What is shadow flicker and does it impact me?
In simple terms, shadow flicker occurs when sunlight on a certain spot is continuously broken by the rotating blades of a turbine. With careful planning and strategic turbine placement, any potential issues from shadow flicker can be minimised.
How does shadow flicker occur?
Shadow flicker occurs when a wind turbine’s rotating blades cast a moving shadow on the ground or nearby structures.
This phenomenon is most noticeable when the sun is low in the sky, typically during early morning or late afternoon, and when the turbine is positioned between the sun and an observer.
Shadow flicker is typically only an issue at close distances, generally no more than 1 to 1.5 km and it only occurs in limited locations and for a few hours per year. [1]
We place our communities at the heart of everything we do. When Vestas develops a project our wind farms and turbines are sited at locations to reduce noise and visual impact, including shadow flicker, on nearby dwellings while protecting biodiversity and existing environmental quality. Most counties have established regulations limiting shadow flicker to a maximum of 30 minutes per day and 30 hours per year.
One such solution is the Vestas Shadow Flicker Control System. We designed this tool to maximise energy production while complying with local regulations and preventing shadow flicker at nearby dwellings . The Shadow Flicker Control system is available for our partners to use at their discretion.
How we work to minimise shadow flicker
We place our communities at the heart of everything we do. When Vestas develops a project our wind farms and turbines are sited at locations to reduce noise and visual impact, including shadow flicker, on nearby dwellings while protecting biodiversity and existing environmental quality. Most countries have established regulations limiting shadow flicker to a maximum of 30 minutes per day and 30 hours per year. Vestas complies with these regulations and goes one step further, employing operational practices and tailored solutions that can mitigate potential exposure to shadow flicker.
One such solution is the Vestas Shadow Flicker Control System. We designed this tool to maximise energy production while complying with local regulations and preventing shadow flicker at nearby dwellings . The Shadow Flicker Control system is available for our partners to use at their discretion.
Determining shadow flicker
The control system uses two light intensity sensors on either side of the turbine tower to detect direct sunlight. By comparing the light data and factoring in the sun’s position, turbine locations and surroundings, the controller identifies if any turbines are causing shadow flicker on inhabited areas.
Managing shadow flicker
The control system can pause turbines to prevent shadow flicker at nearby dwellings, resuming operation afterward, while resuming operation afterward while optimising energy generation. The system can be configured to allow for a certain amount of accumulated shadow flicker per day or per year before pausing the turbines.
How it works
Our Shadow Flicker Control System is designed to tailor turbine operation to minimize the impact of shadow flicker on surroundings.
As pictured on the left, the shadow cast by wind turbine B reaches the nearby building at 5.00 PM. If the light intensity is measured above an established threshold, turbine B is temporarily paused to avoid potential impact of shadow flicker. The remaining turbines in the wind farm continue to operate.
Is shadow flicker a health concern?
According to scientific consensus, there is no evidence to suggest that shadow flicker negatively affects health. [1] More than 20 years of research on the effects of wind turbines on human health shows that when turbines are properly constructed at setback distances approved by permitting authorities, they do not pose a health risk. [2]
1 American Clean Power Association. (2020, November). Wind Turbines and Shadow Flicker: Facts and Proven Mitigation Strategies. Clean Power. https://cleanpower.org/wp-content/uploads/gateway/2021/02/Final_Shadow-Flicker-Fact-Sheet.pdf
2 American Clean Power Association. (2022, November). Wind turbines and public health. Clean Power. https://cleanpower.org/resources/wind-turbines-and-health/