2006 06 severn barrage: is the tide turning? - david kerr, sir robert mcalpine
TRANSCRIPT
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The Severn Barrage
Presentation to
Severn Estuary Forum
8th June 2006
David Kerr
Sir Robert McAlpine
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Bondi study (EP46 - 1981) was the first major studyTripartite study (EP57 - 1989) defined the present schemeCould produce power by 2017 if progressed soon
Tidal Power from the Severn
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Location:• Bristol Channel/ Severn Estuary
• Downstream of Cardiff to Weston-super-Mare
• 16 km length
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Tidal Power
• The Barrage impounds the tide, then the water is released through a turbine to generate electricity
• Proven Technology: La Rance in France has generated tidal power reliably for over 35 years
5 Barrage Operation
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Barrage Layout (1989 Report)
• 216 Turbines, 40MW each, 8640MW total
• 166 Sluices 35,000m2
• Ship Locks
• Small Locks
• Public Road
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Facts and Figures Annual Output 17 TWh (5% of UK consumption)
Installed Capacity 8640 MW
Renewables Obligation:
15% by 2015 (50-55TWh) - Barrage cannot contribute
20% by 2020 would require a further 17TWh. Barrage could contribute all of this - if sanctioned soon
Capital Cost £8Bn 1989 > ~£14Bn 2005 – needs re-estimate
Security of supply benefit
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Environmental Studies 1989
A total of 70 studies, with a budget of £2M, covering:
• Hydrodynamics (tides, currents, waves)
• Sediments, Salinity, Water Quality, Drainage
• Ecology, Birds, Fish
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Main effects of the BarrageTide Range reduced from 14m to 7m (springs) A smaller inter-tidal area
Reduced currents, leading to:-
A large reduction in suspended sediment Sunlight penetration through the water column
An increase in dissolved oxygen to more normal levels
A more stable seabed with more life
Expected to Result in an increase in bird species and numbers
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Flood protection in the Severn Estuary and Rivers
• Flooding in the estuary can occur when extreme high tides coincide with storm surges
• Flooding in the rivers can occur when these same sea conditions coincide also with high river flows
• The water level in the basin can be controlled -
To prevent the flooding in the estuary (upstream of the barrage)
To avoid obstruction to river flow caused by high tides
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Use Of Barrage for Flood Protection
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Environmental Balance ?
• Loss of the unique harsh environment
• Some birds may lose habitat
• Marine life and other birds will increase
• Flood protection to estuary and rivers
• Carbon Saving
The environmental assessment needs to be updated to account for the changes in the Estuary since the 1980’s and also the changes in legislation
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Transport Key IssuesPorts and Shipping
• Forecast Shipping Movements
• Size of Locks to suit Portbury & Avonmouth
Road and Rail
• Cost-benefit of a Barrage Crossing
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Construction : Prefabricated Caissons
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Caisson Construction Sites• 1989 report identified potential UK sites shown
•Potential Sites in Europe
• Project and Employment Benefits of using many Sites
16Turbine Installation
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Cost ILEX April2005 spot
marketforecast
ActualPrice
7 Dec 05
Tax
Equity Return
Transmission Opex
Transmission Capex
Barrage Opex
Barrage Capex
Cost – Price relationship
p/kWh
April 2005 money
ROC recycle
ROC buyout
Wholesale electricity price
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Conclusion
The Severn Barrage should be re-examined as part of the
Energy Review
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Flow Patterns with Barrage
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Construction Sequence
(1989 Report)
22 Areas at Risk from Flooding
Cardiff
Bristol
Gloucester
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Modes of operation Ebb Generation:
Preferred for most schemes
Flood Generation
Less usable water volume
Two Way Generation
No extra Energy
Higher cost of Energy due to more complex turbines
Energy is spread over more of the day
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Outline Programme for Implementation