Shadow flicker complaint investigation

TNEI was appointed by a large international wind farm operator to investigate complaints relating to shadow flicker at a five turbine scheme in south east Ireland.

The assessment was undertaken in accordance with the relevant shadow flicker related planning condition and an associated protocol for the investigation of complaints. TNEI undertook detailed modelling using the specialist software, Windfarm to predict periods when shadow flicker could theoretically occur at the complainant’s properties to enable a comparison to the complaints logs recorded by the resident.

Whilst the modelling was undertaken by our specialists, a flicker survey was also undertaken by TNEI’s technology partner, Visualwind, at the complainant’s property to measure the actual occurrence of shadow flicker at the site. The survey involved collection of high resolution light data and short video clips which correlated very well with predictions of shadow flicker. TNEI and Visualwind identified the turbines causing the shadow flicker and designed a mitigation strategy in a format agreed with the turbine supplier to enable a shadow flicker control system to be implemented.

The mitigation strategy involved the relevant turbines being automatically switched off at the appropriate times to avoid future shadow flicker occurrence. A follow up shadow flicker survey was undertaken to demonstrate the effectiveness of the mitigation which showed that the control system had successfully prevented all occurrences of shadow flicker at the resident’s property.