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WT-BIRD: A Low Cost Solution for Detecting Bird Collisions
Gepubliceerd door: Publicatie datum:
ECN Windenergie 1-4-2004
ECN publicatienummer: Publicatie type:
ECN-C--04-046 ECN rapport
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The large-scale implementation of wind energy is hampered to a large extent by the unknown effects that wind turbines may have on the environment. The collision of birds with turbines and the distortion of the migration routes are in that respect points of great concern. The project ?WT-Bird , A low cost solution for detecting bird collision? focused on developing a reliable and cheaper method for counting bird collisions in order to obtain more insight in the actual size of the problem, especially in offshore applications for which no alternative detection method is available.

The report describes the work that has been performed to meet the objective ?developing and demonstrating a system that determines a bird collision against a wind turbine and with which it is possible to determine the bird species?. The system had to meet among others the following specifications:

· the system should be low cost in order to be competitive with manual counting methods;

· analysis of recorded data by e.g. ornithologist should not be labour intensive, meaning that only actual collisions should be recorded and no false data should be stored;

· the system should be able to operate under all weather and visibility conditions;

· the system should operate in offshore wind farms for long periods in a reliable manner and data should be accessible remotely.

The assembly of the prototypes has been carried out in this project successfully. They behaved robust and reliable during the field tests and only minor problems have been identified. Two major problems have not been solved completely in this project.

1. Triggering

Birds can collide against rotors and towers in many different ways. The tests that have been performed with shooting tennis balls against the flat side of rotor blades and throwing sand bags against the tower did not cover the entire range of possible bird impacts. Secondly, the variety of possible microphone configurations and background noises for especially larger turbines is bigger than originally expected. The determination of a good algorithm for triggering should be further investigated. Within the constraints of the project, more detailed investigations were not feasible.

2. Image recording and recognition of bird species

Already at an early stage in the project it was decided to use the Mobotix camera a.o. because it had a normal lens and a low-light lens, it could be accessed with commonly used web browser technology, and especially because it was cheap. During the field tests, the shortcomings of the camera became clear. The view during night-time was insufficiently clear for recognition of species. Additional light sources were necessary and the exposure time is too long, leading to too low sample frequencies. A large part of the project has been spent on improving the visibility during night-time but without being completely successful.

To solve these problems, further R&D work is recommended. More tests with dummies against larger turbines should be performed and the tests with cameras should be continued. Moreover, much more long-term field tests should be performed in close collaboration with ornithologists.

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