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Scottish Marine and Freshwater Science Report Volume 2 Number 13

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Congruence of the Scoping Study with the Plan of Offshore Wind Energy in Scottish Territorial Waters

The Plan of Offshore Wind Energy in Scottish Territorial Waters incorporated six short term options for offshore wind development, and also a larger number of areas of search with potential for development as medium term options. The short term options have been included in TCE's Scottish Territorial Waters leasing round. Most of these are currently progressing through the licensing system, and five of these sites have recently been awarded agreements for lease. Areas within the medium term option search areas have not yet been offered for lease. The distribution of the STW sites and the medium term areas of search are shown in Annex 1, Figure A1.

In view of the conclusions of the sensitivity analysis of the modelling undertaken for the Plan of Offshore Wind Energy in Scottish Territorial Waters, and the improvements to the modelling undertaken in the current Scoping Study, comparisons have been made between the distributions of the level of constraint, as indicated by the Combined Equal Weighting Model, and the locations of the short and medium term options ( Annex 1, Figures A2).

5.1 East Coast

The short term options on the east coast of Scotland (and the Round 3 lease areas) are concentrated off the Forth and Tay estuaries, and in the north western part of the Moray Firth.

Those off the Forth/Tay are located within medium term site E1, and generally in areas of moderate to low levels of constraint. Higher level of constraint are found in the extreme north and south of E1. The current study is therefore broadly supportive of short and medium term options in the area, and also suggests that additional areas of relatively low constraint may be present immediately inshore of NE3, and also NNE of NE3 off the Aberdeenshire coast.

The short term options in the Moray Firth have similar levels of constraint to those off the Forth and Tay. Two areas of medium term search (NE1 and NE2) have been identified in the Plan. The Scoping Study suggests moderate to high levels of constraint in NE2, and in the southern part of NE1. However, areas of lower constraint exist between the north of NE1 and the Sutherland/Caithness coast.

In the light of this discussion, the boundaries of the search areas on the east coast of Scotland have been revised, and new strategic search areas are shown in Figure 9.

E1 Off the Firths of Forth and Tay
NE1 In the inner Moray Firth
NE2 In the south eastern part of the Moray Firth
NE3 Off the east coast of Aberdeenshire

Figure 9 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters on the east coast of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

Figure 9 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters on the east coast of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

5.2 Northern Isles

The Draft Plan identified a potential large area of search (N2 and N3) north and north west of Orkney. This is supported by the low to moderate level of constraint in this area, and also in other areas with STW around the northern part of Orkney.

The Plan identified several areas of search in the waters around Shetland (N4, N5, N6, N7. N8). The Scoping Study broadly supports this suggestion. While high to moderate levels of constraint have been identified in near shore waters, the level of constraint is much less (low to moderate) in the outer part of STW (approximately 6 - 12 miles offshore) except in the far north (medium term option N8) where moderate to high constraint is identified.

The proposed strategic search areas in the Northern Isles are shown in Figure 10.

N2-3 North of Orkney
N4 - 6 West of Shetland
N7 East of Shetland
N8 North of Shetland

Figure 10 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters round the Northern Isles of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

Figure 10 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters round the Northern Isles of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in

5.3 North and North West of Scotland

The Plan identified medium term options around several small island groups off the north and north west of Scotland (Flannan Islands, North Rona, Sule Skerry etc). The level of constraint in these remote locations is generally low. However, the boundaries of these areas are strongly influenced by the boundaries of the disconnected areas of STW centred on the islands. The medium term options NW8, NW2 and N1 are better viewed as elements of the very extensive area of waters off the west and north west of Scotland, outside the 12 mile limit drawn around the mainland baseline, where environmental, industry and heritage constraints on development are low. Development in these areas currently presents significant technical difficulties. Obviously, there is no grid connection to these islands, and the degree of exposure and depth of water are currently challenging. However, there is very great potential for development of both wind and wave energy in these areas.

The Plan identified three further medium term search areas in and north of the Minch (NW5, NW6 and NW7). The current Scoping Study indicates that the levels of constraint in the Minches (NW5 and NW6) are high to moderate, and that development might therefore be more difficult than in some areas with lower levels of constraint. The large area NW7 at the north of the Minch contains some areas of low to moderate constraint, but also areas of higher constraint north of Lewis and adjacent to the mainland coast. It also includes waters identified in the Saltire Prize Scoping Report as appropriate for wave power development. Regional Locational Guidance will be particularly valuable in this area in refining the boundaries of the areas of search and clarifying the relative suitability of the area for wave and wind power projects.

