environmental statement - Rotherham's Online Application for ...

15. SHADOW FLICKER
INTRODUCTION
15.1 A shadow flicker assessment has been undertaken by TNEI Services
Limited for the Penny Hill Wind Farm proposal.
15.2 Under certain combinations of geographical position, times of day and
year, wind speed and wind direction, the sun may pass behind the rotor
and cast a shadow over neighbouring buildings‟ windows. When the
blades rotate, and the shadow passes a window, to a person within that
room the shadow appears to flick on and off; this effect is known as
shadow flicker. It occurs only within buildings where the flicker appears
through a window opening and only buildings within 130 degrees either
side of north relative to a turbine can be affected. Narrow windows are
affected to a lesser degree than wider windows as the length of time a
shadow falls across narrow windows is less than for wider windows.
15.3 This chapter summarises the findings of the shadow flicker assessment.
The shadow flicker report is included in full in Appendix 11.
METHODOLOGY
15.4 Information specific to shadow flicker may be found in the companion
guide to Planning Policy Statement PPS22 - Renewable Energy. The
Companion Guide states:
„Although problems caused by shadow flicker are rare, for sites where
existing development may be subject to this problem, applicants for
planning permission for wind turbine installations should provide an
analysis to quantify the effect.‟
15.5 Within the UK there is no standard for the assessment of shadow flicker
and there are no guidelines on what exposure levels would be acceptable.
The Companion Guide states that:
„Only properties within 130 degrees either side of north, relative to the
turbines can be affected at these latitudes in the UK – turbines do not cast
long shadows on their southern side…. Flicker effects have been proven to
occur only within ten rotor diameters of a turbine.‟
15.6 The shadow flicker assessment has been based on a 104m rotor diameter
Repower 3.3MW wind turbine. As such it represents a worst case
scenario with the area potentially susceptible to shadow flicker a region up
to 1040m from each turbine (10 x 104m) and 130 degrees either site of
north. The „worst case‟ scenario is assumed due to the 104m rotor
diameter being the largest span the planning permission would allow.
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Penny Hill Wind Farm
Environmental Statement