Field deployments of a self-contained subsea platform for acoustic monitoring of the environment around marine renewable energy structures

Abstract

Abstract-The drive towards sustainable energy has seen rapid development of marine renewable energy devices, and current efforts are focusing on wave and tidal stream energy. The NERC/DEFRA collaboration FLOWBEC-4D (Flow, Water column & Benthic Ecology 4D) is addressing the lack of knowledge of the environmental and ecological effects of installing and operating large arrays of wave and tidal energy devices. The FLOWBEC sonar platform combines a number of instruments to record information at a range of physical and multi-trophic levels. Data are recorded at a resolution of several measurements per second, for durations of 2 weeks to capture an entire spring-neap tidal cycle. An upward-facing multifrequency Simrad EK60 echosounder (38, 120 and 200 kHz) is synchronized with an upward-facing Imagenex 837B Delta T multibeam sonar (120° x 20° beamwidth, 260 kHz) aligned with the tidal flow. An ADV is used for local current measurements and a fluorometer is used to measure chlorophyll (as a proxy for plankton) and turbidity. The platform is self-contained with no cables or anchors, facilitating rapid deployment and recovery in highenergy sites and flexibility in allowing baseline data to be gathered.Five 2-week deployments were completed in 2012 and 2013 at wave and tidal energy sites, both in the presence and absence of renewable energy structures. These surveys were conducted at the European Marine Energy Centre, Orkney, UK. Algorithms for noise removal, target detection and target tracking have been written using a combination of LabVIEW, MATLAB and Echoview. Target morphology, behavior and frequency response are used to aid target classification, with concurrent shore-based seabird observations used to ground truth the acoustic data. Using this information, the depth preference and interactions of birds, fish schools and marine mammals with renewable energy structures can be tracked. Seabird and mammal dive profiles, predator-prey interactions and the effect of hydrodynamic processes during foraging events throughout the water column can also be analyzed. These datasets offer insights into how fish, seabirds and marine mammals successfully forage within dynamic marine habitats and also whether individuals face collision risks with tidal stream turbines.Measurements from the subsea platform are complemented by 3D hydrodynamic model data and concurrent shore-based marine X-band radar. This range of concurrent fine-scale information across physical and trophic levels will improve our understanding of how the fine-scale physical influence of currents, waves and turbulence at tidal and wave energy sites affect the behavior of marine wildlife, and how tidal and wave energy devices might alter the behavior of such wildlife. Together, the results from these deployments increase our environmental understanding of the physical and ecological effects of installing and operating marine renewable energy devices. These results can be used to guide marine spatial planning, device design, licensing and operation, as individual de...

Automatic active acoustic target detection in turbulent aquatic environments

“…Deployments of the FLOWBEC-4D platform (FLOw, Water column and Benthic ECology 4-D) were performed at the European Marine Energy Centre (EMEC) test sites, UK (Williamson et al 2014). These deployments gathered multifrequency echosounder data with synchronized multibeam echosounder measurements (Williamson et al 2015) and were further supported by hydrodynamic model data for the sites (Waggitt et al 2016).…”

“…The data presented in this article and the initial motivation for the development of the proposed method come from echosounder platform deployments in a tidal channel (Williamson et al ). To establish an effective processing approach for the detection of targets, various standard and novel techniques for target detection were explored.…”

A Self-Contained Subsea Platform for Acoustic Monitoring of the Environment Around Marine Renewable Energy Devices–Field Deployments at Wave and Tidal Energy Sites in Orkney, Scotland

“…The FLOWBEC project addresses all of these issues by combining data from the deployment of a self-contained, upwardfacing seabed sonar platform [27], [28] with shore-based bird observations, shore-based marine X-band radar surveys of wave and current data and detailed 3-D modeling of the flow and water column. The purpose of this project is both to address the lack of ecological understanding of mobile predator and prey use of high-energy sites and to identify and quantify which type of habitats (depth of water column, speed of tides, etc.)…”

Control and instrumentation topologies for an integrated wave energy array

“…Other topologies deployed in industry include autonomous sensor platforms, such as the South West Mooring Test Facility (SWMTF) buoy (Johanning 2011) and the FLOWBEC platform (Williamson 2016). Both platforms boast a wealth of instrumentation connected to a data acquisition system.…”