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The role of tidal asymmetry in characterizing the tidal energy resource of Orkney

Neill, S.P. and Hashemi, M.R. and Lewis, M.J. (2014) The role of tidal asymmetry in characterizing the tidal energy resource of Orkney. Renewable Energy, 68. pp. 337-350. DOI: 10.1016/j.renene.2014.01.052

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Abstract

When selecting sites for marine renewable energy projects, there are a wide range of economical and practical constraints to be considered, from the magnitude of the resource through to proximity of grid connections. One factor that is not routinely considered in tidal energy site selection, yet which has an important role in quantifying the resource, is tidal asymmetry, i.e. variations between the flood and ebb phases of the tidal cycle. Here, we present theory and develop a high-resolution three-dimensional ROMS tidal model of Orkney to examine net power output for a range of sites along an energetic channel with varying degrees of tidal asymmetry. Since power output is related to velocity cubed, even small asymmetries in velocity lead to substantial asymmetries in power output. We also use the 3D model to assess how tidal asymmetry changes with height above the bed, i.e. representing different device hub heights, how asymmetry affects turbulence properties, and how asymmetry is influenced by wind-driven currents. Finally, although there is minimal potential for tidal phasing over our study site, we demonstrate that regions of opposing flood- versus ebb-dominant asymmetry occurring over short spatial scales can be aggregated to provide balanced power generation over the tidal cycle.

Item Type: Article
Subjects: Research Publications
Departments: College of Natural Sciences > School of Ocean Sciences
Date Deposited: 09 Dec 2014 16:33
Last Modified: 23 Sep 2015 02:59
ISSN: 0960-1481
URI: http://e.bangor.ac.uk/id/eprint/421
Identification Number: DOI: 10.1016/j.renene.2014.01.052
Publisher: Elsevier
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