Memorandum submitted by Professor S H
Salter, Department of Mechanical Engineering, University of Edinburgh
This note follows the list of questions in the
call for evidence of 11 January 2001 with the addition of material
on research facilities. The call specifically restricts evidence
to non-barrier tidal schemes using the kinetic energy of the water
velocity rather than the potential energy as used at La Rance
and proposed for the Severn.
Is the technology available for efficient generation
from waves and tides?
The technology is not yet mature for either
but the specifications for hardware are well understood, full-scale
items for wave energy are being tested in commercial size prototypes
and the time for efficient generation is not far off. Pilot tidal
stream projects funded by the EC are under way. As in every other
technology the efficiency will improve continuously as designs
and manufacturing evolve, so there will not be a sharply defined
moment.
Will wave and tidal stream energy become commercially
viable in the near future and attractive to the private sector
as a profitable investment?
Commercial viability is difficult to define
for renewable energy systems. With information about wave climate
from the meteorologists and fluid loadings from tank tests we
know exactly what the weight of the plant will be for stresses
that the insurance market will accept. But the cost of a component
as a function of weight is a carefully guarded commercial secret
and jobs would be lost if accurate figures were to leak. Estimates
for capital cost are therefore based on uncertain parametric figures
which could easily be altered by some change in manufacturing
process, for example an increased level of automation for welded
fabrication or the reuse of concrete shuttering. The change could
be by as much as a factor of three or more, as has occurred with
wind. It is also hard to compare new installations with nuclear
stations which were brought by their present owners on rather
favourable terms when electricity was privatised.
However, an even greater uncertainty is because
the costs of electricity from renewable sources are completely
dominated by variations in the interest to be charged on the initial
capital investment. Rates can range from the 15 per cent used
for assessing some UK proposals down to 0.5 per cent for money
borrowed in Japan. This range of 30 to 1 feeds directly into costs
per kilowatt hour. AEA Technology are to be congratulated on the
recently introduced practice of plotting costs of renewable sources
against assumed interest rates.
The only practical tests of commercial viability
are the reducing level of subsidy needed to make private investors
build new plant and the continued solvency of the companies involved.
Wind turbines are only now just starting to be installed with
no form of subsidy or tax relief. Even though there were six million
wind-turbines in use for water pumping in the United States at
the start of the 20th century and the aircraft industry had established
the necessary theory to a far higher level than was available
for waves in 1973, it has taken 27 years and several billions
of pounds for wind generation to achieve this break-through.
It would be reasonable to expect a similar period
for both waves and tidal-stream unless special and unpleasant
circumstances force a more rapid process. However, several investors
are risking their money for research installations and several
research groups are investing something more valuable to them
than money—their working lives—because of the belief
that commercial viability will eventually be achieved.
What projects are currently running in the UK
and how successful have they been? Why did past projects fail?
Tidal streams
The Committee will be taking evidence directly
from people more closely involved with their own tidal-stream
projects and I am hesitant to make comments on the work of others.
Two groups in Britain are led by Peter Fraenkel and Ian Bryden
and funded by the EC. Both are working on pile-mounted tidal-stream
generators using the horizontal-axis rotors. The horizontal configuration
has proved more successful in wind energy than the vertical-axis
one. Indeed the operation of the plant now being built will be
very like that of an underwater wind turbine with dimensions modified
for the much greater power density. The sizes that have been chosen
are sensible for initial experiments. The rotors are sufficiently
far below the surface to reduce wave loading.
My own tidal-stream work has been concerned
with paper studies and design calculations of a vertical-axis
scheme (tried but rejected for wind) using a ring-cam power conversion
mechanism developed initially for wave energy. The figure shows
an artist's impression.
The reasons that the vertical axis did not succeed
for wind were that it uses symmetrical foil sections which have
a slightly worse lift-to-drag ratio than asymmetric ones: that
the blades are subject to reversed fatigue loading; that each
blade had to pass through an idle point twice per cycle; that
rotors with only two blades produced a very uneven torque.
