Neighbouring wind farms might slow each other down
Windfarms built downstream of other windfarms could have their energy generation hampered by slowed wind speeds, according to German researchers from Helmholtz Zentrum Hereon.
The expansion of wind energy in Germany’s coastal areas has accelerated significantly in recent years since the first systems went into operation in 2008.
Today, wind turbines with an output of around 8,000 megawatts rotate in German waters, corresponding to around eight nuclear power plants. Limited space means that wind farms are sometimes built very close to one another.
The researchers believe that downstream windfarms are significantly slowed down in such a setup and have detected “astonishingly” large-scale low wind patterns in such areas.
On average, these patterns can extend 35-40km from the wind farm, and up to 100km in certain wind conditions. This can reduce the energy output of a neighbouring wind farm by 20 to 25 per cent. If wind farms are planned close together, this wake effects need to be considered in the future, the team warned.
They used a computer model typically used by weather services to resolve weather situations regionally in detail - in this case, for the entire North Sea - and combined it with specific data on wind farms such as 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 which contains some facilities that have not yet been built.
The results anticipate a large scale pattern of reduced wind speeds, which show largest extensions during stable weather conditions, typically the case in March and April.
However, during other times of the year, such as storm-prone November and December, the atmosphere is so mixed that the wind farm wake effects are relatively small.
“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 researcher Dr. Naveed Akhtar. “In addition, these cannot be used to determine how a wind farm changes the air flow over a large area.”
While the group has mainly dealt with the extent to which the wind farms influence each other in their current work, they now intend to investigate what influence the reduced wind speeds have on life in the sea, including the salt and oxygen content of the water, its temperature and the amount of nutrients in certain water depths.
Last month, the Biden administration approved its first large-scale offshore wind farm for the US. It hopes the project will launch a new domestic energy industry that will help eliminate emissions from the nation’s power sector.
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