Ice midlands region warwick, 2010

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  • Mean Ebb
    without Velocity Vectors
  • Mean Ebb
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  • Ice midlands region warwick, 2010

    1. 1. 11 The Severn Barrage and Other Options: Hydro-environmental Impact Assessment Studies by Roger A. Falconer FREng Halcrow Professor of Water Management Hydro-environmental Research Centre Cardiff School of Engineering, Cardiff University
    2. 2. 22 A New Dawn www.corlanhafren.co.uk
    3. 3. 33 General Challenges  Growing worldwide increase in energy demand - particularly in India and China  Tidal energy generation has advantage over wind and waves - in that tides are predictable  UK target of 15% of energy from renewables by 2020 - about 35% of electrical energy  Wales’ 2025 target for marine renewables energy is 14 TWh/yr - Barrage would generate over 60%  Severn Estuary basin is ideal for tidal energy
    4. 4. 44 Global CO2 Concentration Steep increase since 1800 Roughly constant for hundreds of years Source - Met Office
    5. 5. 55 Predicted Future CO2 LevelsCO2concentration(ppm) 750 650 550 450 350 250 1990 2010 2030 2050 2070 2090 Year 50% 1990 emissions Constant 1990 emissions Business as usual Source: IPCC
    6. 6. 66 Predicted Mean Temperature Rise Globaltemperaturerise,degreesC High emissions Medium-high emissions Medium-low emissions Low emissions Source - Met Office
    7. 7. 77 Predicted Mean Rainfall Changes For Wales / SW Present day wet events with a 5 yr return period are predicted to occur between 1.5 & 8.5 times more often Source - Met Office
    8. 8. 88 Boscastle - Picturesque Village in U.K.
    9. 9. 99 Boscastle - August 2004 (1:400 yr flood)
    10. 10. 1010 Hurricanes: Link to Climate Change Source - Jorg Imberger Hurricanes inject large amounts of CO2 into upper atmosphere By 2034 predicted there will be 50 more category 4 & 5 storms
    11. 11. 1111 The Perfect Storm  2030
    12. 12. 1212 UK Challenges - Population Growth Population growth not just a challenge for developing countries: UK issue
    13. 13. 1313 Planned Renewable Energy Provision EU target of 20% carbon reduction by 2020 Considerable Scope to increase
    14. 14. 1414 Mean Spring Tidal Stream Resource Source – DTI Atlas of Marine Renewable Energy Resources
    15. 15. 1515 Mean Spring Tidal Range Resource Source – DTI Atlas of Marine Renewable Energy Resources
    16. 16. 1616 WalesWales EnglandEngland Severn EstuarySevern Estuary
    17. 17. 1717 Proposed Tidal Devices for Severn  Tidal Stream Turbines - wind type turbines located in water column and energy created directly from tidal stream currents  Tidal Lagoons (OTIs) - enclosed embayment constructed offshore, creating tidal phased head difference - similar to barrage concept  Tidal Barrage - embankment across estuary - ideal for renewable energy with high tidal range and large upstream plan-surface area
    18. 18. 1818 Potential Power from Tides 2 µPower A H H = level difference across barrage / lagoon A = wetted surface area upstream of barrage  For tidal barrages and impoundments:- 3 µPower V V = mean free-stream tidal current  For tidal stream turbines:-
    19. 19. 1919 Tidal Stream Turbines DeltaStream SwanTurbines • Rotor diameter ≥ 15m  depth ≥ 25m to operate • Nominally ≈ 1.2MW/unit
    20. 20. 2020 Cardiff Turbine Design Flow • Turbine will operate in any flow depth • Design in its infancy – long way to go
    21. 21. 2121 Tidal Lagoon Concept Source – University of Colorado Swansea Bay Lagoon takes over 8hr to empty
    22. 22. 2222  Embankment wall length over 9 km  Plan area ≈ 5km2 = 1000 football fields  Mean spring tidal range ≈ 8.5 m  Energy output of 124 GWh/yr  Severn Barrage ≈ 135 tidal lagoons  Cost ≈ £200 m (?) Key details: Shape and Scale - Swansea Lagoon Plan Area ≈ 5km2 Swansea Harbour Swansea Bay Source – Tidal Electric Ltd Turbine Housing
    23. 23. 2323 Original Proposals 80 km2 Impoundment Environmental Impact?