A vertical axis tidal stream rotor will have
about 10 sets of blades so that the torque is smooth. The provision
of variable pitch reduces the fraction of idle time. Buoyancy
cancellation of weight encourages the use of thick foil sections,
which can be made strong enough to resist fatigue.
The main attraction of the vertical axis configuration
for tidal-streams is that the rectangular profile can fill a large
fraction of the flow window with closely-packed rotors and so
can make better use of the available resource. The ring-cam is
at the full rotor diameter so that torque-related stresses are
not magnified by sending power to a reduced radius. Surprisingly,
the large diameter of the cam makes it lighter because every cam
roller is operated by every cam lobe. All the power conversion
mechanism can be in a relatively spacious compartment above the
surface and much of the sealing problem vanishes. However, the
vertical-axis scheme is much more vulnerable to wave loading.
This will require very careful tank testing in every possible
combination of wave and current direction and there are at present
no facilities for combined wave and current tests. Siting of vertical-axis
rotors will be restricted to the more sheltered channels rather
than the exposed headlands. Rotor diameters sufficient to provide
the necessary stability in pitch and roll would have a power rating
of 10MW or more so that the vertical-axis is not a candidate for
early sea trials.
An interesting feature of closely-packed turbines
is that, if the ocean forcing function and acceptable upstream
water levels allow, they can improve on the Betz efficiency limit
for open field flow by blocking the channel and increasing the
upstream head. This could be controlled so that units always operated
with flow rates of spring tides through the entire lunar month.
The design calculations and an estimate of electricity
cost have been carried out by AEA Technology at Harwell (report
AEAT 3517). More details appear in the attached pre-print of a
paper to be given at the Marec 2001 conference in March,
An indication of previous commercial viability
of tidal-stream technology is that many thousands of tide mills,
consisting of an undershot water-wheel mounted on a pontoon, were
in operation in medieval times. The modern programme has not been
running long enough to have had any failures. Tidal-stream turbines
will not achieve the high efficiency of barrage systems but the
investment is made in much smaller steps. The predictability makes
the resource attractive to the electricity market.
Waves
The first UK on-shore oscillating water column,
built at Islay by Queen's University Belfast, has now been deliberately
demolished, leaving almost no trace. Although it had a very low
power rating it can be regarded as a considerable success if only
through its survival.
A second, larger, offshore oscillating water
column, the Osprey, planned for installation by Applied Research
Technology off Dounreay, was destroyed by heavy waves during the
installation. The Committee will be interested to hear that the
silt on the recovered parts was so radioactive that it would have
been illegal to store it in an open laboratory. I believe that
the root cause of the failure was ultimately traceable to inadequate
tank testing. I was relieved to hear that the company has since
acquired its own wave tank.
Lessons learned from the first Islay plant and
from Osprey have been incorporated in the Queen's University/Wavegen
Limpet, a full-size onshore system built close to the site of
the smaller one. This was connected to the grid at the end of
2000 and is now undergoing trials at levels limited by an undesirably
meagre grid connection. I am sure that the Committee will be hearing
directly from Professor Whittaker and from Wavegen Ltd.
The early installations of wave power devices
have shown that a well-chosen wave site is a poor construction
site and I expect that there will in future be a move toward yard
construction and floating devices. All the people involved with
onshore plant agree that eventually, and perhaps quite soon, the
installations must move offshore because of high power levels
and more sea space. The next move in that direction is to be made
by Ocean Power Delivery led by Richard Yemm. The company has built
a series of models of the Pelamis system at progressively increasing
scales. A full size unit will be launched next year. They have
a 15 year SRO-3 licence to operate two 375 kW units at Machir
Bay on Islay.
