Tidal Hydrokinetic Energy

Brian PolagyeResearch Assistant Professor

University of Washington

SAMPE 2010SAMPE 2010May 17-20, 2010

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Tidal EnergyTidal Energy

Northwest National Marine Renewable Energy Center

Materials Suitability Materials Suitability

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Tidal Energy

Barrage Hydrokinetic

Comparable to hydroelectric

Very high cost and

Comparable to wind

Potentially lower cost andVery high cost and environmental footprint

Potentially lower cost and environmental footprint

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Tidal Hydrokinetic Devices

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“Typical” Sites and DevicesGearbox Generator Ch i hGearbox‐Generator Pile Chain Anchor

Direct Drive Generator

Drive TrainRotor 5 20 m

Tension LegGravity Base

2‐4 m/s

5‐20 m 10‐20 rpm

20‐60 m Foundation

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Tidal Energy Projects in Puget Sound

100‐200 avg. MW practically recoverable

Race RocksDemonstration turbine

p y

Marrowstone IslandDemonstration array

Admiralty InletPilot project

Demonstration array

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Local Drivers■ Initiative 937 obligations

– 15% renewable energy by 2020– 15% renewable energy by 2020

– Excludes conventional hydropower

■ Limited transmission capacity for new■ Limited transmission capacity for new wind energy

Tid l d t■ Tidal energy advantages– Predictable resource

N CO i i– No CO2 emissions

– No visual impact

– Close to load

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Tidal Energy Challenges

Technology ReadinessReadiness

Societal Concerns

iEconomic Viability

Environmental Effects

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Tidal EnergyTidal Energy

Northwest National Marine Renewable Energy Center

Materials Suitability Materials Suitability

NNMREC

Northwest National Marine Renewable Energy Center (NNMREC)

UW‐NNMRECTidal Energy

OSU‐NNMRECWave Energy

Resource and Site 

Assessment

Device and Array 

Optimization

Testing Facilities

Environmental Effects

Materials SuitabilityAssessment Optimization

8 Faculty members involved6 Graduate student researchers supported6 Graduate student researchers supported

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Resource and Site Assessment ‐ Approach

Shipboard SurveyR/V Jack RobertsonR/V Jack Robertson

Land ObservationAIS Ship Tracks

Seabed InstrumentationMeasurement Tripod

AIS Ship Tracks

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ROV Surveys

Seabed– Cobbles (10‐20cm)Cobbles (10 20cm)– Shell fragments– SpongesS ll l– Small slope

Less than 4m visibility (with lighting)

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Sea Spider Instrumentation Tripod

CTDO (conductivity, temperature, depth, 

Acoustic release (redundant recovery)

ADCP 

dissolved oxygen –partnership with WA Dept of Ecology)

( y)

(Acoustic Doppler Current Profiler) Fish Tag Recorder

(partnership with NMFS)

Hydrophone (background noise) T‐Pod/C‐Pod

(porpoise clicks)

Lead Weight(650 lbs)Programmed for 3 

month deployments

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month deployments

Challenging Research Environment

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Ferry Noise Study

Sea Spider

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Device and Array Optimization

Numerical Simulations:P ll l i l ti fParallel simulations of device and array performance

R/V Jack Robertson

Wave‐Current Flume:E i t l t diExperimental studies of device wakes

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Understanding Environmental Effects

■ Near‐field Effects

– Pressure drop (model)– Sediment transport p(model)

– Noise (experiment)

■ Far‐field Effects

id l i ( d l)– Tidal regime (model)

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Tidal EnergyTidal Energy

Northwest National Marine Renewable Energy Center

Materials Suitability Materials Suitability

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Materials Suitability

■ Hydrodynamic performance

■ Structural performance– Metal corrosionMetal corrosion– Composite aging

i i l

Orme, Masters, Griffiths (2001)

■ Long maintenance intervals– 2‐4 years for power train– 20+ years for foundation

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316 Stainless – 3 months immersion

Approaches to Minimize Biofouling

■ Biocides: “Anti‐fouling”– Effective– ToxicToxic

■ Low friction: “Foul‐release”– Cost– Long‐term effectiveness

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Shallow Water Biofouling

Clean Current turbine: 6 months deployment

Before After

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Deep Water Biofouling

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Damage: Composite Aging

■ Water absorption■ Water absorption, leading to loss of strength

I i i■ In‐situ screening tests

– 9 – 18 months exposure– Four composite material systems

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Thank You!Thank You!

More about Tidal Energy:http://depts.washington.edu/nnmrec

More about Wave Energy:http://nnmrec.oregonstate.edu/

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