More and more countries are promoting the expansion of wind farms at sea to support the transformation towards a carbon neutral energy production. However, if these offshore wind farms are set up close to each other, wind energy and hence electricity yield is reduced. A study by the Helmholtz-Zentrum Hereon, which has now been published in the journal Nature Scientific Reports, shows that the losses with increasing offshore wind energy production will be considerable and detectable as large scale pattern of reduced wind speed around wind farms.
The expansion of wind energy in the German Bight and the Baltic Sea has accelerated enormously in recent years. 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 the 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. (Source: PR Hereon)
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Akhtar, N., Geyer, B., Rockel, B., Sommer, P.S., & Schrum, C. (2021): Accelerating deployment of offshore wind energy alter wind climate and reduce future power generation potentials. Sci Rep 11, 11826, doi:10.1038/s41598-021-91283-3
The European Union has set ambitious CO2 reduction targets, stimulating renewable energy production and accelerating deployment of offshore wind energy in northern European waters, mainly the North Sea. With increasing size and clustering, offshore wind farms (OWFs) wake effects, which alter wind conditions and decrease the power generation efficiency of wind farms downwind become more important. We use a high-resolution regional climate model with implemented wind farm parameterizations to explore offshore wind energy production limits in the North Sea. We simulate near future wind farm scenarios considering existing and planned OWFs in the North Sea and assess power generation losses and wind variations due to wind farm wake. The annual mean wind speed deficit within a wind farm can reach 2–2.5 ms−1 depending on the wind farm geometry. The mean deficit, which decreases with distance, can extend 35–40 km downwind during prevailing southwesterly winds. Wind speed deficits are highest during spring (mainly March–April) and lowest during November–December. The large-size of wind farms and their proximity affect not only the performance of its downwind turbines but also that of neighboring downwind farms, reducing the capacity factor by 20% or more, which increases energy production costs and economic losses. We conclude that wind energy can be a limited resource in the North Sea. The limits and potentials for optimization need to be considered in climate mitigation strategies and cross-national optimization of offshore energy production plans are inevitable.