Water Power Peer Review

1
Water Power Peer Review

• C.P. van Dam

• Active Flow Control on Bidirectional Rotors for
  Tidal MHK Applications

• University of California, Davis
• cpvandam_at_ucdavis.edu
• 26 September 2011

2
Purpose, Objectives, Integration

• Objective Design a rotor for bidirectional rotor
  tidal turbines (BRTT), with improved cost
  effectiveness via the application of microtabs
  for active aerodynamic control (AAC).
• BRTT a horizontal axis, axial flow turbine
  designed for tidal sites with currents running in
  only two prevailing directions (in 180opposition
  to each other)
• 4 - 7 less energy capture than traditional
  turbine configuration, but 7.8 - 9.6 less cost
  of energy (UK DTI)
• Aero/hydro-dynamically, bidirectional rotor and
  hydrofoils are inherently less efficient than
  conventional rotors/hydrofoils
• Microtabs small tabs that extend approximately
  normal to an airfoil/blade surface, typically
  1-2 of chord in height, with aerodynamic
  effectiveness similar to conventional flaps
• Extensive research completed for wind turbine
  applications, but mostly for load control, not
  performance enhancement

3
Purpose, Objectives, Integration

• The application of microtabs to a BRTT rotor can
  recapture some of the performance shortfall of a
  bidirectional rotor, further improving cost of
  energy.

Microtab on an 18 ellipse
Rendering of Voith Hydro Ocean Current
Technologys BRTT
4
Purpose, Objectives, Integration

• Improved cost of energy will aid technology
  adoption
• Microtab/active aerodynamic control technology
  can be applied to BRTT MHK turbines, most other
  rotor-based MHK turbines, and has synergies with
  ongoing wind power research in active load
  control
• Getting a head start on smart rotor research
  for MHK
• Wind technology is much more mature than MHK, but
  smart rotor research only began in recent years
• We have future plans for developing this concept
  with industry partnerships with the ultimate goal
  of full commercialization

5
Technical Approach

• Applying a suite of computational tools that have
  been used extensively for wind power RDD
• RANS CFD OVERFLOW
• Air/hydro-foil design XFOIL, various in-house
  tools
• BEM WT Perf, in-house tools
• etc.
• Drawing upon wind power experience, but wary of
  unique MHK phenomena
• Cavitation
• Increased soiling from biofouling
• Air-water interface
• Conducting fundamental research on active
  aerodynamic control on bluff trailing edge
  air/hydro-foils

6
Key Developments yy Hydrofoils

• We have developed a new family of hydrofoils for
  BRTT rotors
• Better performance than traditional foils such as
  ellipse or ellipse-like foils
• yy foils alone can improve BRTT performance
• Currently securing intellectual property

Blue and green are yy foils black is an 18
ellipse red is an ellipse-like foil based on the
NACA 67 series
Lift coefficient
Angle of attack, deg
Drag coefficient
Lift-to-drag ratio
7
Microtabs on Bluff Trailing Edges

• Flow physics of microtabs on bluff trailing edges
  fundamentally different than on conventional,
  sharp trailing edges
• Can have comparable effectiveness, but dependent
  on specific trailing edge geometry
• Can increase or decrease performance depending on
  baseline foil

Microtab on sharp trailing edge
Bluff trailing edge, 18 ellipse
Microtab on bluff trailing edge, 18 ellipse
8
Microtabs on yy Foils

• Microtabs improve performance of yy foils

Gray is yy foil without microtab Black is ellipse
without microtab Green, blue, and red are yy foil
with microtab at various locations near trailing
edge.
Lift coefficient
Angle of attack, deg
Drag coefficient
Lift-to-drag ratio
9
Plan, Schedule, Budget

• Schedule
• Initiation completion date October 2011
• Planned completion date June 2012
• Justification for delays
• Extensive delay in establishing contract at
  beginning of project
• Some engineering difficulties getting
  computational tools initially set up (all
  resolved and completed)
• Design of microtabs on hydrofoils on blunt
  trailing edges more coupled than expected
  (engineering issues and development paths now
  well understood)
• FY11 milestones
• Completion of literature/research review and
  survey
• Completion of design of hydrofoil with microtab
• FY12 milestones
• Completion of initial design of rotor with
  microtabs
• Completion of final design of rotor with
  microtabs
• Budget
• Unfunded, 12-month extension will be requested
  because of delays described above.

Budget History Budget History Budget History Budget History Budget History Budget History
1/1/11-3/31/11 1/1/11-3/31/11 4/1/11-6/30/11 4/1/11-6/30/11 7/1/11-9/30/11 7/1/11-9/30/11
DOE Cost-share DOE Cost-share DOE Cost-share
0 15,072 22,065 7,536 25,332 0