When people are talking about “too close” and wind turbines, normally they mean the neighbors have the misfortune to live too close to the turbines. Recently I came across a survey from the Cullerin Wind Project in Australia, and I was struck by how far out people’s lives were being affected by the noise/infrasound. Large majorities of all the residents at distances even in excess of 5 km were complaining.
After generating an overhead picture of the project on Google Earth it struck me that I’ve now seen 4 Australian projects that have have significant complaints lodged against them by large numbers of neighbors. All of these projects have two things in common. First, they are built on ridges above the neighbors, in order to get the best winds. Second, and perhaps more importantly, the turbines in all four of these projects are either massed or lined up less than 300 m from each other. Distances vary, of course, but all four have typical turbine separations of somewhere around 250 m. Typical industry standards are 4x rotor diameter spacing across the prevailing wind, and 10x (recent research recommends 15x) along the prevailing wind. Obviously 250 m isn’t far enough in any direction. The four projects are: Wonthaggi, Waterloo, Waubra and Cullerin.
Inter-turbine turbulence can be problematical. First, it reduces the efficiency of the downwind turbines by a considerable amount – 30% for the second in the line and more for subsequent ones. Second, it increases stress on the blades as the forces upon them are constantly changing. Third, and most importantly for this discussion, it increases the noise generated.
I have no real conclusion for this posting – I’m just pointing out something I noticed and maybe someone out there will follow it up. It would be interesting to go through more projects and see if this pattern holds. Below are my pictures for these four projects.