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READING PASSAGE 3
Tidal Power
Undersea turbines which produce electricity from the tides are set to become an important source of
renewable energy for Britain. It is still too early to predict the extent of the impact they may have, but all the
signs are that they will play a significant role in the future
A
Operating on the same principle as wind turbines, the power in sea turbines comes from tidal currents which
turn blades similar to ships’ propellers, but,
unlike wind, the tides are predictable and the power input is
constant. The technology raises the prospect of Britain becoming self-sufficient in renewable energy and
drastically reducing its carbon dioxide emissions. If tide, wind and wave power are all developed, Britain
would be able to close gas, coal and nuclear power plants and export renewable power to other parts of Europe.
Unlike wind power, which Britain originally developed and then abandoned for 20
years allowing the Dutch to
make it a major industry, undersea turbines could become a big export earner to island nations such as Japan
and New Zealand.
B
Tidal sites have already been identified that will produce one sixth or more of the UK’s power - and at prices
competitive with modern gas turbines and undercutting those of the already ailing nuclear industry. One site
alone, the Pentland Firth, between Orkney and mainland Scotland, could produce 10% of the country’s
electricity with banks of turbines under the sea, and another at Alderney in the Channel Islands three
times the
1,200 megawatts of Britain’s largest and newest nuclear plant, Sizewell B, in Suffolk. Other sites identified
include the Bristol Channel and the west coast of Scotland, particularly the channel between Campbeltown and
Northern Ireland.
C
Work on designs for the new turbine blades and sites are well advanced at the University of Southampton’s
sustainable energy research group. The first station is expected to be installed off Lynmouth in Devon shortly
to test the technology in a venture jointly funded by the department of Trade and Industry and the European
Union. AbuBakr Bahaj, in charge
of the Southampton research, said: The prospects for energy from tidal
currents are far better than from wind because the flows of water are predictable and constant. The technology
for dealing with the hostile saline environment under the sea has been developed in the North Sea oil industry
and much is already known about turbine blade design, because of wind power and ship propellers. There are a
few technical difficulties, but I believe in the next five to ten years we will be installing commercial marine
turbine farms.’ Southampton has been awarded £215,000 over three years to
develop the turbines and is
working with Marine Current Turbines, a subsidiary of IT power, on the Lynmouth project. EU research has
now identified 106 potential sites for tidal power, 80% round the coasts of Britain. The best sites are between
islands or around heavily indented coasts where there are strong tidal currents.
D
A marine turbine blade needs to be only one third of the size of a wind generator to produce three times as
much power. The blades will be about 20 metres in diameter, so around 30 metres of water is required.
Unlike wind power, there are unlikely to be environmental objections. Fish and other creatures are thought
unlikely to be at risk from the relatively slow-turning blades. Each turbine will be
mounted on a tower which
will connect to the national power supply grid via underwater cables. The towers will stick out of the water and
be lit, to warn shipping, and also be designed to be lifted out of the water for maintenance and to clean
seaweed from the blades.
E
Dr Bahaj has done most work on the Alderney site, where there are powerful currents. The single undersea
turbine farm would produce far more power than needed for the Channel Islands and most would be fed into
the French Grid and be re-imported into Britain via the cable under the Channel.
F
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One technical difficulty is cavitation, where low pressure behind a turning blade causes air bubbles. These can
cause vibration and damage the blades of the turbines. Dr Bahaj said: ‘We have to test a
number of blade types
to avoid this happening or at least make sure it does not damage the turbines or reduce performance. Another
slight concern is submerged debris floating into the blades. So far we do not know how much of a problem it
might be. We will have to make the turbines robust because the sea is a hostile environment, but all the signs
that we can do it are good.’
