Developments in tidal energy : proceedings of the Third Conference on Tidal Power

329 Pages·1990·14.811 MB·English

by  Institution Of Civil Engineers

Developments in
tidal energy
Proceedings of the third conference on tidal
power organized by the Institution of Civil
Engineers and held in London on 28-29
November 1989
Thomas Telford, London
Co-sponsored by the Department of Energy, the Institution of
Electrical Engineers, the Institute of Energy and the Institution
of Mechanical Engineers
Organizing Committee: R. Clare (Chairman), A. C. Baker,
B. Count, R. Price, P. L. Surman and P. C. Warner.
British Library Cataloguing in Publication Data
Developments in tidal energy
1. Alternative energy sources
621.042
ISBN: 978-0-7277-1571-5
® The Institution of Civil Engineers, 1990, unless otherwise stated.
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Published for the Institution of Civil Engineers by Thomas Telford Ltd, Telford
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Contents
Opening address
P. MORRISON 1
Session 1.
1. An introduction to the Severn barrage development
project: project promotion aspects. R. CLARE 3
2. Severn barrage: site investigation and barrage layout.
D. KERR, B. F. WAREHAM and D. COURSEY 11
3. Severn barrage: civil engineering aspects. D. KERR,
B. SEVERN and S. J. DRIVER 29
Discussion on papers 1-3 53
Session 2.
4. Turbine generators for the Severn barrage. D. J. PETTY
and A. MACDONALD 59
5. Energy production. E. GOLD WAG and R. POTTS 75
6. Getting the power away. D. M. BARR 93
Discussion on papers 4—6 107
Session 3.
7. Tidal power from the Mersey: history and prospects.
N. W. HAMMOND and P. WOOD 119
8. Progress on civil engineering and planning of a Mersey
tidal project. N. REILLY and B. I. JONES 129
9. Electrical and mechanical engineering aspects of a
Mersey tidal project. J. R. BOLTER, H. R. GIBSON,
W. D. HOGG and H. HAGUE 145
Discussion on papers 7-9 161
Session 4.
10. Initial assessment of the energy yield and economic
aspects of a Mersey barrage. E. A. WILSON and
R. POTTS 169
11. The use of steel in tidal barrages. R. G. GUY,N. SONDHI
and C. J. BILLINGTON 179
12. In situ construction methods for tidal barrages.
E. T. HAWS and A. O. MITCHELL 198
Discussion on papers 10-12 213
Session 5.
13. Sediment problems arising from barrage construction
in high energy regimes: an example from the Severn
Estuary. R. KIRBY 233
14. Ecological aspects of the Severn barrage. T. L. SHAW 245
15. Environmental aspects of a Mersey tidal project.
J. TOWNER 263
Discussion on papers 13-15 275
Session 6.
16. Regional economic impact of the Severn barrage.
R. McGLYNN 285
17. The local authorities' view of the Severn barrage.
R. H. MOON 299
18. The economics of the Severn barrage. J. G. CARR 307
Discussion on papers 16-18 321
Panel discussion
Panel: G. BEVAN,J. CHESSHIRE,R. CLARE, B. COUNT and
R. T. GALES 327
Opening address
Rt Hon. PETER MORRISON, MP, Minister of State for Energy
Renewable energy sources offer the potential to
increase diversity of supply and will assist in
reducing the threat of the greenhouse effect.
Government intends to stimulate the development and
application of renewable sources of energy wherever
they have prospects of being economically
competitive and environmentally acceptable. We are
supporting a major research and development
programme aimed at developing all those technologies
which are relevant to UK conditions. Our studies on
tidal energy are a key element of this programme.
Over £145 million (over £195 million at 1989
prices) has already been invested so far by the
Department of Energy in renewable energy research
and development. Over £50 million is earmarked for
expenditure over the next three years. Over 250
renewable energy 'projects are under way at present
with a contract value of over £60 million.
It is a growing programme. Nearly 200 projects
worth over £100 million are at the planning and
formulation stage. We expect to start a further
70-80 projects this year. The programme is
undertaken in close collaboration with industry and
generating boards and over 20% of the cost of the
programme is met by external contributions. Around
25% of the cost of the programme is expected to come
from external sources in 1989/90.
