36. Wind power is now well established and accepted as a commercial source of electricity with no production of particulates or harmful gases. The UK has one of the windiest climates in Europe. Scotland, having a significant amount of this resource, is well placed to exploit it.

The Process

39. The power produced by wind turbines depends on two key factors - the strength of the wind, and the area swept by the rotor. The energy produced is strongly dependent on the annual mean wind speed at the site. The power available increases with the cube of the wind speed. A machine on a site with a mean wind speed of 6 metres per second will produce less than half as much energy as the same machine on a site with a mean wind speed of 8 metres per second. The area swept by the rotor increases with the square of the rotor diameter, so a machine with a 15-metre diameter rotor will produce only a quarter of the power of a machine with a 30-metre diameter rotor. Advances in technology now allow turbines to operate efficiently at lower wind speeds than previously.

40. Assessing whether a particular site will harness wind power satisfactorily entails using historical meteorological data (available from the Meteorological Office) and information derived from anemometers (on masts, typically 30 metres tall, on a site for about 12 months). The data help to determine whether or not a site is technically suitable and, if it is, help to identify the best positions for wind turbines within the site. Other technical considerations will include an adequate means of vehicular access (capable of taking articulated vehicles) and the availability of a connection to the electricity distribution grid.

Characteristics

41. There are essentially two types of wind turbine, vertical and horizontal axis machines. Within each type there are various technical differences, the most obvious being the number of blades. Turbines currently preferred, or likely to be so, in Scotland in the foreseeable future are of the horizontal axis, three bladed type.

42. Wind turbines are available in a range of sizes, from small battery charging units with rotor diameters of less than a metre to very large turbines with rotor diameters greater than 70 metres rated at several megawatts.

43. Current wind power technology is based largely on the considerable experience in Denmark through several generations of development. Machines rated between 500kW and 1MW are now commonplace. The technology has now advanced beyond the 1 to 1.5MW size to 2MW machines, intended originally for use offshore but now featuring in proposals onshore.

Location

Type

Tower height

Rotor diameter

Novar (Highland)

Bonus 500

35m

41m

Windy Standard (Dumfries & Galloway)

Nordtank 600

35m

37m

Whitelee (Eaglesham Moor)
Proposed

>2.0 MW (type not specified)

>70m

>80m

Burger Hill (Orkney)

NEG Micon 2.0

68m

72m

44. Turbine towers are fixed to a concrete foundation about 7 metres in diameter whose surface will normally be flush with the surrounding ground. The land area actually used by the turbines is therefore very small. On land normally used for agricultural purposes, agricultural use can continue up to the edge of the foundations.

45. Wind turbines can be deployed singly, in small groups or in larger numbers in wind farms. Technical factors, which may influence the size of a development, include the physical nature of the site, and the capacity of the local electricity distribution grid. It is likely that the wind resources of the UK will be harnessed most satisfactorily using a mixture of different scales of development. While it is likely that larger developments will continue to be proposed in rural areas, smaller schemes can be expected on both urban and rural sites.

46. Grouped turbines need to be positioned, for operational reasons, so that the separation distance between individual turbines is around 5 -10 rotor diameters. This represents a compromise between compactness, which minimises capital cost, and the need for adequate separation to lessen energy loss through wind shadowing from upstream machines. Land use planning, ground conditions and operational requirements will usually result in a compromise between maximising energy capture and minimising visual impact. The improved productivity of the current generation of wind turbines is largely the result of improved technology (including better micro-siting methodologies) and higher hub heights.

47. A wind farm requires a central monitoring system, consisting of a computer, which supervises the operation of the turbines. This can be housed in a small building on-site linked to a headquarters off-site. Most modern wind farms are un-manned, with their operational status regularly checked through the central monitoring and remote link facility. There is also likely to be a slender mast with anemometers and wind vanes to provide control information for the site.

48. A possible but rare source of danger to human or animal life from a wind turbine would be the loss of a piece of the blade or, in most exceptional circumstances, of the whole blade. Many blades are composite structures with no bolts or other separate components. Even for blades with separate control surfaces on or comprising the tips of the blade, separation is most unlikely. The build-up of ice on turbine blades is unlikely to present problems on the majority of sites likely to be developed in the near future. In those areas where icing of blades does occur, fragments of ice might be released from blades when the machine is started. However, most wind turbines are fitted with vibration sensors to detect any imbalance which might be caused by icing of the blades. This enables the operation of machines with iced blades to be inhibited.

