Memorandum submitted by R V Power Company
RVco is a company which has been specifically
set up to exploit the opportunities for electrical power generation
offered by global offshore and estuarine tides and current. It
employs novel RV technology which suffers from none of the disadvantages
inherent in traditional tidal barrage schemes. In the RV system,
there are no moving electrical or mechanical components under
water, there is little environmental impact, and the output is
in the form of compressed air which can be piped, underground,
to the generating station without significant power loss. Turbines
driven by compressed air are more compact and efficient than those
driven by relatively slow moving water, so the capital cost of
the generators is much less than in a comparable barrage scheme.
The founders of RVco Ltd were the author, Dr
Geoff Rochester, and Dr John Hassard. Our present team includes
Professor Sir Eric Ash (director), Dr Keith Pullen (turbine expert),
Nigel Stokes MBA (director), Niall McGlashan (engineer), Dr Joseph
Neil (US Co-ordinator), Dr Colleen Lee (UK Co-ordinator), Professor
Dennis Anderson (business adviser).
It has been estimated (1), that if all the opportunities
for generating power from water currents around the UK were exploited,
it might ultimately be possible to win 200 TWh per annum, which
is equivalent to the continuous operation of a 23 GW power station,
or about half the nation's electrical energy needs. These water
currents themselves represent, however, only a fraction of the
total tidal potential energy around the UK, as much of this energy
is lost to turbulence.
Because the energy resource in the tides is
so vast, the possibility of turning it into useful power has long
attracted interest. The extraction of this power is difficult,
though, because the energy density is so low; large scale installations
are needed to harness it. This is particularly difficult in a
hostile marine environment.
Mostly, the schemes proposed in the past have
involved setting up a tidal barrage, such as that currently operating
at La Rance. Similar barrages across the Severn and the Mersey
have been considered. However, even La Rance, although technically
successful, has proved uneconomic. The Severn and Mersey schemes
have been shelved on the grounds of cost and environmental impact.
While the Inquiry to which this Memorandum is
addressed does not include the consideration of tidal barrages,
they will provide a useful benchmark against which other proposals
may be measured.
Conventional tidal barrier schemes work by trapping
the water at high tide and then letting it out at low tide, while
the head falls from the high tide level to some minimum below
which the turbines cannot work efficiently. As the biggest output
is obtained at exactly low tide, this means that, ideally, to
take full advantage of the available potential energy, there has
to be a huge generating capacity which is used for only a very
In the similar situation, an RV, which does
not attempt to trap the tide and only partially obstructs the
flow, will develop a smaller head of water than that which is
contained by a barrage. This small head, which arises as long
as the tide flows, is amplified, by the unique design of the RV
to something comparable with the height of high tide. The amplified
head is then used to drive a relatively small quantity of water
around a secondary water circuit. The secondary flow can be maintained
for a good fraction of the tidal cycle, so the output is much
less sharply peaked than it is from a barrage. This means that,
for an equivalent electrical energy output, the generating capacity
can be less and the duty cycle greater, thereby increasing the
economic viability of the project. Tests on a scale model have
shown that it should be possible, even on a conservative estimate,
to convert 20 per cent of the total water power dissipated in
the RV into electricity.
It has been requested in the press notice that
this Memorandum addresses the following issues.
3.1 Technological Viability
It is undoubtedly the case that RV technology
is feasible. This has been proved in laboratory tests. The laboratory
tests also showed that a high conversion efficiency, from tidal
power to electrical output, can be expected.
3.2 Commercial Viability
Currently, large scale tests of RV's are being
prepared. These will confirm commercial viability. It is clear
that, ultimately, commercial viability will depend upon the site
of the installation. Some sites will be much more tractable than
others. In order to carry the project forward, once commercial
viability has been proved in principle, the easiest sites, namely
those with favourable tides and geology, and fewest conflicting
interests, will be tackled first. The experience thereby gained
will be used to assess the profitability of building similar structures
in more difficult locations. As we accumulate knowledge and experience,
it is possible that the return on investment will increase, despite
the sites becoming more challenging.
Our present estimates suggest we can produce
electrical power at between two and ten pence per kWh, with the
most viable sites clustering around two pence or three pence per
kWh. The greatest uncertainties in our costings come from site-specific
issues, marine civil engineering estimates and planning permission.
