The interaction of bats (Microchiroptera) with wind turbines: bioacoustic and other investigations
2011-02-16T10:09:09Z (GMT) by
The phenomenon of bat mortality at wind turbine installations has been generating increasing concern, both for the continued development of the wind industry and for local ecology. Bat-turbine interactions appear to be globally widespread, but are not well understood. The work outlined in this thesis primarily addresses the acoustic properties of moving turbine blades and the way in which bat-like pulses interact with them. In addition, possible factors for bat attraction to wind turbine installations are assessed. The main contributions of this thesis are (1) the formulation and application of a novel equation to rate turbine rotors in terms of bat detectability, identifying that features such as rotor angular velocity, number of blades, blade width and bat species all influence the likelihood of rotor detection; (2) passive and active ultrasonic measurements from turbine rotors in order to assess the nature of acoustic bat interaction with turning blades, showing that frequency and amplitude information in returned echoes can vary significantly, echoes may be attractive to bats as mimicry of echoes returned from flying insects, and that some turbines do not emit ultrasonic noise detectable to all bat species; (3) assessment of the Doppler shift profiles generated by moving blades in order to investigate the changing nature of frequency information returned to an echolocating bat, concluding that blades turning under low wind speed conditions may not be detectable by some bat species; (4) Monte Carlo simulation of bat-like rotor sampling to account for the temporally short nature of reflected echoes, with the result that some bat species may not be able to achieve enough echoes to accurately interpret blade movement in the short approach time-window; (5) the creation and utilisation of artificial bat-like pulses for lab-based experimental work and (6) the investigation of insect attraction to turbine paint colours to determine the potential abundance of bat prey around turbine installations, finding that existing turbine colours are significantly attractive to insect species. By applying the conclusions of this work suggestions for the mitigation of the problem are detailed, the implementation of which may help to reduce the issue of bat mortality for both the wind industry and bat species in the future.