Beautiful Photo Shows Wake Effects of Wind Turbines

Photo: Aeolus
Study Explores the Effect of Turbine Wake on Energy Production
The picture above is truly an amazing photo, in my opinion. I found it on David JC MacKay's blog (he's a physicist and wrote the excellent book Sustainable Energy Without the Hot Air which I highly recommend), along with a study about the impact that wind turbine wakes have on energy production (specifically, at the Horns Rev offshore wind farm). Hopefully knowing more about this effect can help us design more efficient wind farms that produce more clean electricity on average.

wind turbine wake graph

Image: Wake effects at Horns Rev and their influence on energy pro-

This paper presents analysis of the power output in a row of operating turbines and the dependency on wind direction relative to the row direction. The aim is to describe the magnitude of the wake effects and give an indication of the importance of wind direction. For the majority of the selected cases the turbines were operating at wind speeds with high rotor thrust. Comparison of the results for different spacing at Horns Rev (along rows and columns and for diagonal spacing) will provide insight to the mechanism of wake development and expansion.

Turbines that are after row 1 produce about 20-30% less power, but the main conclusion of the paper is that "The analyses also showed that the direction and where it is measured is very important for the results. It is difficult to use one wind direction for the entire wind farm especially for the turbines far from the mast. This implies that there is no such thing as steady state for a physical system of this size and it must be expected that the wind will always vary from one point in the wind farm to another causing the data points to be scattered. One has to accept that working with wind farm data is a statistical process that implies a significant spread in the data basis."

Could these statistical analyses be used to model future offshore wind farm and find out turbine positions that are more power-efficient? Is the trick simply increasing the space between turbines, or is there a certain turbine formation that works better (maybe not from all angles, but from the dominant local wind direction)? Sounds like this would be a useful follow up to this study.

Via DonEnergy (pdf), David JC MacKay
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