A top American fluid-dynamics boffin says that new, larger wind turbines now going into service are going to have to be placed much further apart - which will have serious implications for the amount of energy produced by wind farms of the future.
The latest wind farms now going into service use huge turbines with rotor diameters in the 100m range, expected to offer large outputs. But according to engineering professor and fluid dynamics expert Charles Meneveau of Johns Hopkins University, there's a problem.
“The early experience is that they are producing less power than expected,” says Meneveau. “Some of these projects are underperforming.”
The prof, who has investigated air flow in wind farms for years, looked into the matter of the underperforming monster turbines along with Johan Meyers of the Katholieke Universiteit Leuven in Belgium.
“I believe our results are quite robust,” says Meneveau. “They indicate that large wind farm operators are going to have to space their turbines farther apart.”
Big turbines are at the moment generally installed about seven rotor diameters apart, but Meneveau and Meyers say that the optimum spacing is actually 15 diameters, slightly more than twice as far apart.
If this plan were followed, a wind farm covering a given area would only be able to install a quarter of the number of turbines it could have under today's planning assumptions. Though the amount of energy generated per turbine would be the best possible, it seems unlikely that such efficiency gains could possibly compensate for the cut in numbers.
On the other hand, if windfarms continue to be constructed with turbines crowded more closely together, they will continue to produce less electricity than their builders had expected.
Overall the professor's research would appear to mean that projected output figures for large new windfarms - for instance the UK's planned, enormous offshore Round 3 facilities, expected to be built in the North Sea from 2015 - will have to be revised downwards one way or another.
Professor Meneveau presented the research, based on wind tunnel studies carried out at Johns Hopkins, at a physics conference recently. The outlines of it are reported in The Johns Hopkins University Gazette. ®