    24. 24. 2424 EIA Studies Needed for Lagoons Model studies needed to predict changes for:- Tidal currents:- speed, levels, eddies, river plumes Wave climate:- height, length, refraction, reflection Suspended sediments:- distribution along channel Sediment deposition:- in and out of impoundment Coastal morphology:- changes to beach profiles Water quality:- turbidity, nutrients, light penetration Pre-/post-construction:- short & long term impacts Mitigating measures:- changes to design/operation
    25. 25. 2525 Government Short Listed Proposals
    26. 26. 2626 Severn Barrage - 1849 First proposed by Thomas Fulljames - 1849
    27. 27. 2727 The Other Challenge
    28. 28. 2828 Severn Barrage Proposal Site Some key facts:  2nd highest spring tidal range ≈ 14 m  Cardiff to Weston  Length about 16 km  Generate ≈ 5% of U.K. electricity  Total cost ≈ £20 bn  Save > 6.8 million tonnes carbon paSlide – courtesy of STPG
    29. 29. 2929 Barrage Layout (1989 Report) Key facts:  216 turbines each 40 MW ≈ 17 TWh pa  166 sluices  Ship locks  Fish pass?  Public road & railway Slide – courtesy of STPG
    30. 30. 3030 Construction: Prefabricated Caissons Slide – courtesy of STPG
    31. 31. 3131 Turbine Installation Slide – courtesy of STPG Slide – courtesy of STPG
    32. 32. 3232 Tidal Power Generation Slide – courtesy of STPG
    33. 33. 3333 Proposed Operation - Ebb Generation Slide courtesy of STPG
    34. 34. 3434 Proven Technology - La Rance La Rance Barrage, France, has reliably generated tidal power for over 35 years
    35. 35. 3535 Barrage Effect on Tides Estuary Bed Tide Enters Severn Estuary Flow through turbines Barrage
    36. 36. 3636 Existing Estuarine Environment  Tide Range - 14 m on springs, 7 m on neaps High tidal currents and large inter-tidal areas 30 Mt sediment suspended on springs, 4 Mt neaps Little sunlight penetration through water column Reduced saturation dissolved oxygen levels  Ecology Harsh estuarine regime with high currents Limited aquatic life in water column / bed Bird numbers per km2 are relatively small
    37. 37. 3737 Changing Natural Environment  Climate Change  Temperature rise will affect ecology, birds etc  Sea level rise will lead to increased flood risk  Water Quality  Cleaner effluent discharges with EU WFD  Nutrient reduction will affect aquatic life  Legislation  Long term projects (>120 yr) require assessment against future - not just current - environment
    38. 38. 3838 Wigeon - 8,062 Pochard - 880 Ringed Plover - 665 Curlew - 2,545 Whimbrel - 222 Spotted Redshank - 10 Wigeon - 3,977 Pochard - 1,686 Ringed Plover - 227 Curlew - 3,096 Whimbrel - 246 Spotted Redshank - 3 Nationally important bird populations Shelduck - 3,272 Dunlin - 23,312 Redshank - 2,566 European Goose - 942 Shelduck - 2,892 Dunlin - 41,683 Redshank - 2,013 European Goose - 3002 Internationally important populations of migratory birds Bewick’s Swan - 276Bewick’s Swan - 289 Internationally important populations of Annex 1 species Species numbers between 2000 – 05 (Red - Less, Blue - More) Species numbers between 1988 - 93 Citation category Source - RSPB Bird Species in SPA Citation
    39. 39. 3939 Main Effects of Barrage  Spring tide range reduced from 14 m to 7 m  Significant loss of upstream inter-tidal habitats  Reduced currents up & downstream of barrage  Reduced turbidity / suspended sediment levels  Increased light penetration through water column - with increased water clarity  Increased primary productivity and changed bio- diversity of benthic fauna and flora  Upstream tidal range of 7m is still relatively large compared to most deltas world-wide
