Camilty Wind Farm - Partnerships for Renewables

Camilty Wind Farm
14 Shadow Flicker
14.1 Introduction and Overview
14.1.1 Shadow flicker is the effect caused when rotating blades of a wind turbine cause a shadow to
be cast on neighbouring properties and receptors. As the blades rotate, shadows on the
ground or nearby properties move, resulting in a flicker effect. The effect occurs under
certain combinations of factors, including geographical position and time of day and can
occur inside buildings, where the flicker appears through a window opening.
14.1.2 The likelihood and duration of effects depends on:
• The position of the observer in relation to the turbine(s) – In the UK, only properties
within 130 degrees either side of north, relative to the turbines, are likely to be
affected as turbines do not cast long shadows on their southern side;
• Distance from turbine(s) – The further the observer is from the turbine, the less
pronounced the effect would be. Due to factors such as shadow duration and focus,
shadow flicker effects have been proven to occur only at distances up to ten times the
turbine rotor diameter;
• Wind direction – The turbine will not always be directed towards the receptor i.e.
‘square-on’ which is the worst case scenario, therefore the effect will be minimised;
• Turbine height and rotor diameter – The turbine height and rotor diameter can effect
the distances at which shadow flicker can occur;
• Time of year and day – The intensity of the sunlight can be diminished depending on
the time of year, for example the sun does not shine brightly enough at certain periods
of the year (e.g. winter months) to create the necessary contrast; and
• Weather conditions – Cloud cover diminishes the intensity of sunlight.
14.1.3 An assessment has been carried out to identify whether shadow flicker is likely to occur at
properties neighbouring the proposed wind farm, and if so, to predict times of day/year and
duration of these potential effects.
14.1.4 It should be noted that, due to the design of the proposed wind farm layout in relation to
potentially sensitive receptors, there is not considered to be the potential for significant
shadow flicker effects to arise. However, in recognition of the interest in this potential effect,
this chapter has been retained within the ES to provide information on the way in which
potential shadow flicker effects were assessed and addressed through the design evolution
process (see Chapter 3: Design Evolution).
14.2 Methodology
14.2.1 A study area was initially defined based on a distance of ten times the maximum proposed
turbine rotor diameter and mapped using Geographical Information Systems (GIS) software
(based upon Scottish Government advice – see below). The study area is then further
refined to only include areas within 130 degrees either side of north of each turbine location
March 2013 14-1 ES Chapter 14
Shadow Flicker
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