Wind Turbines

Over the past 20 years the size and electrical output of wind turbines has increased dramatically. At the time of construction of our first project Bessy Bell the largest turbines available on the market were 500kW machines with a rotor diameter and hub height of around 39metres (i.e. a tip height of around 60metres). Today turbines of 3000kW with 90 to 100metre rotor diameter (or larger offshore) are common (i.e. tip height of 125metres or more). However, these large scale turbines are not necessarily appropriate for all locations and many smaller sites are better suited to smaller scale machines.

Each prospective project site will have its own unique characteristics and wind regime and it is at the preliminary site assessment phase when a suitable turbine type is usually considered.
Not only does the turbine need to suit the wind resource (wind speed, turbulence etc), but it must also fit in with the scale of the surrounding landscape and from a practical perspective it must be possible to deliver the individual turbine components to the site over the existing public road network.

Maximum tip heights for small scale projects will be dependent on site wind speed and landscape criteria but likely to fall within the range of around 50 – 75metres or less. This the reduces potential for wider visual impacts and is likely to make planning permission somewhat easier.

Rotor diameters will vary with the turbine power capacity but is likely to be in the range 30-50metres i.e. blade length 15-25metres. From a road transport perspective it is usually the blade transport requirement which dictates the level of realignment necessary on the public road system. A 3MW machine is likely to have a single blade of 45-50metres in length and even with a rear wheel steering trailer turning radius’s are substantial.