APPENDIX 2
Memorandum submitted by Dr Andrew Turnpenny,
Fawley Aquatic Research Laboratories
SUMMARY AND
CONCLUSIONS
This evidence concerns environmental issues
relating to the potentially serious (but perhaps not insuperable)
impacts on migratory fish of tidal power generation. It is based
on the author's experience as former head of the Aquatic Technology
research section of the Central Electricity Research Laboratories
(subsequently of National Power) in the UK Tidal Power programme
of the 1980s and early 1990s and subsequent research applied to
freshwater hydropower generation. Conclusions of the evidence
are:
1. The issue of migratory fish passage across
tidal power barrages was one of the major barriers to tidal power
development during the 1980s. Owing to the continued decline of
migratory fish species in the UK, the fish protection issue will
have become even more sensitive.
2. Research into fish injury mechanisms in
turbines has advanced since the 1980s-early 1990s and there are
now much better prospects of quantifying possible damage to fisheries
and, more importantly, designing and operating turbines to be
more "fish-friendly". The AHT project in the USA would
merit investigation.
3. The development of acoustic fish guidance,
originally investigated for tidal power application, has advanced
in the last 10 years from a concept to a reality. It is now widely
regarded as the "best available technology" for estuarine
fish screening. The possibilities of safely diverting fish around
a turbine should not be realisable.
4. From the fisheries point-of-view, the
case for tidal generation merits re-opening but consideration
should be given to a small scheme, with limited environmental
damage potential, in the first instance (ie not the Severn).
1. INTRODUCTION
1.1 I respond on behalf of my organisation,
Fawley Aquatic Research Laboratories Ltd (FARL), although mainly
in a personal capacity, as much of my experience in this field
in this field pre-dates FARL. Until 1991, I was head of Aquatic
Technology research within the CEGB then National Power. I sat
for some years on the Fisheries Committee of the Severn Tidal
Power Group (STPG) and in my capacity within the Central Electricity
Research Laboratories, attended meetings on several of the UK
tidal energy schemes that were proposed in the 1980s. These related
entirely to environmental matters and associated research and
development, and it is to these issues I address my comments.
I also serve presently as Fisheries Co-ordinator on the Environment
Committee of the International Hydropower Association.
1.2 Within the power industry research divisions
I ran research programmes into assessing and solving fisheries
problems relating to tidal power, especially looking into the
consequences for migratory fish including Atlantic salmon, sea
trout, shads and eels. My group was also investigating other ecological
aspects, including effects on the benthic environment, on shrimps
and prawns and on phytoplankton communities.
1.3 My present company, FARL, was formed
in 1991 as a private independent company, specialising in research
and consultancy into the effects of power generation on the aquatic
environment. FARL is based in the former marine research laboratories
of the CEGB at Fawley and has continuity with the original research
group engaged in tidal energy studies. Much of the work that began
in the Tidal Power programme of the 1980s has continued but is
now directed inter alia towards freshwater hydropower generation.
I will provide a brief summary below.
1.4 We have had no involvement in wave energy
matters although related environmental matters are within our
competence.
2. FISHERIES
ISSUES RELATING
TO TIDAL
POWER
2.1 Much of the scientific discussion into
fisheries issues arising from tidal power was devoted to consideration
of the proposed Severn Tidal Barrage. While, as far as I can remember,
something like 60 UK estuaries were identified as having possible
tidal power potential, only three were given serious consideration.
These were the Severn (although this contains several sub-estuaries
that may have been included in the 60), the Mersey and the Conwy.
However, the issues raised in these studies would probably encompass
all potential environmental issues affecting smaller estuaries.
Therefore, a general model can be drawn from the historical work.
2.2 The single largest fishery problem arising
from tidal power generation is the inevitable passage of migratory
fish through the hydroelectric turbines, with consequent injury
risk. These fish include a number of threatened or declining species,
including Atlantic salmon (Salmo salar), sea trout (S.
trutta), Allis shad (Alosa alosa), Twaite shad (A.
fallax) and the European eel (Anguilla anguilla). While
there is a recognised problem for these species on conventional
terrestrial hydropower plant, the problems are heightened at tidal
power schemes for a number of reasons:
2.2.1 Tidal power schemes are designed to
maximum tidal flux capacity, so generate from practically all
of the water flux in the estuary, whereas freshwater schemes are
designed to operate within certain limits and spill water at high
river discharges; downstream migrants tend to favour spate flows
for their migrations and so a large proportion tend to avoid passing
through the turbines.