The Pelamis produces power by hydraulic pumps
at the joints of a segmented spine lying parallel to the wave
direction. The company has placed particular emphasis on survival
rather than on productivity or best use of sea space, but the
combination of rigorous tank tests and numerical computer models
has produced a very creditable power-to-weight ratio—quite
as good as that of larger systems. It has been Richard Yemm's
policy to use no material or component that does not have an established
track record in offshore conditions. The programme will provide
a great deal of information about the use of hydraulics for wave
energy.
A final wave scheme using wave overtopping with
a free-floating vessel, developed by Sea Power International,
has been awarded a SRO licence to generate at a site off Shetland
but I am not close enough to the project to make any comment.
As part of an EC JOULE programme the Edinburgh
group designed and built parts for a turbine and a fast control-valve
to be used in a Portuguese oscillating water-column in the Azores.
Low-pressure air has been the preferred power conversion medium
and the Wells turbine the mechanism. However, the Wells turbine
does not have a very wide bank of efficient operation in real
sea conditions because the blades stall at higher air flows. Our
task was to build a variable-pitch version of the Wells turbine
so as to prevent stall. The withdrawal of the commercial partner
responsible for making the turbine blades has meant that the machine
has not yet been commissioned. Our Portuguese partners, Instituto
Superior Technico in Lisbon, hope to raise money to finish the
blades and then install the variable-pitch turbine alongside a
fixed-pitch one. The question about whether or not the extra complexity
of variable pitch outweighs the smaller sizes, lower idle losses
and increased productivity will be known when the first full-power
efficiency data are available from the Limpet. This should be
very soon and I would not like to predict where the balance will
be.
If I had to supply reasons for the failure of
the first UK wave programme I would cite over-optimism, the attempt
to make very big (2GW) power stations and to assess infant devices
too quickly. The programme was properly supported and enthusiastically
led from 1976 to 1983, a period of only seven years, and then
entered a very unhappy phase where researchers felt that they
were always on the defensive. An account of this has been given
to a Committee of another place (HL paper 88, 21 June 1988 page
178 and 190-206) and it does not, at present, seem helpful to
repeat it here.
What role should wave and tidal stream energy
have in the Government's renewable energy strategy? Should they
have a higher priority?
This must depend on whether the Government and
its civil servants really want renewable energy to succeed or
whether they want to appear to be supporting a programme but really
want it to fail. Over the years many of the officials with whom
we dealt certainly seemed to want success but this often proved
to be a dangerous career move. I must warn the Committee that
this danger is not confined to officials. There was a Commons
Energy Committee which looked into renewables in 1992. A copy
of my evidence (pages 62 to 68 of volume III) is attached. One
of the Committee's recommendations was the resurrection of the
wave energy programme. The Energy Committee was immediately disbanded!
Always there seems to be a layer, or indeed
layers, of senior people with negative views about renewables
and the power to make them stick. This power seems to be inversely
related to technical knowledge of the subject or technology in
general. If the concerns about carbon levels, global warming and
long-term supplies of fossil fuels are well founded, then the
Government policy should be that every possible renewable source
should be thoroughly researched to the point that it could rapidly
be employed at some stage in the future. The demonstration of
this capability would do much to limit the dangers of a manipulated
market for oil or gas and could be regarded as part of a nation's
defences. The costs of a vigorous research programme are very
small compared with the total spending on fuel or the possible
future consequences of having insufficient energy supplies. The
spin-off in unexpected directions has, so far, been quite sufficient
to justify what has been spent. Diversity between renewable sources
with different availability reduces the problems caused by lack
of firmness of supply. This could be further reduced by the use
of renewable sources for the manufacture of hydrogen, methanol,
ammonia or even potable water.
Wave energy has an enormous potential for Europe
particularly if, in future, we build a spur north-west from Cape
Wrath. This is discussed in an attached memorandum written at
the request of the EC DG XVII Small Hydro Strategy meeting. Tidal-stream
energy is smaller but attractively predictable. Both are clean
and have rather low conflicts with other human activities.
What research and development is being undertaken
at present?
