Underwater works: the natural ebb and flow of the tide could
produce ultra-clean electricity which would bring major economic
and environmental benefits for seaboard nations globally.
The elusive goal of discovering a
practical way to produce electric
power with no risk to the
environment could soon be in
sight - thanks to the certain and
unceasing flow of the
seas’ tides.
United Kingdom engineers
are researching the
practical prospects of
generating ultra-clean
power in experiments off
the coast of Wales. They
are delighted with their
progress in proving the
potential of a new submerged
system that could
bring major economic
and environmental benefits
for seaboard nations
worldwide.
Following highly
promising underwater rig
tests, marine engineer
Richard Ayre and his UK
company Tidal Hydraulic
Generators are designing
an underwater turbine, similar to a
small wind turbine, that can be submerged
in a scour channel - an undersea
valley through which a constant
tidal flow of between two and four
knots provides a high-energy source of
usable power.
The ballasted turbine unit will rest
on the scoured seabed at a depth of
some 60 metres, where it will reap the
full benefit of tidal flow. There, it will
be deep enough to avoid potential
damage from the effects of storms that
can whip up random and violent surface
waves 14 metres or more in
height, disturbing underwater tidal
flows. The turbine head is designed to
turn through 360 degrees to seek the
tidal direction.
Richard Ayre says: “The environmental
impact is virtually zero. There
is no need for foundations that would
disturb the seabed; nothing on the surface
of the sea, so no visual impact;
and lubrication is by vegetable oil.
There is no risk to the environment and
low risk in technical terms, because the
system uses a combination of existing
technologies in a novel way.”
He added that, unlike previous
schemes to generate power from the
sea, the capital investment required for
this tidal flow power system is highly
cost-competitive. It could generate
power at between half and the same
cost as proposed off-shore wind farms,
with no visual or structural presence to
spoil coastal views or impede shipping.
Energy generation would be fully
predictable with operators aware of
exactly how much power it would produce,
and when. And the modular system
is designed to be installed in and
removed from its subsea location in
just one day.
Free flowing currents,
strong and consistent
enough to guarantee costeffective
power generation
are found in many
close-to-shore locations
globally.
“Initial trials in
Milford Haven waterway
revealed very interesting
results,” said Mr. Ayre.
“We have determined stable
data for power output
to water speed, compared
with maximum power
over a variety of turbineblade
tip speeds and output
revolutions per
minute. The hard data we
have gained means we
can model the inter-relationship
of multiple turbines with a
great deal of confidence. This will lead
to the design of an operational seabed
unit. We have also developed a self-cleaning
system that prevents encrustation
and fouling of the turbine.”
The next series of trials will focus
on a rig placed in the estuary of the
River Severn in south-east Wales
where immensely powerful and variable
tidal flows will test the integrity
and reliability of the system under
harsh conditions.
Meanwhile, the UK team is also
working on an inexpensive and efficient
method of transmitting energy
away from an operational tidal flow
farm by converting the electrical
power it generates into hydrogen in a
purpose-built unit inside the trial rig.
The project was launched in 1997
following joint research with the
Pembrokeshire Coast Marine Nature
Reserve into the practicality of positioning
a wave-monitoring buoy
three kilometres offshore, part of a
scheme to investigate methods of
protecting this rich area of marine
life from trawlers.