2.2.2 Flow in riverine systems is one-way
and fish are at risk only once for each passage of the scheme,
whereas in the estuarine phase, fish may swill back and forth
with the tide, potentially being forced through the turbines several
times during a single migration.
2.2.3 Conventional hydropower schemes are
designed to operate with maximum efficiency at the design hydraulic
head, which is set by the height of the dam, the percentage head
change due to rainfall input being low; tidal power turbines operate
on a tidally varying hydraulic head and suffer a large percentage
change in operating head, hence they are at their maximum efficiency
point only for a small proportion of the time. The wasted energy
when operating off-design is shed in the form of turbulence, which
is damaging to fish, causing scale loss, eye injuries and torsion
injuries (eg gill covers or even heads being torn off).
2.2.4 The conventional method of preventing
fish entry into turbines on riverine schemes is to place fine-meshed
screens ( ~ 12 mm mesh) across the water intakes, the fish being
guided into a downstream bypass. This method is not practical
in estuaries, owing to the much higher debris loads, including
seaweed, jellyfish, maritime debris, whole trees, etc. Self-cleaning
travelling screens (eg band screens) could potentially be used
to remove the debris but these by themselves can inflict fatal
injuries on delicate species such as salmon and shad. I recall,
also, that when the installation of travelling screens on the
Severn scheme was considered, the estimated cost was prohibitively
high.
3. HISTORICAL
FISHERIES R&D IN
THE UK RELATING
TO TIDAL
POWER
3.1 A commissioned review by Solomon (1988)
of factors causing injury to fish during turbine passage led to
the view that there was insufficient understanding of the specific
injury mechanisms. Without knowing such mechanisms, it was not
possible to give guidance to design engineers or turbine manufacturers
that might allow turbines to be either designed or operated in
a more "fish-friendly" way; nor was it feasible to come
up with reliable estimates of likely fish injury rates in the
turbines.
3.2 Accordingly, a joint laboratory study
was set up by the UK Department of Energy (DoE) and the CEGB,
which was carried out under my leadership at Fawley. Special apparatus
was designed and constructed to stimulate separately the various
stress factors, including rapid pressure change, hydraulic shear
stress and turbulence, cavitation and runner blade strike. This
allowed greatly improved estimates of fish injury rate to be made
for the key species. For the nine metre diameter turbine design
proposed for the Severn, the following injury rates were predicted:
| Fish (length) |
Injury Rate |
| Adult salmon (100 cm) | 40%
|
| Salmon smolt (15 cm) | 10%
|
| Adult eel (70 cm) | 28%
|
| Juvenile shad (7 cm) | 53%
|
3.3 The study was not published in full at the time (1992),
as the DoE wished further research to be carried out before findings
so potentially harmful to the tidal power initiative were made
public. However, owing to great public interest that followed,
a "glossy" summary was produced in June 1993, which
presented the key findings. I have attached a copy of this as
Appendix 1[1]. Further,
more detailed accounts were presented to international conferences
in Vienna (Turnpenny, 1998) and Monterey (Turnpenny & Everard,
1999). The full original report is held now at FARL.
3.4 The next stage of the research concentrated on developing
means of efficiently diverting fish around the turbines. It was
decided that the generating units could be constructed in modular
fashion and that for each unit there would be a bypass slot made
in the barrage, through which fish might be diverted. Having established
that physical screens would not be practicable to effect this
diversion, recent developments in the USA, which indicated that
fish might be repelled and guided by underwater sound, came to
our attention. A study, funded by the Department of Trade and
Industry (DTI) was set up at Fawley, in collaboration with the
lead scientist from the USA (Dr Paul Loeffelman), to evaluate
the effectiveness of underwater sound against the UK species in
question. The results were reasonably encouraging and a report
was published (Turnpenny et al., 1993). A summary of this
study is included here as Appendix 2.[2]
This led to an initial field trial which was carried out at Hinkley
Point nuclear power station in Somerset, with interesting results
(Turnpenny et al., 1994).
