tidal currents2,3 (Georgia Tech Research Corporation, 2011). The model used in the study was the three-dimensional Regional Ocean Modeling System (ROMS),4 which is often used in modeling studies of coastal oceanography and tidal circulation. The model was configured with eight vertical layers and set up for 52 model domains, with grid resolutions in the range of 350 m. Each domain included a section of coast or a particular bay, with offshore boundaries that included part of the adjacent continental shelf. The models were forced at their offshore boundaries by predicted tidal constituents, using the Advanced Circulation Model (ADCIRC) tidal database5 for the East Coast and Gulf of Mexico regions and the TPXO database6 for the West Coast region. River inflows and atmospheric forcing (such as wind) were not considered, and stratification and density-induced currents were not simulated. The landward model boundaries and bathymetry were defined using coastline data from the National Ocean Service of the National Oceanic and Atmospheric Administration (NOAA) and digital sounding data from NOAA’s National Geophysical Data Center. The effect of tidal flats was initially evaluated but not considered in the final model setup and runs.
The tidal resource assessment group calibrated the tidal models by adjusting the single friction coefficient to improve the comparison among model results, NOAA predictions of tidal elevation and currents, and limited observations of depth-averaged tidal currents. Model calibration parameters include harmonic constituents for tidal currents and water levels, maximum/minimum tidal currents, and high/low tides. An independent model validation was performed by the Oak Ridge National Laboratory (ORNL), which compared model predictions with observed tidal elevations and currents at selected stations that were not included in the calibration exercises7 (ORNL, 2011). Error statistics between model results and observed data were generated in this validation.
Model output was used (1) to provide an upper bound, Pmax , of the power available from tidal in-stream turbines for each bay and (2) to create a Web-based geographic information system (GIS) interface of quantities
2 K. Haas, Z. Defne, H.M. Fritz, and L. Jiang, Georgia Tech Savannah; S.P. French, Georgia Tech Atlanta; and B. Smith, Oak Ridge National Laboratory, “Assessment of energy production potential from tidal streams in the United States,” Presentation to the committee on November 15, 2010.
3 K. Haas, H.M. Fritz, and L. Jiang, Georgia Tech Savannah, “Assessment of tidal stream energy potential for the United States,” Presentation to the committee on February 8, 2011.
6 See http://www.esr.org/polar_tide_models/Model_TPXO71.html. Accessed June 21, 2011.
7 V.S. Neary, K. Stewart, and B. Smith, Oak Ridge National Laboratory, “Validation of tidal current resource assessment,” Presentation to the committee on February 8, 2011.