Building offshore windfarms too close to one another could adversely affect yield and overall productivity, a German study has found. In extreme cases, doing so could reduce productivity of neighbouring windfarms by 25%
The study suggests that, as a result, countries in the North Sea should co-ordinate the development of offshore wind.
“By optimising the spatial distribution of windfarms, offshore wind can become a key pillar of the European energy system,” the authors the study undertaken on behalf of Agora Energiewende and Agora Verkehrswende said.
The study said it is important to “maintain the greatest possible distance between sites,” particularly in the North Sea, and that this would entail “transnational planning co-ordination.”
As part of the study, researchers at Technical University of Denmark (DTU) and the Max Planck Institute for Biogeochemistry (MPI-BGC) applied two different models to examine various scenarios.
The scenarios differed in terms of windfarm location and the number and capacity of turbines per square kilometre. Total wind power yields were then estimated for each scenario, all of which looked specifically at Germany’s exclusive economic zone in the North Sea.
Although the models varied considerably in terms of their underlying approach, the results were “remarkably consistent,” researchers Axel Kleidon at MPI-BGC and Jake Badger at DTU noted.
Agora Energiewende director Dr Patrick Graichen said, “Policymakers and offshore planning authorities would be well advised to ensure future windfarms have adequate space between them.
“As Germany and its neighbours in the North Sea plan to significantly expand offshore wind energy, joint planning is essential, and will enable optimal windfarm deployment.”
“The mechanism that motivated the study is simple: when kinetic energy is withdrawn from the lower atmosphere by a windfarm, the area around it has reduced energy-harvesting potential that must be ‘replenished’ from higher atmospheric layers,” the researchers said.
This phenomenon is similar to the well-known ‘wake effect’ that can occur between turbines and windfarms located in close proximity.
The study concluded that German offshore windfarms should be not be built in the German Bight but further offshore, because the windfarms could otherwise be too close together, which would reduce their annual yield.
The researchers believe their findings apply primarily to large-scale offshore windfarms.
The study, Making the Most of Offshore Wind is available for download here.