My own present research work on waves (initially
privately funded but now supported by DTI and EPSRC) involves
a modification to a Swedish buoy system which makes it move along
an adjustable slope rather than in the conventional heave direction.
The buoy uses an internal reaction reference and has an ingenious
stroke-limiting technique which gives it outstanding survival
features. The slope idea has been shown to be very good with models
constrained to run along a fixed guide rail. Slope gives productivity
gains of four in long period waves. Our present task is to see
if this remains true for a free-floating tank model. If so, a
full scale device would be suitable for power generation in very
deep water. The programme has recently come under threat because
of a decision by Edinburgh University to demolish our test tank
this July because the land is needed for other purposes.
Most of my previous work on waves was for the
duck system. This was intended to make the very best use of the
sea-space by employing large numbers of close-packed devices and
using every hydrodynamic trick to improve efficiency. Official
analysis of the cost of duck electricity fluctuated wildly depending
mainly on assumptions about reliability and was often the highest
or the lowest of the many devices being assessed. The full historical
list of official cost estimates is given in an attached paper,
written for an IEE conference.
For the 2 gigawatt duck design we had taken
the opposite approach from Richard Yemm. We wanted to maximise
the use of the available sea space. This meant that every part
had to be optimised for its task and we found that many of them
had to be invented. Some of the consultants employed by Harwell
to assess our work reacted just as the Wright brothers would have
done to drawings of a Boeing 707. However, since the closure of
the first UK wave programme, we have found ways to exploit the
new technologies in other applications with support from Denmark
and Canada. The duck will go to sea when it is thought that there
is not enough sea space and there is a need to use as much as
possible of it. I do not think that the duck programme failed,
merely that it will be long delayed. If the first UK wave programme
were to be judged on the output of essential wave energy theory
and talented young engineers, many of whom are now in senior industrial
positions, I would judge it to be a great success.
I understand that an official from EPSRC, who
has better information about the whole picture of academic R&D
will also be giving evidence to your Committee.
How much funding is available and how easy is
it for innovative ideas to gain support?
Again, EPSRC will be giving evidence.
Is national funding being well co-ordinated?
Several factors make co-ordination difficult.
Private investors must protect their investment by secrecy in
a way that is totally foreign to academics, even if a large fraction
of the money is coming from public sources. There are even stronger
motives for secrecy following poor productivity or the loss of
a prototype. Mistakes will then be repeated by others. It does
not have to be like this. Following an aircraft accident there
is a very expensive investigation with the most detailed information
supplied to and carefully studied by the entire industry. This
should be an obligation in return for receipt of public money.
A strict direction by DTI would tend to violate
the independence of the EPSRC. This independence is important
because there is also documentary evidence that an official from
ETSU tried hard, but apparently without the approval of DTRI,
to discourage support for wave energy from Brussels. Over-strict
co-ordination stifles original ideas. I am, therefore, on balance
in favour of open published consultation between independent bodies
and a degree of anarchy. However, this general view has been suddenly
challenged by a serious co-ordination problem concerning test
tank facilities which I would like to draw to the attention of
your Committee. It concerns test facilities for wave energy research,
which I regard as essential and which are expensive enough to
have to be nationally co-ordinated. I discuss this further in
the section on research facilities on page 11.
What sort of peer review processes are being undertaken?
During the "seventies and eighties"
funding for almost the entire renewable energy programme of academic
and industry was supplied by the DTI (or Department of Energy
when it existed) through the Energy Technology Support Unit at
Harwell, then part of the United Kingdom Atomic Energy Authority.
Now (with many of the same people in the same buildings but a
changed arrangement of fences) this group has been renamed as
AEA Technology. I do not know if any peer review process was involved
but I expect that everything was decided by ETSU and the Department
of Energy, with long range control of a committee known as ACORD
that was recruited largely from the nuclear and the depletable
energy industries. It has not been possible to get minutes of
their meeting of 19 March 1982 from which the wave programme manager,
Clive Grove-Palmer, was excluded and at which it was decided to
close the UK wave programme.
