Hydrokinetic Power in Navigable WaterwaysWilliam H. McAnallyNorthern Gulf Institute

Sandra L. Ortega-Achury and James L. MartinCivil and Environmental Engineering

Mississippi State University

Trey E. Davis and Jeff LillycropU.S. Army Engineer Research and Development Center

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In-stream Hydrokinetic Electric Power

• Turbines capturing the energy of naturally flowing water – stream flows, tidal flows, or wave motion – without impounding the water.

• Devicesplaced in tidal waters and non-tidal rivers

(Source: Bedard et al., 2006)

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Power Generation

Power generated proportional to the velocity cubed

(Source: Hydropower Reform Coalition, 2008)

(Courtesy: Hydro Green Energy)

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FERC Permits

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Hydrokinetics: Pro

• Potential for adding 25K-30K MW to U.S. generating capacity

• Requires no new impounding dams• Operations do not contribute to greenhouse

gas emissions or other air pollution • Aesthetically preferred to wind farms• Contribute to energy independence

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Hydrokinetics: Concerns

• Cost effective?• Construction & Maintenance Impacts• Potential effects on:– Physical environment – water level, flow, water

quality, sedimentation– Navigation – safety and efficiency– Biotic environment – fish, migration, habitat

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Physical Environment Example: Hypothetical WaterwayMass & Energy Conservation Eqns

Variable ValueDischarge 10,000 m3/secRoughness Coefficient, n 0.025Length of Channel 2,000 mBottom Slope 0.0001KE Coefficient 1Channel Width 2,000 mTailwater Depth Fixed 3 mExtraction Loss Fraction 0 to 30 %

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Extraction of 10% KEOne Cross-Section

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Extraction of Various KE at 8 Cross-Sections:

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Physical Environment Effects

Hydrokinetic generators in tidal and non-tidal rivers can cause (positive or negative impacts):• Decreased flow speeds• Altered water levels• Increased sediment deposition in the vicinity• Altered salinity intrusion• Altered water quality• Altered transport patterns and habitats• Scour around the structures

Precise resolution of effects must be addressed by multi-dimensional numerical site-specific models.

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Direct Navigation EffectsProbability of Vessel Strike

Vessel

Probability Distribution of Vessel Path

X-Section View of Channel

Distorted Horizontal Scale

Area = Probability of right side excursion

Defined ChannelHydrokinetic Installation Locations

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Some Historical Data• 936 vessel accidents in the Lower Mississippi

River 1979 thru 1987: 207 collisions, 422 rammings, 297 groundings and 10 unknown.*

• Equals 0.32 Out-of-Channel accidents/channel mile-year

• Applicable to hydrokinetic structure collisions?* Blanc and Rucks (1996) Courtesy aolnews.com 2010

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Simulated Vessel Passes Thru TurnCorps of Engineers Simulator

Can be used to generate vessel excursion probabilities.

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Conclusions• Hydrokinetic power offers a significant contribution to U.S.

electricity needs. • Do not contribute to greenhouse gas emissions and have less

visual aesthetic impact than wind turbines.• Benefit to cost ratio for power companies can be calculated.• B/C ratio of hydrokinetic installations on public-interest

include:– Decreased flow speeds & altered water levels – Localized bed scour & far field sediment deposition– Altered salinity intrusion in estuaries – Altered water quality– Altered habitats– Vessel accidents in navigation channels

• These cumulative changes plus site conditions will dictate whether a specific hydrokinetic generator is in public interest.

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Interested?

ASCE Coasts, Oceans, Ports and Rivers Institute• Marine Renewable Energy Committee – Bil

Stewart, Chair– MRE In-Stream Hydrokinetic Sub-committee – Jim

VanZwieten, Jr., Chair• Waterways Committee – Kelly Barnes, Chair– Navigation Engineering Sub-Committee – Bill

McAnally, Chair

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Contact Information

William H. McAnallymcanally@cee.msstate.edu