Privatisation of the electricity industry will
create many opportunities for renewable energy. We
expect a significant number of renewable energy
contracts in the initial obligation. The 600 MW of
capacity we have reserved exclusively for renewables
in the Non-Fossil Fuel Obligation should encourage
further developments.
If every reasonable practicable estuary were to be
harnessed for tidal power, about 20% of the present
electricity demand in England and Wales could be met
by this means. A Severn barrage could contribute
about 7% of the electricity demand and is by far the
Developments in tidal energy. Thomas Telford, London, 1990
DEVELOPMENTS IN TIDAL ENERGY
largest single renewable project which could be
built in the UK.
The main objective of the Department of Energy's
tidal energy research and development programme is
to reduce uncertainty on costs, performance,
regional and environmental issues to the point where
it will be possible for private industry to make
decisions on whether or not to plan for the
construction of tidal barrages. The Department has
funded about £4 million towards studies of a Severn
barrage so far. The study carried out by the Severn
Tidal Power Group, published by HMSO as Energy Paper
Number 57, cost about £4 million. This cost was
shared equally by the Department of Energy, the
STPG, and the CEGB.
The Department is also providing funding for
studies of the feasibility of a Mersey barrage. The
total cost of Phases 1 and 2 of the project is about
£2 million shared equally by the Department and the
Mersey Barrage Company. We have also funded generic
tidal research and development, including funding
support for pre-feasibility studies of small-scale
barrages such as the River Conwy study. The total
cost of generic work completed since 1986 and
currently under way amounts to about £1.5 million.
The possible impact of tidal barrages on the
environment is a crucial factor in the consideration
of barrage schemes and you will not be surprised to
learn that two-thirds of the Department's generic
research and development programme, i.e. about £1
million, has and is being allocated to environmental
work. This work includes studies of the possible
impact of barrages on birds, fish and on the general
ecology of estuaries.
I welcome the recently published report on the
Severn tidal barrage. Publication will provide an
excellent opportunity for consultation with
interested parties and this third conference on
tidal power will form an important early part of
this process. The Severn study gives a clearer
picture than hitherto on costs, performance,
regional and environmental issues. Much further
work remains to be done, particularly on
environmental issues.
This conference comes at an important time for
tidal barrages in the UK. The Severn and Mersey
studies have presented us with an opportunity to
discuss tidal prospects in much more detail than was
hitherto possible. I wish to thank the ICE for
organizing the conference, thank the other sponsors,
thank the Royal Institute of British Architects for
providing the venue, and finally wish the conference
every success in its deliberations.
1. An introduction to the Severn barrage development
project: project promotion aspects
R. CLARE, Sir Robert McAlpine & Sons Ltd
SYNOPSIS
Following publication by the STPG* in 1986 of its report
"Tidal Power from the Severn", it was agreed that a further
study to be known as the Severn Barrage Development Project
should be undertaken. The cost of this was set at £4iM to
be shared equally between the Department of Energy, the
Central Electricity Generating Board and the STPG. The
latter were to be responsible for the execution of the work
and the objectives were established as follows.
1. To reduce uncertainty on the costs and performance of
a tidal barrage near Cardiff and Weston.
2. To examine further the regional and environmental
effects of a tidal barrage near to Cardiff and Weston in
consultation with all other interested parties.
3. To reassess the economic viability and financing of a
tidal barrage near to Cardiff and Weston in the light of the
further studies carried out.
4. To consider further the organisational, procedural,
administrative and legal options of a Severn Tidal Power
Barrage and to discuss their implications with other
interested parties.
Due to the Government's decision, announced in February
1988, to privatise the ESI, the Parties funding the Project
agreed that it would not be practical to pursue studies into
project promotion and financing during the period of change
hence these subjects were deferred from the Development
Project, reducing the cost to £4.lM.
A detailed content and programme for the Project was drawn
up and widely circulated in February 198 7 as a Consultation
Document. Many responses were received and appropriate
*STPG : The Severn Tidal Power Group consisting of :
Sir Robert McAlpine & Sons Ltd.
Balfour Beatty Ltd.
Taylor Woodrow Construction Ltd.
Wimpey Major Projects Ltd.(in assn.with W.S.Atkins & Ptnrs.)
GEC Turbine Generators Ltd.
Northern Engineering Industries PLC.
Developments in tidal energy. Thomas Telford, London, 1990
DEVELOPMENTS IN TIDAL ENERGY
adiustments made to the content and programme and the
principle subdivisions eventually adopted, following the
omissions referred to above, were as set out below.
