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

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.

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)?

Tidal Phase in Puget SoundLarge phase changes

across Admiralty Inlet and Tacoma Narrows

Large power dissipation across these sills

High velocity through narrow channels

Current Measurements

Current VelocityDoppler profiler

NNMREC Sea Spider

Sites A & B

Site FSites D & E

Near-Headland Sites (A & B)

tUtK 321

A B

5-minute average to filter most turbulence

Near-Headland Sites (D & E)

D E

Headland and Center Channel (A & F)

A F

Turbine-Adjusted Power Density

rated3rated

ratedincut

incut

21

0

UtUUUtUUtKtP

UtU

Ucut-in = 0.7 m/s

Urated = 2.0 m/s

Array Phasing: Headland – Center Channel

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)

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

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.