Communications Systems

"Approximation of the Laws of the Member States Relating to Electro-Magnetic Compatibility",

(89/336/EEC)

The European Commission Directive of 3 May 1989

51. Wind turbines (in common with all electrical equipment, including those used in the home) do produce electro-magnetic radiation and this can interfere with broadcast communications and signals. Since a large number of bodies use communication systems (some commercially sensitive or of strategic or military importance), it is impossible to obtain a definitive picture of all the transmission routes across a potential site. The Radiocommunications Agency (RA), which holds a central register of all civil radio communications installations in the UK and acts as a central point of contact, will identify any radio installations in the neighbourhood of a wind farm site, but will not identify their owners. Although the RA is obliged to pass on any enquiry to all other interested parties, who should respond to an application, an applicant for planning permission would be well advised to make direct contact with any authorities or bodies which are likely to have an interest. In addition, it may be necessary to consult the local emergency services, local authority services departments, the gas and electricity companies.

"Safeguarding of Aerodromes, Technical Sites and Explosives Storage Areas".

Scottish Executive

Consultation Paper : March 2001

Military Low Flying

60. The Ministry of Defence uses several areas of the countryside for low flying training. The Hansard extract below indicates the current MoD position on this issue. Further information on Military Low Flying can be obtained from the MoD web-site www.mod.uk/issues/lowflying

“In principal the MoD has no objection to wind farms. The UK has three specially designated Tactical Training Areas (TTA) that are available for authorised military Operational Low Flying (OLF) training. The three TTAs are located in Central Wales (LFA7T), North Scotland (LFA14T) and the border region of northern England / southern Scotland (LFA20T). Within these areas military fast jet and Hercules aircraft may operate at heights between 250ft and 100ft. In addition, units make use of these specifically surveyed areas to conduct specialised night training.

Flying down to 100ft is also authorised over the Electronic Warfare Tactics Range (EWTR), LFA13. The EWTR is a RAF facility made available to other NATO countries on a repayment basis, or under other special arrangements. It is located in the north of England/southern Scotland TTA. In addition to tactical radar avoidance training, the airspace associated with use of the EWTR is made available for test and evaluation flying, specialised night training and some operational low flying training. Low flying within LFA13 is associated almost entirely with operation of the EWTR.

Conclusions of a study conducted by the RAF Signals Engineering Establishment, into the Effects of Wind Generators on Radar Performance, were that wind turbines cause interference to primary surveillance radar and harm the ability to detect and track aircraft flying over wind farms. Moreover, the presence of unlit constructions of significant size would be highly dangerous to aircraft flying down to 100ft.
In the interests of flight safety, the safety of aircrew and members of the public, it is vital that any hazard to low flying aircraft are minimised. Any extraneous distraction or possible reduction in external support capabilities, such as that provided by ground radar, can have a deleterious effect upon aircraft safety, and thus the safety of aircrew as well as those on the ground.

It is, therefore, MOD opinion that obstacles in excess of 100ft in height, unlit by night and with the ability to cause interference to radar, have the potential to create an acute safety hazard to aircraft engaged in operational low flying , tactical radar avoidance training, specialised night flying and test and evaluation flying, however, each case has to be considered on its merit.”

Dr Lewis Moonie MP Parliamentary Under Secretary of State for Defence
(Hansard 22 March 2001).

Television Reception

61. There may be a particular concern that turbines will interfere with television reception. Considerable experience has shown that when this occurs it is of a predictable nature and can generally be alleviated by the installation or modification of a local repeater station or some cable connection. The interference effects can also be reduced by local site plan changes and this possibility should be discussed with the transmitter operators.

Proximity to Roads and Railways

62. Pre-application discussions are advisable with the Scottish Executive [Road Network Management & Maintenance Division] for developments in proximity to trunk roads and the local roads authority for all other publicly maintained roads. This is particularly important for the movement of large components (abnormal load routing) during the construction period, periodic maintenance and for decommissioning. Subsequent planning applications may require consultation with the relevant roads authority as required by the GDPO. In the case of railway lines, the authorities are Railtrack (area Civil Engineering) for operational lines and Railtrack Property Board for non-operational lines.

63. Although wind turbines erected in accordance with best engineering practice should be stable structures, it may be advisable to achieve a set-back from roads and railways of at least the height of the turbine proposed, to assure safety. Driver distraction may, in some circumstances, be a consideration. The provision of appropriately sited lay-bys can be helpful.

