Tidal Energy Resource Characterization in the Western Passage, Maine, USA

Michelle Fogarty and Levi Kilcher, National Renewable Energy Laboratory, Golden, CO, United States
The Western Passage near Eastport, Maine is a top-ranked U.S. tidal energy site. Knowledge of both mean and turbulent current flow characteristics at this potential early-market tidal site is essential for resource characterization, device design, and the validation of regional high-resolution circulation models. In 2017, current measurements were made at three stations in the Western Passage. From April – July, bottom-mounted acoustic Doppler current profilers (ADCPs) at two stations collected vertical current profiles over the 50 m water column. In May, a Stable Tidal Turbulence Mooring (STTM) positioned ~ 10 m above the seabed was deployed for one week during the spring tide. Data from an acoustic Doppler velocimeter with an inertial motion unit and a bottom-tracking ADCP on the STTM allow us to report high temporal resolution, motion-corrected flow and turbulence characteristics at a potential hub height. Flood/ebb asymmetry in current magnitude, direction, and turbulence statistics is observed at all stations. Flooding currents flow toward the north-northwest with typical depth-averaged speeds of 1.4 ms-1, while ebbing currents flow southeast more slowly with typical depth-averaged speeds of 0.9 ms-1. Similarly, turbulent statistics are generally larger in magnitude on flood tide than on ebb tide. For example, Turbulence Intensity is an additional 2% larger for the same current speeds during flood than for ebb. Results of this data collection campaign will aid both research and commercial endeavors to improve resource characterization and device design.