1 LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu Tidal In-Stream Energy Overview Brian Polagye Research Assistant University of Washington Department of Mechanical Engineering September 11, 2006
Dec 18, 2015
1LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Tidal In-Stream Energy Overview
Brian PolagyeResearch Assistant
University of WashingtonDepartment of Mechanical Engineering
September 11, 2006
2LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Agenda
• Resource and Performance
• TISEC Devices
• Siting Arrays in Puget Sound
• UW Research
3LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Tidal power is different than other forms of renewable energy
017,09-07-06,SNOPUD.ppt
Tidal Power- Comparison to Wind -
WindWind
Resource • Driven by uneven heating of earth’s surface by sun
• Occurs throughout the world
• Driven by gravitational pull of moon and sun
• Highly localized - requiring specific tidal range and bathymetry
TidalTidal
Availability • Intermittent• Long-term predictions as good
as a weather forecast
• Intermittent• Predictable centuries in advance
Proximity to Loads
• Often distant from load centers • Often close to load centers
Resource and PerformanceResource and Performance
Maturity • Mature technology • Developing technology
4LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
There are two very different approaches to harnessing the energy of the tides
Resource and PerformanceResource and PerformanceTidal Power
- Utilizing the Resource -
016,09-07-06,SNOPUD.ppt
BarrageBarrage In-stream TidalIn-stream Tidal
• Dam constructed across estuary― High cost ($ Bn)― Long construction period (decade)
• Power produced by closing dam at high tide and allowing water to run through turbines once ocean has returned to low tide
― Completely alters estuary circulation― Power produced in twice-daily surge― All attendant problems of hydro-
electric dams
• Low-cost power production at very large scale
• Turbines installed in estuary at constrictions in groups called arrays
― Moderate unit cost ($ MM)― Short unit construction time (weeks)
• Power produced directly from tidal currents
― More continuous (but still intermittent) power production
― Smart choice of turbines and layout of arrays should avoid significant environment impact
• Moderate-cost power production at varying scales
5LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
At a very basic level, tidal currents are generated by the rise and fall of the tides – water runs downhill
Resource and PerformanceResource and PerformanceTidal Currents
015,09-07-06,SNOPUD.ppt
Seabed
Tidal Basin
Flood tide
Ocean
• Slack water― Constant water height― No velocity
• Flood Tide― Water level higher outside
estuary than in main basin― Water flows into estuary
• Ebb Tide― Water level higher in basin
than ocean― Water flows out of basin
Ebb tide
Slack water
Tidal Basin
Ocean
Water level decreasing
Water level increasing
Side ViewSide View Top ViewTop View
6LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Tidal currents vary primarily on a fourteen day lunar cycle
Resource and PerformanceResource and PerformanceTidal Cycle
014,09-07-06,SNOPUD.ppt
-4
-3
-2
-1
0
1
2
3
1-Feb 6-Feb 11-Feb 16-Feb 21-Feb 26-Feb
Date
Cu
rren
t V
eloc
ity
(m/s
)
Neap Tides (weakest)
Spring Tides (strongest)
7LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Flow power has a cubic dependence on velocity – small velocity changes have a large effect on power
018,09-07-06,SNOPUD.ppt
Device Performance- Resource Utilization -
Resource and PerformanceResource and Performance
0
200
400
600
800
1000
1200
1400
0.0 1.0 2.0 3.0 4.0 5.0
Current Velocity (m/s)
Pow
er (
kW
)
Fluid Power
Electric Power
0
1000
2000
3000
4000
5000
6000
7000
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9000
0:00 4:48 9:36 14:24 19:12 0:00
Time
Pow
er (
kW
)
Fluid Power
Electric Power
Device PerformanceDevice Performance Representative DayRepresentative Day
Rated Speed
Cut-in Speed
Area Velocity Density 2
1 3 xxx
8LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Power generation varies day-to-day, but is consistent on a monthly basis and shows no seasonal dependency
019,09-07-06,SNOPUD.ppt
Device Performance- Variable Predictability -
Resource and PerformanceResource and Performance
0
50
100
150
200
250
300
350
400
450
500
1/1 2/20 4/11 5/31 7/20 9/8 10/28 12/17
Date
Ave
rage
Pow
er (
kW
)
Daily AverageDaily Average
0
50
100
150
200
250
Jan
Feb
Mar
Apr
May Ju
n
Jul
Aug
Sep Oct
Nov
Dec
Month
Ave
rage
Pow
er (
kW
)