3.5 Regrettably, at this time, the UK tidal power programme
was closed down, and there was therefore no opportunity to carry
this work through to its conclusion with respect to tidal power.
As I shall report below, the work has continued most successfully
in other directions.
4. HISTORICAL OVERSEAS
PERSPECTIVE
4.1 It is worth mentioning here that as the Severn Tidal
Power Group's (STPG) Fisheries Committee, we carefully scrutinised
experience elsewhere, particularly at the two existing schemes
at La Rance (Brittany, France) and Annapolis Royal (Nova Scotia,
Canada). This involved meeting with scientists associated with
these schemes and reviewing scientific documents.
4.2 The La Rance scheme, the only full-scale commercial
scheme, proved disappointing as a model. There was little published
or other material made available to us about the estuary and its
fisheries prior to construction of the barrage. Surprisingly,
its operators (E de F) claimed that there was no apparent adverse
effect of the barrage on fisheries. Possibly, its closure during
the construction phase may have removed any migratory fisheries
that existed previously.
4.3 The Annapolis scheme was set up in the Bay of Fundy
(which has largest tidal range in the world) as a pilot scheme
with a single test turbine. Its impact on fisheries has been intensively
studied (see Solomon, 1988), showing generally a very high impact
level on migratory fisheries, concurring with the results of our
own studies mentioned above. I believe this may be the main reason
why the scheme never developed beyond the pilot stage.
4.4 I recall hearing of another small tidal power scheme
in China but know of no details.
5. CURRENT UK FISHERIES
R&D RELEVANT TO
TIDAL POWER
Acoustic Fish Guidance
5.1 I mentioned above that work on acoustic fish guidance
has continued and achieved success, in the absence of the tidal
power programme. Following on from the promising results of the
early trials, Nuclear Electric supported further work at Hartlepool
nuclear power station, which resulted in the successful exclusion
of 50-60 per cent of estuarine fish from the cooling water (CW)
inlets of the power station. This has led to the development and
commercialisation of underwater sound generating equipment by
FARL through a company known at Fish Guidance Systems Ltd (FGS).
FGS has now installed 40 or more systems in UK and Europe, on
thermal and hydroelectric power plant and drinking water abstraction.
Several of these systems have been independently evaluated and
shown to achieve ~ 80 per cent fish diversion efficiency, with
95 per cent or higher for sound-sensitive species such as herring.
Two new UK estuarine thermal power stations (at Great Yarmouth
and Shoreham, respectively) have been fitted with this technology
at the request of the Environment Agency. Testing at the recently
commissioned Shoreham station has shown this plant has exceptionally
low impact on estuarine fish, as a result.
5.2 In 1997-98, the DTI funded a review by FARL of fish
screening legislation in England, Wales and Scotland, and the
preparation of a Best Practice Guide for fish screening at hydroelectric
turbine intakes (Turnpenny et al, 1998). This document
would also have relevance to tidal generation.
5.3 The use of acoustic fish guidance to protect fish
at a tidal generating plant would therefore be a much more realistic
prospect than it was 10 years ago when first mooted.
Fish Injuries in Turbines
5.4 While no research into tidal power turbines has been
undertaken since that mentioned above, the DTI has funded work
at FARL to apply the results from the earlier tidal power study
to small hydroelectric schemes (Turnpenny et al, 2000).
This has meant that the research capability in this area is alive
and well. In particular, the field of computational fluid dynamics
(CFD), the means by which the stress conditions for fish during
turbine passage can be calculated, has advanced considerably since
the original study.
6. USA RESEARCH: THE
ADVANCED HYDRO-TURBINE
PROJECT
6.1 At the time when the original turbine fish-passage
study was completed, the findings led to no obvious solutions
on behalf of the turbine designers and manufacturers but the study
attracted the attention of US researchers. The US Department of
Energy has funded an Advanced Hydro-Turbine (AHT) project. This
project (for which I have acted as a casual adviser), seeks to
develop a "fish-friendly" turbine design. The AHT project
(Odeh, 1998) took the results of the Fawley study, along with
others, to try to define the ideal turbine from the fish passage
aspect. The original work has been extended by additional laboratory
studies. They now have a conceptual design, tested by CFD, and
are approaching (or may have begun) the construction of a small-scale
prototype.
