Shadow flicker occurs when the shadow of the rotating turbine blades is cast onto a building, or a given location, and viewed through a narrow gap such as a window.
It is possible to predict the potential for shadow flicker because it requires a combination of predictable conditions to coincide for it to take place. The occurrence of shadow flicker is dependent on the time of day, location of the sun in the sky, how clear the sky is and the orientation of nearby residential properties and their windows.
The passage of the sun during the year is known and therefore predictions can be made with regard to particular days and times shadow flicker might occur. Because it can be predicted a wind farm development can be designed to avoid shadow flicker.
Where the potential for shadow flicker is identified measures can be put in place, such as turning the turbines off at times when shadow flicker might occur.
Developers use worst case scenarios for their predictions by presuming that the sun is always shining in a clear sky.
Any potential effects will be resolved through planning conditions put in place by the local planning authority.
The Department for Energy and Climate Change (DECC) website contains further information on shadow flicker.