The previous Science and Engineering Research
Council funded some of the projects but nobody could understand
the reasons for the separation. This has now been changed. I am
told that my own grant from DTI is the last to be given to a university.
From now on, only industrial work will be supported by the DTI
on a shared cost basis so that industry must find some of its
own money or do some very creative accounting on its overhead
rate. Nobody in renewable energy can yet do this nearly as well
as the defence industry.
Funding for most academic work, now including
waves, is the responsibility of the Engineering and Physical Sciences
Research Council, which is given money by Government but notionally
makes independent decisions. I have some evidence that this independence
was not complete when, in 1986, a proposal for work on wave energy
was rejected on the grounds that it was not strategic, as defined
by the Renewable Energy Advisory Group set up by the DTI.
There are two modes of application. In the responsive
mode, any academic can propose any research topic in any field
and it will be directed to the most suitable section of EPSRC.
The chances of success are about 30 per cent. For the second managed
mode, with a slightly higher chance of success, EPSRC issues calls
for research into particular areas such as renewable energy and
University teams can apply before the given closing date. Schemes
exist for applications from young, newly-appointed staff and for
decisions about projects below £60,000 to get quick decisions.
I strongly approve of these. For larger projects in both managed
and responsive modes, copies of the grant proposal consisting
of six pages and a computerised form are sent to three or four
experts in the field, one of whom will have been picked from a
list of three provided by the applicant. Replies from the experts
are considered by a panel of about 15 people with a general engineering
background. The panel will have been drawn from a college nominated
by fellow academics. Two of them will have been asked to study
the proposal in detail beforehand but others may be seeing it
for the first time at the afternoon of the meeting.
Sometimes the panel will decide about an award
in a way which goes contrary to the indication of the referees'
comments. Sometimes they will approve a proposal, but the Council
will not have sufficient funds to make an award. It used to be
the case that a reduced award would be offered but then everybody
increased their cost estimates by the expected reduction factor
and so that has now been changed. Grants are given in full or
not at all: if you put in extravagant estimates you reduce your
chance of success.
EPSRC give useful guidance on how to write proposals
and the computerised forms, which do some of the calculations
automatically, are appreciated. These forms are not nearly as
complex as those for a DTI or an EC project. Success depends greatly
on the choice of referees and the author of an unsuccessful proposal
is often angry about the ignorance and even carelessness that
is sometimes shown. A particularly valuable recent change is that
the applicant now sees referee comments before the panel meeting
and is given the chance to reply to them. I understand that EPSRC
do remove from their list of referees those who appear inadequate
or biased.
Everything seems very slow to somebody with
a hot idea and a research team to feed. A particular subject area
(not of course renewable energy!) can develop a small charmed
circle which protects its own interests, awards itself money and
seeks to exclude newcomers. Except for getting international referees
who will be less likely to know the applicants it is difficult
to see how this can be avoided.
The EC grant process goes to very great lengths
to prevent fraud. The identities of the expert advisers are kept
secret. The first half of the process uses forms which conceal
the identity of the proposer. Experts are summoned to Brussels
where they are kept secluded for an intensive week of appraisal
so that their work rate can be observed by officials. There seem
to be many fewer of these officials than for the DTI and all those
that I have met have been very well qualified technically as well
as distinguished linguists. EC projects require a combination
of partners across European borders. This does form European bonds
but it remains true that if you want to make something that is
already difficult even harder, do it with people who speak different
languages and who are a long way apart.
The extreme efforts made to prevent corruption
do slow the procedure to the point where it becomes very difficult
to keep small companies and research groups intact through the
gaps. It might be useful to calculate the ratio of money spent
preventing corruption to the amount of money lost by it. I would
prefer to have more severe penalties but less delay.
