Scottish Marine and Freshwater Science Volume 3 Number 2: Scoping Study For Offshore Wave Energy Development In Scottish Waters

5 Identification of Areas of Search for Wave Energy Plan Option Areas

The similarities between the outputs from the four combined models described in Section 4 above led to the equal weight model being used for the identification of areas of search for wave energy plan option areas in Scottish waters. The area considered was limited to the area identified as having potentially adequate wave power resource ( Figure 1). A further filter was applied by water depth to reflect the ranges of depths for which development projects are currently under discussion (0 - 60m, and 60 - 90 m).

5.1 Wave Energy Areas in 0 - 60m Depth of Water

Areas with potential for wave energy developments in water depths of 0 - 60m within the resource area ( Figure 9) and with low overall levels of constraint are mainly in the west of Scotland, south west of Mull and west of the Outer Hebrides. Other smaller areas are found west of Shetland and north of Orkney. Inshore waters around Orkney and Shetland generally have higher levels of constraint, although the significance of this will be influenced by the characteristics of the devices being considered for deployment.

5.2 Wave Energy Areas in 60 - 90m Depth of Water

Areas with potential for wave energy developments in water depths of 60 - 90m within the resource area ( Figure 10) and with low overall levels of constraint are more widely distributed to the west of Scotland and in an area north of Orkney and west of Shetland. An area of low constraint is also found in the North Sea east of Aberdeenshire, although technical constraints are relatively high in this area.

5.3 Wave Energy Areas in 90 - 200m Depth of Water

There is currently little developer interest in areas with water depths greater than 90m. However, areas with potential for wave energy developments in water depths of 90 - 200m ( Figure 11) and with low overall levels of constraint are very extensive within the resource area. Large areas of these deeper waters are found to the west, north and north east of Scotland, and generally show low to medium levels of constraint. Although much of this area is outside the depth range of current developer interest, there is clearly considerable potential for development beyond the immediate term.

The potential locations for wave energy developments are limited to the locations where the wave climate is sufficiently energetic. However, large areas of sea to the west, north and north east of Scotland experience a sufficiently energetic wave climate to make the wave resource suitable for exploitation. The resource areas for wave energy include the exposed waters along the western-facing coastline facing the width of the North Atlantic (particularly west of the Hebrides), waters to the north of the Scottish mainland and around Orkney and Shetland, and also areas in the central part of the northern North Sea.

Consideration of the resource areas, and the constraints on development arising from environmental, industry and socio-cultural factors discussed above, lead to the identification of four key areas of search for wave energy development options in Scottish waters ( Figure 12). The areas are limited to water depths of less than 90m, to broadly reflect the depths for which developer interest is currently being expressed. The areas are:

A. West of the Hebrides

B. North West of Cape Wrath

C. Orkney and Shetland

D. North Sutherland coast

The geographical extent of these areas A - C is large enough for there to be opportunities for fully commercial scale development of wave energy projects. Area D is relatively small and close to the boundary of the resource area. The resource areas, and areas of search, for wave energy developments occur both within and beyond Scottish Territorial Waters In detail, there is variation between low and moderate levels of constraint within these broad areas, and more detailed assessment through Regional Locational Guidance will be required to derive plan options for wave energy.

This analysis should not be taken to imply that there are no useful wave resource areas elsewhere around Scotland. The identification of resource areas has been based upon wave energy maps taken from the DECC Renewables Atlas ( DECC, 2008). The wave information in that Atlas is presented as a grid of data, with cell size of 1.8 km. Resource areas smaller than this may well not be represented, and uncertainties in the boundaries of resource areas up to the scale of a few cells, or immediately adjacent to the coast, may be poorly represented. One consequence is that the boundary of the resource area appears to skirt round the coast of, for example the Western Isles and Orkney. In such areas, where precise local data are not available to the assessment, cells at the coast should be considered to have similar levels of resource and constraint as adjacent cells away from the influence of this coastal artefact.

It is also likely that some smaller wave energy devices may be able to function economically in areas of less than 20 kw/m available energy. Such areas will not have been captured by this scoping study, but in favourable locations may offer considerable potential for small (and perhaps medium) scale developments for testing or commercial purposes.

Figure 9 Levels of constraint on wave power developments in areas of 0 - 60m depth of water, in relation to the resource area for wave energy.

Figure 10 Levels of constraint on wave power developments in areas of 60 - 90m depth of water in relation to the resource area for wave energy.

Figure 11 Levels of constraint on wave power developments in areas of 90 - 200m depth of water in relation to the resource area for wave energy.

Figure 12 Areas of search for Plan option areas for wave energy development in waters of 0 - 90m depth within the wave power resource area.