Bill Cooper - ABP MER Severn Tidal Power Resource Bill Cooper is Managing Director of ABP Marine Environmental Research. Bill has over 26 years of practical experience in coastal projects since he graduated from Swansea University where he obtained his first degree in Oceanography. Bill has previously worked at the Tidal Waters Unit of Welsh Water and for an engineering consultancy based in South Wales. Since 2004, Bill has contributed to a variety of marine renewable energy projects, ranging from development of standards and guidance, strategic scale studies for UK Government, to major infrastructure projects like the Severn Tidal Power schemes and also local developments such as the Swansea Bay Tidal lagoon. This presentation aims to provide an objective overview of the Severn Tidal Power Resource, as a personal examination and without prejudice. An explanation is offered as to why the resource in the Severn is so unique in contrast to other UK estuaries and why some of these properties present issues of their own. The presentation highlights some of the implications of harvesting the resource and interest features that may be involved.

1. Severn Tidal Power Resource
Bill Cooper
Severn Estuary Forum, Bristol
11 September 2012
A personal, independent and objective view

2. 1
Contents
 Defining a resource
 Establishing a tidal resource
 What creates the tidal resource
 Harvesting the tidal resource
 Major studies
 Other resources

3. 2
Defining a resource
 A natural resource is anything obtained from the environment to satisfy
human needs and wants (Wikipedia)
 Different types of resource with different values to different users
 Local examples of natural resources include:
 marine sands for aggregates, cooling waters for power stations, high
natural dispersion for outfalls, Severn Bore for surfers, and many
others
 Energy generation from tidal power is a potential natural and
sustainable resource

4. 3
Establishing a resource
Theoretical resource – unconstrained top-level estimate of the energy in
the system
Technical resource – the proportion of the theoretical resource that can be
exploited using available technology
Practical resource – the proportion of the technical resource after
consideration of other constraints

5. 4
UK Atlas of Marine
Renewable Energy
Theoretical resource
unconstrained top-level
estimate of the energy in
the system

6. 5
Establishing a tidal resource
Theoretical resource
 Severn Estuary has a good theoretical resource because of:
 Very large tidal range; and
 Large tidal prism (i.e. the volume of water exchanged by the tide
between high water and low water).

7. 6
Establishing a tidal resource
Technical resource
 Severn Estuary is most suited to tidal range options relying on low head
hydropower generation (i.e. barrages and lagoons)
 Form of estuary imposes some engineering constraints on locations
 Estuary typically too shallow for present tidal stream technologies in
large arrays (no convenient space)
 Potential tidal stream opportunities further to the west in the Bristol
Channel

8. 7
What creates the tidal resource
 Large tidal range originates from the open setting of the Bristol Channel
facing a wide continental shelf out to the approaching North Atlantic tide
 Distance approximates the resonant condition of a quarter wavelength
of the principal lunar semi-diurnal M2 tidal component
 Shelf resonance creates a mean spring tidal range of around 5m for the
Outer Bristol Channel
 Thereafter, the funnel shaped estuary increases energy density leading
to a mean spring tidal range of around 12m at Avonmouth

9. 8
M2 tidal constituent

10. 9
Harvesting the tidal resource
Optimising energy capture:
 Function of tidal head (range), tidal volume (prism), capacity to install
multiple turbines
 Maximum mean spring tidal range occurs around The Shoots at 12.3m,
coincides with a minimum distance across estuary (4.1km), but lower
tidal prism
 Mean spring tidal range at Cardiff of 11m, larger distance across estuary
(16.1km), but higher tidal prism

11. 10
Harvesting the tidal resource
Suggested generating potential:
 The Shoots (English Stones), installed capacity of 1.05GW, generating
2.75 TWh per year, with load factor of 30%
 Cardiff - Weston, installed capacity of 8.64GW, generating 17.00 TWh
per year, with load factor of 22.5%
 Conventional fossil fuel power stations operate at around 50% to 65%
load factor, new nuclear may be around 90%
 Offshore wind typically 35 to 45%

12. 11
Major estuary studies
 First technical study of the estuary by Professor Gibson (1926 to 1933),
based on a physical model
 Economic Advisory Council later recommended English Stones
scheme with secondary storage basin to increase load factor (to
compete with coal power stations)
 STPG studies (1984 to 1989) used numerical models, acquired
improved primary data
 Preferred Cardiff - Weston scheme
 DECC Feasibility Study (2008 to 2009) based on improved models,
updated engineering considerations, used existing data

13. 12
Gibson model
Focussed on the
upstream effects
of tow barrage options
physical model 45ft long
1 in 8,500 horizontal
scale
1 in 100 vertical scale
changed to 1 in 200 to
better represent slopes of
banks

14. 13
STPG models
Two models, but different
approach to offshore
boundaries

15. 14
DECC Feasibility Study
Two models, same grids
and offshore boundaries
considered both barrage
and lagoon options

16. 15
 Changes upstream and downstream of any barrage a product of relative
position, mode of operation and amount of energy extraction
 Upstream changes in the impounded area, more focused and stepped
physical change to the system, maximum tidal effects likely to be
reduced to present neap tide conditions
 Downstream changes unconfined, more dispersed effects over a wider
area, but changes in tide also linked to resonant behaviour
 Need an appropriate scaled study to consider both upstream and
downstream issues
Key effects

17. 16
Other resource users

18. 17
Other resource users

19. 18
Other resource users

20. 19
Other resource users
© Paul Williams

21. Thank you for you attention
Bill Cooper
bcooper@abpmer.co.uk