Shadow Flicker

64. Under certain combinations of geographical position, time of day and time of year, the sun may pass behind the rotor and cast a shadow over neighbouring properties. When the blades rotate, the shadow flicks on and off; the effect is known as "shadow flicker". It occurs only within buildings where the flicker appears through a narrow window opening. The seasonal duration of this effect can be calculated from the geometry of the machine and the latitude of the potential site. Where this could be a problem, developers should provide calculations to quantify the effect. In most cases however, where separation is provided between wind turbines and nearby dwellings (as a general rule 10 rotor diameters), "shadow flicker" should not be a problem.

Noise

65. Well designed wind turbines are generally quiet in operation. The table below gives an indication of the noise generated by wind turbines compared with other everyday activities.

Source / Activity

Indicative noise level dB(A)

Threshold of pain

140

Jet aircraft at 250m

105

Pneumatic drill at 7m

95

Truck at 30mph at 100m

65

Busy general office

60

Car at 40mph at 100m

55

Wind farm at 350m

35-45

Quiet bedroom

35

Rural night-time background

20-40

Threshold of hearing

0

66. There are two quite distinct types of noise sources within a wind turbine. The mechanical noise produced by the gearbox, generator and other parts of the drive train; and the aerodynamic noise produced by the passage of the blades through the air. Since the early 1990s there has been significant reduction in the mechanical noise generated by wind turbines and it is now usually less than, or now of a similar level to, the aerodynamic noise. Aerodynamic noise from wind turbines is generally unobtrusive; it is broad band in nature and in this respect similar to, for example, the noise of wind in trees.

67. Wind generated background noise increases with wind speed, and at a faster rate than wind turbine noise increases with wind speed. The difference between the noise of the wind farm and the background noise is therefore liable to be greatest at low wind speeds. Varying the speed of the turbines in such conditions can if necessary, reduce the sound output from modern turbines.

68. The Report, "The Assessment and Rating of Noise from Wind Farms", describes a framework for the measurement of wind farm noise and gives indicative noise levels thought to offer a reasonable degree of protection to wind farm neighbours, without placing unreasonable restrictions on wind farm development or adding unduly to the costs and administrative burdens on wind farm developers or planning authorities. The report presents a series of recommendations that can be regarded as relevant guidance on good practice.

• The current practice on controlling wind farm noise by the application of noise limits at the nearest noise-sensitive properties is the most appropriate approach;

• Noise limits should be applied to external locations and should apply only to those areas frequently used for relaxation or activities for which a quiet environment is highly desirable;

• Noise limits set relative to the background noise are more appropriate in the majority of cases;

• Generally, the noise limits should be set relative to the existing background noise at the nearest noise-sensitive properties and that the limits should reflect the variation in both turbine source noise and background noise with wind speed;

• It is not necessary to use a margin above background noise levels in particularly quiet areas. This would unduly restrict developments which are recognised as having wider national and global benefits. Such low limits are, in any event, not necessary in order to offer a reasonable degree of protection to wind farm neighbours.

• Separate noise limits should apply for day-time and for night-time as during the night the protection of external amenity becomes less important and the emphasis should be on preventing sleep disturbance.

• Absolute noise limits and margins above background should relate to the cumulative effect of all wind turbines in the area contributing to the noise received at the properties in question. Any existing turbines should not be considered as part of the prevailing background noise.

• Noise from the wind farm should be limited to 5dB(A) above background for both day- and night-time, remembering that the background level of each period may be different.

• The L_A90,10min descriptor should be used for both the background noise and the wind farm noise, and that when setting limits it should be borne in mind that the L_A90,10min of the wind farm is likely to be about 1.5-2.5dB(A) less than the L_Aeq measured over the same period. The use of the L_A90,10min descriptor for wind farm noise allows reliable measurements to be made without corruption from relatively loud, transitory noise events from other sources.

• A fixed limit of 43dB(A) is recommended for night-time. This is based on a sleep disturbance criteria of 35dB(A) with an allowance of 10dB(A) for attenuation through an open window (free field to internal) and 2dB(A) subtracted to account for the use of L_A90,10min rather than L_Aeq,10min.
• Both day- and night-time lower fixed limits can be increased to 45dB(A) to increase the permissible margin above background where the occupier of the property has some financial interest in the wind farm.

• In low noise environments the day-time level of the L_A90,10min of the wind farm noise should be limited to an absolute level within the range of 35-40dB(A). The actual value chosen within this range should depend upon; the number of dwellings in the neighbourhood of the wind farm; the effect of noise limits on the number of kWh generated; and the duration of the level of exposure.

