Spatially varying seasonal modulation to tidal stream energy potential due to mixed tidal regimes in the Aleutian Islands, AK

We provide an assessment of the tidal stream energy resource of the Aleutian Islands, Alaska via a validated barotropic tidal numerical model of the region. Eight island passes are identified as energy “hotspots”. The annual mean kinetic energy fluxes, KEF, calculated at each pass vary from 1000 to 11,000 MW, while the annual available energy, AAE, varies from 5 to 42 MWh m−2. Notable seasonal modulation to monthly power density averages and ranges are noted at some passes and not others. Seasonal adjustment is linked to the semi-annual solar declination cycle which enhances (dampens) diurnal (D1) tidal amplitudes in summer/winter (spring/fall) as well as the time-varying phase lag between D1 and semidiurnal (D2) fortnightly tidal cycles. Annual variability in monthly mean power density scales with the tidal current form factor, Fu, with the largest seasonal change occurring for Fu>1 (D1 dominated tide). The spread in power density over a month is on average smaller for passes with mixed tides (Fu=1) than those with D1 or D2 dominance, as changes to fortnightly phase lag become influential to net power density ranges when tides are mixed. This study outlines overlooked, but relevant, long-term modulation to tidal streams in regions with mixed tides.