How 'shadow flicker' can cast a pall over wind projects

Study of people living near wind turbines provides surprising results.

Wind turbine. Michele Ursino/flickr.

(A native of England, Matthew Diebel is a veteran journalist who has worked at NBC News, Time, USA Today and News Corp., among other organizations. Having spent his childhood next to one of the world's fastest bodies of water, he is particularly interested in tidal energy.)

Excuse me, but are you bothered by shadow flicker?

Er, no. And what exactly is shadow flicker?

Well, it turns out that it’s a thing, the culprit being wind turbine blades casting moving shadows on nearby homes and yards.

And now, with scientists always wanting more stuff to study, it’s the subject of just-released research from the Lawrence Berkeley National Laboratory, a Department of Energy (DOE) Office of Science lab managed by University of California. And, like a lot of science, it’s complicated, confusing and confounding.

First, what they did: A team at the Berkeley Lab identified shadow flicker exposure at nearly 35,000 homes near 61 wind projects across the U.S. It then compared its maps with residents’ reactions to the turbine-induced flickering, using responses from 747 of those homes.

The finding: The team found that residents’ irritation didn’t fluctuate based on how often the turbines threw shadows onto a home. “We find that [shadow flicker] exposure is not significantly correlated with annoyance,” said the researchers in their report.

Instead, annoyance was “primarily a subjective response,” or dependent on factors such as whether they thought the turbines were visually intrusive, how noisy the surrounding environment was, whether there had been compensation for the wind project and whether the person had gone to college.

In particular, the study focused on a small — 17% — but “very annoyed” group of residents. Those residents were less likely to have attended college or received compensation from the wind company for siting turbines near them, and they tended to be younger compared with people who weren’t disturbed by shadow flicker. The group also tended to say they didn’t like the look of the turbines, because they “did not fit” with the landscape.

The results, said Ben Hoen, lead author of the study, were unexpected. “We had assumed that higher levels of shadow flicker would lead to higher levels of annoyance,” he told E&E News. “We were sort of surprised that it didn’t. There are other things that lead to that annoyance that should be looked at instead.”

Unexpected, but important as more and more wind turbines are erected. Shadow flicker is “a commonly raised issue for communities that are considering wind energy,” Hoen added, and something that has helped nix some wind projects.

Sounds like they should be built near rich elderly people with advanced degrees.