investors. Only limited full-scale device data is available in order to inform designers of performance, due to only small numbers of o shore deployments. Smaller-scale laboratory testing can provide greater understanding of device performance and loading. Understanding device performance and loading are important as they will impact on projects finances by affecting energy yield and allowing extreme loading to be designed for to avoid unplanned maintenance. The loading of MCEC devices in constrained flow fields is currently not well understood at either full or laboratory-scale.

The aim of this study is to investigate the influence of constrained flow fields on MCEC device loading and wake development. The results will inform: the limits of current analytical MCEC performance models, the calibration of empirical wake models, and the limits of existing computational fluid dynamic array models. The findings will therefore aid the development of design tools used in MCEC device modelling. This work presents the results from a series of small-scale laboratory static porous disk experiments in which the changes in loading and wake structure of a single device are characterised with variation in channel properties such as: area blockage ratio, Froude number and channel aspect ratio. Dual-array devices are also studied with the effects of device spacing and channel geometry upon wake formation and device loading characterised.

Thrust coefficient is shown to be a function of Froude number, area blockage ratio and channel aspect ratio; with each non-dimensional parameter contributing significantly to differences in loading. Despite differences in thrust coefficient with changes in channel aspect ratio it is shown that one-dimensional linear momentum actuator disk theory models are capable of accounting for these differences. Wake velocity profile, wake expansion, transition point from near to far wake and wake recovery are shown to be different in the vertical and horizontal planes in some channels geometries. Variation in channel geometry, i.e. the proximity of bounding surfaces, is shown to have an effect on these parameters indicating that it may be possible to calibrate semi-empirical wake models to predict wake development in either flows of constrained geometry or within array deployments. Device spacing in a dual-array is also shown to affect wake structure and device loading. The relationships between these two parameters are shown to be a function of device diameter/water depth ratio.

Text
Final e-thesis for e-prints - KEOGH 21534853.pdf - Version of Record
Available under License University of Southampton Thesis Licence.
Download (11MB)

More information

Published date: January 2016
Organisations: University of Southampton, Researcher Development, Energy & Climate Change Group

Identifiers

Local EPrints ID: 393735
URI: http://eprints.soton.ac.uk/id/eprint/393735
PURE UUID: fc384a74-a28c-4dbf-9a05-b3c6c54df1a8
ORCID for Bradley Keogh: ORCID iD orcid.org/0000-0003-2960-0918
ORCID for Abubakr Bahaj: ORCID iD orcid.org/0000-0002-0043-6045

Catalogue record

Date deposited: 05 Jul 2016 15:10
Last modified: 15 Jun 2018 00:36

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×