Bird in an offshore wind farm

"We need to understand the real risk wind farms pose to birds"

Thermal cameras will record bird collisions at the Hollandse Kust Zuid wind farm in a test starting this August. "We are still looking for the right technology to understand the risk of bird collisions," says Jesper Kyed Larsen, Bioscience Expert at Vattenfall.

In spring and autumn, millions of birds migrate over the North Sea and come close to wind farms. When a large number of birds is expected to pass through, the so-called start/stop procedure is activated (see box below the article), which means that Vattenfall has to shut down the wind turbines for a few hours and no power can be generated. "We want to avoid that, as far as possible," says Larsen. “If the turbines are shut down, other assets, such as gas-fired plants, have to top up to compensate for the fall in supply. The start/stop procedure is therefore announced two days in advance to give time to organise this. The question is whether the turbines will stop at the right time, simply because it is hard to predict so far in advance exactly what route the birds will choose and how quickly they will pass the area containing the wind farm.”

Collecting evidence

Together with Wageningen Environmental Research, part of Wageningen University, and Wildlife Imaging Systems, a US technology solution provider, Vattenfall will be trialling a thermal camera-based system for collecting evidence of birds colliding with offshore wind turbines at its HKZ wind farm. "This is trickier at sea than on land, where you can walk around and see what has fallen to the ground. When a bird hits a wind turbine at sea, it falls into the water and floats away. By placing 16 thermal imaging cameras on one of the turbines, we can monitor the conditions under which a collision might occur. The cameras run 24 hours a day and look out horizontally in all directions just below the rotor to see if anything falls down. The videos are analysed using artificial intelligence."

Bird flights around a wind turbine captured by camera systems. The image is a summary of 5 minutes of video in a single image. The yellow parts of the image are birds recorded by the software. Source: Wildlife Imaging Systems.

Vattenfall is already using cameras and artificial intelligence to monitor collision risk at the Aberdeen Bay Offshore Wind Farm in Scotland. There, daylight cameras are used to record the flight movements and behaviour of seabirds around the turbines, but not collisions.

With all the available material, Larsen and the researchers can see whether any patterns in bird activity and collisions can be identified and whether they may be related to certain weather conditions. While most migrating birds normally fly over wind turbines, when the weather deteriorates during their migration, they may be forced to fly lower.

Although it focuses on migration of small birds like songbirds and thrushes, the study covers all bird activity and looks at bats as well.


The primary goal of this pilot project is to test how well the thermal cameras and supporting technology work and get a more accurate fatality count. A next step could be to attach cameras to more wind turbines to get more certainty about the number of collisions and more representative figures. "This test is just the beginning," says Larsen. "Once we have more data, we can share our findings with authorities and experts, who can use it to improve their start/stop models."

Larsen is aware that results from studies of this kind conducted by the energy sector itself are sometimes greeted with scepticism. "I understand that very well," he explains. "That's why we are not doing this research alone. We have engaged Wageningen Environmental Research as an independent research partner. We also plan to invite key experts from the authorities, universities and NOGs to follow the project close-up. We want everyone to be able to use the results of the research."

Start-stop procedure

  1. A bird migration prediction model indicates an expected bird migration in the wind energy areas in the Dutch North Sea two days in advance in spring and autumn.
  2. When the birds density exceeds the threshold, a bird alert is sent to all those directly involved.
  3. Network operator TenneT notifies the Ministry of Economic Affairs and Climate. This ministry decides whether to stop the wind farms and gives notice of this with start and end times in the Government Gazette. This is a formal decision.
  4. Owners of wind farms stop the turbines at the specified time. That means reducing to less than two rotations per minute, because a complete shutdown is not desirable for technical reasons.
  5. The Enforcement Department of Rijkswaterstaat (RWS), an implementing organisation of the Ministry of Infrastructure and Water Management, carries out an administrative check.
  6. RWS analyses the data to see whether a bird migration actually took place and to further improve the prediction model.

Source: Shutting down offshore wind turbines during peak bird migration

See also:

Vattenfall takes seabird tracking to the next level with AI technology 

Picture above article: Charles Walker

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