Offshore wind farms were shut down for the first time this week to prevent migratory birds from colliding with the blades. In fact, according to ecologists, the blades pose a danger to certain species of birds flying by. At the same time, several utilities have reported in recent months that, on the contrary, it does not seem to be too bad. What's going on here?
The "collision risk" of birds with wind turbine blades at sea is low, showed earlier this month. and drew similar conclusions earlier this year. Vattenfall even says that during the two-year study, not a single bird collided with a rotor blade.
The survey results paint a different picture than Wageningen Marine Research's expectations. Earlier this year, an ecologist from the research institute stated that 4,400 gannets are expected to die annually from collisions with wind turbines at sea as of 2050. The research institute also expects 3,650 fatal collisions annually for gulls by 2050. The AD article was widely picked up by other media where force terms and accusations such as "" and "" were not shunned.
"The AD cited research by the government-funded 'Wind at Sea Ecological Program') on ecological effects of wind at sea," said Tim van Oijen, policy officer at Vogelbescherming Nederland. "Part of this is the KEC impact assessments. KEC stands for Framework Ecology and Cumulation. Model calculations were used to estimate what happens to bird populations under different scenarios for the expansion of wind turbines at sea."
More turbines, more collisions
So the figure of 4,400 gannets comes from one such KEC calculation and in this case applies to a scenario of X number of offshore wind turbines in 2050. With all the projects now planned, the North Sea Foundation expects 4,332 by 2050. There are currently 602 turbines in this sea area.
KEC calculations involve quite a few assumptions, Van Oijen says. "But clearly dozens of species are at risk. And specifically four species, including the gannet, are at increased risk. These impact assessments can be improved with new knowledge. They best reflect the state of affairs as far as we are concerned."
Playing with blades
But what about the Vattenfall and Eneco studies? "First of all, let it be said that these kinds of studies are very welcome," says Van Oijen. "These show that various bird species are well able to avoid wind turbines. From this and other research we know that some birds change their course at a great distance from turbines, while still others can practically play with the blades."
The Vattenfall researchers looked very specifically at one site: the wind farm near Aberdeen, Scotland. "It seems that the birds that occur there during the day are good at dodging," says Van Oijen. "But the fact that they identified zero bird kills calls for nuance. 'The study didn't look at what happens at night, and during extreme or foggy weather, whereas true seabirds are constantly flying at sea."
Eneco also conducted field studies at a specific wind farm using cameras and radars. During the four years that research firms Waardenburg Ecology and Dansk Hydraulisk Institut monitored the site, they filmed only two collisions. Once a herring gull had to pay for it, another time an "unidentified great gull.
But the disturbance of birds by wind turbines goes beyond the chance of a blow from the blades. "When wind farms are placed near nesting areas, it can seriously disrupt habitat," Van Oijen says. "The consequence, for example, can be that birds have to look for food elsewhere. And flying around is energy loss. There are risks associated with that as well."
Wind farms shut down
There is still little insight into how many migratory birds fall victim to wind turbines in the North Sea. It is known from radar data that a large proportion of the millions of birds that migrate across the North Sea in spring and autumn fly at the height where the turbine blades turn. To reduce the risk of collisions, several wind farms in the North Sea were therefore virtually shut down for the first time last Saturday for four hours.
A "bird migration prediction model" developed by a PhD student at the University of Amsterdam makes it possible to predict mass bird migration two days in advance based on weather data and bird radars. That prediction is also juxtaposed with predictions by bird experts. The two-day time frame allowed grid operator TenneT to anticipate wind farm shutdowns in time and guarantee grid stability.
Taking bird migration into account more often
In any case, Van Oijen is pleased with . "Twice a year, in spring and autumn, millions of birds migrate across the North Sea on some nights. With the growth in the number of wind farms in the North Sea, it is extremely important that we do this in the most ecologically responsible way possible with minimal impact on the North Sea. Temporarily shutting down the turbines during bird migration contributes to this."
The procedure will become an official measure starting this fall. Rijkswaterstaat, the body that developed the procedure of shutting down wind farms, will further optimize the process in the coming period.
Technology and paint
Meanwhile, research into bird collisions with blades continues. Advanced technology such as vibration meters and thermal cameras is making it increasingly possible to measure actual collisions, rather than relying on assumptions. Such measurements can also be used to test how effective shutting down wind farms is.
Smart prevention is also being worked on. At the end of last year, for example, was as an experiment. Because of the difference in color, birds are more likely to spot the blades, and are expected to avoid the turbines more quickly.