Ministerial guidelines
Wind Energy Development Guidelines
Siting, design, noise and shadow flicker for wind farms. A revised draft was published for consultation in 2019.
Department of the Environment, Heritage and Local Government · June 2006 · 119 pages
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- 45 Planning Guidelines 6.8 Height Height relates to the full extent of turbines, comprising tower, nacelle and maximum blade length in an upright position. Height involves both the actual height and/or perceived height relative to topography. It includes the profile of the wind energy development as a whole, whether even or uneven. Different possibilities are acceptable, depending on context. • Turbine height is critical in landscapes of relatively small scale, or comprising features and structures such as houses, and must be carefully considered so as to achieve visual balance and not to visually dominate. • A wind energy development comprising two distinct turbine heights may be acceptable provided the resulting composition is carefully considered, so as to achieve an aesthetic effect. This situation may result from the combination of an old and a new wind energy development or where certain turbines would be critically visible from a sensitive viewpoint. Other than the height difference, the wind energy developments in the same viewshed should relate with regard to their main design features and colour. . • Where possible, the perception from more sensitive viewpoints, of turbine blade sets cutting the horizon should be avoided. • A skewed profile where one or more turbines are perceived to run at an angle relative to the horizon is acceptable in landscapes which are not of high sensitivity or where some aesthetic effect can be demonstrated.
- 46lanning Guidelines Fig 27: Wind energy development comprising turbines of two distinct heights used to aesthetic effect - careful spacing and simplicity of layout achieve a successful solution. Alternative sequences and rhythms may also be appropriate. 6.9 Landscape Character Types as a Basis for Guidelines Landscape character types provide a useful basis for practical application of siting and design guidelines in relation to wind energy development and can be incorporated into the plan-led approach discussed in Chapter 3. Six landscape character types have been selected to represent most situations: • Mountain moorland • Hilly and flat farmland • Flat peatland Fig 24: Turbines are too high relative to the scale of the hill - this results in spatial dominance. Fig 25: Turbines are too short (squat) relative to the scale of the hill - this results in visual irritation Fig 26: Height of turbines is appropriate.
- • Transitional marginal land • Urban / industrial • Coast It is, however, common that a wind energy development is located in one landscape character type but is visible from another, for example, where the site comprises an unenclosed moorland ridge standing above a broad flat farmland. In such an instance, the entire visual unit should be taken into consideration. It will be necessary to decide whether the moorland ridge or the farmland might more strongly influence the approach. The guidance on the siting and design possibilities in each of the landscape character types is proactively indicative of how wind energy developments best fit different landscapes and is necessarily independent of the issue of sensitivity, that is, of whether wind energy developments are appropriate in a given location. Thus, one might ably demonstrate how a proposed wind energy development could fit aesthetically into the landscape while recognising its inappropriateness due, for instance, to a critical heritage designation. It should also be emphasised that actual realisation of preferred solutions as depicted in these guidelines is not always feasible due to the variations of a particular landscape type and the different viewing possibilities for each. 6.9.1 Mountain Moorland Key characteristics of this landscape are: • Peaked, ridged or rolling mountains and upland with steep sides or gently formed valleys; • Generally unenclosed; • Landcover comprising blanket bog, a mottling of heather, wild grasses and some rush in wet flushes; and • A landscape type of relative remoteness and often comprising pristine, unspoilt and remote landscapes. 47 Planning Guidelines
- Given exposure and smoothness of terrain, these landscapes are often sought for wind energy development. The exposure of mountains and the preference for wind energy developments to be located at high elevations result in high visibility. Mountain moorland may be inappropriate for wind energy development for reasons of natural heritage and the fact that some of these landscapes are of rare scenic quality and/or support some of the last wilderness areas of relatively pristine, unspoilt and remote landscapes. However, many examples of these landscapes should be open for consideration subject to appropriate design and landscape siting to minimise adverse impact and optimise aesthetic effect. Siting and design guidance for mountain moorland Location It may be acceptable to locate wind energy developments on ridges and peaks. They may also be appropriate, in certain instances, in a saddle between two peaks where they will be partially contained or “framed”. A third acceptable location is lower down on sweeping mountainsides. Spatial extent Given the typical extensive areas of continuous unenclosed ground, larger wind energy developments can generally be accommodated because they correspond in terms of scale. However the spatial extent of a wind energy development would need to be reduced where a suggestion of smaller scale is provided by nearby landscape features. 48lanning Guidelines
- 1(a) Large wind energy development with random layout, irregular spacing and high turbines - this siting and design option is appropriate given the scale of this landscape . 1(b) Wind energy development with many turbines of medium height – this can be inappropriate. The spatial extent of a wind energy development can be reduced by using taller turbines. This may be a preferable solution in some situations. 1(c) Wind energy development with relatively few and tall turbines. Spacing All spacing options are usually acceptable. Where a wind energy development is clearly visible on a crest or ridge there is considerable scope to vary the rhythm, though on simple ridges, regular spacing may be more appropriate. On sweeping and continuously even areas of mountain moorland or upland plateaux regular spacing may be most desirable. 49
