Turbine scale
3.18 Size comparisons between wind turbines and other tall structures may help people to be able to visualise how tall a proposed development would appear in the landscape. Table 1 shows the heights of some tall elements in the Scottish
landscape that may provide useful scale comparisons. It is important to appreciate, when making comparisons of this sort, that wind turbines are typically not viewed in the same way as monuments or landmarks, which generally have much greater ‘solidity’. In addition, although the visibility extent of turbines will obviously increase with their greater height, the relationship between visual impact and turbine size is not directly proportional. Principally, this is because a windfarm is viewed within a surrounding context, which varies; and also because the actual size of a wind turbine is usually difficult to perceive.
Landscape elements which may be used as scale comparisons
Landscape Element Typical Height (in metres)
Metal Pylons 25 to 50
Telecommunications Masts 15 to 20
Television Transmission Masts 300
MoD Masts 70 to 80
Cockenzie Power Station Chimney 149
Inverkip Power Station Chimney 212
Forth Road Bridge Towers 150
Domestic Buildings (1.5–2 storey) 6–10
Mature Deciduous Trees (depending on species) 10–20
Ancillary infrastructure
3.19 Ancillary elements for a windfarm development should also be designed to relate to the key characteristics of a landscape. It is essential that these elements do not confuse the simplicity of the windfarm design, or act as a scale indicator for the turbines themselves. Undergrounding power lines within the windfarm, using transformers contained within tower bases (where possible), and careful siting of substations, connecting transmission lines, access tracks, control buildings and anemometer masts will all help to enhance a windfarm design. Simplicity of appearance and use of local, high quality materials will further enhance this.
3.20 There may also be practical constraints in delivering large turbine components to site, because of, for example, the limitations of rural bridges, road junctions or corners. Additional landscape and visual impacts, associated with widening of
roads, access tracks and corners in order to enable transport of long turbine blades, should be taken into account.
3.21 Detailed advice on the siting and design of tracks can be found in the SNH publication ‘Constructed tracks in the Scottish Uplands’ (SNH Natural Heritage Management Series, 2006).
Turbine layout / array
3.22 Turbines can be arranged in many different layouts within a windfarm. The layout of a windfarm should relate to the specific characteristics of the landscape. This means that the most suitable layout for every development will be different. The development process for a windfarm typically begins with a layout that responds mainly to wind speed and wind turbine specification, sited within defined land ownership / tenure boundaries. For a small windfarm, this might comprise a single row of wind turbines along a ridge; while, for a larger development, a grid of wind turbines is often taken as the starting point, with the turbines spaced at minimum separation distances to avoid turbulence (often equating to 4–5 rotor diameters).
3.23 From this starting point, turbines will typically be moved or removed due to physical constraints, such as watercourses, areas of deep peat and steep slopes, and in response to sensitive habitat or wildlife species. During this process of modification, landscape and visual issues will also inform the layout. Although landscape and visual concerns such as the need to avoid visibility from a particularly sensitive viewpoint - may present an absolute constraint, many landscape and visual sensitivities can be addressed through good design in wind farm layout. This commonly involves a number of changes to create the most appropriate wind farm to fit the design objectives of the project.
3.24 There are a number of common types of layout, chiefly divided into regular or irregular formats. Generally, the fewer the number of wind turbines and the simplest of layout upon the most even of land form, the easier it is to create a positive feature - visually balanced, simple and consistent in image as it is viewed from various directions. This is most easy to achieve with a simple line upon level ground. As soon as there is deviation from this, the visual image becomes more complicated.
3.25 A regular shape, such as a double line, a triangle, or a grid can appear appropriate within a wide open and level space where there is a regular landscape pattern, such as within agricultural fields. However, as soon as you move through the landscape and see it from different directions and elevations, views of the grid change and reveal a variable effect, seeming ordered along some rows, but in others overlapping. In addition, the rationale of the position of turbines is confused if they appear at variable elevation.
3.26 Irregular layouts can be more appropriate in landscapes of variable elevation and pattern, as is most common in Scotland. However, irregular forms pose an even greater challenge in terms of creating a simple image as the turbines will interact in varying ways with each other as well as with the underlying landscape. This can result in effects that do not correspond to good design principles, such as varying visual density of wind turbines, overlapping turbine rotors (often termed ‘stacking up’), partial screening behind a skyline and turbine outliers separate from the main group.