The proposed strategic search areas to the north and north west of Scotland are shown in Figure 11.

NW7 North Minch

Figure 11 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters in the north west of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

Figure 11 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters in the north west of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

5.4 West of Scotland

The boundary of Scottish Territorial Waters to the west of Scotland between Barra and Kintyre is rather further from the mainland coast than in some other parts of the country, and therefore encompass a large sea area. The Scoping Study identifies a low to moderate levels of constraint in the outer parts of STW between Barra and Islay. This is reflected in the medium term options W1, W2 and W3, and in the STW sites off Tiree and Islay. More detailed analysis of the area through Regional Locational Guidance may be used to develop a regional approach in this area.

The small medium term option area NW4 is located in the north western part of an area of moderate to low constraint west and north west of Coll and Tiree. This area is contiguous with the STW area of low constraint SW of Tiree and may offer opportunities for integrated offshore wind development. Similarly, it may be possible to consider waters of moderate to low constraint west of Colonsay together with the adjacent areas of lower constraint further offshore.

An area of low constraint is identified immediately south of Islay. This area has not been included in either the short or medium options in the current Plan, and may present an opportunity for development, and for integration with other potential development sites west of Scotland.

There is an area of low to moderate constraint in the outer part of the Clyde Sea area. To a degree, this was recognised through the identification of the medium term option area W4. However, the current scoping study suggests that the boundaries of this area could be reviewed to incorporate areas of low and low to moderate constraint south and southwest of W4. There may also be an area of low constraint close inshore on the eastern side of the Clyde Sea north of Ballantrae.

The proposed strategic areas in the west of Scotland are shown in Figure 12.

NW4 South Minch
W1-3 Sea of the Hebrides
W4 South of Islay
W5 South of Islay
W6 West of Ayrshire

Figure 12 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters in the west of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

Figure 12 Proposed strategic search areas for offshore wind farms in Scottish Territorial Waters in the west of Scotland. The proposed areas are outlined in red, the medium term sites from the 2010 Plan in black, and the 12 mile limit in blue.

5.5 The Solway Area

The Solway area generally shows moderate to high levels of constraint. However, within the medium term search area SW3, SW4 and SW5 there is a strip of water of low to moderate constraint along the boundary between Scottish and Isle of Man waters. This area may therefore present opportunities for development in areas that are less sensitive than areas closer to the Galloway coast. Waters in the northern part of the search region (SW5) have higher levels of constraint.

SW3-6 Solway region

5.6 Waters Between 12 and 200 miles Beyond Baseline

The Technical Model ( Figure 1) emphasises the increasing technical difficulty of developing wind energy projects further offshore. The main difficulties are associated with distance from opportunities for terrestrial grid connections, difficulties of construction in deeper water, and the generally more adverse wave climate in these areas. Gaps in data have curtailed the technical Model west of the Hebrides, but it may be anticipated that high levels of technical difficulty will be found in more westerly areas, as in the far north of Scottish waters. In general, the technically least constrained areas off the east of Scotland lie between about

5 and 20 miles offshore. The current progress with the STW and Round 3 sites off the east coast suggest that additional large areas of sea can be considered as technically feasible areas of search for development sites without significant new technical developments. To the west of Scotland, the least technically constrained areas are within STW, and include areas around NW7 and W1 - W3, where other constraints are also not high.

The combined environment, heritage and industry constraint maps indicate that there are large areas or relatively low constraint both east and west of Scotland, and that therefore there may be very considerable opportunity for development in deeper water further offshore. The technical constraints on projects in these areas are likely to decrease as other developments occur. For example, the construction of offshore transmission grid networks to the east and west of Scotland may remove the necessity to bring power to the shore from the point of generation to obtain grid connection.

At the present time, the offshore wind industry is planning to develop projects in water up to about 60m deep. This is considerably deeper than was the case in early projects in Rounds 1 and 2, and reflects continuing engineering development. While seabed-mounted foundation become more difficult in deeper water, the current engineering and developer interest in floating wind turbine structures holds the prospect of removal of the constraint arising from depth of water, and may lead to the recognition of very large areas of remote Scottish offshore waters as having potential for offshore wind energy projects.

The depth of water is clearly an important aspect of the feasibility of development of offshore wind farms at the current time. The initial Round 1 and Round 2 sites were generally located in rather shallow water, while the deeper water found in Round 3 and STW sites reflects the progressive improvements in the technical ability to construct projects in deeper water. However, depth of water remains a very important consideration in project design and development opportunity.

