Wind Turbine Shadow Flicker Study

What the shadow flicker study is

The shadow flicker study analyses the effect of the rhythmic variation in sunlight caused by the rotation of wind turbines on sensitive receptors around a wind farm. When the blades of an operating turbine intercept sunlight, they cast a moving, intermittent shadow that can cause nuisance to people working or living in interiors with windows facing the turbine.

The shadow flicker study is mandatory in the processing of wind farms in almost all Spanish autonomous regions, and its results determine the minimum distances to sensitive receptors and, where applicable, the turbine control systems used to limit exposure time to the flicker effect.

How it is calculated

The flicker calculation combines the turbine geometry with the annual solar paths for the site:

1. Identification of sensitive receptors (dwellings, buildings with daytime activity) around the farm.
2. Modelling of the shadow cast by each turbine onto each receptor, according to the orientation, hub height and rotor diameter.
3. Calculation of the annual exposure time (hours/year) and daily exposure (minutes/day) to the flicker effect at each receptor, in the worst-case scenario and in the real scenario with sunshine data.
4. Assessment against the thresholds set by regional regulation or European criteria (usually 30 hours/year and 30 minutes/day in the real scenario).
5. Proposal of measures where thresholds are exceeded: automatic turbine shutdown systems when flicker exceeds the threshold at a specific receptor.

Applicable regulation

There is no specific national regulation on shadow flicker in Spain. The assessment criteria are set by the autonomous regions in their technical guidance for wind farms or in the conditions of the DIA. As an international reference, the criteria of the German Wind Energy Association (BWE) and the UK ETSU-R-97 guidance are used.

Why choose Ideas Medioambientales

We carry out shadow flicker studies for wind farms as part of the EIA or as a standalone document, with validated calculation tools and knowledge of the specific criteria of each autonomous region. We integrate the result with the wind noise study and the visibility analysis when they form part of the same environmental assessment file. Our in-house multidisciplinary team, with more than 25 years of experience and ISO 9001, 14001 and 45001 certification, works across the whole of Spain from our offices in Albacete and Madrid.

Tell us the location and number of turbines in the farm and we will tell you which receptors we identify initially and how quickly we can deliver the study.