Dutch and Belgians clash over 'wind theft' in North Sea
According to the British newspaper The Times, the Dutch have accused the Belgians of "stealing the wind." Dutch wind farms in the North Sea are generating less energy due to the proximity of Belgian turbines. "This is not theft but a 'wake effect,'" explained Dr. Tomasz Harackiewicz from the Maritime University in Gdynia.
According to the newspaper, some Belgian wind farms located to the southwest of the Dutch ones are taking up to 3% of the energy generated by their neighbours, which "creates the risk of future conflicts over air currents."
It's hard to call it wind theft. This is the "wake effect," known and described by scientists as an aerodynamic wake effect in wind energy – explained Dr. Tomasz Harackiewicz, director of the Offshore Wind Energy Centre at the Maritime University in Gdynia.
Dr. Harackiewicz emphasised that to drive a turbine, the wind must impart kinetic energy, which is transformed into electrical energy, causing the wind speed to decrease.
"It's not just about the energy given to the turbine blades, but also the turbulence created behind them, which can stretch for miles and change the wind direction. This is what the 'wake effect' is about," said the expert, adding that if wind turbines are aligned, with each successive one, the wind weakens.
Air flowing through a wind turbine loses speed and creates turbulence, which can negatively affect the turbines located behind it, reducing the energy efficiency of subsequent devices. As described on the website renovables.blog, when a turbine is exposed to wind with a lower speed, it generates less electrical energy, and furthermore, "turbulent flow can increase the mechanical wear of the blades, shortening their lifespan."
"This happens on every wind farm where the turbines are relatively close to each other. Additionally, for example, 100 turbines gathered on one wind farm can influence the functioning of other wind farms," emphasised Harackiewicz.
Impact on wind energy
The aerodynamic wake effect can vary in size depending on the number of turbines, their height, blade span, and the arrangement of turbines on the farm. It also depends on the prevailing wind directions in a given area and the distance between individual wind farms.
Remco Verzijlbergh, a specialist at the Dutch weather forecasting company Whiffle, discussed the impact of this physical effect with a British newspaper. In a conversation with Belgian broadcaster VRT, he explained that when numerous wind turbines are positioned close together in a wind farm, the wind speeds behind them tend to decrease.
In his opinion, the current arrangement of Belgian farms is causing losses for the Dutch, and considering the increase in the number of wind farms in the North Sea, "there will be more and more wind theft." According to the "Times," the UK, Belgium, Germany, France, Norway, the Netherlands, Denmark, Ireland, and Luxembourg have agreed to create the world's largest offshore wind energy zone in the North Sea. By 2030, all these countries aim to generate 120 GW of power in the North Sea. Currently, they reach a level of 30 GW.
Harackiewicz says the "wake effect" may increasingly trouble wind power producers. "The weakening of the wind affects power generation and can have a noticeable impact on the financial outcome of an investment in a wind farm," assessed the expert. However, he believes such situations can be avoided by predicting the "wake effect" occurrence at an early planning stage.
"Sometimes countries consult each other on the locations of wind farms in their exclusive economic zones to avoid contentious situations and conflicts of interest. It seems that in this case, there were no such consultations at the permitting and location stage," stressed Dr. Harackiewicz.
In his view, complaints about the negative impact of other wind farms may be justified, but "the problem is that there are no detailed regulations in this area on which to base."