3.3 Current Projects and Earlier Failures
As far as we know there are only two other current
tidal energy projects in the UK. One is that run by IT Power (www.itpower.co.uk),
funded with 1M Euro by the EU, which involves placing a 300 kW
submarine propeller driven turbine under the sea off Cornwall.
Clearly, this will suffer all the drawbacks of having mechanical
components (turbine and gearbox) and electrical components (generator
and wiring) in a hostile and corrosive marine environment. However,
we believe that IT Power's cost estimates, which predict power
production at six pence per kWh or better, are well founded. Their
group has great expertise in the necessary technologies. Their
work will assuredly lead to a far greater understanding of the
economics of such installations, and is to be highly commended.
The other proposal, from the Southampton Oceanic Institute, is
to put a similar device in the Solent.
We believe that RV technology suffers from none
of the drawbacks inherent in the technology being applied by these
In 1994 ETSU carried out a survey of tidal stream
technology for the Department of Trade and Industry (2). This
survey concluded that the extraction of such energy would be uneconomic.
It suggested, for instance, that the unit cost for a tidal scheme
in the Pentland Firth or off the Channel Islands, where the currents
are especially strong, would be 10 pence per kWh at 8 per cent
discount, or 16 pence per kWh at 15 per cent discount. Their summary
stated "Tidal streams do not therefore appear at present
to offer an economically viable energy source". However,
ETSU's costings have been widely discredited as being far too
conservative and its assumptions biased against tidal energy.
Moreover, RV technology was not considered in ETSU's survey, which
points out that "the costs partly reflect the hostile environment
where the resource is located. The strong currents and large waves
would represent major hazards to support vessels and particularly
to divers; moreover, shipping channels pass through or near five
of the 33 sites considered. Machinery would be subject to potentially
severe corrosion damage, encrustation by marine organisms and
fluctuating forces, which would increase fatigue and shorten plant
life". The RV approach sidesteps these issues.
A Renewables Strategy should be at the heart
of a coherent, consistent, comprehensive, long-term Energy Policy.
This should take account of the following:
1. The rate at which oil reserves are being
discovered is slowing down. When rising demand meets falling supply,
the price will skyrocket. The same logic applies to gas. Gas prices
have already doubled in the past year. This increase is unambiguously
associated, at least in part, with a new realism about total reserves.
Hence, in the long term, the relative cost of
renewable energy supplies can only improve. Global demand is due
to increase enormously as countries such as China and India strive
to reach consumption levels taken for granted in the West. Hence,
investment in renewables now is certain to bear fruit later. The
UK is in the enviable position of being in the lead in many of
the areas required for tidal energy extraction, and could capitalise
on investment commitments made now, in the same way that Danish
and German companies are reaping the benefits of early investment
in wind energy technology and expertise.
2. The per capita demand for electricity
is rising in the West as citizens buy more electrically powered
items, transport relies increasingly on electrification, and new
power sinks such as computer server farms and air conditioning
become more common. The ongoing crisis in California illustrates
how vulnerable advance economies have become, and while the UK
and EU do not face such brown-outs in the immediate future, a
convergence of factorsthe phasing out of nuclear power,
the Kyoto Accords, and the increasing cost of fossil fuelsmakes
renewable energy more attractive.
3. Exceptional demand for electricity due
to climate change are also possible, either for air-conditioning,
or, if the Gulf Stream fails, for additional winter heating.
4. Even if global warming, for which there
is now abundant evidence, is not a consequence of human activity,
it still needs to be brought under control. Ideally, all electricity
should be derived from renewable sources. This means reducing
demand as well as securing an environmentally friendly source
of supply. Pressure to reduce demand will also develop as the
price of fossil fuels rises. Options here are improvements in
efficiency, subsidisation of insulation, and a carbon tax.
5. If the Greenland ice sheet melts and
turns off the Gulf Stream, northern Europe is likely to be plunged
into a Siberian climate. This could put overhead transmission
lines at risk from ice storms. It could therefore be prudent to
abandon the policy of having a few huge generating stations in
favour of a much more widely distributed network of smaller local
installations. This change of attitude would favour renewable
6. Further to the above, the increase in
transport costs which will follow rising oil prices will tend
to enhance the significance of local communities and their products
at the expense of global trade. Local, renewable, power schemes
would harmonise with this philosophy. RV's are particularly suitable
here, as they promise to be as effective on a small, as on a large,
Hence, a firm Renewables Strategy would anticipate
future trends and give the UK a lead in what is likely to be an
expanding global market. One way to put this Strategy on a sound
footing would be to impose a carbon tax, as this would transform
the economics of wave and tidal power overnight. To tax users
of electrical irrespective of its origins, as in the incoming
Climate Change Levy, is perverse.