• For single turbines or wind farms with very large separation distances between the turbines and the nearest properties, a simplified noise condition may be suitable. If the noise is limited to an L_A90,10min of 35dB(A) up to wind speeds of 10m/s at 10m height, then this condition alone would offer sufficient protection of amenity, and background noise surveys would be unnecessary.

69. Power lines connecting the individual turbines to the on-site substation will be underground. To avoid visual confusion, routing and design of power lines, connecting the wind farm substation to the electricity distribution system, will require sensitive treatment (see paragraph 28).

70. In order to minimise wind speed variations, commercial wind farms need to be located in areas of relatively smooth and rounded relief. They also require ready access to the electricity transmission and distribution system unless they are intended solely for private use. The current generation of turbines is capable of operating at lower wind speeds than previously which has the effect of increasing the types of areas (and landscapes) that may attract developer interest. Public concern over the visual impact of past (and many current proposals) has been a recurring feature. Experience, following construction, suggests that much of the fear is unnecessary. It is, nevertheless, an issue that continues to need to be addressed.

71. Scotland has a variety of landscapes. Some will be able to accommodate wind farms more easily than others, on account of their landform and relief and ability to limit visibility. Some are highly valued for their quality. There are no landscapes into which a wind farm will not introduce a new and distinctive feature. Given the Scottish Ministers’ commitment to addressing the important issue of climate change and the contribution expected from renewable energy developments, particularly wind farms, it is important for society at large to accept them as a feature of many areas of Scotland for the foreseeable future.

72. This is not to suggest that areas valued for their international or national landscape and nature conservation interest will have to be sacrificed. Nor that elsewhere, attempts to lessen the impacts by integrating the development into the surrounding landscape would not be worthwhile. On the contrary, it emphasises the need for account to be taken of regional and local landscape considerations. Development that has been carefully sited and tied into the surrounding landscape will still be visible but the impact will be less than had this effort not been made and the development left less well related to its surroundings.

73. The landscape and visual impact of wind turbines is influenced by :

• land form and landscape characteristics;

• number, size and layout of turbines

• how the turbines relate to the skyline

• design and colour;

• access tracks; and

• ancillary components like power lines and substations.

74. The capacity of the landscape to accommodate wind farm development depends on two considerations :-

• the degree of impact the development will have on the existing character of the landscape; and

• the extent to which this impact can be modified and reduced by design.

The ability of the landscape to absorb development depends on careful siting, the skill of the designer, and the inherent characteristics of the landscape such as landform, ridges, hills, valleys, and vegetation.

75. A cautious approach is necessary in relation to particular landscapes which are rare or valued, such as National Scenic Areas and proposed National Parks and their wider settings. Here, it may be difficult to accommodate wind turbines without detriment to natural heritage interests. In a regional context care should also be exercised within Areas of Great Landscape Value and Regional Parks. Other landscapes are not especially valued and a significant change in some landscapes may be considered acceptable. For example, areas recovering from past degradation, such as those semi-rural areas of the central belt affected by historic mineral extraction, may be appropriate areas to accommodate wind farm development.

76. Scottish Natural Heritage has carried out a comprehensive national programme of Landscape Character Assessment. These assessments cover all of the council areas of Scotland and broadly define the variety of Scotland’s landscape types. While not directed specifically at potential wind farm developments, they identify landscape characteristics that may be sensitive to wind farm development. Within such broad areas there will be areas of varying landscape characteristics with different implications for development.

77. Three pilot projects are being undertaken by SNH, in conjunction with the planning authorities in Argyll & Bute, Highland and Ayrshire and Lanarkshire. These will assess the landscape capacity to accommodate wind farm developments and are intended to inform the preparation of development plan policies and the possible identification of areas of search.

Visual Impact

78. Turbines in wind farms are likely to be tall, frequently located in open land, and therefore likely to be highly visible. Domestic turbines will be smaller. It will normally be unrealistic to seek to conceal them. Developers should seek to ensure that through good siting and design, landscape and visual impacts are limited and appropriate to the location. The visual effect will be dependent on the distance over which a wind farm may be viewed, whether the turbines can be viewed adjacent to other features, different weather conditions, the character of the development and the landscape and nature of the visibility. The following is a general guide to the effect which distance has on the perception of the development in an open landscape.

