Tidal InStream Energy Overview

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Tidal In-Stream Energy Overview
Brian Polagye EPRI PhD Fellow University of
Washington Department of Mechanical Engineering
Presented March 6, 2007 at People for Puget Sound
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Agenda

• Tidal Energy Status
• TISEC Device Overview
• TISEC in Puget Sound
• UW Research

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Past development of the tidal resource has
involved barrages
Status
Barrages - Past Development -

• Dam constructed across estuary requiring long
  construction time and large financial commitment
• Power produced by impounding tidal waters behind
  dam
• Drastically alters circulation of estuary in
  addition to attendant problems with conventional
  hydroelectric
• Low-cost power production at very large scale

250MW barrage in La Rance, France (constructed
1960)
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Present development interest is focused on
free-stream turbines
Status
Tidal In-Stream Energy Conversion (TISEC) -
Present Development -

• Turbines installed in groups allowing for more
  rapid, phased build-out
• Power produced directly from tidal currents
• Should be possible to generate power from tides
  with limited environmental impact
• Moderate-cost power production at varying scales

1.5 MW TISEC Device (Marine Current Turbines)
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TISEC looks like the wind industry about twenty
years ago
Status
State of the Industry - Device Developers -

• More than a dozen device developers
• Dominant design has yet to emerge
• Most developers are UK based due to significant
  government investment in marine renewables
• Many developers have tested small-scale models
• Laboratory and field tests to verify expected
  performance
• Difficult to address big picture questions in
  the lab
• Full-scale testing just beginning
• 300 kW turbine in water in Devon, UK for three
  years (MCT)
• 1.5 MW turbine planned for Strangford, UK in
  2006/2007 (MCT)
• 6 x 34kW turbine array permitted for East River,
  NY in 2007 (Verdant)
• kW scale ducted turbine at Race Rocks, BC (Clean
  Current)
• OpenHydro testing at EMEC (European Marine Energy
  Center) since December 2006

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Significant interest in developing this resource
in Pacific Northwest
Status
State of the Industry - Pacific NW Activities -

• Many applications have been filed for preliminary
  permits from the FERC (Federal Energy Regulatory
  Commission)
• Permit gives applicant three years to study site
  and precedence for application of full permit
• Applications from utilities (municipal utilities
  given precedence) and site developers
• Permit is needed to hook device up to grid, but
  does not authorize construction and installation.
  Subject to the same permitting requirement as any
  marine construction project.
• A number of studies have been recently carried
  out, most notably, the ERPI North American
  Feasibility Study
• 8 prospective sites in US and Canada. For
  Washington, considered Tacoma Narrows
• EPRI also recently produced a report on the
  in-stream resource in southeast Alaska
• The FERC has recently awarded a number of
  preliminary permits in Puget Sound
• Tacoma Power Tacoma Narrows (awarded early 2006)
• Snohomish PUD Deception Pass, Agate Pass, Rich
  Passage, San Juan Channel, Spieden Channel,
  Guemes Channel (awarded February 2007)
• Competing applications for development in
  Admiralty Inlet still pending decision

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Agenda

• Tidal Energy Status
• TISEC Device Overview
• TISEC in Puget Sound
• UW Research

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All turbines have a number of common components,
but many variants
TISEC Devices
Turbine Overview
Gearbox

• Increase rotational speed of shaft from turbine
• 80-95 efficient

Generator and Power Conditioning
Powertrain or Drivetrain

• Generate electricity
• Condition electricity for grid interconnection
• Turns at high RPM
• 95-98 efficient

Rotor

• Extracts power from flow
• Turns at low RPM
• Efficiency varies with flow velocity (45 max)

Foundation

• Secure turbine to seabed
• Resist drag on support structure and thrust on
  rotor

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Foundation selection is usually driven by site
water depth
TISEC Devices
Foundation Types
Monopile
Gravity Base
Heavy foundation of concrete and low cost
aggregate placed on seabed
Hollow steel pile driven or drilled into seabed

• Deep water installation feasible

Pros

• Small footprint
• Established technology used in offshore wind

Pros

• Large footprint
• Scour problems for some types of seabed
• Decommissioning problems

Cons

• High cost in deep water
• Installation expensive for some types of seabed

Cons
(10-40m)
Chain Anchors
Tension Leg
Chains anchored to seabed and turbine
Submerged platform held in place by anchored
cables under high tension

• Small footprint
• Deep water installation feasible

Pros

• Small footprint
• Deep water installation feasible

Pros

• Problematic in practice
• Device must have high natural buoyancy

Cons

• Immature technology now being considered for
  offshore wind in deep water

Cons
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Ducted turbines have been proposed to augment
power production
TISEC Devices
Power Augmentation

• Enclosing turbine in diffuser duct may boost
  power but a number of questions remain unanswered
  regarding this approach
• Is it economically justified?
• Ducts were never justified for wind turbines
• Different set of circumstances for tidal turbines
• Is there an increased hazard to marine mammals
  and fish?
• Can a large fish or mammal become trapped in the
  duct?
• Is screening of ducts feasible?

