barrage or what? engineering options prof colin taylor ceng fice professor of earthquake engineering...
TRANSCRIPT
Barrage or What?Engineering Options
Prof Colin Taylor CEng FICEProfessor of Earthquake EngineeringHead, Department of Civil Engineering
The technical options
• Barrage• Lagoon• Tidal reef• Tidal fence• Tidal stream
Source: Marc Paish, Severn Tidal Fence Group
Barrage
Barrage turbine
Source: Roger Falconer
Tidal lagoon
Source: University of Colorado
Fleming lagoon flow computation
Filling Discharging
2 2.5 3 3.5 4 4.5 5 5.5 6
2 m/s
Water level (m)
Flood
Frame 001 01 Sep 2008 Hydrodynamic Results in Nodes
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
2 m/s
Water level (m)
Ebb
Frame 001 01 Sep 2008 Hydrodynamic Results in Nodes
Source: Roger Falconer
Evans tidal reef
Source: Evans Engineering
Evans tidal reef
Low-head turbine for reef
Source: Rod Rainey, Atkins
Tidal fence
Source: Marc Paish, Severn Tidal Fence Group
Tidal stream
Source: DeltaStream Turbines
Source: Swanturbines
Short listed options
Severn Tidal Fence Group
Barrage issues
• Significant environmental impacts
• Reduction of water levels and tidal range
• Loss of inter-tidal habitats • Impacts on bird and fish
populations in the Severn• Inhibits port traffic • Protection from effects of
storm surges, sea level rise• Reduced turbidity• Established technology
La Rance, France
Lagoon issues
• Significant reduction in tidal range within the impounded area
• Loss of inter-tidal habitats• Other environmental effects
are similar to smaller barrages • Less impacts on fish and
navigation as not a full a barrier across the estuary
• Enclosure construction uncertain (e.g. embankment, caissons, innovative modular concrete/earth units?)
• Longer than barrage
Reef issues
• Unproven technology• Long development
period• Less loss of tidal
range• Lower efficiency?• Inhibits shipping
Source: Evans Engineering
Fence issues
• Unproven technology• Long development period• Less loss of tidal range• Lower efficiency?• Less impact on shipping
(but vulnerable to ship impact?)
Source: Marc Paish, Severn Tidal Fence Group
Cost comparisons
Source DECC Analysis of Options report