3.5 Research and Development
Getting ideas to the market place has always
been difficult in the UK. Once a technical principle has been
proved, the next question invariably concerns the economic viability
or the cost effectiveness. Finding an answer to this question
can involve considerable financial risk. At this level, nine ideas
may fail, before the 10th produces big returns. Generally, UK
funding agencies are unwilling to take this risk. It is at this
stage that the idea goes abroad.
3.6 Environmental Aspects
Traditional tidal barrages have a significant
detrimental environmental effect. Water heights are permanently
altered, marine life is segregated from the area of trapped water,
shipping is obstructed and hardware tends to be visually obtrusive.
The proposed RV installations would restrict
the flow of water but not bring it completely to a halt. Indeed,
in environmentally sensitive locations, the fraction of energy
extracted can be reduced until the environmental impact is brought
down to an acceptable level. Our studies show that, in many locations,
a fraction of the energy, even within natural variations, can,
when extracted, still produce a viable return on investment.
In an RV
(a) Water heights are not permanently altered.
The times at which high and low tides occur are slightly delayed.
(b) Marine and bird life will be unperturbed.
Marine life may even be enhanced, because the submerged RV can
be designed to be an attractive habitat for fish and crustaceans.
(c) Most of the RV will be underwater, and
therefore visually unobtrusive, but in some locations it may emerge
at low tide, like a jetty or breakwater.
(d) The RV can be incorporated into existing
or planned constructions, such as coastal defences, off-shore
windmills or oil-rigs, bridges, causeways and tunnels.
(e) Energy, in the form of compressed air,
can be piped underground some distance from the offshore RV to
the generator, sited near existing electricity grid lines. The
eyesore of pylons in scenic locations should therefore be avoided.
(f) The impact on shipping is more uncertain.
Initially, sites for RVs will be chosen where shipping is not
an issue. However, there would be difficulties on busy routes.
If an RV were installed in the Thames, for instance, shipping
movements would have to be restricted to about one quarter of
the tidal cycle, necessitating compensation payments to shipowners.
Elsewhere, the RVs would come near enough to the surface to have
to be lit and marked with buoys. The partial obstruction of channels
by RVs would also result in increased currents in the shipping
The RV strategy is to cherry pick the best sites,
those at which no conflicts of interest occur, moving on to the
more difficult ones as expertise builds. Fortunately, there are
hundreds of sites round the UK which are suitable, thousands round
the EU and tens of thousands around the world, including those
in the open ocean. As the benefits of tidal energy become apparent,
we believe remaining difficulties can and should be solved.
(g) In contrast to the traditional tidal
barrage, the RV electricity generating plant will be running for
at least half the tidal cycle. This means that, to generate the
same amount of power, the capital costs of the generators and
their capacity is correspondingly less. Furthermore, the turbines
will be driven by compressed air, allowing the use of small compact
units. The power generating plant is therefore expected to be
easily accommodated within existing planning regimes.
3.7 International Comparisons
All the other being done in this area, in the
UK or abroad, involves placing turbines under the surface of the
sea, either in a fast natural current or in one which has been
We have high hopes that the generation of electricity
using RV technology will prove environmentally benign as well
as profitable. It is based upon entirely new ideas and therefore
offers an opportunity for the UK to take a lead in contributing
to a solution to the problem of global warming. The RVs are scalable,
making them adaptable to different circumstances, and modular,
allowing many units to be connected to the same generator, thereby
achieving economies of size. A subsidiary advantage is that they
can be used to aereate and thereby purify the water at the same
time as providing electrical power. The potential global market
is huge, and could provide both employment within the UK and income
from abroad. If we can seize the initiative by installing a wide
range of different types of generator and proving their various
abilities in different circumstances, as well as using them to
make a significant positive contribution to the electricity budget
of the UK, so that Britain acquires the reputation of being a
world leader in this technology, then, when the price of oil and
gas starts to rise, the UK will be in a superb position to dominate
the market. However, the lead time for these developments is measured
in years, so it would be as well to make an early start.
2. ETSU T/f05/00155/REP
8 January 2001