The Danish support for new wave projects is
in extraordinary contrast to all the others. They want to be certain
beyond all reasonable doubt that every potential idea is given
the very best chance to survive and prosper. Anybody with an idea
for wave energy conversion is given the Kroner equivalent of £5,000.
It does not matter if the idea seems bad. It does not matter if
it has already been tried and failed several times before. It
does not even matter if the inventor is Danish or not. They have
set up a small-scale test site at a fiord at Nissum Bredning in
North Jutland with a pier, power-supplies, data-logging, analysis
software, shelter, hand-tools, moorings and wave gauges. Anyone
who turns up gets the money and can, literally, dive in and get
to work.
Inventors of devices which show the slightest
degree of promise are then given larger amounts of money for tests
in the controlled conditions of university test tank facilities.
The enthusiasm of everyone and the rate of progress is impressive.
It is easy to see how a country which had no aerospace programme
has come to dominate the world wind industry. They have yet to
learn some of the lessons from the wave UK programme but I do
not think that this will take them long.
The problems of maintaining continuity for small
companies and research teams are discussed in the attached notes
for the DTI through a study conducted by Ove Arup.
What are the environmental aspects of wave and
tidal stream energy, particularly for marine life? How will such
devices affect shipping?
Waves
The environmental aspects of wave energy appear
to be surprisingly benign. The onshore devices are built into
cliffs of sharp rock; where the water is deeper it is nearly always
too dangerous for leisure activities. It is quite wrong to imagine
ugly obstructions in the middle of beautiful bathing beaches.
The concrete of onshore installations quickly matches the rock
around it because the same weed and lichens are growing. It is
quite difficult to see an installation from a short distance offshore.
Some designs of air-turbine may produce unpleasant noise which
could well be audible above the background of wind and breaking
waves.
For offshore devices the problems seem even
less, and several effects are positive. Any part of a wave plant
which is not in contact with the wave is not generating useful
work and so many designs show very little above the surface, some
none at all. Lights and radar reflectors will have to be added
but the visual intrusion to people ashore will be low. They will
be better marked than moving sand banks and submerged rocks and
should have a net positive effect on marine safety though improved
navigation markers. Cargo ships usually keep to the shortest great-circle
routes between ports which are well away from the Irish and Hebridean
wave fields.
There will be more of a conflict with fishing
activities. Fish like being near wrecks and oil platforms, perhaps
because they get food and protection. Fishermen know this well
and get as close to oil platforms as they dare. Clams grow fatter
from the warmth generated by undersea electrical cables, and clam-dredgers
will deliberately work along the cable routes causing a large
fraction of marine cable failures. Quite apart from the risk of
collisions, fishing gear can get fouled by invisible parts of
mooring systems. It would probably be best both for wave energy
and, in the long term for the fishing industry itself, if a strip
of sea either side of a wave installation was designated as a
fish-breeding reserve and strictly protected. A consolation to
fishermen is that the skills, courage and endurance need for their
present trade would be very much in demand for the installation
and maintenance of offshore wave energy devices.
Behind a large offshore installation there will
be a tendency for growth rather than erosion of beaches but the
magnitudes of the effect are not yet known. In moderate conditions
the sea behind a close-packed wave plant will be noticeably calmer
and so would add to the many attractions of sailing off the west
coasts of Scotland and Ireland.
Tidal-Streams
The environmental impact of tidal stream plant
will be greater than for offshore waves because the highest currents
are in channels and headlands close to shore. There will be conflicts
with shipping and perhaps concerns about the wake vortex on small
sailing vessels.
Seamen are used to all sorts of marine hazards
and usually prefer them visible, so the vertical axis rotors may
have some advantage. Installations can be marked on charts more
accurately than moving sandbanks. They can carry lights and radar
reflectors and will not make any sudden manoeuvres. They do not
carry dangerous chemicals or explosives. We can expect that tidal
stream plant will be less of a hazard to ships than natural hazards
and other ships.
Marine creatures have to develop skills to avoid
fast-moving attackers. There is therefore reason to hope that
fish can use the pressure field around the foils to avoid them.
