Wind Turbine Shadow Flicker - Pager Power Assessments
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Wind Turbine Shadow Flicker

Wind Turbine Shadow Flicker
May 27, 2018 Mike Watson


Wind Turbine Shadow Flicker can affect residents living nearby. Shadow Flicker can be experienced as flashing effect that occurs as wind turbine blades cause intermittent shadow effects as they rotate.

Pager Power can assess times and dates that wind turbine shadow flicker is predicted to occur at specific dwellings and locations in the vicinity of a wind development.

Figure 1: Wind Turbine Shadow Flicker Chart


Wind Turbine Shadow Flicker is normally assessed for residences in the vicinity of a wind turbine. Typically the maximum assessed distance between wind turbine and residence is a function of the wind turbine’s rotor diameter.

Sometimes other buildings, such as businesses and educational establishments, are also assessed. The perceived impact of shadow flicker is greater in a room with a window facing a wind turbine than for an observer outdoors. This is because the light in the room comes from the direction of the wind turbine whereas the light outdoors comes from all directions – making the shadow flicker effect less pronounced.


The greatest wind turbine shadow flicker impacts occur when the sun is not obscured by cloud and passes directly through the wind turbine blades into a room with a window facing the wind turbine. The sun’s position in the sky varies throughout the year depending on the date and time.

Assessment Parameters

The following information is required to undertake a wind turbine shadow flicker assessment:

  • The wind turbine location
  • The receptor location
  • The receptor height
  • The wind turbine dimensions

A shadow flicker assessment typically predicts:

  • The number of hours of effect per year
  • The number of days per year on which there will be some effect
  • A schedule of specific times and dates when effects are forecast

Wind Turbine Shadow Flicker mitigation

There are a number of methods that may be used to mitigate shadow flicker effects. The most common are:

  1. To programmatically shut the wind turbine down at times that severe shadow flicker effects are predicted to occur
  2. To provide physical shielding in the vicinity of the affected property – which could be in the form of vegetation planted between the wind turbine and the window of concern.

How can Pager Power help?

Pager Power can undertake the following wind turbine shadow flicker services:

  • Determining which properties should be assessed
  • Determining whether a wind development will cause shadow flicker effects at specific properties
  • Determining when shadow flicker effects will occur
  • Advising on mitigation
  • Providing full shadow flicker assessments


Wind turbine shadow flicker is caused by turbines “chopping” direct sunlight illuminating a room. Shadow flicker effects can be accurately predicted and can be mitigated if required.


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