- Layout All layout options are usually acceptable. However, the best solutions would either be a random layout, and clustered where located on hills and ridges (fig 1(a)), or a grid layout on sweeping and continuously even areas of moorland or plateaux (fig 1(b)). Where a wind energy development is close to a linear element, such as a river, road or long escarpment, a corresponding linear layout or staggered line might be most desirable. 1(d) A wind energy development with a grid layout with tall turbines – the rhythmic grid layout is appropriate to the open expanse of moorland, especially when it relates to the geometric blocks of conifers. Height There would generally be no height restrictions on mountain moorlands as the scale of landscape is so great. However, shorter turbines may be more appropriate where they are located on small peaks and outcrops in order to maintain an appropriate scale. Profile, whether even or uneven, is dependent on topography: the more rugged and undulating (e.g., knolls and crags) the more uneven it will be. The profile of the wind energy development should not necessarily run in parallel to that of the topography. 50
- 51 Planning Guidelines 1(e) Cumulative effect involving two wind energy developments – this situation would possibly be acceptable due to the similar siting and design approach adopted for each wind energy development Cumulative effect The open expanse of such landscapes can absorb a number of wind energy developments, depending on their proximity. The cumulative impact will also depend on the actual visual complexity of landform, whether steeply rolling, undulating or gently sweeping. The more varied and undulating an area is topographically, the greater its ability to absorb and screen wind energy developments. The aesthetic effect of wind energy developments in these landscapes is acceptable where each one is discrete, standing in relative isolation.
- 52lanning Guidelines 6.9.2 Hilly and Flat Farmland Key characteristics of this landscape are: • Intensively managed farmland, whether flat, undulating or hilly; • A patchwork of fields delineated by hedgerows varying in size; • Farmsteads and houses are scattered throughout, as well as occasional villages and towns; • Roads, and telegraph and power lines and poles are significant components; and • A working and inhabited landscape type. The essential key here is one of rational order and simplicity, as well as respect for scale and human activities. The predominance of field pattern introduces an organised patchwork landcover structure that not only prompts a similar response in the siting and design of wind energy developments, but also provides a spatial structure and rhythm. Although hilly and flat farmland type is usually not highly sensitive in terms of scenery, due regard must be given to houses, farmsteads and centres of population. Siting and design guidance for hilly and flat farmland Location Location on ridges and plateaux is preferred, not only to maximise exposure, but also to ensure a reasonable distance from dwellings. Sufficient distance should be maintained from farmsteads, houses and centres of population in order to ensure that wind energy developments do not visually dominate them. Elevated locations are also more likely to achieve optimum aesthetic effect. Turbines perceived as being in close proximity to, or overlapping other landscape elements, such as buildings, roads and power or telegraph poles and lines may result in visual clutter and confusion. While in practice this can be tolerated, in highly sensitive landscapes every attempt should be made to avoid it. Spatial extent This can be expected to be quite limited in response to the scale of fields and such topographic features as hills and knolls. Sufficient distance from buildings, most likely to be critical at lower elevations, must be established in order to avoid dominance by the wind energy development.
- 53 2(a) Wind energy development of large spatial extent – this example is inappropriate given the scale of this landscape. 2(b) Wind energy development of small spatial extent – this example is appropriate given the scale of this landscape. 2(c) Wind energy development with random layout - this response is inappropriate given the patchwork field pattern of this landscape. 2(d) Wind energy development with grid layout - this response involving any form of linear layout and regular spacing is appropriate given the patchwork field pattern of this landscape.
- 54 2(e) Small wind energy development with regular linear layout - the rhythmic order is more appropriate to this landscape due to the order created by the field pattern. Spacing The optimum spacing pattern is likely to be regular, responding to the underlying pattern field pattern. The fields comprising the site might provide the structure for spacing of turbines. However, this may not always be the case and a balance will have to be struck between adequate spacing to achieve operability and a correspondence to field pattern. Layout The optimum layout is linear, and staggered linear on ridges (which are elongated) and hilltops (which are peaked), but a clustered layout would also be appropriate on a hilltop. Where a wind energy development is functionally possible on a flat landscape a grid layout would be aesthetically acceptable. Height Turbines should relate in terms of scale to landscape elements and will therefore tend not to be tall. However, an exception to this would be where they are on a high ridge or hilltop of relatively large scale. The more undulating the topography the greater the acceptability of an uneven profile, provided it does not result in significant visual confusion and conflict. 2(f) Small wind energy development located close to modern farm buildings - a thematic association is established involving modern materials and construction. Careful consideration needs to be given to tall turbines in this landscape given the potential proximity of houses.
Source Department of the Environment, Heritage and Local Government: Wind Energy Development Guidelines (June 2006) · Licence the publisher's termsText read from the publisher’s PDF; tables, maps and drawings do not survive as text, and page numbers are the PDF’s (its first page is 1). Check the original before relying on a passage.