Inflow Characterization for Marine and Hydrokinetic Energy Devices. FY-2010 Annual Progress Report

Marine and Hydro Kinetic devices (MHK) are being widely studied as a source of renewable energy. The Marrowstone Island site is a potential location for installing MHK devices because the tidal currents observed that are sufficient for power generation. In order to quantify the effects of turbulence on MHK devices and the surrounding environment at this site, a prelimi- nary fluid flow field study was conducted here by the Pacific Northwest National Lab (PNNL) in collaboration with the Applied Physics Lab at the University of Washington (APL-UW). This study entailed continuous The Acoustic Doppler Velocimetry (ADV), Acoustic Doppler Current Profiler (ADCP) and Conductivity, Temperature and Depth (CTD) measurements from May 4, 2010 to May 22, 2010, in order to obtain information about turbulence effects during different tidal conditions. The instruments used for collecting the above measurements were deployed at the Marrowstone site using a R/V Jack Robertson provided by the University of Washington (APL-UW). All the measurements were taken at the site with an average depth of 22 m below the sea surface. ADV acquired velocity data at 32 Hz sampling frequency at 4.6 m above the seabed, and ADCP acquired velocity profile data at a sampling frequency of 2 Hz, from a height of 2.6 m above the seabed to the surface with a bin resolution of 0.5 m. The ADV and ADCP measurements showed that the horizontal velocity had a turbulence intensity of 10%. Further- more, the spectral analysis from ADV measurements showed that the flow is fully turbulent with -5/3 slope in the inertial sub-range of the spectra. Moreover, the temporal-frequency analysis showed presence of ”eddies” at high frequencies. These preliminary studies provided initial flow field and site characteristics, showed the limitations of the instruments used and highlighted changes that need to be made in the experimental setup for deployment in FY-2011 studies