    40. 40. 4040 Severn Estuary Hydraulic Model
    41. 41. 4141 Severn Barrage - Grid Configuration Inner Barrage Cardiff
    42. 42. 4242 Grid Refinement Around Barrage Shipping locks 80 Sluices 12 Sluices Sub-stations 168 Turbines 48 Turbines Sub-stations 74 Sluices Embankment Flat Holm Steep Holm Embankment Cardiff Weston
    43. 43. 4343 (a) Velocity Field Around Barrage 2 m/s water level(m) -4 -3 -2 -1 0 1 2 3 Frame 001  12 Apr 2008  Hydrodynamic Results in Nodes 2 m/s water level(m) 2 2.5 3 3.5 4 Flood Ebb
    44. 44. 4444 Level of water inside impoundment Option 1: Generate over ebb tide only Proposed: One Way Generation
    45. 45. 4545 Alternative: Two Way Generation Level of water inside impoundment Option 2: Generate over full tide Rapid filling and emptying of basin required at either end of tidal cycle
    46. 46. 4646 Three Modes of Operation Studied Waterlevel(m) Filling Generating Holding Holding Filling Hmin Hst (a) Ebb Generation A B C D C D Time(h) Ebb only Time(h) Waterlevel(m) Generating Holding Holding Hmin Hst (b) Flood generation A D B C D Releasing Releasing Flood only Time(h) Waterlevel(m) FillingGenerating Hmin Hst (c) Two-way generation Generating GeneratingReleasing Filling HoldingHolding A B C D Two-way Model predictions resulted in peak power output for:- Starting Head = 4.0 m Minimum Head = 2.0 m
    47. 47. 4747 Maximum Water Levels - Ebb Only Without Barrage Maximum Water Level (m) Tenby Cardiff Minehead Weston Ilfracombe Barry Swansea Gloucester Newport Bristol Avonmouth N 4.0 4.5 5.0 5.5 5.5 3.5 4 4.5 5 5.5 6 6.5 7 7.5 Frame 001  05 Nov 2009  Maximum Water Level With Barrage Reduced flood risk
    48. 48. 4848 Without Barrage With Barrage Maximum Water Levels - Two-Way Reduced flood risk
    49. 49. 4949 Peak Water Levels 0 1 2 3 4 5 6 7 8 020406080100120140160180200 Existing Cardiff-Weston Barrage Fleming Lagoon Shoots Barrage Swansea Minehead Newport Avonmouth Beachley(M48) Sharpness Cardiff Distance from Gloucester (km) HighWaterLevel(m) (DatumrelativetoAvonmouth) Epney Newnham
    50. 50. 5050 Maximum Tidal Currents - Ebb Only Without Barrage Maximum Velocit y(m/s) Tenby Cardiff Minehead Weston Ilfracombe Barry Swansea Gloucester Newport Bristol Avonmouth N 0.3 0.7 1 1.3 1.7 2 Frame 001  05 Nov 2009  Maximum Water Level With Barrage
    51. 51. 5151 Maximum Currents - Ebb and Two-Way Maximum Velocit y(m/s) Tenby Cardiff Minehead Weston Ilfracombe Barry Swansea Gloucester Newport Bristol Avonmouth N 0.3 0.7 1 1.3 1.7 2 e 001  05 Nov 2009  Maximum Water Level Ebb Only Two-Way
    52. 52. 5252 Water levels and Power Output I II III II I=Filling (4.3h) II=Holding (1.6h+1.0h) III=Generating (5.5h) 4m 2m (a)(a) I II Releasing (0.8h+1.1h) II=Holding (2.0h+1.3h) III=Generating (2.8h+4.4h) 4m 2m III III (d) I=Filling and (c) Ebb Only  48.8 GWh/24.8h  5.2 m mean tide  High tide 4.6 m Two-Way  48.4 GWh/24.8h  4.4 m mean tide  High tide 3.2 m
    53. 53. 5353 High Suspended Sediment Levels Dynamic region of high turbidity
    54. 54. 5454 Suspended Sediment Levels Mean Flood Without Barrage With Barrage Mean Flood - Spring Tide Reduced sediment levels & clearer water
    55. 55. 5555 Effects of Turbidity Changes But what type of birds? Dunlin or other birds?
