50-9 Developing Capabilities for Tidal Hydrokinetic Blade Strike Monitoring
A blade strike monitoring system is being developed to conduct post-installation monitoring at a pilot tidal energy project in northern Admiralty Inlet, Puget Sound, Washington. A high definition stereo camera system has been selected for primary detection. However, at the project depth of 55 m, artificial lighting is required, which may attract or repel particular species. Tidal currents at the site exceed 3.5 m/s and it is anticipated that most marine animals at risk for strike will be oriented with the flow direction. Because the turbine rotor is aligned perpendicular to the flow, a camera angle that maximizes species identification (perpendicular to the direction of animal motion) does not provide effective coverage of the turbine rotor. The converse is true for observing blade strike, where a camera angle perpendicular to the rotor (and parallel to the direction of animal motion) is preferred. For this reason, the initial design employs two pairs of orthogonally-mounted stereo cameras. During testing, a stereo camera pair and strobe lighting in modular pressure housings are mounted to an aluminum frame in a downward-looking orientation. A test frame is rigidly connected to the camera frame at a fixed range (2-5 m) and equipped with targets to evaluate the possibility of species identification at different angles relative to the camera, as well as the potential to identify strike events. The approach for integrating lighted cameras into a broader post-installation monitoring system is described and preliminary results from freshwater testing are presented.