In order to further explore the opportunities for development outside Scottish Territorial Waters, a series of maps have been prepared ( Figures 13 - 16) which illustrate the levels of constraint on development in waters of 0 - 60m depth, 60 - 80m, 80 - 120m, and 120 - 300 m depth. 60m corresponds approximately to the maximum depth of water encountered in areas (Round 3 and STW) where projects are currently being developed. 60 - 80m approximates to the possible limits to the applicability of current designs of rigid foundations. Some developers are beginning to express interest in water depths of 80 - 120m, primarily as potential areas for the deployment of floating (moored) wind turbines, while depths of 120 - 300 m are less likely to be considered as potential development areas in the near future. There have been no clear expressions of interest in development in water of greater than 300m depth.

5.6 1 Potential development areas in water 0 - 60 m depth outside Scottish Territorial waters ( STW)

Figure 13 shows the output from the Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 0 - 60 metres depth.

The main areas of low to moderate levels of combined constraint, with water depth less than 60m, are in the east of Scotland:

  • North east of the Round 3 site off the Forth and Tay
  • East and south of the Round 3 site in the Moray Firth

5.6.2 Potential development areas in water 60 - 80 m depth outside Scottish Territorial waters ( STW)

Figure 14 shows the output from the Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 60 - 80 metres depth.

The main areas of low to moderate levels of combined constraint, with water depth of 60 - 80m, outside STW are:

  • An extensive area east of Scotland between Peterhead and the Tay estuary
  • In the outer part of the Moray Firth from Fraserburgh to Orkney
  • An area north of Orkney
  • Areas off the north coast of the Scottish mainland
  • Smaller scattered areas west of the Outer Hebrides and south west of Tiree

5.6.3 Potential development areas in water 80 - 120 m depth outside Scottish Territorial waters ( STW)

Figure 15 shows the output from the Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 80 - 120 metres depth. At this time, the emphasis for this depth of water will be to identify potential sites for demonstration projects to establish the technical viability of development in depths that exceed those currently being used in Round 3 or STW sites.

There are very extensive areas of water of 80 - 120 m depth all round Scotland, out to the median line in the North Sea, towards the shelf edge in the north west, and around the southwest, south and east of Shetland. The area within 80 -120m depth zone exceeds that of all waters shallower than 80m. The generally lower levels of constraint in the deeper, offshore waters emphasises the potential opportunities that could arise from the development of engineering solutions appropriate to offshore wind farms in these remote areas.

The requirements for demonstration sites differ from those for fully commercial sites, with greater emphasis on the ease of access, and reduced exposure that can be found in areas closer to the shore. Figure 15 suggests that test sites in 80 - 120 m depth of water may be found in areas of low to moderate levels of combined constraint, such as:

  • Off the coast of east Scotland from Fraserburgh south to the northern boundary of the Round 3 site off the Tay
  • In the strategic search areas identified round Shetland
  • In an area between Orkney and the Farr Point wave power area
  • In the STW strategic area at the northern end of the Minch (NW7)
  • In the STW strategic area at the mouth of the Clyde Sea area (W4), and in scattered areas north and south of this between Islay and the Mull of Galloway

5.6.4 Potential development areas in water 120 - 300m depth outside Scottish Territorial waters ( STW)

Figure 16 shows the output from the Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 120 - 300 metres depth.

There is currently very limited commercial interest in water of greater than 120m depth. There are extensive areas of Scottish waters of 120 - 300m depth in the extreme north around Shetland, and to the north west of Scotland along the edge of the continental shelf possibly with long term development potential. There is probably greater development potential in the medium term in the Fladen area east of Scotland from Orkney to Peterhead.

The scope for inshore test sites is limited, but opportunities may exist north west of Orkney, south of Barra, and in scattered locations west of the Mull of Galloway.

Figure 13 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 0 - 60 metres depth.

Figure 13 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the rel

Figure 14 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 60 - 80 metres depth.

Figure 14 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the rel

Figure 15 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 80 - 120 metres depth.

Figure 15 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the rel

Figure 16 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the relative levels of constraint in waters of 120 - 300 metres depth.

Figure 16 The Combined Restriction model, giving equal emphasis to the environmental, industry and heritage themes, showing proposed strategic areas in STW, existing STW and Round 3 offshore wind sites, the 12 mile limit (boundary to STW) and the rel