The Severn Estuary - A sustainable low carbon energy resource. Presented by Peter Kydd at the Sustainable Severn Conference held in April 2013.

1. The Severn Estuary
A sustainable low carbon energy resource
Peter Kydd
Chair, SWMEP
Director of Strategic Consulting, Parsons Brinckerhoff
April 2013
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2. Low carbon drives significant electricity growth
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Beyond 2020

3. Possible growth roadmap for UK
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Beyond 2020
Decade 1
2013-2020
Cap. 100 GW
New Gas build
On and Offshore Wind
Biomass, Biofuel and Solar
Investment begun in new nuclear
Interconnector to Ireland/Norway?
Decade 2
2020-2030
Cap. 120 GW
New nuclear build
Offshore Wind – and early wave
Possible CCS technology?
Interconnectors to Europe
Smart Grid technology
Decade 3
2030-2040
Cap. 150 GW
Electrification of heat and transport
Wind at peak - floating wind
First large wave projects
Gas with CCS? Cost?
Energy storage solutions
Decade 4
2040-2050
Cap. 200 GW
All Low Carbon Technologies
deployed at scale
Tidal stream first arrays
First Tidal Lagoon 200-600MW
New turbine and caisson designs
developed – low head, fish friendly
Larger Tidal Stream Arrays
Tidal Tech. for shallow/slower sites
Lagoons using new tech proven with
lower installations costs
Larger lagoon schemes- Severn /UK
Full potential of Severn harnessed
with combined technology approach
Inc. wave and floating wind
Larger tidal range projects UK &
worldwide - Asia and sub-continent

4. Balanced Technology Approach
RegenSW document published in November 2012
Sustainable Severn
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5. Tidal Power Opportunities
Sustainable Severn
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6. An Incremental Approach
Stepping Stones – a tidal lagoon designed to reduce cost and impact.
Objectives
• To demonstrate that tidal power can be generated from the Severn Estuary with acceptable
cost, environmental and social impacts and build UK confidence in ocean energy
• To be informed by the Severn Tidal Power Feasibility Study research and add to that
research base through full scale demonstration
• To be financeable in the private sector but developed in partnership with the public sector
Constraints
• Should not compromise future development of the short listed options in the Severn Tidal
Power Feasibility Study
• Should not impact Severnside Ports
• Should not involve significant habitat and ecological loss
• Should be competitive with offshore wind in the long term
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A new concept for the Severn

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Downstream of STPFS projects
Stepping Stones Tidal Lagoon
Stepping Stones
Tidal Lagoon

8. Key Details
Technical Data
• 600MW of installed capacity (bulb turbines operating on ebb and flood tides)
• 1.2TWh per year of energy production
• £1.7bn construction cost (built up using same principles as STP)
• Lagoon surface area: 18sq km
• Length of lagoon impoundment: 10.6km
• Construction Period: 4 years (preceded by 5 years in planning/consents)
• Largest tidal power plant in the world
• Cost of Energy @ 10% (including construction + decommissioning costs)
• Financing period (30 years): £193/MWh or £160/MWh @ 2% inflation (based on ratio of
cost to energy over the period)
• Residual operating life (90 years): £30/MWh, (or less in real terms as ratio of cost to
energy will reduce with inflation)
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Stepping Stones Tidal Lagoon

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A stepping stone to tidal power development
Stepping Stones Tidal Lagoon

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Uses conventional construction and technology elements
Stepping Stones Tidal Lagoon
Lagoon Long Section
Embankment from Aberthaw PS – 1.4km, crest level +8mAOD with 2.5m wave
wall, access road and cable conduit, 1:2.5 and 1:2 side slopes, crest width 10m
600m Plain caissons, depth 25m with 2.5 m wave wall, access road and cable conduit
480m turbine caissons, depth 32m
Plain caissons, crest level: +6mAOD, depth 22m
(2.4km), 24m (1.5km) and 25m (3km)
Embankment from Barry – 0.66km
420m Plain caissons, crest level: +8m AOD,
depth 24m and 40m lock caisson, depth 26m

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New Plain Caisson design to form main lagoon wall
Stepping Stones Tidal Lagoon

12. Environmental considerations are important
Key Points
• Ebb and flood operation and lagoon site - loss of habitats minimised;
• Avoids rivers that are important for migratory fish;
• Avoids direct loss of internationally designated habitats although there is some impact on
East Aberthaw SSSI;
• The scheme does not enclose the mouth of the estuary and hence impacts on ports,
navigation and the famous tidal ‘bore’ are small;
• The size of the lagoon means that material ‘far-field’ effects on water levels are unlikely;
• The risk of water quality effects within the lagoon, already identified as small in STP
studies, will be reduced further because the lagoon does not enclose any major outfalls or
rivers;
• Aberthaw PS outfall adjacent to the lagoon will require detailed study
• Sea bed conditions known so uncertainty issues of deep silt/mud are much lower project
risk
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Stepping Stones Tidal Lagoon

13. Potential Regional Economics Benefits
Key Points
• Severnside Ports and other commercial sea-bed users are not expected to be adversely
impacted;
• Existing technology = low risk and ready to go...
• 4,000 jobs created (of which 2,000 would be local construction jobs) over the 4 year
construction period with a further 1,800 of associated indirect jobs in the local community
• 80 permanent jobs would be created to operate the new power station
• As the largest tidal power plant in the world, tourism and educational opportunities would
be created
• Over 1 million tonnes of carbon dioxide emissions would be saved annually
• Potential to replicate in other locations
• Positions UK as global hub for ocean energy and green investment
• Able to contribute off peak energy in alignment with smart grid for distribute storage/electric
vehicle charging et al, as that market develops
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Stepping Stones Tidal Lagoon

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Thank you
Stepping Stones Tidal Lagoon