Water Power Peer Review

1 | Program Name or Ancillary Text eere.energy.gov

Water Power Peer Review

2.1.3: Effects on Physical Systems Dr. Zhaoqing Yang

Pacific Northwest National [email protected] 206-528-3057November 3, 2011

Development of an MHK Model for the Assessment of In-stream Energy

Removal and Environmental Effects

2 | Wind and Water Power Program eere.energy.gov

Purpose, Objectives, & Integration

Extraction of in-stream energy needs state-of-the-art numerical models to enhance our understanding

— Resource characterization – maximum energy potential

— Technology and environmental barriers

— Processes at various spatial and temporal scales

Development of an MHK model to assess— Resource characterization

— Effects on physical environment at local and system wide scales

— Optimal siting and array configuration

Results of the MHK model can be used for— Categorizing and evaluating effects of stressors

— Assessing environmental risks to aquatic biota and habitats


Technical Approach

3D Finite Volume Coastal Ocean Model (FVCOM)— Unstructured grid – well suited for complex geometry and various scales

— Parallel computing – large domain and number of tidal turbines

— Water quality

— Sediment transport

— WRF met forcing

— Coupled SWAVE

— Public domain

Cell size ~ 15m

Velocity Field

Turbines


Technical Approach

Momentum sink approach (retarding force)

Modification of momentum governing equations

Turbine representation

— Turbine blades

— Supporting structures

— Turbine foundations

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Technical Approach

Validation to analytical solution (2D mode) Idealized tidal channel and bay with

realistic dimensions and forcing

Open boundary M2 tide (2m range)

User-friendly MHK parameter input

— Turbine elevation from seabed

— Turbine diameter

— Turbine thrust coefficient

— Turbine blade drag coefficient

— Areas of supporting poles and base

— Drag coefficients for poles and base

Open Water Channel Dimension (m) Basin Dimension (m) River Flow

Depth (m) Length Width Depth Length Width Depth (m3/s)

200 30,000 6,000 60 150,000 20,000 100 1,350


Plan, Schedule, & Budget

Schedule Initiation date: October 1, 2009 Milestones:

— FY10 Q2: Refinement/validation of Puget Sound models— FY10 Q4: Online dissemination of model results for the real-time Puget Sound Operational

Forecast System (PS-OPF)— FY11 Q2: MHK model development— FY11 Q3: MHK model validation— FY11 Q4: Analysis of effects on flux, flushing, and array configurations

Plan Planned completion date: September 30, 2012 Analysis of MHK effects on water quality, sediment transport and food web

Budget

Budget History

FY2009 FY2010 FY2011

DOE Cost-share DOE Cost-share DOE Cost-share

$275K $0 $90K $0 $155K $0


Accomplishments and Results

• MHK model results agree well with analytical solution– Diminishing return of extractable

power occurs when volume flux reduces by 42%

• MHK model is also validated with widely used bottom drag approach in 2-D mode

Tidal currents without turbines

Reduced current speed with turbines

Number of Turnbine per Grid Cell

0 20 40 60 80 100

Vol

umn

Flu

x R

atio

(%

)

0

20

40

60

80

100

120

Ext

ract

able

Pow

er (

MW

)

0

1000

2000

3000

4000

5000

6000

Volume Flux PercentageExtractable Power

Maximum Power

42% Reduction

Flood Tide Flood Tide



• Three-dimensional effects– Volume flux reduction at maximum extractable power is smaller in 3D

than that in 2D mode– Maximum extractable power varies with turbine height due to 3D

structure of velocity profiles

Number of Turnbine per Grid Cell

0 20 40 60 80 100

Vol

umn

Flu

x R

atio

(%

)

0

20

40

60

80

100

120

Ext

ract

able

Pow

er (

MW

)

0

1000

2000

3000

4000

5000

6000

Volume Flux PercentageExtractable Power

Extractable Power and Volume Flux Reduction in 3D mode

Maximum Power

33% Reduction

Velocity Profiles vs. Turbine Height

0

10

20

30

40

50

60

0 0.5 1 1.5 2 2.5 3 3.5 4

Dep

th (m

eter

)

