Bird Collision Risk

Bird collisions with anthropogenic objects are well documented in the literature, including those involving wind turbines. The purpose of this study was to evaluate and help improve the effectiveness of an automated detection and deterrent system designed to minimize the risk of raptors colliding with wind turbines. We evaluated the DTBird® system (Liquen Consultoría Ambiental, S.L., Madrid, Spain), which is designed to detect and deter raptors flying near and in the risk zone of wind turbines. The DTBird system includes a camera/video-based detection module that detects and tracks objects based on settings calibrated for birds with specific wingspans, and a collision-avoidance or deterrence module that emits sounds designed to discourage birds from proceeding into the collision risk zone of an operational turbine. The deterrence module first emits an audible warning signal when the surveillance system estimates that a detected flying object (whether a bird or an inanimate object) has crossed a calibrated distance threshold. If the surveillance system estimates that the tracked object crosses a second, closer distance threshold, then it emits a stronger dissuasion signal intended to scare the bird away from the signal noise and turbine.

Calculating a Theoretical Collision Risk Assuming no Avoiding Actions

Guidance Note Series, Scottish Natural Heritage, 2000

Windfarms may impact on ornithological interests in a number of ways. There may be: loss of habitat due to the construction of turbine bases and tracks, displacement of birds as a result of disturbance, and potential mortality through collision. SNH Guidance note describes a methodology for assessing in full the impact of windfarms on ornithological interests, taking account of each of these effects. The methodology includes a two-stage process for the assessment of collision risk.

The purpose of this document is to compare the bird collision analysis method and equation employed by Scottish Natural Heritage (SNH) for horizontal axis wind turbines (HAWTs) with those that were derived from a similar method for vertical axis wind turbines (VAWTs). WHI repurposed SNH’s equations, approximations, assumptions and techniques, which SNH described for determining the frequency of bird strikes for HAWTs.

Use of Avoidance Rates in the SNH Wind Farm Risk Collision Model

Blair Urquhart, Policy & Advice, Scottish Natural Heritage, 2010.

The SNH Collision Risk Model (CRM) provides an estimate of the potential number of bird collisions likely to occur at a proposed wind farm. Birds react to a wind farm in different ways. Some may be displaced from the area of the wind farm, while others may avoid turbines or take other evasive action to prevent a collision. The CRM first estimates the number of collisions that would occur if the birds were to take no avoidance action. It then applies an avoidance rate to take account of the likely degree of successful avoidance.

WHI’s VAWT-Bird Collision Calculator

Matt Wylder, Wind Harvest International, August 2014

WHI commissioned UCD engineer Matt Wylder to take the Scottish Natural Heritage model for calculating bird strikes in HAWTs and redo it for VAWTs.    His paper “Vertical Axis Wind Turbines and Birds:  Calculating a Theoretical Collision Risk Assuming No Avoiding Action” summarizes a number of runs he made using the VAWT collision model he developed.  We welcome people to use and improve upon this tool.

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