Monthly AverageMonthly Average
9LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Agenda
• Resource and Performance
• TISEC Devices
• Siting Arrays in Puget Sound
• UW Research
10LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
All turbines have a number of common components, but many variants
TISEC DevicesTISEC DevicesTurbine Overview
009,09-07-06,SNOPUD.ppt
Rotor• Extracts power from flow• Turns at low RPM• Efficiency varies with flow
velocity (45% max)
Gearbox• Increase rotational speed of shaft
from turbine• 80-95% efficient
Foundation• Secure turbine to seabed• Resist drag on support structure
and thrust on rotor
Generator and Power Conditioning
• Generate electricity• Condition electricity for
grid interconnection• Turns at high RPM• 95-98% efficient
Powertrain or Drivetrain
11LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Two basic types of rotors have been developed – horizontal axis and vertical axis
TISEC DevicesTISEC DevicesRotor Variants
013,09-07-06,SNOPUD.ppt
Horizontal AxisHorizontal Axis Vertical AxisVertical Axis
Gearbox and Generator
Gearbox and Generator
12LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Ducted turbines have been proposed to augment power production
TISEC DevicesTISEC DevicesPower Augmentation
012,09-07-06,SNOPUD.ppt
• Enclosing turbine in diffuser duct boosts power
• 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?
13LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Foundation selection is usually driven by site water depth
TISEC DevicesTISEC DevicesFoundation Types
010,09-07-06,SNOPUD.ppt
Monopile
• Small footprint• Established technology used
in offshore wind
Gravity Base
Chain Anchors Tension Leg
Hollow steel pile driven or drilled into seabed
Pros:
• High cost in deep water• Installation expensive for
some types of seabed
Cons:
Heavy foundation of concrete and low cost aggregate placed on seabed
• Deep water installation feasible
Pros:
• Large footprint• Scour problems for some
types of seabed• Decommissioning problems
Cons:
• Small footprint• Deep water installation
feasible
Chains anchored to seabed and turbine
Pros:
• Problematic in practice• Device must have high
natural buoyancy
Cons:
Submerged platform held in place by anchored cables under high tension
• Small footprint• Deep water installation
feasible
Pros:
• Immature technology now being considered for offshore wind in deep water
Cons:
(10-40m)
14LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
TISEC DevicesTISEC DevicesMaintenance Options
011,09-07-06,SNOPUD.ppt
• Marine intervention extremely costly and must be minimized if TISEC devices can hope to compete economically
• All device developers pursuing low-maintenance philosophies
Divers
Device Retrieval Integrated Lift
Divers service turbine
• Divers widely availablePros:
• Difficult to work underwater• Very high intervention cost• In deep water, dive time
measured in minutes per day
Cons:
• Less costly than divers• Deep water feasible
Crane barge mobilized to retrieval entire turbine
Pros:
• High cost to mobilize heavy-lift crane barge
Cons:
Lifting mechanism integrated directly into turbine support structure
• Maintenance without specialty craft
• Deep water feasible
Pros:
• Cost of lifting mechanism• Support structure may be
surface piercing (aesthetic and shipping concerns)
Cons:
15LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Marine Current Turbines is furthest along in the development process
TISEC DevicesTISEC DevicesMarine Current Turbines (MCT)
002,09-07-06,SNOPUD.ppt
Power trainPower train
FoundationFoundation
MaintenanceMaintenance
DevelopmentDevelopmentLarge Scale
(18 m diameter)Large Scale
(18 m diameter)
Horizontal axis (2 bladed)Planetary gearboxInduction generatorRated from 1.2 – 2.5 MW
Monopile drilled or driven into seabedTwo turbines per pile
Lifting mechanism pulls turbine out of water for servicing
3 years of testing prototype in UK1.5 MW demonstration planned for
installation in 2006/2007Conceptual fully submerged units
16LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Verdant is positioned to install the first array of TISEC devices in the world
TISEC DevicesTISEC DevicesVerdant
002,09-07-06,SNOPUD.ppt
Power trainPower train
FoundationFoundation
MaintenanceMaintenance
DevelopmentDevelopment
Monopile drilled or driven into seabed
Retrieval of power train by crane bargeDivers employed during installation
Small Scale (5 m diameter)Small Scale (5 m diameter)
Horizontal axis (3 bladed)Planetary gearboxInduction generatorRated at 34 kW