£ K
Definition of Programme of Work 75
Tide Regime, Hydrodynamics and Energy Capture,
Sediment & Salinity modelling and Water Quality 570
Foundation Investigation Work and Review of
Alignment 780
Power System 500
Civil Engineering 780
Annual Costs 25
Regional Development 3 75
Ecological Studies 435
Proiect Economics 50
Legal Data Assembly 105
Management & Reporting 380
It should be noted that the Definition of the Programme of
Work included initial work on all subiects together with the
costs of the Public Consultation.
Additional ecological studies were commissioned directly by
the Department of Energy and will be reported later in the
Conference.
As a result of the geological survey commissioned at the
start of the Proiect the proposed alignment of the barrage
has been modified and the civil engineering reviewed. This
and the hydrodynamic studies have permitted some
optimisation of the installed generating capacity, though
this is not considered to be the final optimisation which
would require further study.
The preferred alignment considered was seaward of Cardiff
and Weston-super-Mare and is illustrated in figure 1. The
maiority of the barrage length would comprise reinforced
concrete caissons, constructed in shore facilities, floated
to site and sunk into position. There would be embankments
adiacent to the Welsh shore, near Steep Holm Island and
traversing deep sediments adiacent to the English shore.
The alternative to use of caissons, namely insitu
construction, has been studied but discarded on grounds of
high risk and long construction duration.
PAPER 1. CLARE
4 * Weston- *V
super-Mare L« A ^ ^W
Flat
Lavernock Holm
e
' P0Jnt LOCKS
FIG. 1
Basic data for the scheme are given below:
Number of turbine generators 216
Diameter of turbines 9.0m
Operating speed of turbines 50 rpm
Turbine generator rating 40 MW
Installed capacity 8640 MW
Number of sluices, various sizes 166
Total clear area of sluice passages 35 032 m2
Average annual energy output 17.0 TWh
Operation mode Ebb generation with flood pumping
Length of barrage, total 15.9 km
including: powerhouse caissons 4.3 km
sluice caissons 4.1 km
other caissons 3.9 km
embankments 3.6 km
Proiect design life 120 years
In the reference design large locks are included which would
be capable of passing the largest ships currently trading to
the ports within the basin (Panamax vessels) at most states
of the tide. Small craft locks would be provided near each
shore for inshore fishing vessels, pleasure craft and the
like. Alternative designs for larger and smaller shipping
locks have also been considered.
DEVELOPMENTS IN TIDAL ENERGY
A dual carriageway public road linking to the main highway
system on both shores could cross the barrage and a separate
service road would be provided.
Power would be transmitted by cable from the barrage
substations to shore substations on both sides of the
estuary where it would link into the national grid.
A 7 year construction programme to closure of the barrage is
proposed although this could be reduced by one year with
some increase in cost. On closure, those turbines already
installed would be commissioned and commence generation
whilst the remainder would be installed and commissioned
over a further two years giving an overall construction
programme of 9 years.
A maior consideration in determining the acceptability of
any barrage scheme will be its effects on the environment,
hence the work carried out in this study has been aimed to
develop a sufficiently detailed understanding of the system
to make a first comprehensive prediction of the
environmental effects of the construction and operation of
the barrage. The programme assembled available data,
collected further data on the present regime, identified
continuing changes without the barrage, and assessed the
implications of changes likely to be caused by the barrage.
The central processes in the estuary are the hydrodynamics
of tides (levels and currents) and waves. These influence
sediments, salinity and water quality which have a maior
bearing on the remainder of the ecosystem including man.
The work on these environmental matters does not constitute
a full environmental assessment, more work needs to be done,
but it has not revealed any insuperable difficulty.
The Severn Barrage would produce its primary benefit for the
national economy through the generation of electricity by
harnessing tidal forces in the Severn Estuary. In
addition, the barrage would also have a maior socio-economic
impact on the region in which it is sited. This regional
analysis has been made in five sections :
- Tourism and recreation
- Construction/operation of the Barrage
- Industrial and commercial property development
- Road Transportation
- Ports and shipping
These effects are largely "regional" and the benefits in the
form of income and employment are not all directly additive
to the benefits coming from the energy generation.
Nevertheless they represent significant regional benefits
and those arising from a cross barrage road may be
considered in national as well as regional terms. This