indicates anarea withalower density. with ahigherdensityoftidalflow energy, whilebluecolor Sound area are shown below. The red colorindicatesanarea velocities. Results ofcomputedenergydensityinthePuget Puget Sound area were basedondepth-averaged performed, methodology, computationsoftidalenergydensityinthe Based onnumericalmodelingresults andusingCHE circulation model. in Puget Sound, usinga3-Dimensional SELFEtidalflow on conceptualnumericalmodelingoftidalflow circulation Potential sitesfortidalpower estimateswere determinedbased Tidal PowerPotentialSites data, statisticalanalysis,andlimitednumericalmodeling. on acompilationofdatafrom NOAA buoys, processing ofthe for Tacoma PUD. Wave power estimateswere conductedbased numericalmodelingandmethodologydeveloped preliminary Tidal power estimateswere conductedusingresults of Washington. and wave energy power attheopencoastGrays Harbor, tidal energypower atspecificsites inthe Puget Sound area, (CHE) conductedapreliminarily assessmentofavailable On behalf ofSeattle CityLight, Coast&Harbor Engineering Harbor, Washington and Wave Energy Resources inGrays Energy Resources inPuget Sound Appendix of C–Assessment Tidal

Appendix C– Assessment of Tidal EnergyResources inPugetSoundand Wave Energy Resources inGraysHarbor, Washington Tidal CurrentEnergyDensity(kW-hr/year/m^2) Graph: Results ofcomputedenergydensityinPuget Sound area 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 500 C-1

Seattle City Light 2008 Integrated Resource Plan C-2 Seattle City Light 2008 Integrated Resource Plan

Appendix C– Assessment of Tidal EnergyResources inPugetSoundand of energyusingexistingtidalpower extractiontechnologies. Washington Narrows isnotsufficientforindustrialproduction In summary, available tidalpower inRosario Straight and the Rosario Strait and Washington Narrows areas. conclusions from the Tacoma Narrows studylikelyapplyto Washington Narrows are smallerthanin Tacoma Narrows, and Tacoma Narrows area. Power densitiesatRosario Strait and technology thatcaneconomicallyextracttidalpower forthe The studyconcludedthatatpresent, there isnoavailable analysis ofdeploying theturbinetoextracttidalpower. The Tacoma Narrows feasibilitystudyincludedaneconomic Narrows, wouldproduce energyequalto430,000kWh/year. The sameturbine,placedinthemostenergeticarea of Tacoma Strait isestimatedtobeapproximately 400,000kWh/year. produced by thisturbineinthemostenergeticarea ofRosario diameter turbineandeffectiveness of18%,totalyearly power diameters are intherangeof3-7meters.Assuminga5.5-meter exceed 20%. This studyalsohasrevealed thatavailable turbine that maximumeffectiveness ofexistingturbinesdoesnot Based ontheprevious Tacoma Narrows studyitwasfound evaluation oftidalpower: Washington Narrows, were analysisand selectedforfurther Rich Passage. The remaining twosites,Rosario Strait and Port Narrows, Admiralty Inlet, Deception Pass, AgatePassage, and the areas withhighdensitytidalenergyatfive sites: Tacoma Tacoma PUDandSnohomish CountyPUDcover mostof Federal EnergyCommission(FERC) Regulatory licensesto tidal flow energy were identified: analysis ofmodelingresults, seven areas withrelatively high Modeling wasconductedforathree-day period.Based on • • • • • • •

Rich Passage Agate Passage Port Washington Narrows Deception Pass Rosario Strait Admiralty Inlet Tacoma Narrows Wave EnergyResources inGrays Harbor, Washington Grays Harbor estuary, thefollowing isconcluded: Summarizing theanalysisofwave energyattheentrance tothe Wave Energy, GraysHarborEstuary energy extractiondevicesinthefuture: are recommended toconsiderinevaluation ofpossiblewave not inthescopeofthiscurrent study. The following criteria Selection andanalysisofawave energyextractiondevicewas • • • • • • •

water. At Grays Harbor entranceat depth 38metersand wave energyisconcentratedintheuppercolumnof months peryear. 5 kW/m.Periods oflow wave energymaylastforseveral wave energy periods,wave energyfluxdoesnotexceed 2- the coastline. 254,900 kWh/year perlinearmeterofshoreline along 38-meter depthcontour. This corresponds toenergyof to beapproximately 29kW/mofwave crest atthe energy fluxperlinearmeterofwave crest isestimated isquiteenergetic. estuary The annualaverage wave than 30meters. typical wave length,100-300metersandlarger. area. The area ofthedeviceshouldbecompatiblewith column. no benefitsofdeviceextendingthrough theentire water energy from theuppercolumnofwater. There are shoreline. economical toextracttheenergybelow thiselevation. upper 7-9metersofwatercolumn.It isunlikelytobe deeper, mostofthewave energyisconcentratedinthe For thedeepwater areas andbefore wave breaking depth, The wave energy ishighlytimevariable. During low In general,offshore oftheentrancetoGrays Harbor The deviceshouldoperateatdeepwater, atdepths deeper The deviceshallextractwave energyfrom alargesurface The deviceshouldbecapableeffectively extractingwave Wave energyisreduced by propagation toward the