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Tidal Energy Opportunities in the
Bristol Channel and Severn Estuary
Roger Falconer1 and Chris Binnie2
1Hydro-environmental Research Centre, Cardiff University
2Independent Water Consultant
1
2
Key details:
• Completed in 1966
• 24 x 5.5m dia. bulb
turbines & 6 sluices
• Turbine trials ebb-
only (+ pumping)
• Generate 0.54TWh/y
• Energy cost €20/MWh
cheapest in EU
• No baseline studies
prior to construction
La Rance Tidal Barrage Scheme
3
Swansea Bay Lagoon - Current DesignKey details:
• Wall 9.7km long
• Area 11.6km2
• 16 x 7.3m diam bulb
turbines & 8 sluices
• Turbines: two-way +
pumping HW & LW
• Generate 0.54TWh/y
• Potential for large
wakes and eddies
LEGE ND
Order limits
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Sources Ordnance Survey
This drawing may contain: Ordnance Survey material by permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office © Crown Copyright 2013. All rights reserved. Reference number 0100031673 OS
Open data / © Natural England / © DEFRA / © DECC / © English Heritage. Contains Ordnance Survey data © Crown copyright and database right 2013 I Aerial Photography
REFER TO DRAWING NUMBER 3513/PL/002.3Plan 3of6
REFER TO DRAWING NUMBER 3513/PL/002.1Plan 1of6
REFER TO DRAWING NUMBER 3513/PL/002.4Plan 4of6
REFER TO DRAWING NUMBER 3513/PL/002.6Plan 6of6
REFER TO DRAWING NUMBER 3513/PL/002.2Plan 2of6
T: 01865 887050
No
rth
SCALE@A0 1:10,000
STATUS Planning
REV . DESCRIPTION APP. DA TE
DOC REF NO: 2.4.1
No dimensions are to be scaled from this drawing.
All dimensions are to be checked on site.
Area measurements for indicative purposes only.
© LDA Design Consulting LLP. Quality Assured to BS EN ISO 9001 : 2008
PR OJ EC T TI TLE
TIDAL LAGOON SWANSEA BAY PROJECT
D R A W I N G T I T L E
Masterplan Key Plan
DATE 06.02.2014 DRAWN JH
CHECKED LJ
APPROVED AK
ISSUED BY Oxford
DWG. NO 3513_PL_001
10.5
9.5
5.2
1.0
0.0
5.5
4.5
0.2
Highest Astronomical Tide (HAT)
Mean High Water Springs (MHWS)
Mean Sea Level (MSL)
-4.0 Mean Low Water Springs (MLWS)
-5.0 Lowest Astronomical Tide (LAT)
10.0
9.0
N/A
1.5
5.0
4.0
N/A
-3.5
Highest Astronomical Tide (HAT)
Mean High Water Springs (MHWS)
Mean Sea Level (MSL)
Mean Low Water Springs (MLWS)
Tidal bar - Outside of the lagoon (NTS)
0.5 -4.5 Lowest Astronomical Tide (LAT)
Tidal bar - Inside of the lagoon (NTS)
Chart
Datum
(m)
Ordnance
Datum
(m)
Chart
Datum
(m)
Ordnance
Datum
(m)
Turbine location: Option B
REFER TO DRAWING NUMBER 3513/PL/002.5Plan 5of6
Turbine location: Option A (refer to inset for option B)
Swansea Bay - Design Modification 1
7
Swansea Bay - Design Modification 1
Revert turbine/sluice location to Option B - submitted to DCO
Wake would be parallel to, and away from, dredged channel
8
Swansea Bay - Design Modification 2
Focusing turbines and sluice gates leads to high wake/jet effects
Flow through turbines emptying 2 Olympic swimming pools/sec
https://www.ice.org.uk/ICEDevelopmentWebPortal/media/.../6-Ioan-Jenkins.pdf
9
Wider distribution of turbines & sluices leads to weaker eddies
0
Original Modified
Swansea Bay - Design Modification 2
General Findings:
Larger impoundment
size greater impact
Multiple schemes in
close proximity have
cumulative impacts
Impacts reduced by
refined turbine/sluice
design
10
Cumulative Impacts Studied
Velocities Elevations
0
Velocities Elevations
11
Tidal Lagoon - Barrage Interactions
Various Barrage lines (STPG & Atkins) and Lagoons (Cardiff
& Swansea) considered, with interactions studied:
Note: Figures do not include effects of pumping
Results show Barrage would reduce Cardiff output 60% and Cardiff would reduce Barrage output 13%
Run Barrage/Lagoon Annual Energy*
Alone (TWh/yr)
Annual Energy*Combined
1 Severn (HRC) 19.82 17.184
2 Severn (Atkins) 19.77 17.141 (est)
3 Cardiff Lagoon 4.680 1.783
4 Swansea Lagoon 0.586 0.531
Sustainable Severn Forum27th April 2017
Energy opportunity for the estuary
Updating the Severn barrage
By
Prof Chris BinnieMA, DIC, HonDEng, FREng, FICE, FCIWEM
chrisbinnie@btopenworld.com
Conclusions of the DECC studyfrom the Executive Summary
• Half of the schemes, including the Cardiff lagoon, were judged to be unviable and were not included in the more detailed consideration.
• The Welsh Grounds lagoon, (Newport lagoon), is no longer considered feasible.
• The Cardiff-Weston, Severn, barrage, 15.6 TWh/y, offers the best value for money.
• Combinations of smaller schemes do not offer cost or energy yield advantages over a single larger scheme between Cardiff and Weston.
Reasons the Severn barrage was not supported.
• Enormous loss of inter-tidal habitat, 118-163 km2
• Birds. Reduction in SPA feeding ground, significant negative effect on 30 species
• Land Drainage. area affected 372km2
• Fish mortality, SAC, possible local extinction of shad and salmon.
• Navigation, • delays to ships transiting the barrage
• BPC planned Deep Sea Container Terminal
Improvements to turbines and operationachieved by TLP, Andritz and GE.
• Ebb/flood generation• Improved basin water levels and generation output
• Pumping• Basin water levels become near normal
• Triple Regulation• Improvement in energy generation
• Non-synchronous generators• Reduced fish mortality
• Smoother passageway• Reduced shear so greatly improved shad mortality
Statistics of the revised barrage
• Energy increased from 15.6 TWh/y to 20.5 TWh/y
• Low water at the barrage increased from 0.34m CD to 0.39m CD, an increase of 0.05m.
• High water at the barrage reduced from 13.84m CD to 13.40m CD, a reduction of 0.44m.
• Mean water level marginally reduced.
Revised impact
• Loss of SAC inter-tidal habitat considerably reduced.
• Loss of bird feeding ground considerably reduced.
• Drainage issue eliminated.
• Fish impact considerably reduced.
• Navigation. Two new container terminals at Liverpool and London Gateway. BPC DSCT postponed.
Comparison of Cardiff and Updated Severn barrage
• Cardiff and Newport lagoons about 8 TWh/y
• Severn barrage about 20 TWh/y.
• Loss of national energy source of about 10 TWh/y
• Severn barrage impact much reduced but still more navigation and fish impact than lagoons.
• Before proceeding, independently update the comparison?
• Welcome Hendry Review and support for Swansea Bay Lagoon as “Pathfinder Project”.
• Swansea Lagoon needs to be successful and would suggest further consideration of two design aspects.
• DECC 2010 Severn Barrage had high impact.
• Tidal energy parameters now much improved.
• Lagoon and barrage impact much reduced.
• Need for independent updated comparison?
Concluding Remarks
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