Transcript Tidal Generation Ltd - The John Ray Initiative
Energy From the Severn Estuary
Trinity College, Bristol, March 10 th 2007
Energy Extraction Technologies ●
Barrages
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Tidal Lagoons
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Tidal Stream
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Tidal Fences
Tidal Power – Lagoons (Pictures: WWF Wales)
Tidal Power – Tidal Streams (Picture: Tidal Generation Ltd)
Tidal Fences
Tidal Power – Lagoons (Pictures: Tidal Electric)
Tidal Power – Lagoons (Picture: WWF Wales) Pictures Courtesy Tidal Electric Ltd
Tidal Power - Lagoons Pictures Courtesy Tidal Electric Ltd
Summary of Lagoons ●
Energy claimed at 3.4p/kWh
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Large volumes of aggregates & transport required
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Uncertainties of sealing, sedimentation, seabed preparation & storm integrity
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Some environmental issues to be resolved (e.g. area of sea-bed usage, blockage to sea users, & fish entrapment)
Tidal Power – Tidal Streams (Picture: Marine Current Turbines Ltd)
Features of Tidal Stream ● ● ● ●
Short lead time
less capital intensive
Modular
income starts on installation of first unit
Low impact Competitive
avoids main barrage env. issues early farms in the region 7-8p/kWh ● BUT: ● The Severn resource is ~10-15% of that from a barrage ● Although some tidal stream resource may be extractable in addition to a barrage ● Foundations could double for offshore wind turbines
Environmental Impact ●
Controllable extraction
- modular units can be sited to minimise effects on shipping or fishing ●
No blockage
- marine life relatively undisturbed, zero to low mortality ●
Tidal heights not affected
- no effect on salinity, inter-tidal or sub-tidal zones ●
Some issues to be addressed
- rotor/mammal interactions, electromagnetic and acoustic noise emissions
Wind and Tidal Stream
Challenges of Tidal Stream ●
Harsh environment
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Pinning large loads to the sea bed
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Retrieval for maintenance in water up to 100m
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Sub-sea cabling and connections
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Grid capacity onshore Sea mammal interaction – uncertainties
Not an easy environment…..
Photo courtesy Seacore Ltd
Specialist Construction Equipment
Flow Turbulence
Current Velocity
3000 2500 2000 1500 1000 500 0 09:36:00 10:48:00 12:00:00 13:12:00
Time
14:24:00 15:36:00 16:48:00
Energy Flux
Power Density
6000 5000 4000 3000 2000 1000 0 09:36:00 10:48:00 12:00:00 13:12:00
Time
14:24:00 15:36:00 16:48:00
Maintenance Windows
How much resource is there?
UK – up to 4GW 3 of these….
Potential Tidal Stream Sites
(Source: DTI UK Atlas of Marine Renewable Energy)
Systems already demonstrated (1) (Picture: Marine Current Turbines Ltd)
Systems already demonstrated (2) (Picture: IT Power Ltd.)
Systems already demonstrated (3)
Larger recent demonstrations Hammerfest Strom, Norway
Larger recent demonstrations ENERMAR 120kW Variable-pitch Darrieus (Italy)
Larger recent demonstrations Engineering Business 150kW Stingray reciprocator (UK)
Larger recent demonstrations Open Hydro Marine Current Turbines
Diversity of solutions…..
And more…
State of Tidal Stream Industry ●
Being led by the UK
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Strong UK Govt support for R&D & capital Many device concepts – no convergence as yet
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A few medium scale prototypes are in the sea: many more to follow Market entry costs are high – £10m min
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Commercial machines a few years off
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Some planning, environmental and grid capacity issues to be addressed
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An environmentally benign offering to the sustainability mix
Cables coming ashore at Cauldale and the new grid station
Emissions and Materials Consumption ● Cradle to grave assessment required ● Tidal Stream : shorter construction time, pay back quicker. Steel in construction is energy intensive but less aggregate and concrete ● Tidal Lagoons: very high aggregate demand but little ancillary infrastructure ● ● Tidal Barrages: large material requirement, transport and ancillary infrastructure e.g. roads, port facilities; long pay-back time
(Slide by Morgan Parry, WWF Wales)
Species and Habitat Impacts ● ● ● ● ● Tidal Stream Energy devices possible
:
environmental appraisals currently being carried out on individual devices. Fish and mammals may avoid them, acoustic deterrence Tidal Fences: than individual devices, but not complete barrier like barrage greater obstacle to fish and mammals Tidal Lagoons: fish and mammals may avoid the area but risk of fish entrapment during flood generation Tidal Barrages : reduce tidal range creating a loss of habitats. Water quality reduced if dispersal/dilution inadequate. Barrier to fish movements
(Slide by Morgan Parry, WWF Wales)
Sediment Flow ● ● ● ● ● Tidal Stream Energy devices elsewhere
:
current turbines currently being modelled in Strangford Lough and Tidal Fences
:
considerable reduction in energy of water column but less than barrage Tidal lagoons Choice of location can reduce sedimentation in shipping channels : currents and wave patterns altered. Tidal barrage: nutrient flux upstream and downstream. Navigation impacts highly modified sediment regime and
(Slide by Morgan Parry, WWF Wales)