Abstract
Tidal In-Stream Energy Conversion (TISEC) is a promising source of clean, renewable and predictable energy. One of the preliminary steps in developing the technology is establishing a standardized and repeatable methodology for the characterization of potential deployment sites. Stationary Acoustic Doppler Profiler (ADCP) velocity data collected at four sites near Marrowstone Island, Puget Sound are used to test the applicability of metrics characterizing maximum and mean velocity, eddy intensity, rate of turbulent kinetic energy dissipation, vertical shear, directionality, ebb and flood asymmetry, vertical profile and other aspects of the flow regime deemed relevant to TISEC. Based on these analyses, the flow at three sites clustered along the east bank of Marrowstone Island (referred to as the “D” sites) are found to be mainly bidirectional and have similar ebb and flood velocities and relatively low levels of turbulent activity. The site near the north point of Marrowstone Island (the “C” site) has higher maximum and mean ebb velocities, but is more asymmetrical and has higher levels of turbulent activity. In addition, methods are applied to data from another Puget Sound site (Admiralty Inlet), and results are compared. A two-dimensional “velocity map” is developed for the more promising “D” sites, showing the spatial variation of velocities throughout the area. This map is based on data collected using a vessel-mounted ADCP in linear transects running roughly perpendicular to the flow at the site. Interpolation between these transects along isobaths yields a rough grid of velocities, from which the velocity map can be determined using a two-dimensional interpolation scheme. Results are promising, although this method may not work well at sites with different bathymetric and geographic characteristics. The methods and conclusions are device-neutral, however device specific considerations will be important prior to developing TISEC sites.