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Braked wind power

Wind power is an important component in the electricity mix for renewable energies. Wind turbines are therefore being expanded in many regions. But what happens when more and more turbines slow down the wind? Do they then mutually deprive each other of the energy source? Researchers have now quantified this effect.

Wind is a renewable energy source: in areas suitable for wind farms it blows almost constantly, even if not always with the same force. The systems generate electricity from the kinetic energy of the wind - they use it to drive their rotors. In doing so, however, they take away part of the wind's power. For this reason, there have already been indications that wind turbines that are too close together are slowing each other down.

Braking effect limits electricity yield

How strong this braking effect is and how it influences the generation of wind power has now been investigated by Lee Miller from the Max Planck Institute for Biogeochemistry in Jena and his colleagues using simulations. "You shouldn't assume that wind speeds will stay the same when you install many wind turbines in a region," explains Miller.

It turned out: In fact, an unlimited amount of wind power cannot be generated on a certain area. Once the installed systems have reached a certain output, the amount of electricity that can be generated no longer increases - because the wind turbines slow down the wind too much. This braking effect can reduce the wind speed by up to half, as the researchers found.

Much more than 0.5 watts per square sea is not possible

But what does this mean for the expansion of wind energy? Using their models, Miller and his colleagues have also calculated how much electricity can be generated from wind power per area worldwide. If the braking effect is taken into account, this is almost ten times less than previous estimates of the wind energy potential predict.

The results show that on most land areas only wind turbines with a capacity of around 0.5 watts per square meter can be installed without the braking effect causing excessive losses. Only on three to four percent of the world's land surface are the conditions so favorable that more than one watt per square meter can be generated, as the researchers report.

Important for future expansion

In the case of larger areas, it could even be significantly less: "Our results suggest that you should plan no more than 0.3 watts per square kilometer when areas of more than 10,000 square kilometers are involved," say Miller and his colleagues. For the further expansion of wind energy, this would mean that one would probably have to rely on significantly larger distances between the wind turbines in order to achieve the current efficiency of wind power in the future.

"It is important to note, however, that the current development status of wind power is well below the limits described here," emphasize the researchers. "In 2914, a global capacity of 0.372 terawatts was installed - with land-based wind turbines this corresponds to a reduction in wind speed of only 0.05 percent on average." do.

Source: Max Planck Institute for Biogeochemistry, Article: Proceedings of the National Academy of Sciences, doi: 10.1073 / pnas.1602253113

© natur.de - Nadja Podbregar
November 16, 2016