Shadow flicker

Wind farm shadow flicker assessment

We conduct wind farm shadow flicker assessment using WindPro 2.7.

Shadow flicker from wind turbines is defined as short reductions in light intensities caused by the rotating blades of the turbine casting shadows on receptors on the ground and stationary objects such as a window at a residence. Shadow flicker occurs when a particular combination of conditions coincide in specific locations at particular times of the day and year. It happens when the sun is low in the sky and shines on a building from behind a turbine rotor . This can cause the shadow of the turbine blades to be cast onto the building, which appears to flick on and off as the turbine rotates.

Taking the movement of the sun in our latitude into consideration, then it can be said that there are never shadows to the south from the turbine. Shadow flicker is wider to the east and west from the turbine and shadow flicker lasts longest in the area near the turbine in north-west, north and north-east side of the turbine.

Shadow flicker effect is expressed in terms of frequency (summarised hours per year) on receptors.

Shadow flicker can be a nuisance to people living near a wind farm. It can be bothersome to people within relatively darkened enclosed spaces where significant shadow flicker impinges upon the window that provides the majority of the light to the space. In this case, the light level appears to be fluctuating rapidly within the room. If this kind of event appears frequently, it may cause annoyance. Also, it may be difficult to work in a room if there is a shadow flicker on the window.