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

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					Water Power Peer Review




     Development of an MHK Model for the
       Assessment of In-stream Energy
      Removal and Environmental Effects



                                     Dr. Zhaoqing Yang
2.1.3: Effects on Physical Systems   Pacific Northwest National Laboratory
                                     zhaoqing.yang@pnnl.gov 206-528-3057
                                     November 3, 2011


1 | Program Name or Ancillary Text                                    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



2 | Wind and Water Power Program                                             eere.energy.gov
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                                              Cell size ~ 15m

      — Sediment transport
      — WRF met forcing
      — Coupled SWAVE
      — Public domain

                       Turbines




           Velocity Field

3 | Wind and Water Power Program                                              eere.energy.gov
Technical Approach

Momentum sink approach (retarding force)
 Modification of momentum governing equations
        u    u    u    u          1 P         u 
           u    v    w     fv             Km      Fu  FMHK u
        t    x    y    z           o x z     z 

       v    v    v    v          1 P         u 
          u    v    w     fu             Km      Fv  FMHK v
       t    x    y    z           o y z     z 
 Turbine representation
                                          1               
       — Turbine blades            S1     (CT  Cb ) Ab u u
                                          2
                                          1       
       — Supporting structures     S 2   C p Ap u u
                                          2
       — Turbine foundations              1        
                                   S3   C f A f u u
                                          2

4 | Wind and Water Power Program                                           eere.energy.gov
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 F
              Depth (m)            Length    Width      Depth   Length     Width     Depth            (m3/
                  200              30,000     6,000       60    150,000    20,000     100              1,35
5 | Wind and Water Power Program                                                            eere.energy.gov
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

6 | Wind and Water Power Program                                                                      eere.energy.gov
Accomplishments and Results

• MHK model results agree
                                                                     6000                                                            120

  well with analytical solution                                      5000
                                                                                                 Maximum Power
                                                                                                                                     100

      – Diminishing return of extractable




                                            Extractable Power (MW)




                                                                                                                                           Volumn Flux Ratio (%)
                                                                     4000                                                            80
        power occurs when volume flux                                                                    42% Reduction
                                                                     3000                                                            60
        reduces by 42%
                                                                     2000                                                            40

• MHK model is also validated                                        1000
                                                                                     Volume Flux Percentage
                                                                                     Extractable Power                               20

  with widely used bottom                                              0                                                             0

  drag approach in 2-D mode                                                 0   20             40             60
                                                                                     Number of Turnbine per Grid Cell
                                                                                                                        80        100




                           Flood Tide                                                       Flood Tide



                       Tidal currents                                                 Reduced current
                      without turbines                                               speed with turbines


7 | Wind and Water Power Program                                                                                             eere.energy.gov
   Accomplishments and Results

• 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
                                                                                                                                     Velocity Profiles vs. Turbine Height
                                    Extractable Power and Volume Flux
                                                                                                                            60
                                           Reduction in 3D mode                                                                       No Turbine
                         6000                                                 120                                                     58.6 m
                                                                                                                                      55.7 m
                                                                                                                            50
                                                Maximum Power                                                                         52.9 m
                                                                                                                                      50 m
Extractable Power (MW)




                                                                                    Volumn Flux Ratio (%)
                         5000                                                 100                                                     47.1 m
                                                                                                                                      44.3 m
                                                                                                                            40        41.4 m




                                                                                                            Depth (meter)
                         4000                                                 80                                                      38.6 m
                                                                                                                                      35.7 m        Turbine
                                                                                                                                      32.9 m
                                                                                                                            30        30 m
                                                                                                                                                   Location
                         3000                                                 60                                                      27.1 m
                                        33% Reduction                                                                                 24.3 m
                                                                                                                                      21.4 m
                                                                                                                            20        18.6 m
                         2000                                                 40
                                                                                                                                      15.7 m
                                                                                                                                      12.9 m
                                              Volume Flux Percentage                                                                  10 m                                             No Turbine
                         1000                 Extractable Power               20                                            10        7.1 m
                                                                                                                                      4.3 m
                                                                                                                                      1.4 m
                            0                                                 0                                              0
                                0        20          40         60     80   100                                                  0     0.5         1      1.5      2      2.5      3        3.5      4
                                        Number of Turnbine per Grid Cell                                                                       Along Channel Velocity during Flood (m/s)


8 | Wind and Water Power Program                                                                                                                                                        eere.energy.gov
Accomplishments and Results

• 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


                                    Flushing Time vs. Number of Turbines                                             Flushing Time Increment vs. Flow Reduction
                          350                                                                                  700

                          300                                                                                  600




                                                                                 Flushing Time Increment (%)
                          250                                                                                  500
   Flushing Time (days)




                          200                                                                                  400

                          150                                                                                  300

                          100                                                                                  200

                          50                                                                                   100

                           0                                                                                     0
                                0       10        20           30      40   50                                       0     5     10       15      20     25   30     35
                                                 Number of Turbines                                                                   Flow Reduction (%)



9 | Wind and Water Power Program                                                                                                                              eere.energy.gov
Accomplishments and Results

• Effects of different array configurations
        “Optimal” vs. practical constraints
        Placement of turbines in the channel
        Extracted power, volume flux, flushing time, etc.
                                                      Extracted                                  Extracted
                                                       power:                                     power:
                                                       207 MW                                     171 MW




                                    Dye concentration for center               Dye concentration for side
                                    configuration (408 turbines)              configuration (408 turbines)




                Velocity for MHK Center Configuration              Velocity for MHK Side Configuration
10 | Wind and Water Power Program                                                                  eere.energy.gov
Accomplishments and Results

• 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


                   Tide

                                                                              River inflow


                                                                              Bottom
                                                                          elevation = 50m

11 | Wind and Water Power Program                                               eere.energy.gov
Accomplishments and Results

• MHK effects at local                                                                Longitudinal Velocity Profile

  and system scales                                           2.08
                                                                         Without Turbine      Between Turbine Array        Align with Turbine Array

                                                              2.06




                                           Velocity (m/s)
       – Slow down the river                                  2.04
                                                              2.02

       – Increase water level                                 2.00
                                                              1.98


       – Local variations                                     1.96
                                                                 -6000       -4000         -2000         0             2000          4000         6000
                                                                                 Distance from Center of Turbine Array (m)

                                                                                            Without Turbine
                Velocity (m/s)      Downstream                                                                                                               Upstream
                                                                                             With Turbine

                                                                                      Longitudinal Water Depth Profile
                                                                                            Without Turbine           With Turbine
                                                              8.48
                                            Water Depth (m)

                                                              8.46
                                                              8.44
                                                              8.42
                                                              8.40
                                                              8.38
                                                              8.36
                                                                 -6000        -4000        -2000         0             2000          4000             6000
                                                                                 Distance from Center of Turbine Array (m)

                                                                                             Without Turbine
            Water Depth (m)
                                                                                                   With Turbine

12 | Wind and Water Power Program                                                                                                                            eere.energy.gov
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 impacts
                                                                Predicted tidal currents with
                                                                PNNL Puget Sound model
13 | Wind and Water Power Program                                                     eere.energy.gov
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)

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

				
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posted:9/13/2012
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