The blades will move in a very predictable way with velocities
lower than the fastest marine predators. There are no reports
of fish being killed by going through the turbines of the tidal
barrage turbines at La Rance or by waves on sharp rocks.
Operators of tidal stream plant will have their
own very strong incentives not to spill oil, and the oils used
will be light and clean.
Marine fouling on hydrofoils will induce a serious
drop in efficiency and some anti-fouling paints are highly toxic.
This will probably be the environmental factor of greatest concern
but concentrations will be much lower at good tidal stream sites
than in the confined conditions of a yacht harbour.
How does Britain compare with comparable nations
in R&D in this field? What projects are currently being undertaken
abroad and how successful have they been?
Britain enjoyed a dominant position in both
the theory and testing of wave energy during the first programme
but this has faded since the mid-eighties. It was difficult for
overseas governments to believe that, if wave energy could not
work in the good wave climate of the British Isles, it might still
work for them. It took a considerable period for their local groups
to counter negative reports from here.
Enthusiasm for waves is naturally influenced
by local wave climate and so is strong in Portugal and Ireland.
However, the less attractive wave climate of Denmark does not
diminish their enthusiasm. I am most familiar with work in Portugal,
which was built up a very effective group working on oscillating
water columns as part of multination European projects. The construction
of the full-size unit at Pico in the Azores was delayed by incomplete
civil work for two winters in succession. Damage to the half-finished
structure during winter storms was serious. It was difficult to
decide whether to complete the civil works or abandon the project
but finally it was completed and a fixed-pitch turbine has been
installed. The Portuguese have learned how expensive it can be
to work so far from an industrial base and their next oscillating
water-column will be on the mainland.
The Committee will be able to obtain better
information about overseas work from Tom Thorpe at AEA Technology.
Following the publication of HL paper 88, 21 June 1988, Thorpe
was appointed to carry out a review of wave energy. At that time
the confidence of the UK researchers in ETSU and the DTI was at
rock bottom. Even though some of Thorpe's early cost estimates
were above the previously disputed ones from ETSU consultants,
the fairness and transparency of his analysis completely reversed
the attitudes of the research community. One extraordinary change
was that, instead of the ban on communications between research
teams and assessors which had been imposed by Harwell, he supplied
copies of his spread-sheets to all the research groups. This allowed
them to see where the problems were and what should be done to
remove them. His reputation spread through the world wave community,
leading to a number of overseas device assessments, and he therefore
has an unrivalled knowledge of the subject. I very much hope that
AEA Technology will allow him to give evidence to your Committee.
Work on tidal streams is proceeding in Norway,
Italy and China. The Chinese have many sites between islands and
the mainland where currents are particularly strong and where
supplies of new power are urgently needed.
Research Facilities
A central part of wave energy research at Edinburgh
has been the testing of models in tanks. I believe very strongly
that safe and cost-effective designs can evolve only through the
most rigorous measurements of the behaviour of small-scale models
in controlled and repeatable conditions. It is possible, for example,
to generate exactly the same 100 year wave every 30 seconds with
the model position changed by small amounts. My views are also
shared by leading authorities on numerical simulation of wave
behaviour, which has improved greatly in recent years but is still
limited to linear conditions. There are several examples of seemingly
intractable problems solved after a theoretician saw a wet model
under test. My work on wave tanks may now have to come to an end
for reasons which should be of concern to your Committee. It is
important to realise the difference between tanks for wave energy
and those that were used for towing ships.
Test tanks were originally built to improve
the design of ships by reducing drag and also for accurately predicting
the propulsion power that a full shape would require. There was
not much variation between experiments and the time and cost of
the test could be accurately predicted. A new hull could be checked
in an afternoon. This also tends to be true for work on oil platforms
where the main requirement is for insurance purposes with observations
of fluid loading and over-topping in a set of specified extreme
conditions.