6.2 The AHT concept is similar to that of a fruit-pump:
a type of screw pump developed to pass fruit without pulping it.
Similar pumps are used on fish farms to transmit live fish unharmed
from one containment to another. CFD modelling results indicate
that efficiencies of the order of 90+ per cent might be achieved
from this design. If it works, it could solve the problem of fish
passage at tidal power schemes, but it is too soon to be too optimistic.
A key issue would be whether the AHT concept offered high efficiency
at varying tidal level.
7. CONCLUSIONS
7.1 The issue of migratory fish passage across tidal
power barrages was one of the major barriers to tidal power development
during the 1980s. Owing to the continued decline of migratory
fish species in the UK, the fish protection issue will have become
even more sensitive.
7.2 Research into fish injury mechanisms in turbines
has advanced since the 1980s—early 1990s and there are now
much better prospects of quantifying possible damage to fisheries
and, more importantly, designing and operating turbines to be
more "fish-friendly". The AHT project in the USA would
merit investigation.
7.3 The development of acoustic fish guidance, originally
investigated for tidal power application, has advanced in the
last 10 years from a concept to a reality. It is now widely regarded
as the "best available technology" for estuarine fish
screening. The possibilities of safely diverting fish around a
turbine should now be realisable.
7.4 From the fisheries point-of-view, the case for tidal
generation merits re-opening but consideration should be given
to a small scheme, with limited environmental damage potential,
in the first instance (ie not the Severn).
REFERENCES
Odeh, M, 1999. A summary of environmentally friendly turbine
design concepts. US Departments of Energy, Idaho Operations Office.
Report No. DOE/ID/13741, July 1999, 39 pp.
Solomon, D J, 1988. Fish passage through tidal energy barrages.
Energy Technology Support Unit, Harwell. Contractor's Report No.
ETSU TID4056, 76 pp.
Turnpenny, A W H, 1998. Mechanisms of fish damage in low-head
turbines: an experimental appraisal. In: Fish Migration and
Fish Bypasses (Ed. Jungwirth, M, Schmutz, S and Weiss, S).
Fishing News Books, Oxford, Blackwell: 300-314.
Turnpenny, A W H, Thatcher, K P, Wood, R and Loeffelman,
P H, 1993. Experiments on the use of sound as a fish deterrent.
Fawley Aquatic Research Laboratories Ltd, Report to the Energy
Technology Support Unit (ETSU), Harwell, Didcot, Oxfordshire OX11-ORA,
Contractors Report No. ETSU T/04/00171/REP.
Turnpenny, A W H, Wood, R and Thatcher, K P, 1994. Fish deterrent
trials at Hinkley Point Power Station, Somerset. Fawley Aquatic
Research Laboratories Ltd, Report to the Energy Technology Support
Unit (ETSU), Harwell, Didcot, Oxfordshire OX11-ORA, Contractor's
Report No ETSU T/04/00198/REP.
Turnpenny, A W H, Struthers, G and Hanson, P, 1998. A UK
guide to intake fish-screening regulations, policy and best practice
with particular reference to hydroelectric power schemes. Fawley
Aquatic Research Laboratories Ltd, Report to the Energy Technology
Support Unit (ETSU), Harwell, Didcot, Oxfordshire OX11-ORA, Contractor's
Report No ETSU H/06/00052/REP. 117 pp.
Turnpenny, A W H and Everard, J K (1999). Can cavitation
injure fish? In: Innovations in Fish Passage Technology
(Ed.: Odeh, M.). American Fisheries Society ISBN 1-888569-17-4,
197-205.
Turnpenny, A W H, Clough, S., Hanson, K P, Ramsay, R and
McEwan, D (2000). Risk assessment for fish passage through small,
low-head turbines. Fawley Aquatic Research Laboratories Ltd, Report
to the Energy Technology Support Unit (ETSU), Harwell, Didcot,
Oxfordshire OX11-ORA, Contractor's Report No. ETSU H/06/00054/REP.
19 January 2001
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