Perception

Up to 2 kms

Likely to be a prominent feature

2-5 kms

Relatively prominent

5-15 kms

Only prominent in clear visibility - seen as part of the wider landscape

15-30 kms

Only seen in very clear visibility - a minor element in the landscape.

79. The visual impact of wind farms will be affected by their siting and layout in relation to local land form and landscape characteristics, and the qualities of the specific site, as well as by the number of turbines. Different layouts will be appropriate in different circumstances. For example, grouped turbines can normally appear acceptable as a single, isolated feature in an open, undeveloped landscape, while rows of turbines may be more appropriate in an agricultural landscape with formal field boundaries. Although wind farms may be complex, they should not appear confusing in relation to the character of the landscape. Ideally they should be separate from surrounding features to create a simple image. The design of each development must be appropriate to its site.

80. The style and colour of turbines may also be relevant. Experience suggests that solid towers appear less complex than lattice and tapering towers are generally regarded as being more elegant than cylindrical. In terms of colour, white or off-white is generally preferred, but other colours may be acceptable in appropriate circumstances. A semi-matt surface is required to reduce the reflection of light. However, colour choice can not be a substitute for good siting and design.

81. Ancillary elements also need to be fully addressed, as their impact can often be as significant as those of the turbines. Access tracks should be routed and designed to minimise both visual and habitat impacts. This can be minimised by careful route selection, which takes account of layout and appropriate surfacing material together with the impact of cuttings, embankments and drainage channels. Managing problems of erosion and providing for reinstatement of vegetation along the track is essential. Power lines, fencing, buildings and anemometer masts should be located and designed in a way which minimises clutter.

"Guidelines for Landscape and Visual Impact Assessment" published by SPON (1995) on behalf of the Landscape Institute and the Institute of Environmental Assessment (now the Institute of Environmental Management and Assessment). A second Edition is due in March 2002.

82. There are a number of techniques which may be used to inform visual assessment of a proposed development :

• a zone of visual influence map will show where a wind farm may be seen from;
• viewpoint analysis based on key viewpoints throughout the surrounding area;
• computer generated wireline diagrams will indicate how wind turbines will appear from specific viewpoints;
• photo- and video montages are images whereby an impression of a proposed development is superimposed upon an actual photograph or video of the proposed site.

All of these have strengths and limitations.

83. In comparison with other, well-established, forms of development in the countryside, wind turbines are relatively unfamiliar, prominently vertical and have the significant characteristic of movement. Individually or in groups, they will be distinctive features in the landscape. The visual impact of wind turbines must be assessed with these characteristics clearly in mind.

Birds and Habitats

"European Protected Species, Development Sites and the Planning System - Interim Guidance for Local Authorities on Licensing Arrangements".

Scottish Executive Environment Group Oct 2001

84. Experience indicates that many bird species and their habitats are unaffected by wind turbine developments and the impact of an appropriately designed and located wind farm on the local bird life should, in many cases, be minimal. To date, the most common concern has been the risk of "bird strike" i.e. birds flying through the area swept by the blades and being hit, causing injury or death. This will depend on a number of considerations such as, the particular species and numbers, the nature of the bird flight and any relevant seasonal patterns. Most birds in flight can be expected to take action to avoid obstacles but different species will vary in their reaction (see Fig.9). However, some areas in Scotland are important for a variety of bird species protected under the EU and UK legislation (SPAs, SACs and SSSIs) These could represent potential constraints to wind farm development. As indicated in NPPG 6 the importance of complying with international and national conservation obligations must be recognised and wind farms should not adversely affect the integrity of designated sites. Protected species, such as eagles and hen harriers, occupy many areas outwith designated sites and are protected across Scotland. These factors have to be considered against the positioning and size of turbines, including the size of the area swept by the blades in relation to the air space used by the birds in the vicinity of the development.

85. In addition, under the EC Habitats Directive, other species or habitats of special interest may be present. For example montane and bog habitats can be adversely affected by track construction unless attention is paid to minimising impact on the hydrology of the site. They may also be affected by any changes in land management which may be brought about as a consequence of improved access.

86. Developers should instruct their ecological advisers to enter into early discussions with SNH about the presence and importance of species and habitats in and around their proposed development site. Discussions should assess how serious the problems are and the scope for taking ameliorative action or seeking alternative sites nearby.

