AWAC's Deployed in Bay of Fundy for Tidal Power Study
Tidal power development is going strong in the Bay of Fundy, Canada. The Bay of Fundy pushes over 100 billion tonnes of water every tide - more than all the freshwater rivers and streams in the world combined. This creates exciting conditions for developers, researchers, and the public to better understand the potential of in-stream tidal technology to deliver clean, renewable power for generations to come.
The Fundy Ocean Research Centre for Energy (FORCE) is leading the charge by developing a comprehensive test bed for full scale tidal power turbines. The test site, located in the Minas Passage, hosts shared observation facility, submarine cables, grid connection, and environmental monitoring at its four pre-approved test site. The site is ideal for testing, with water depths up to 45 meters at low tide, a sediment-free bedrock sea floor, straight flowing currents, and water speeds up to 5 meters per second. The four test sites will host full scale turbines from Alstom Hydro, Atlantic Resources, Marine Current Turbines, and OpenHydro.
As part of the environmental monitoring effort, FORCE has contracted Oceans LTD to measure the currents at the four test sites. The measurement requirements included observations of full water column current profiles, surface waves, and burst sampling velocity to observe the turbulence intensity and eddy scales. To meet this sophisticated list of requirements, Oceans LTD turned to Nortek. The Nortek AWAC was selected for its ability to meet all aspects of the project.
Two AWAC's were selected for the job. A 400 kHz AWAC was deployed in 45 m (low tide) and a 600 kHz AWAC was deployed in 30 m (low tide). Because of the extraordinarily high suspended sediment load, acoustic attenuation is very high, and instrument frequency a little lower than normal must be used to get the full water column profile. A Nortek Vector Velocimeter was also deployed to measure near-bottom velocities to help in transmission cable engineering.
The AWAC's were configured to profile the full water column, as normal. The velocity burst measurement (wave cell) was configured in a "static" position and located at the "hub height" of the turbine (nominally 15 m above the bottom). This velocity cell is sampled at 1 Hz (600 kHz) / 0.75 Hz (400 kHz) in burst mode to collect a time series of velocity in order to estimate turbulence intensity and the length scales of the eddies. During this burst mode, the acoustic surface tracking (AST) is sampled in a region from the hub height to the surface and measures the wave height.
The instruments were deployed in early July for 30 day measurements at each of the four test sites. For more information about the instrumentation, please contact Nortek. For more information about the deployment and mobilization in this challenging location, please contact Oceans LTD.
Conceptual diagram showing AWAC deployment location and position of sampling regions. The dashed black lines indicate the water column velocity cells. The yellow region indicates the "hub height" measurement cell. The vertical blue cone indicates the acoustic surface tracking (AST) beam.
Location of the FORCE test facility in the Bay of Fundy, Nova Scotia, Canada