Shadow Flicker

Shadow Flicker happens when rotating turbine blades pass between an observer and the sun. To experience Shadow Flicker at a particular location, a number of factors must coincide: sun location, wind direction and clear skies, among other things.

Shadow Flicker predictions involve estimating the probability of these factors coinciding at potential receivers. In general, Shadow Flicker becomes insignificant beyond about 10 rotor diameters, or 824m at Curraheen (DoEHLG Guidelines, 2006).

Shadow Flicker predictions have been carried out for Curraheen Windfarm. The key results are shown below, as contours of predicted Shadow Flicker per day and per year. The results clearly show that the expected Shadow Flicker at surrounding dwellings will be below the DoEHLG Guideline figures of 30 hours per year. The expected shadow flicker will also be below the Guideline figures of 30 minutes per day after mitigation.

For details of the layout plan view the contour map

Rotors have three blades and rotate at about 22 revolutions per minute. This implies a frequency of Shadow Flicker of about 1.1 per second or 1.1Hz. This is well below the levels at which observers experience flicker as a particular nuisance (5-10Hz).