A Study of Landscape Sensitivities and Constraints to Wind

Looking to the Future3.28. It is speculative to make statements about future types of wind turbines, since technology is continuing to evolve and respond todifferent pressures and needs. Some ideas are set out below on current developments in the industry and how the technologymight be expected to change in the future.3.29. Currently the largest onshore turbines are 31MW machines, with planning permission recently being given for seven 3MW turbinesnear Sedgefield in County Durham. Machines of this power rating in the UK are up to about 125m total height. It is likely thatmachines with a greater power rating will be developed in the future (4MW and 5MW machines already exist as part of offshoreschemes). However, as technology becomes more efficient, a greater power rating does not necessarily imply that turbines will beof a greater height.3.30. At the other end of the scale micro-generation wind technologies are also set to become more common, with the Energy Act 2004committing the government to produce a Micro-generation Strategy by early 2006. The British Wind Energy Association (BWEA)defines small-scale wind energy systems as anything from less than 100 W (i.e. for charging batteries) to up to 50KW for individualhouses/communities or businesses. These can be standalone turbines or building-integrated. Although, termed small scale, suchtechnologies can include towers of up to 40 m to take advantage of greater wind speeds and blade diameters of up to 15 m.Currently most turbines developments of this size are constructed as single structures, although in the future such technologies maybe promoted as mini ‘wind-farms’ with a greater number of machines for example on a field-scale.DEFINING WIND TURBINE TYPOLOGIES3.31. From the above, it is clear that there is very little or no consistent guidance or definition of what constitutes small-scale wind energydevelopment; definitions are subjective and can vary considerably according to their context. The following section defines aseries of turbine typologies for consideration by this study in order to assess sensitivities and constraints to turbine development withinthe North Wessex Downs AONB. The definition of typologies is not intended to suggest that these are the types of development thatare considered appropriate within the North Wessex Downs, nor are they an attempt to provide a definition of what constitutessmall scale wind turbine development.Defining Upper and Lower Thresholds for Turbine Typologies3.32. For the purposes of this study we have considered wind turbine developments of up to 12MW in size (i.e. a maximum of 4MWturbines). This is a threshold imposed simply to determine an upper limit of turbine typologies for consideration by the study. It isrecognised that a development of this size is not what might conventionally be termed small scale in terms of built structures.Neither, does the use of this upper threshold imply that this might be considered an acceptable scale of development within theNorth Wessex Downs. Nevertheless, it is clear that developments of this scale (and greater) may come forward in protectedlandscapes in the future and therefore it is important to consider their likely impacts if this study is not to become quickly dated.North Wessex Downs AONB: Landscape Sensitivities 22The Policy Framework, Current Wind Turbine Schemesand and Constraints to Wind Turbine Development Definition of Turbine Typologies