Group 4 – Marine Energy

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Group 4 Marine Energy
Project Definition
Marine Current Resource and Technology Matching

• Investigate the characteristics of the tidal
  resources in Scotland and demonstrate how to
  match those resources with the appropriate Marine
  current technology

• James Glynn
• Kirsten Hamilton
• Tom McCombes
• Malcolm MacDonald

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Project Flowchart
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A. Resource Investigation - Summary
Sites Mapped

• Pentland Firth
• Orkney Isles
• Butt of Lewis
• Sound of Harris
• Barra Sound, South Uist
• Barra Head, South Uist
• Head of Ardmurchán
• Tiree Coll
• Firth of Lorne, Mull
• Strait of Islay Jura
• West Bank Islay
• Middle Bank, Islay
• Kildonan Pt, Arran
• Mull of Kintyre

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Mapping Method
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Velocity Distribution Model TOMS

• Bathymetric profiles (channel cross-sections)
  from mapping data is inserted into TOMS software,
  Topological Oceanographic Modelling for Shear.
• This provides shear profiles of flow having
  inserted values for surface flow and roughness
  coupled with Mannings equation.
• The shear profiles enable the velocity profiles
  for sites of varying cross-section to be
  calculated
• A simple tool to quickly assess the effect the
  topography of a sites affects the velocity of the
  flow

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Velocity Distribution Model TOMS
Computational Model Update

• Mapped profile
• Horizontal shear influence on velocity
• Vertical shear influence on velocity
• Overall velocity profile

• Model currently being applied to various areas in
  the west of Scotland
• Also being validated against known results such
  as Straits of Messina, currently shows good
  correlation
• Next step is to include seabed roughness and
  shoreline effects
• Next week we hope to conclude resource model,
  show results and use it to develop matching
  methodology

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B. Technology InvestigationContinued
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Horizontal Axis Turbine Model

• Able to predict
• Blade element forces and moments
• Blade element performance
• Thus
• Torque, power, thrust and loading of device
• Device efficiency
• For
• Plain, common-or-garden free flow turbines
• Co-axial, contra-rotating
• Shrouded (ducted fan) type MCTs
• In
• Uniform non-uniform flow normal and yawed to
  the disk plane

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Oscillating Hydrofoil Model

• Predict system forces
• Specified foil geometry
• Optimum angle of attack
• Balanced arm Vs foil design
• Resolve system forces
• Torque
• Sinusoidal angular velocity
• Cyclic power output profile
• Dual Foil Generation
• Out of phase cycle
• Constant power profile
• Neutral vertical lift

• Standard NACA 0015 Airfoil Section
• Symmetrical Profile
• High Lift, Low Drag

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Environmental Agencies Impact

• A part of the project is to identify a generic
  proposal structure that would incorporate the
  necessary information for all the agencies
  concerned
• Found their relevant literature or contacted them
• Will help us compile criteria of importance for
  developers, as an initial aid
• At first glance, appears that consent process
  between relevant bodies quite convoluted
  authority/overlap unclear
• On further inspection, doesnt get better
• Some potential developers gone elsewhere for
  easier life.. Iceland, Norway.
• Some employees we spoke to agreed more
  standardisation across the board was required
• At least 6 distinct groups that require a part in
  the consultation process. Brief rundown

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Agencies and their Roles
Scottish Environmental Protection Agency
Environmental Concerns EIA MOD MOD fully
reflects the Governments policies on
Sustainable Development In total, the estate
comprises some 240,000 hectares (ha) with over
4,000 sites an area equivalent to about one per
cent of the UK landmass Submarine testing areas
etc, of which there are many Scottish Natural
Heritage Provides Government advice- enables
energy policy to account for natural
heritage Detailed advice is limited - early
stages of technology development Outwith areas
of high scenic or marine wildlife value, tidal
stream generators may offer the potential to
generate electricity with lower
impacts.. Assessment on marine impact on going.
Highest velocity streams off limits Many Scottish
estuaries wildfowl, land or intertidal areas
designated SPAs/ SACs
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Agencies and their Roles

• Crown Estate
• Own waters to territorial limits 12nm, and to
  continental shelf 200nm
• Rents/leases sites and grants licenses.
• 3rd party liability insurance essential
• Northern Lighthouse Board
• Navigation, danger to surface craft. Request
  consultation on case by case basis.
• Stipulate flasher-buoys, notice to mariners, or
  mapping for farm deployment etc
• Has authority for rejection. EIS with
  application. Standardised with IALA for RE.
• MCA and the DTi
• Apply to DTis Offshore Renewables Consent Unit
  MCA is their consultation body
• Currently updating/creating standards e.g., MGN
  275.
• Remit is coastal protection (act devolved to SE)
  safety at sea. Carry a lot of weight
• International Hydrographic Organization (IHO)
  Order 1 standard multibeam bathymetry survey
  required, and scale dependent EIS etc

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Studies Recommendations

• Studies advocate on-going assessment, general
  consensus at this time impacts minimal, though
  many unknowns
• Potential effects
• flow patterns, sediment transport, scour,
• flow reduction significant,
• marine life, ecology, navigational effects,
  diving seabirds
• acoustic emissions, vibrational effects,
  installation disturbances
• Highlighted Effects in studies
• shipborne and shore-based radar interference
• electromagnetic interference
• Collision risks, shadow effects
• Potential obligations
• Refuge in piled structures
• Site traffic surveys,
• International navigation
• Parametric models for seabed disturbance and
  impact
• 24h manned control units for emergency
  shutdownCCTV

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WIP and Completed

• SIF
• ..if tidal farms began to significantly reduce
  the flow in their area, this would have a
  detrimental effect on the energy output of the
  farm, something developers will wish to avoid..
  DTi (2005)
• Advocated approach by RGU and Carbon Trust gt
• Velocity head loss after extraction etc
• GGS, (Gorlov et al) new Betz limit?
• Seaflow recorded max 0.6 Cp
• Chow, Yamell, Manning open channel hydraulics,
  obstructions, back water, head loss.
• Compound spheres of influence, turbulence
• Investigating maximum extractable portion, and
  tool development
• Model Validation
• GH 31MW sound Mull see how correlates, more
  like 10MW
• Velocity models accurate for Sound of Islay and
  Mull,
• Website, technology modelling, case studies, and
  the methodology

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Next Steps Complete Technology Investigation
and start identifying optimum operating
conditionsBegin stage 2 Methodology
Any Questions?Recurring Questions

• Q. Why use an integral rather than a finite
  difference (numerical) method?
• -Numerical methods can make fewer assumptions but
  relies on excellent input data and a solution is
  not general. Also it is extremely time consuming.
  There would have to be a massive number of grid
  points if all eddy (1dm-1km) scales are to be
  solved on the grid.
• Q. What are the problems with existing data?
• -Scarcity tidal data is available, but nearly
  all studies are based on surface data, and do not
  take into account seabed bathymetry.
• -Resolution Shallow Water Equation application
  (and others) are generally of a 1 minute
  resolution.
• -Inverse simulation, by SWE does NOT integrate
  depthwise so sub-surface velocity profiles are
  unknown.
• Q. What is the effect of the horizontal shear
  contribution to the velocity profile?
• -Negligible in channels where there is very
  gentle undulation of the depth across width not
  so in channels where there is more severe
  variation in depth.