Hydrodynamic Effects of Kinetic Power Extraction by In-stream Tidal Turbines
The hydrodynamic effects of extracting kinetic power from tidal streams presents unique challenges to the development of in-stream tidal power. In-stream tidal turbines superficially resemble wind turbines and extract kinetic power from the ebb and flood of strong tidal currents. Extraction increases the resistance to flow, leading to changes in tidal range, transport, mixing, and the kinetic resource itself. These far-field changes have environmental, social, and economic implications that must be understood to develop the in-stream resource. This dissertation describes the development of a one-dimensional numerical channel model and its application to the study of these effects. The model is applied to determine the roles played by site geometry, network topology, tidal regime, and device dynamics. A comparison is also made between theoretical and modeled predictions for the maximum amount of power which could be extracted from a tidal energy site. The model is extended to a simulation of kinetic power extraction from Puget Sound, Washington. In general, extracting tidal energy will have a number of far-field effects, in proportion to the level of power extraction. At the theoretical limit, these effects can be very significant (e.g., 50% reduction in transport), but are predicted to be immeasurably small for pilot-scale projects. Depending on the specifics of the site, far-field effects may either augment or reduce the existing tidal regime. Changes to the tide, in particular, have significant spatial variability. Since tidal streams are generally subcritical, effects are felt throughout the estuary, not just at the site of extraction.
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Theoretical Performance of Instream Turbines
Literature Review of Farfield Extraction Effects
Tidal Energy Extraction from Channel Networks
Tidal Energy Extraction from Puget Sound
3D Models for Farfield and Nearfield Extraction Effects
Conclusions and Future Work
Boundary Conditions for ID Models
actuator disc Admiralty Inlet array Bainbridge Island barotropic blockage ratio boundary conditions channel networks channel segments comparison constricted channel cross-section currents cut-in speed decreases dissipated by turbines dissipated power dissipation coefficient diurnal drag drag coefficient energy extraction environmental equations extracted power extraction coefficient extraction effects extraction to dissipation far-field effects free-stream Froude number Garrett and Cummins geometry grid Hood Canal in-stream turbines increases Johnstone Strait kinetic power density kinetic power extraction Lavelle Main Basin mixing multiply-connected networks Non-dimensional response open boundary parameterized turbine Pmax predictions Puget Sound quantified ratio of extraction reduced region relative change response to extraction rotor row of turbines seaward Segment number semidiurnal shallow water equations shown in Figure simulation single constriction network South Sound Strait of Georgia streamtube velocity ratio SUNTANS Table Tacoma Narrows terminal basin theory tidal amplitude tidal forcing total power dissipated transport turbine operating turbines MW upstream vertical Whidbey Basin wind turbines