Along Channel Velocity during Flood (m/s)

No Turbine58.6 m55.7 m52.9 m50 m47.1 m44.3 m41.4 m38.6 m35.7 m32.9 m30 m27.1 m24.3 m21.4 m18.6 m15.7 m12.9 m10 m7.1 m4.3 m1.4 m

No Turbine

Turbine Location



• MHK effects on flushing time of the bay– Model results show that MHK devices have greater effect on the

relative change in flushing time than the change in volume flux– Relative change of flushing time increases exponentially as a function

of percentage reduction of the volume flux

0

50

100

150

200

250

300

350

0 10 20 30 40 50

Flus

hing

Tim

e (d

ays)

Number of Turbines

Flushing Time vs. Number of Turbines

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30 35

Flus

hing

Tim

e In

crem

ent (

%)

Flow Reduction (%)

Flushing Time Increment vs. Flow Reduction



• Effects of different array configurations “Optimal” vs. practical constraints Placement of turbines in the channel Extracted power, volume flux, flushing time, etc.

Velocity for MHK Center Configuration

Dye concentration for center configuration (408 turbines)

Extracted power:207 MW

Dye concentration for side configuration (408 turbines)

Extracted power:171 MW

Velocity for MHK Side Configuration



• The MHK model can be applied to river and ocean current environments– Cumulative effect and interaction of multiple projects

– Change of hydrodynamic conditions at local and system scales

• Model setup for an idealized river connected to a bay– Bay depth = 200m; length = 100km; width = 750m; slope = 5x10-4

– Forcing: M2 tide (1.0m tidal range); river flow = 15,000 m3

– Grid size varies from 36 m (river) to 580 m (bay)

– 10 projects along the river with 90 turbines per project

River inflow

Tide

Bottom elevation = 50m



• MHK effects at local and system scales– Slow down the river

– Increase water level

– Local variations

Water Depth (m) Without Turbine

With Turbine

Velocity (m/s) Without Turbine

With Turbine

Downstream Upstream

8.36

8.38

8.40

8.42

8.44

8.46

8.48

-6000 -4000 -2000 0 2000 4000 6000

Wat

er D

epth

(m

)

Distance from Center of Turbine Array (m)

Longitudinal Water Depth ProfileWithout Turbine With Turbine

1.96

1.98

2.00

2.02

2.04

2.06

2.08

-6000 -4000 -2000 0 2000 4000 6000

Ve

loci

ty (

m/s

)

Distance from Center of Turbine Array (m)

Longitudinal Velocity ProfileWithout Turbine Between Turbine Array Align with Turbine Array


Challenges to Date

Further model validation and application— Long-term physical and biogeochemical data with MHK devices installed

— Tidal turbine parameterizations (collaboration with developers)

— Model simulations in real world, even pilot-scale study (e.g., Puget Sound)

Need of theoretical analysis— Alternative for model validation

— General guidance to the relationship between energy extraction, turbine size, circulation and transport processes

Balancing energy extraction and environmental effects

— Integration of other environmental stressors

— Regulatory criteria for environmental impactsPredicted tidal currents with PNNL Puget Sound model


Next Steps (FY12)

Modeling analysis of MHK effects on water quality— Development of a generic, good baseline condition of water quality model

— Realistic atmospheric forcing, heat flux and boundary conditions

— Simulation of salinity, temperature, and algal/nutrient dynamics

— Long-term simulations (seasonal variations) – high performance computing

MHK effects on sediment transport and food web— Analysis of MHK effects on relative changes of deposition/erosion patterns

— Food web – what is the main physical driving force, temperature?

Future research— Modeling analysis in the real world (tides and river)

Hydrodynamics (far-field effects: tide flats)

Water quality – mixing and hypoxia

— Ocean currents (FVCOM in modeling test bed project for Gulf of Mexico)

Water Power Peer Review

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