Installing 6 turbines off Roosevelt Island, NY City (Starting mid-Sept)
First permitted test project in US
17LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Lunar Energy has adopted a different philosophy with an emphasis on a “bulletproof” design
TISEC DevicesTISEC DevicesLunar Energy
001,09-07-06,SNOPUD.ppt
Power trainPower train
FoundationFoundation
MaintenanceMaintenance
DevelopmentDevelopment
Large Scale (21 m diameter inlet)
Large Scale (21 m diameter inlet)
Horizontal axis (ducted)Hydraulic gearboxInduction generatorRated at 2 MW
Gravity foundation using concrete and aggregate
Heavy-lift crane barge recovers “cassette” with all moving parts
Tank testingNearing end of design for first large
scale unit
18LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Agenda
• Resource and Performance
• TISEC Devices
• Siting Arrays in Puget Sound
• UW Research
19LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Environmental issues are probably the biggest unknown for siting arrays of tidal in-stream turbines
007,09-07-06,SNOPUD.ppt
Case StudyCase StudySitingSiting
Environmental Issue
Environmental Issue Key QuestionsKey Questions Answers (so far)Answers (so far)
Direct “impact” of turbine on marine life
• Will a turbine make sushi in addition to electricity?
• No. Maximum tip velocity limited by cavitation. (~10 RPM for large turbines)
Indirect impacts • Developers are testing inert, glass-based anti-fouling paints to minimize this impact.
• Will anti-fouling paints used on turbines and supports degrade environment?
Environmental Issues- Marine Life Considerations -
• Will the rotor injure or harass fish and marine mammals?
• Unknown. Considerable cost and effort being expended by developers to prove technology is benign. No Altamont Passes.
• How much of the seafloor will be disturbed during installation?
• Depends on type of foundation and construction techniques. Choices will be driven by site depth and local concerns.
• Not in large quantities, but developers are working to minimize any leakage.
• Will oils and lubricants leak from the turbine?
20LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu 008,09-07-06,SNOPUD.ppt
Case StudyCase StudySitingSitingEnvironmental Issues
Effect of energy extraction on the environment
• What is the effect of energy extraction?
• Altered circulation in estuary• Effects complicated and counter-
intuitive― Velocity increases downstream of
an array and water depth decreases― Overall flow rates are reduced
Environmental Issue
Environmental Issue Key QuestionsKey Questions Answers (so far)Answers (so far)
• How much energy can be extracted without substantially altering circulation?
• Rough estimates. 15% of the kinetic energy in a channel used as placeholder in resource studies.
― Overly conservative in some cases, overly optimistic in others.
― Question needs to be addressed on a case-by-case basis
21LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
In addition to environment, a number of factors need to be considered when siting turbine arrays. Most have not yet been addressed for sites in Puget Sound.
005,09-07-06,SNOPUD.ppt
Case StudyCase StudyArray Siting Issues- General -
SitingSiting
IssueIssue Key QuestionsKey Questions StatusStatus
Resource Size and Quality
• How large is the extractable resource?
• How many turbines in an array?
• Preliminary estimates using NOAA single-point current predictions
• Next Step: Current measurements
Electrical Infrastructure
• Will new transmission lines need to be built?
• What local loads exist?
• Not yet determined – requires consultation with local utilities
Bathymetry and Seabed Geology
• What foundation types are suitable for water depth?
• What foundations can seabed support?
• Not yet determined – requires geologic survey
Port Facilities • Are there local marine contractors capable of performing installation and maintenance of an array?
• Not an issue in Puget Sound for most types of construction
22LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
And the list goes on…
006,09-07-06,SNOPUD.ppt
Case StudyCase StudySitingSiting
IssueIssue Key QuestionsKey Questions StatusStatus
Shipping Traffic
• What is the maximum draft of shipping traffic in channel?
• Not yet determined – requires consultations with marine exchange and Coast Guard
Large-scale Turbulence
• Not yet determined – requires consultations with oceanographic experts
Multiple Use • How is the site currently used?• Does the site overlap with
major recreation or fishing areas?