87. SNH, in consultation with the British Wind Energy Association (BWEA), is preparing a "Methodology for assessing the effect of wind farms on ornithological interests". In addition ETSU have published a report "Cumulative effects of wind turbines" in which Section 3 deals with "Cumulative effects on birds". Both will be of use to developers when assessing the potential impact of proposed developments on bird life. Royal Society for the Protection of Birds (RSPB), World Wildlife Fund (WWF), English Nature and BWEA have also published "Wind Farm Development and Nature Conservation". While intended for an English audience, it contains material that is equally relevant in a Scottish context.

88. The risks of disturbance to bird species during construction and operation of the wind farm is also an important consideration. For some species this is of greater potential significance than collision mortality.

Fig 9 : Examples of Bird Species Sensitivity

Golden Eagles

Golden eagles, during the breeding season, tend to centre much of their activities within 2-3km around the nest site and on ridges nearby. Hence terrain close to the nest site will tend to be most sensitive to disturbance from / collision with developments. Many areas will have only one pair but some may have several. In areas with many adjoining eagle pairs, the impact of an occasional casualty on the eagle population may be less significant than in areas with only one or few pairs. (See Case Study 6)

Geese & Swans

The risks to barnacle geese, whitefront geese and whooper swans are likely to arise mainly through flights between feeding areas and between feeding and roosting grounds. Distances involved are highly variable between species and locality. Geese fly in typical V skeins and their ability to avoid obstacles depends on the alertness of the lead bird. It is likely to be more difficult to accommodate developments in areas which contain nationally or internationally important concentrations of birds, than areas where these birds are present but for which important concentrations are not recorded.

Harriers & Owls

Where hen harriers and short-eared owls are present, only a small percentage of the terrain is likely to offer conflicts between development and the birds. Both species make use of a wide range of moorland habitats, tending to nest in areas with long heather and hunt over rough grassland and flush-dominated plains. However, there is considerable variation in habitat use by these species. Male hen harriers are probably most vulnerable to collision while displaying, and inexperienced juveniles may find it difficult to avoid turbine blades.

Divers

Black and red throated divers are potentially vulnerable where a development might impede flight between breeding and feeding areas. Black-throated divers tend to nest in large lochs and feed in these or in nearby lochs. They fly low as they take off from lochs. The identification of flight lines requires investigation when development is proposed. Red-throated divers nest in small lochs and lochans. They tend to feed in the sea, so flightlines are more likely to be predictable and occur on the seaward side of these nesting areas. Divers appear to have relatively poor manoeuvrability. Flight lines, around nesting and when approaching and leaving feeding areas, tend to be low and impacts with developments are possible within a radius of 0.5 to 1.0 km from such areas.

89. The cumulative impact of a number of neighbouring developments may also be a relevant consideration. The nature and character of the location, and the landscape in which a development is located, will in part determine the acceptability or otherwise of siting proposals in proximity to each other.

"A Guide to Assessing the Cumulative Effects of Wind Energy Development"

W/14/00538/REP

ETSU 2000

90. A number of factors have influenced the current geographic distribution of wind farm proposals in Scotland, for example :

• the distribution of the viable wind resource;
• technical and economic constraints to the viability of exploiting different wind speeds;
• electricity grid access constraints;
• protected areas;
• planning policy.

These have tended to focus developments in a relatively limited number of areas. However there have been few instances where cumulative effect has had to be addressed but with more proposals coming forward this could change.

"Beinn An Tuirc :

Assessment of Effects on the Landscape Resource and on Visual Amenity".

Special report by Turnbull Jeffrey Partnership for ScottishPower June 1998

91. The cumulative effects of wind farm development can arise as the combined consequences of:

• an existing wind energy development and a proposed extension to that development;
• proposals for more than one wind energy development within an area;
• proposal(s) for new wind energy development(s) in an area with one or more existing development(s);
• any combination of the above.

In assessing cumulative effects, it is unreasonable to expect this to extend beyond schemes in the vicinity that have been built, those which have permissions and those that are currently the subject of undetermined applications.

92. Wind turbines can be decommissioned and sites cleared and restored easily and rapidly. This should be covered in the conditions and/or legal agreement accompanying the consent and will be triggered by the expiry of the consent or in the event of the project ceasing to operate for a specified period. Planning authorities should satisfy themselves that funding for decommissioning will be available when required.

93. It is likely that the duration of the consent will be linked to the expected operational life of the turbines. However during this period, proposals may be forthcoming to extend the life of the project by re-equipping or to replace the original turbines with new ones. While there are obvious advantages in utilising established sites, such cases will have to be determined on merit and in the light of the then prevailing policy and other relevant considerations.