Initial work on wave energy can be done in a
narrow tank with a single wave maker but even at this stage devices
have to be tested for productivity with a wide range of amplitudes
and periods as well as in rare extremes. Furthermore, there are
many more variables of shape, immersion, trim, power-conversion
technique and reaction stiffness so that, even with highly automated
testing, many hundreds of hours are needed. Things get still more
demanding for devices which must be tested in a wide tank with
all the variations of wave direction and spectral shape.
In 1977 we were given permission to build a
new and initially controversial design of wide tank which had
control of directional spectra over a wide area and wave makers
that could absorb energy reflected from models. The control unit
and safety interlocks were planned to allow visitors to use everything
themselves and we routinely allow access to undergraduate students.
It was soon so much in demand that in 1980 a second one was built
and, for a time, both tanks were working 24-hours shifts. The
tank was built on land earmarked for the future wing of a large
building and I had to promise that I would not oppose its removal
after a period of five years.
Last year, Edinburgh University made a successful
bid for £7 million to the Joint Infrastructure Fund which
distributes money from the Wellcome Foundation and the Office
of Science and Technology for major university building projects
for specific research topics. Selection is based on advice form
the EPSRC referees, who could not be expected to know about EPSRC
grants for wave energy.
When I heard of the possibility of the bid I
told the University authorities I would of course honour the promise
I made in 1977 but that I would like money for tank relocation
to be included in the application. This would have amounted to
about 1 per cent of the total building cost. I was given a written
assurance that this would be done. I have just learned that this
clause was not included and that the site on which our tank stands
will have to be vacated in June. A brand new replacement of the
tank would cost about three-quarters of a million pounds and the
loss of the tank means that I will seriously compromise a research
project for EPSRC valued at nearly a quarter of a million. Neither
the OST, nor EPSRC and certainly not Wellcome, can be blamed for
an unfortunate change of policy in a university which is the result
of the financial pressure now being suffered by all universities.
However, perhaps any similar bids in future could carry a specific
question about unintended collateral damage arising from what
should have been a very happy event.
The JIF bid could eventually perhaps have a
fortunate outcome. We have been working on designs for a new tank
which would be able to generate both waves and currents independently
round the full 360 degrees, with continuous sweeps through all
the variables of spectrum, direction and current-velocity. Its
design has been influenced by the requirements of tidal-stream
research but there will be many other applications. It is known
from ship losses off Cape Agulhas and the Pentland Firth that
some very interesting and dangerous things occur when currents
move directly into waves. The tank could also be used for work
on low-head hydro, tidal surges, flood defences and rising sea
levels. A pre-print of a paper to given at the Marec 2001 conference
describing the design of the new tank is attached.
ATTACHMENTS[3]
Proposal for a large, vertical-axis tidal-stream
generator with ring-cam hydraulics. Pre-print of a paper to the
Marec 2001 conference, Newcastle March 2001.
Evidence to the Energy Committee, 11 March 1992
volume III pp62-77. HMSO.
Changing the 1981 Spine-based ducks. IEE Renewable
Energy Clean Power 2000.
Conference 17-19 November 1993. IEE London.
pp121-130
(Discusses improvements suggested by the release
of the Thorpe analysis.)
Memorandum to the Small Hydro Strategy Meeting,
4 September 1996.
(Discusses the European dimension and the Cape
Wrath spur.)
Political Decisions about Wave Energy. Note
written at the request of DTI following the appointment of John
Battle as Minister for Energy.
(Discusses UK problems and includes a discussion
on the hazards of the marine environment and argues the case that
the land can be even worse.)
Edinburgh Input to Ove Arup study on wave energy
for DTI. 21 August 2000.
(Discusses further research needs.)
Proposals for a combined wave and current tank
with independent 360º capability. Pre-print of a paper to
the Marec 2001 conference, Newcastle March 2001.
VHS video tape of wave energy experiments on
models in test tanks.
9 February 2001
3 Not printed. Back
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