• Not yet determined – requires consultations with regional stakeholders
Economics • Will turbines produce cost-effective power?
• Tacoma Narrows study predicted a cost of energy of ~10 cents/kWh
• Next step: Feasibility study
• Are there local geographic features that would give rise to large-scale eddies?
Array Siting Issues- General -
23LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
There are a number of prospective tidal energy sites in Puget Sound
020,09-07-06,SNOPUD.ppt
Puget Sound Resource Study- Overview - SitingSiting
Spieden Channel
San Juan Channel Deception
Pass
Admiralty Inlet
Agate Passage
Rich Passage
Guemes Channel Site Power Density
(kW/m2)Resource
(MW)Depth
(m)
• Tacoma Narrows
• Admiralty Inlet―Point Wilson―Marrowstone―Bush Point
• Deception Pass―Deception Pass―Yokeko Point
• Guemes Channel
• Bainbridge Island―Agate Passage―Rich Passage
• San Juan Islands―San Juan Channel―Spieden Channel
1.7
5.50.4
1.5
1.50.9
0.60.60.4
0.60.6
106
263
35
39
167195132
4556
40
3016
14
615
607175
6369
Tacoma Narrows estimated COE ~10 cents/kWh. Other sites?
24LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
San Juan Channel represents a substantial resource, but the channel is quite deep
024,09-07-06,SNOPUD.ppt
San Juan Channel- Overview - SitingSiting
Preliminary Array LayoutPreliminary Array Layout
Preliminary Array Performance
Preliminary Array Performance• 116 turbines (20 m diameter)
• Average installation depth ~95m • 5 MW average electric power• 16 MW rated electric power• 39,900 MWh annual generation
0.6 kW/m2
Turbine + Lateral Spacing
Turbine + Lateral Spacing
Preliminary Turbine Layout
Preliminary Turbine Layout
0.8 km (0.5 mi)
San Juan Channel Ref.
San Juan Channel Ref.
25LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Spieden Channel also represents a substantial resource, but is again a deep water channel
025,09-07-06,SNOPUD.ppt
Spieden Channel- Overview - SitingSiting
Preliminary Array LayoutPreliminary Array Layout
Preliminary Array Performance
Preliminary Array Performance
• 168 turbines (20 m diameter)• Average installation depth ~83m
• 8 MW average electric power• 26 MW rated electric power• 62,700 MWh annual generation
0.6 kW/m2
Limestone Point Ref.
Limestone Point Ref.
Turbine + Lateral Spacing
Turbine + Lateral Spacing
Preliminary Turbine Layout
Preliminary Turbine Layout
1 km (0.6 mi)
26LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Agenda
• Resource and Performance
• TISEC Devices
• Siting Arrays in Puget Sound
• UW Research
27LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Question 1: How much tidal energy can be environmentally extracted?
003,09-07-06,SNOPUD.ppt
Case StudyCase StudyExtraction Limits
- Balancing Resource Against Environmental Impact -UW ResearchUW Research
Admiralty Head
Point Wilson
Bush Point
Marrowstone Point
Indian Island
• How much kinetic energy can be extracted by an array?
― Current estimates are 15% of kinetic energy in a channel (little physical reasoning)
― Probably much more site specific and closely related to frictional losses in channel
• 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― Very interesting preliminary results― Will be expanding to 2-D and 3-D cases
?
?
?
28LABORATORY FOR ENERGY AND ENVIRONMENTAL COMBUSTION http://www.energy.washington.edu
Question 2: How tightly can turbines in an array be packed?
004,09-07-06,SNOPUD.ppt
Case StudyCase StudyArray Packing
- Most Economic Use of Resource -UW ResearchUW Research
• Regions of high power flux may be relatively short and narrow
San Juan Island
Lopez Island
Low Power Density
High Power
Density
Low Power Density
• How close is too close?― Since flow is bi-directional, wind
turbine spacing rules are probably too conservative
― Downstream turbines must be beyond wake of upstream turbines
― Wakes degrade performance and accelerate metal fatigue
• Approaching with a combination of analytical and computational tools
― Little or no physical data available (since no arrays operating)
― Plan to leverage results of CFD modeling to suggest “engineering rules” for array layouts
• Economic reasons to site as many turbines in high power density regions as possible