1. North Wales Tidal LagoonJim Poole2 October 2008

2. Concept T

3. Tidal Lagoon – Plan View Dam wall Outside Inside Water passing through turbines

4. Tidal Lagoon – Cross Section Water at different level inside and outside lagoon Dam Wall Sea Bed

5. Operating Cycle - Simplified Outside Inside Outside

6. Build up Head Generate Electricity Generate Electricity Build up Head

7. Tidal Lagoon – Operation Step 1: Build up head inside the lagoon by water level falling outside from high tide to low tide T

8. Tidal Lagoon – Operation Step 2: Generate electricity by emptying lagoon from high tide level to low tide level T

9. Tidal Lagoon – Operation Step 3: Build up head outside lagoon by water rising from low tide to high tide T

10. Tidal Lagoon – Operation Step 4: Generate electricity by filling lagoon from low tide level to high tide level T

11. Proposed Location (Indicative)

12. Wind Farms (npower renewables)

13. For maximum generation • Water transfer takes place at high and low tide • The lagoon fills and empties completely over the full tidal range • Hence the mean head is equal to half the tidal range

14. Maximum generation over 2 tidal cycles • Potential Energy = 2  g A T2 • = density of sea water g = acceleration due to gravity A = Area of lagoon T = Tidal range For proposed scheme (60km2), maximum power = 343 MW

15. Practical Operation

16. Practical Operation • Only half the water is exchanged each time the lagoon empties or fills (rather than all of it) • The mean head is roughly 1/3 of the tidal range (rather than a half) • Hence electricity generated is only 1/3 of that potentially available

17. MAREC Paper – Headlines • Impoundment area: 60km2 • Mean tidal range: 5.1m • Mean power output: 110MW • Construction cost: £285m - £540m • Net income @ 3p/kWh: £25.9m/yr • Design life: 100yr (Turbines/Generators: 40yr) (Mean power output of wind farm covering same area: 168MW)

18. Marec Paper – Reference • Evans, S., Poole, J.E.P. and Williams, K.P., “The North Wales Offshore Tidal Impoundment Scheme: a Preliminary Study of the Requirements, Constraints and Opportunities”, Third International Conference on Marine Renewable Energy, IMarEST, (Ed. C. French), Newcastle, July 2004, pp.97-107

19. The "Four-legged Table" A Model for Sustainability Quality of Life Env Ec Soc Nat Res

20. The "Four-legged Table" Attacking the Gap

21. Context for North Wales Tidal Lagoon • The global picture • The local area • UK SD framework andenergy policy

22. Global Context • Climate change • Rising sea level • Run-down in supplies of oil and gas • Increased use of renewable energy

23. Local Area - Environment • Shallow, gently-shelving coastal bay • Sea bed predominantly gravely sand • Mean spring tidal range: 6.7m • Mean neap tidal range: 3.5m • Coastal land below highest tide level • Sea wall in Towyn breached in 1990 • One significant river – Afon Clwyd

24. Local Area – Towns • Victorian seaside resorts • “Faded glamour” • Rhyl contains one of the most deprived electoral wards in Wales • Now undergoing some redevelopment

25. Rhyl

27. Closed August 2007

28. April 2004

29. April 2004

30. April 2004

31. Towyn 1990

33. Towyn – strengthened defences

34. Cap’n Noahs Meeting place for North Wales Coast Renewability Trust

35. Energy Review 2006 General Strategy: • Save energy • Increase generation from renewables – from 4% to 20% • Strengthen EU Emissions Trading Scheme • Streamline planning system

36. Energy Review 2006 Tidal Impoundment Schemes: • Potential to make significant contribution to carbon reductions • But generally not competitive • Interested in improving understanding of tidal resource

37. UK SD Commission Turning the Tide: Tidal Power in the UK (Oct 2007): “We therefore recommend that the Government investigates options to encourage one or more tidal lagoon demonstration projects. This could take the form of inclusion in the Renewables Obligation, or an open competition to solicit private sector or community interest. The additional expenditure would not need to be large, but the potential benefits could be extensive considering the resource available, both in the UK and internationally”.

38. Size and Positioning of Tidal Lagoon • Theory • Practice • Options

39. Theory (1) For a given shape: • Construction costs = aL • Power generated = bL2 Where a, b are constants, L is the length of the impoundment wall So: • Bigger is better

40. Theory (2) All other things being equal: • Rounder is better (more volume enclosed per unit length of impoundment wall) • Shallower is better (less “wasted” height below tidal range)

41. Practice • Consider potential uses • Consider potential options for size and location • Assess options against uses

42. Potential Uses • Power generation • Coastal protection • Recreational boating • Marina facilities • Enhancing biodiversity (“atoll”)

43. Learn from elsewhere

44. Blyth – Power Generation

45. Blyth – Energy Research

46. Barry – Recreational Boating

47. Swansea Marina

48. Biodiversity

49. Size and PositioningOptions • Offshore • Inshore • Onshore • Maximum power • Demonstration

50. Offshore Minimum visual impact River Clwyd