Two offshore North Sea wind farms have had their turbines “stopped” to allow migrating birds to fly through the area safely in a trial that could become routine for ecologically responsible wind generation.
Based on complex modelling by migration experts of data from bird radar systems and weather forecasting, the farms at Borssele, off the southwest coast of the Netherlands and Egmond aan Zee, further north, were stopped for four hours last Saturday.
“This is an international first, the first time anywhere in the world that wind turbines have been halted to allow huge flocks of migrating birds safe passage,” confirmed Dutch energy minister Rob Jetten.
“We want to lead the way in keeping the impact of wind farms on nature as small as possible – and this is one important way of doing it.”
According to the wild bird conservancy organisation Vogelbescherming Nederland, millions of birds cross the North Sea during some spring and autumn nights.
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It’s estimated that collisions with turbine blades kill some 50,000 birds annually off the Dutch coast as wind farms become more numerous.
The turbinesdo not come to a complete halt as the birds pass by. The giant blades reduce their speed to a maximum of two revolutions per minute, which technical experts and ornithologists agree is slow enough to remove the danger.
“ Given the economic pressure to generate as much renewable energy as possible as quickly as possible, it’s crucial for the future that North Sea wind farm development is done in a responsible way,” said Tim van Oijen of the conservancy.
A doctoral student at Amsterdam University recently developed a much more accurate migration prediction model that allows significant bird movements to be anticipated as close as two days in advance.
As a result, close liaison between the migration experts and the turbine operators to ensure the blades are turned off in time will remain essential.
The Borssele wind farm has 173 turbines covering an area of 344sq km and has been in operation since 2021. Egmond aan Zee, by contrast, has 36 turbines over 27sq km and was the first wind farm built in the Dutch section of the North Sea in 2007.
Between them, the two wind farms generate about 1,600 megawatts of offshore wind capacity: 1,500 megawatts from Borssele which is operated by Orsted and Shell/Eneco respectively, and another 108 megawatts from Egmond aan Zee, operated by Shell.
Swedish state power company Vattenfall, whose 1,500 megawatt North Sea farm, Hollandse Kust Zuid, is due to come online later this year, is also expected to join the migration system which is scheduled to move from trial to operational in autumn.
The wind farm operators will not be compensated financially for drops in their energy output during the times when the turbines are “off”, a government spokesperson confirmed.