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Marine Current Turbines is furthest along in the
development process
TISEC Devices
Marine Current Turbines (MCT)
Horizontal axis (2 bladed) Planetary
gearbox Induction generator Rated from 1.2 2.5
MW
Power train
Monopile drilled or driven into seabed Two
turbines per pile
Foundation
Lifting mechanism pulls turbine out of water for
servicing
Maintenance
3 years of testing prototype in UK 1.5 MW
demonstration planned for installation in
2006/2007 Conceptual fully submerged units
Development
Large Scale (18 m diameter)
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Verdant is positioned to install the first array
of TISEC devices in the world
TISEC Devices
Verdant
Horizontal axis (3 bladed) Planetary
gearbox Induction generator Rated at 34 kW
Power train
Foundation
Monopile drilled or driven into seabed
Retrieval of power train by crane barge Divers
employed during installation
Maintenance
Small Scale (5 m diameter)
Development
Installing 6 turbines off Roosevelt Island, NY
City First turbine in water producing power
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Lunar Energy has adopted a different philosophy
with an emphasis on a bulletproof design
TISEC Devices
Lunar Energy
Horizontal axis (ducted) Hydraulic
gearbox Induction generator Rated at 2 MW
Power train
Foundation
Gravity foundation using concrete and aggregate
Heavy-lift crane barge recovers cassette with
all moving parts
Maintenance
Large Scale (21 m diameter inlet)
Tank testing Nearing end of design for first
large scale unit
Development
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GCK is developing a vertical-axis turbine
TISEC Devices
GCK (Gorlov Helical Turbine)
Vertical axis (3 bladed) Power train TBD Rated at
7 kW
Power train
TBD neutral buoyant platform proposed for
arrays, bottom mount for single units
Foundation
TBD divers?
Maintenance
Small Scale (1 m diameter)
Testing of single or multiple devices from fixed
platforms Power take-off has been problematic
Development
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Agenda

• Tidal Energy Status
• TISEC Device Overview
• TISEC in Puget Sound
• UW Research

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A number of prospective tidal energy sites have
been identified in Puget Sound
Puget Sound
Puget Sound Site Identification
Agate Passage
Guemes Channel
Spieden Channel
San Juan Channel
Deception Pass
Rich Passage
Point Wilson
Marrowstone Point
Tacoma Narrows
Bush Point
Large resource Strong currents
700 MW of tidal resources identified
Small resource Weaker currents
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Case 1 Deception Pass Exceptional resource
quality, small cross-section
Deception Pass Narrows
Siting
High Power Region
Feasible Array Layout

• 20 turbines (10 m diameter)
• Average installation depth 30m
• Exceptionally strong currents may complicate
  installation and surveys

1 km
Preliminary Array Performance

• 3 MW average electric power
• 11 MW rated electric power
• Power for 2000 homes

2 km
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Case 2 Admiralty Inlet Moderate resource
quality, large cross-section
Admiralty Inlet
Siting
Feasible Array Layout
3 km

• 450 turbines (20 m diameter)
• Average installation depth 60m
• Given lower power density can installation be
  economic?

0.9 km
Preliminary Array Performance

• 20 MW average electric power
• 68 MW rated electric power
• Power for 15,000 homes

Key Next Step

• Velocity survey of Admiralty Inlet to refine
  power estimates

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Case 3 Tacoma Narrows High resource quality,
moderate cross section
Tacoma Narrows
Siting
Bathymetry
Study Array Layout

• 64 turbines (2x18 m diameter)
• Average installation depth 56m

Point Evans Ref.
Study Array Performance
Dual Rotor Turbine Footprint

• 14 MW average electric power
• 46 MW rated electric power
• Power for 11,000 homes

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The question of where to site turbines is a
relatively complex one
Siting
Siting Decision Tree
Is there an in-stream resource?
No
Is there a low-cost interconnection point?
No
Yes
How deep is the water?
lt10m
gt60m
Yes
Are there marine construction facilities?
No
Moderate Depth
Can seabed support foundation?
No
Yes
No
Are there other stakeholders?
Potential for multiple use?
Yes
Yes
Marine traffic in area?
How much of channel occupied?
Yes
Most/All
No
Yes
OK to Build
No
Limited
Large-scale turbulence?
Yes
Environmental considerations?
No
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Environmental issues usually dominate the
discussion and the key questions may be harder to
identify, much less answer
Siting
Environmental Issues
Death of or injury to fish and marine mammals

• Will a turbine make sushi in addition to
  electricity?

Fluidic impact of energy extraction

• Will turbine operation alter sedimentation
  patterns?
• Will flow rates in the estuary be reduced?
• Will the tidal range be altered?

• Will the rotor injure or harass fish and marine
  mammals?

Local environmental degradation

• Toxicity of anti-fouling paints and lubricants?

• Does turbine operation cause acoustic harassment?

Ecological implications of fluidic impacts

• Mudflat ecosystems?
• Oxygen levels in south Sound and Hood Canal?

• How will turbine operation and installation
  affect salmon recovery?

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Agenda

• Tidal Energy Status
• TISEC Device Overview
• TISEC in Puget Sound
• UW Research

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Research Question How much tidal energy can be
extracted?
Extraction Limits - Balancing Resource Against
Fluidic Impact -
Case Study
UW Research

• How much kinetic energy can be extracted by an
  array?
• Current estimates are 15 of kinetic energy in a
  channel (little physical reasoning)
• Preliminary results indicate limits are site
  specific, but also indicate it may be possible to
  tune turbines to site to minimize impact
• Does the construction of one array preclude the
  construction of others?
• Can 20 MW arrays be built at Pt. Wilson,
  Marrowstone and Bush Point?
• Can an array be built at Admiralty Inlet if one
  already operating in Tacoma Narrows?
• Building an understanding with 1-D models
• Validating 1-D results
• 2-D modeling work planned in conjunction with
  SnoPUD

Admiralty Head
?
Point Wilson
?
Marrowstone Point
Indian Island
Bush Point
?
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