Locating wind farms too close together could reduce output, German research shows

As offshore wind turbines become more powerful and larger, there is a danger that if they clustered too close together they will produce less power, according to a new German study from Helmholtz-Zentrum Hereon suggests.

The growth in the number of wind turbines in the German Bight and the Baltic Sea has accelerated enormously in recent years, and the implicit assumption has been that the wind was an infinite resource. Clearly the laws of physics dictate that every bit of energy created through the wind turbine is taken away from the atmosphere, but the amount was so minuscule relative to the total energy in the atmosphere that no difference could be detected.

Wind turbines with an output of around 8,000 MW currently rotate in German waters, equal to the power generated by about eight nuclear power plants. However, German waters are not infinite, and some wind farms have been built very close to one another.

A team led by Dr Naveed Akhtar from the Helmholtz-Zentrum Hereon found that wind speeds at the downstream wind farm of such pairs were significantly slowed down. The output of a neighbouring wind farm up to 40km away could be reduced by 20% to 25%.

“Conventional flow models for analysing wind farms have a very high spatial resolution, but only look at a wind field over a short period of time,” said Akhtar. “In addition, these cannot be used to determine how a wind farm changes the air flow over a large area.”