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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)

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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