Wind Turbine Shadow Flicker Assessments

Wind Farm Shadow Flicker Assessments

Tall structures, such as wind turbines, cast shadows which vary in length according to the sun’s altitude and position according to the suns bearing. Rotating turbine blades cast moving shadows which could, under certain conditions, cause flickering. Shadow flicker is generally not a problem in the open as light outdoors is reflected from all directions. The possibility of disturbance from shadow flicker is greater for occupants of buildings when the moving shadow is cast over an open door or narrow window, since the light source is more directional.

Wind Farm Shadow Flicker AssessmentsShadow flicker occurs when a certain 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 the blade of a turbine. This can cause the shadow of the turbine blades to be cast onto the building, which appears to flick on and off as the blade rotates. When this flicking shadow is viewed through a narrow opening it is known as shadow flicker.

Any properties which may potentially be affected can be identified and the risk of shadow flicker calculated. We are able to advise our clients on any potential impact, and also suggest alternative design layouts to minimise the potential for shadow flicker at residential properties.

If our desktop study reveals that shadow flicker may be an issue on a particular development, we can also visit the site to survey the at-risk properties in order to identify any important factors, such as the size and position of the windows on the property, what the room is used for, whether it is likely to be occupied at the time when shadow flicker is predicted to occur and whether there is any screening from nearby vegetation.

We have been assessing the potential impacts of shadow flicker for a number of years, and over that time we have evolved a detailed methodology to accurately predict the occurrence of shadow flicker. We are able to use a combination of software modelling and site specific data (such as the geometry of the turbine blade and the latitude of the site) to calculate the extent of this effect. Once this assessment has been undertaken, if required, we can provide advice on mitigation techniques such as calculating shutdown times for specific turbines.

Our experience and expertise in this specialist area of wind farm development has been recognised by the Centre for Sustainable Energy (CSE) who have appointed Philip to their Expert Support Network, as an expert in the field of Shadow Flicker. The CSE is an independent body which is managed by the Department of Business Enterprise and Regulatory Reform and the Department of Energy and Climate Change.

More recently, we have been contracted to undertake shadowing assessments on bridleways, predicting periods in which horses may experience shadowing whilst travelling along bridleways. Whatever your need, we are able to tailor our Shadow Flicker and Shadowing assessments to your specific needs and requirements.