The project entitled: “A Biomimetic Ultrasonic Whistle for Use as a Bat Deterrent on Wind Turbines ” will focus on design and manufacturing of a biomimetic ultrasonic pulse generator for use as a bat deterrent on wind turbines. During the design a whistle-like device emulated based on a bat larynx, mechanically powered via air flow over the wind turbine blade. We will carry out an iterative process of whistle design alternating with laboratory testing on bats to create a series of devices which effectively induce a flight avoidance response for at-risk bat species. Ultimately, the goal is to provide a reliable, cost-effective means of alerting bats to the presence of moving turbine blades, reducing bat mortality at wind facilities, and reducing regulatory uncertainty for wind facility developers.
Initially, we will directly model the larynx of the greater horseshoe bat (Rhinolophus ferrumequinum) in order to reproduce key aspects of its acoustic behavior. Specifically, we intend to create a biomimetic device that (i) produces a short, broadband sound spanning the ultrasonic range in which hearing sensitivity is highest in the bats most impacted by wind turbines (20-55 kHz), (ii) displays a rapid drop in frequency across a small change in pressure gradient to produce a downward frequency-modulated (FM) sweep similar to a naturalistic bat sonar pulse, and (iii) produces consistently high sound pressure level across a range of impinging air pressure. Physical models will be produced using a three-dimensional digital fabrication method which allows for rapid prototyping. The prototype whistles will be tested using a pressurized airline with manual control as well as in the UMass wind tunnel.
Concomitant with these efforts, we will conduct a series of laboratory and field experiments on at-risk bat species to evaluate flight response to acoustic stimuli, specifically identifying frequency ranges, intensity, and patterns of sound that induce avoidance responses across three Vespertilionid species. We will use Y-mazes and perch selection in the laboratory, as well as flight trajectories of free-flying bats in the field, to assess bat response. These will inform design parameters regarding target ultrasound frequency, intensity, and patterns.
We will use computational modeling and laboratory experiments to adjust mechanical properties of the device to produce a range of pulse types over a range of predicted wind speeds and pressure gradients. A series of iterative testing and modeling will be used to optimize acoustic features to evoke avoidance behavior in bats. Bandwidth, intensity, directionality and beam projection pattern of the device will be optimized for positioning on turbine blades.
Because the source of sound generation will be mechanical in nature, these innovative devices will require no external power source, should require little maintenance, and will be small and cost-effective. The small size of these devices will allow us to position them at intervals along the turbine blade, addressing the issue of rapid attenuation of ultrasound in the atmosphere, without reducing blade efficiency.
This interdisciplinary project was initiated as an outgrowth of the UMass Offshore Wind IGERT program, and involves collaborations between a number of Departments at UMass-Amherst, as well as the Department of Biology at Texas A & M University. Dr. Paul Sievert of the Department of Environmental Conservation at UMass-Amherst will direct the project, with Principal Investigator Dr. Yahya Modarres-Sadeghi, of the Department of Mechanical & Industrial Engineering at UMass, and Collaborator Dr. Michael Smotherman, of the Department of Biology at Texas A & M University, overseeing activities in their respective programs. Dr. Elizabeth Dumont of the Department of Biology at UMass and Dr. Matthew Lackner of the Department of Mechanical & Industrial Engineering at UMass will serve advisory roles in connection with bat larynx modeling and whistle placement, respectively.