German Chancellor Merkel surveys an offshore wind site [image credit: evwind.es]

German Chancellor Merkel surveys an offshore wind site [image credit: evwind.es]

Wind ‘farms’ are allergic to each other it seems, sometimes leading to sizable drops in output. Awkward when space isn’t unlimited, some of the best sites are already taken, and the plan is to multiply the existing fleets. Weather dependency is even greater than expected.
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The expansion of wind energy in the German Bight and the Baltic Sea has accelerated enormously in recent years, TechXplore.

The first systems went into operation in 2008. Today, wind turbines with an output of around 8,000 megawatts operate in German waters, which corresponds to around eight nuclear power plants.

But space is limited. For this reason, wind farms are sometimes built very close to one another.

A team led by Dr. Naveed Akhtar from Helmholtz Zentrum Hereon has found that wind speeds at the downstream windfarm are significantly slowed down.

As the researchers now write in the journal Nature Scientific Reports, this braking effect results in astonishingly large-scale low wind pattern noticeable in mean wind speeds. On average, they extend 35 to 40 kilometers—in certain weather conditions even up to 100 kilometers.

The output of a neighboring wind farm can thus be reduced by 20 to 25 percent, which ultimately leads to economic consequences. If wind farms are planned close together, this wake effects need to be considered in the future.

Combination of climate and wind farm data

With their study, Naveed Akhtar, an expert in regional climate modeling, and his colleagues took a look into the future and assessed the wind characteristics for a medium-term target state of offshore expansion.

They used the computer model COSMO-CLM, which is also used by weather services and which is able to resolve weather situations regionally in detail—in this case for the entire North Sea and combined it with the future wind farm characteristic—their area and the number and size of the turbines.

They used the wind farm planning for the North Sea from 2015 as a basis. This contains wind farms, some of which have not yet been built.

Braking effect especially in stable weather conditions

Naveed Akhtar used the COSMO model to calculate the wind speed over the North Sea for the period from 2008 to 2017 covering a range of different weather conditions.

The results clearly show that we will face a large scale pattern of reduced wind speed, which show largest extensions during stable weather conditions, typically the case in March and April. In stormy times, on the other hand—especially in November and December—the atmosphere is so mixed that the wind farm wake effects are relatively small.

Full article here.

via Tallbloke’s Talkshop

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June 4, 2021