Feature Articles—September 2009 Issue
Using Sonar to Investigate Interactions Between Marine Life,Subsea Turbines
BioSonics’ Hydroacoustic System will be Used to Help Research Marine Mammals’ Behavior
Near Potential Kinetic Hydropower Sites
By Eric Munday
General Sales Manager
BioSonics Inc.
Seattle, Washington
Success in the emerging ocean renewable energy industry does not come easy. Some of the challenges that ocean energy project developers face include dealing with corrosive subsea conditions, establishing grid connectivity in remote and rugged areas and securing investment capital amid a global economic crisis. But one of the most significant challenges facing ocean energy developers is gaining regulatory approval in a time when regulators cannot provide clear direction on monitoring requirements.
Currently there is no rule book for installing an ocean energy, or kinetic hydropower, turbine, and so navigating the regulatory process can often be complex and confusing. Governing authority can vary widely and may involve multiple federal, state, tribal and provincial agencies. Monitoring priorities differ with each project depending on what local resources are likely to be impacted and the scarcity or uniqueness of and level of economic dependence on these resources.
In high-latitude regions where optimal energy harvesting potential exists, marine mammals such as seals, sea lions and porpoises are common, and there is widespread concern over the potential effects of turbine installations on the feeding and migratory behavior of these animals. However, questions on this topic are not easily addressed due to a lack of baseline data on fine-scale behavior at potential kinetic hydropower project sites to compare with any changes in behavior that may occur as a result of turbine installation. Some researchers believe marine mammals may be attracted to a large turbine structure due to curiosity about the sound emanating from the device or its tendency to aggregate forage fish. Others have suggested that marine mammals will detect and avoid such a device and the area in general. Today these theories remain untested, and many questions about marine mammal interactions with ocean energy turbines remain unanswered.
Insight on the Interactions
Edinburgh, Scotland-based Sea Mammal Research Unit Ltd. (SMRU), part of the Scottish Oceans Institute at St. Andrews University, and the European Marine Energy Centre (EMEC), are on a mission to provide some answers. In an effort to better understand how marine mammals, fish and other marine animals will interact with kinetic hydropower devices, SMRU and EMEC recently set out to develop hydroacoustic systems and methodologies for the detection and monitoring of marine mammals and diving birds and their potential interactions with tidal energy devices.
This project is an important undertaking that will help to prioritize marine areas for use as potential ocean energy project locations. It will also assist project developers and device manufacturers in addressing permitting issues and concerns over turbines placed in marine habitat areas.
Digital Echosounder Technology
The sonar systems used for this project will be provided by BioSonics Inc. After an intensive evaluation by a project steering committee comprised of representatives from the U.K. government, marine renewable energy developers and marine wildlife experts, BioSonics’ DT-X digital echosounder technology was selected based on its unique capabilities and potentially “mammal friendly” characteristics. BioSonics was also chosen due to its established track record in deploying fixed-position monitoring systems at the sites of ocean energy projects and performing baseline studies for site selection.
BioSonics has worked extensively with the emerging hydrokinetic industry to develop high-resolution, cost-effective monitoring systems and techniques with a client list that includes Verdant Power (New York, New York), Devine Tarbell and Associates (Portland, Maine), Alaska Power and Telephone (Port Townsend, Washington) and Snohomish County Public Utility District (Everett, Washington). BioSonics has also worked with the University of Washington Applied Physics Laboratory and Oregon State University on the Northwest National Marine Renewable Energy Center project. BioSonics’ systems are capable of 3D tracking and classification of marine mammals, fish and diving birds at long ranges and operate at frequencies and energy levels above the hearing ranges of marine life.
BioSonics automated hydroacoustic monitoring systems provide data to help both environmental regulators and kinetic hydropower developers determine the environmental impact of particular technologies, optimize site selection and aid in design improvements.
One of the primary issues regulators are interested in studying is how animals interact with turbines and what behavioral impacts occur as a result of turbine installation. This type of study requires long-term observation and the collection of a time series of data, similar to the information captured by a security video camera.
When conducted underwater for the observation of marine mammals, observational studies of this nature require an automated, noninvasive remote sensing methodology.
BioSonics detection and tracking systems automatically determine each target’s relative size and behavioral attributes, such as swimming speed and changes in depth and direction relative to current flow, to distinguish marine mammals from fish or debris. Classification of tracked targets is determined by a combination of acoustic and behavioral attributes. Data storage and preprocessing functions are completely automated, along with e-mail alerts and system status reports.
The system concept involves the fixed installation of one or more transducers oriented on a horizontal axis and cabled to a surface mount electronics package.
A transducer may be positioned on the device looking up-current or mounted at a distance and aimed in the area immediately adjacent to the turbine field. Coverage area is a function of the number of sensors and the integration of a motorized rotator. In effect, the hydroacoustic system projects an acoustic curtain in front of regions of interest and records reflections of any target moving through the curtain. Processing algorithms count the objects, determine their relative size and measure their direction of travel. Processed data files of target detections can be extrapolated temporally and spatially to estimate total numbers of targets moving in and out of the study area.
Invaluable Data and Next Steps
The synergies afforded through this alliance between SMRU, EMEC and BioSonics are significant. SMRU’s staff includes some of the world’s leading authorities on marine mammals, and over the next several months, these researchers will contribute expertise and collect data on marine mammals and their swimming behavior. This information will allow BioSonics engineering staff to develop specific classification matrices and optimize their existing hydroacoustic systems for the defined purposes.
“The end product will be a revolutionary new technology to help tidal power move forward in a safe and environmentally responsible manner,” said BioSonics president Tim Acker.
In early April, various mobile surveys and fixed position system trials were conducted at EMEC in Orkney and at the SeaGen Project in Strangford Loch, Northern Ireland. BioSonics and SMRU technical teams worked in tandem on these initial field trials and data collection.
“This is an exciting first step in what we expect will be a long and productive partnership,” said Douglas Mundie, managing director at SMRU. “It’s also an excellent demonstration of government, academic and private sectors working together to expand the use of marine renewables.”
Through consultation with SMRU, BioSonics will develop its hydroacoustic and software systems to an even greater level of specialization.
The next step is to deploy a BioSonics automated monitoring system at a turbine installation where marine mammals are commonly found. This will allow for the collection of an important baseline data set.
The result will be a summary of “tracks” indicating the size, time, location and, most importantly, the swimming path of every marine mammal passing near the turbine. These data will allow for refinement of the BioSonics classification software and more positive identifications.
“Essentially, we will document how many marine mammals passed under, over, around or through the turbine field,” Acker said. “BioSonics is proud to be a part of this endeavor and extremely excited about this next phase. This information will be invaluable to regulators, device manufactures and project developers. This project will help significantly to advance this industry.”
Eric Munday joined BioSonics in late 2007 with a decade of experience in technology sales and online marketing. Prior to joining BioSonics, he held executive and sales management positions with several successful marine-related Internet startup companies. Munday has a B.Sc. in fisheries science from the University of Washington.
Sea Technology is read worldwide in more than 110 countries by management, engineers, scientists and technical personnel working in industry, government and educational research institutions. Readers are involved with oceanographic research, fisheries management, offshore oil and gas exploration and production, undersea defense including antisubmarine warfare, ocean mining and commercial diving.
