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Implications of Tidal Phasing for Power Generation at a Tidal Energy Site
Brian Polagye and Jim ThomsonNorthwest National Marine Renewable Energy Center
University of Washington
Current: Resource CharacterizationApril 11, 2013
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Spatial Variability in Mean Currents
Meaningful variations in flow characteristics on spatial scales as small as 100 m
Important implications for resource assessment and power estimates
1.8±0.04 kW/m2
Admiralty Head
1.4±0.06 kW/m20.6±0.02 kW/m2
Polagye, B. and Thomson, J., 2013, “Tidal energy resource characterization: methodology and field study in Admiralty Inlet, Puget Sound, US,” Proc. IMechE Part A, J. Power and Energy, doi:10.1177/0957650912470081.
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Phase Variations
Iyer, A. S., S. J. Couch, G. P. Harrison, and A. R. Wallace. "Variability and phasing of tidal current energy around the United Kingdom." Renewable Energy 51 (2013): 343-357.
If currents are out of phase between locations, this be theoretically exploited to reduce the intermittency of power generated
Investigated on a national scale in the UK
What about phase variations on a local scale (< 10 km)?
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Tidal Phase in Puget SoundLarge phase changes
across Admiralty Inlet and Tacoma Narrows
Large power dissipation across these sills
High velocity through narrow channels
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Current Measurements
Current VelocityDoppler profiler
NNMREC Sea Spider
Sites A & B
Site FSites D & E
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Near-Headland Sites (A & B)
tUtK 321
A B
5-minute average to filter most turbulence
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Near-Headland Sites (D & E)
D E
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Headland and Center Channel (A & F)
A F
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Turbine-Adjusted Power Density
rated3rated
ratedincut
incut
21
0
UtUUUtUUtKtP
UtU
Ucut-in = 0.7 m/s
Urated = 2.0 m/s
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Array Phasing: Headland – Center Channel
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Array Phasing Potential
Thyng, K.M., 2012, “Numerical simulation of Admiralty Inlet, WA, with tidal hydrokinetic turbine siting application,” PhD dissertation, University of Washington, Seattle, Washington (USA)
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Conclusions
Large power density phase variations can occur over relatively short distances (< 10 km)
Exploiting these differences may be able to reduce the intermittency of power output from arrays at the same nominal “site”
To realize these benefits in practice, out of phase locations need to have similar power density and intermittency
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Acknowledgements
This material is based upon work supported by the Department of Energy
under Award Number DE-FG36-08GO18179.
Many thanks to Joe Talbert and Alex DeKlerk for maintaining the Sea Spider platforms over several years of deployments and to Captain
Andy Reay-Ellers for helping us put them in the right place.