    56. 56. 5656 Riverine and WwTW Source Inputs? RiversRivers WwTWsWwTWs
    57. 57. 5757 EU Bathing Water Directive
    58. 58. 5858 Diffuse Pollution Effects? Wales Population: Humans - 2.75m Sheep - 10.5m
    59. 59. 5959 Enteric bacteria water column Wastewater outfalls Catchment runoff Water birds input Advection with diffusion/dispersion output Overall reduction Decay Adsorption Deposition Sediment re-suspension and desorbed into water Enteric Bacteria Flux
    60. 60. 6060 Enterococci T90 Experiments  Samples taken from 5 sites along estuary  Dark and irradiated microcosms tested 4 times for each site Cellulose diacetate bandpass filter Mixing unit Chiller/heater Matt black lining  Artificial light source calibrated to provide average radiation conditions during July and August
    61. 61. 6161 Relationship with Turbidity/SS  Empirical relationships developed between turbidity and suspended solids and T90 values  Real-time T90 included in numerical model - varying with time, location, predicted SS level and radiation patterns
    62. 62. 6262 Sediment Associated Experiments 2  Two beakers incubated at 15˚C  one mixed and one allowed to settle - two sites tested Mixed beaker -concentrations remained constant Settled beaker – concentrations fell as finer particles settled
    63. 63. 6363 Mean Ebb Bacteria Levels Without Barrage With Barrage Mean Ebb - Rivers in Flood Reduction in bacteria levels
    64. 64. 6464 Welsh Grounds Lagoon
    65. 65. 6565 2 2.5 3 3.5 4 4.5 5 5.5 6 2 m/s Water level (m) Flood ame 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 Velocity Field Around Lagoon (a) During Filling Mode (b) During Generating Mode
    66. 66. 6666 I – Filling II – Holding III – Generating I II III Predicted Power Generation
    67. 67. 6767 Shoots Barrage Shoots Barrage Second Severn Crossing M4 Severn Bridge Key facts  30 x 7.6m diam 35 MW turbines ≈ 2.75 TWh/yr  Construction period ~ 4 yr  Less plan area  Slightly higher tidal ranges  Cost ≈ £2.6 bn
    68. 68. 6868 Other Issues to Consider  Barrage would bring jobs:  30,000+ jobs at construction peak, distributed over UK - about half in Cardiff - Bristol region  10,000+ permanent jobs in Severnside  Regional economic impact:  Availability of skilled labour and materials?  Local infrastructure needs - housing, schools etc  Concerns about supply chain, deep ports etc  Opportunities for expansion of Port Talbot etc  Considerable tourism and recreational potential  Road / rail links between Wales, London and EU
    69. 69. 6969 Summarising  Severn Barrage would have a lasting impact on a unique UK macro-tidal estuary:  Provide 5% of UK’s electricity from renewables  Reduce intertidal habitats by about 14,000 ha  Reduce flood peaks - upstream and downstream  Reduce tidal currents and suspended sediments - increasing light penetration and water clarity  Change ecology and benthic flora and fauna  Enhance opportunities for tourism and recreation  Two-way generation - enables optimal energy provision for minimal environmental change  Fish migration would remain a major challenge
    70. 70. 7070 UK Relative Water Stress High water stress Low water stress
    71. 71. 7171 Severn Barrage: More than a Renewable Energy Project
    72. 72. 7272 BBC Documentary on Barrage by Jonathan Porritt
    73. 73. 7373
    74. 74. 7474 Addendum
    75. 75. 7575 The ChallengeThe Challenge For engineers and scientists to deliverFor engineers and scientists to deliver UK’s marine renewable energy targetsUK’s marine renewable energy targets The OpportunityThe Opportunity For UK to deliver renewable energyFor UK to deliver renewable energy with minimal environmental impactwith minimal environmental impact
    76. 76. 7676 Thank YouThank You Professor Roger A. Falconer Email: FalconerRA@cf.ac.uk

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