Science & Environment
World's first lagoon power plants unveiled in UK
- 2 March 2015
- From the section Science & Environment
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Plans to generate electricity from the world's first series of tidal lagoons have been unveiled in the UK.
The
six lagoons - four in Wales and one each in Somerset and Cumbria - will
capture incoming and outgoing tides behind giant sea walls, and use the
weight of the water to power turbines.
A £1bn Swansea scheme, said to be able to produce energy for 155,000 homes, is already in the planning system.
Energy Secretary Ed Davey says he wants to back the project.
The
cost of generating power from the Swansea project will be very high,
but the firm behind the plan says subsequent lagoons will be able to
produce electricity much more cheaply.
It says the series of six lagoons could generate 8% of the UK's electricity for an investment of £30bn.
As
well as Swansea, the proposed lagoon sites are Cardiff, Newport, and
Colwyn Bay in Wales; Bridgwater in Somerset; and West Cumbria.
Each
will require engineering on a grand scale. In Swansea, the sea wall to
contain the new lagoon will stretch more than five miles and reach more
than two miles out to sea.
The Cardiff lagoon could include up to
90 turbines set in a 14-mile (22km) breakwater around Cardiff Bay and
could generate power for about 14 hours each day.
A planning application for the project is expected in 2017.
If approved, it could be generating power by 2022.
The cost would be funded by
electricity bill-payers under the existing government scheme to promote
home-grown, low-carbon energy.
Tidal Lagoon Power aims to negotiate with the government over how much it can charge for its power.
It wants £168 per MWh for electricity in Swansea, reducing to £90-£95 per MWh from a second, more efficient lagoon in Cardiff.
'Energy dance'
The
£90 figure compares favourably with the £92.50 price for power from the
planned Hinkley nuclear station, especially as the lagoon is designed
to last 120 years - at a much lower risk than nuclear.
Mr Davey
told BBC News: "I can't make a decision on this yet because discussions
are ongoing. But I'm very excited by the prospect of tidal power.
"We
have got some of the biggest tidal ranges in the world and it would be
really useful if we could harness some of that clean energy."
How does tidal lagoon power work?
The lagoons operate a system similar to a lock gate to alter the water level either side of a sea wall.
When the tide starts to rise, gates in the wall are closed and water builds up outside the lagoon.
When the tide is full outside the lagoon, the gates are opened and water rushes past the turbines to fill up the lagoon.
When the tide turns to go out, the gates are shut to hold the water inside the lagoon.
As
low tide is reached outside the wall, the gates are opened to generate
power again as water flows through from the raised water level in the
lagoon.
Power firms also like the idea of lagoons-energy because, unlike power from the sun and wind, it is predictable.
Turbines
capture energy from two incoming and two outgoing tides a day, and are
expected to be active for an average of 14 hours a day.
Mark
Shorrock, CEO of Tidal Lagoon Power, told BBC News: "We have a wonderful
opportunity to create energy from the dance between the moon and the
earth.
"It is admittedly rather expensive to begin with but as
time goes on and the capital costs are paid off it becomes incredibly
cheap."
Environmental concerns
A
previous plan for a barrage on the River Severn to create tidal power
was scuttled after environmentalists protested it would prevent the
daily exposure of mud flats vital for wading birds.
The Swansea
lagoon plan is more widely accepted as it does not impede estuaries and
allows the tides to flow as normal - albeit delaying each tide inside
the lagoon for a few hours.
Gareth Clubb, Director of Friends of the Earth Cymru, said the group is broadly in favour of the Swansea lagoon.
"It's not unqualified approval - we want to make sure that the environmental impact can be managed," he said.
"But if it helps us to close Aberthaw power station - one of the most polluting in the world - it'll be a good thing."
Anglers,
though, fear the impact of the lagoon on fish migrating to spawn in
local rivers which are only recently recovering from generations of
pollution.
Phil Jones, who fishes on the River Tawe, said the plan had not been questioned "loud enough or widely enough".
"We would very strongly oppose any plans for this and other lagoons down the South Wales coast," he said.
The
firm agrees some migrating fish will stray into the turbines, but
project the numbers will be tiny, and that the new sea wall will benefit
fish by creating its own reef habitat.
Follow Roger on Twitter @RHarrabin
http://www.bbc.com/news/science-environment-31682529
Penulis : Drs.Simon Arnold Julian Jacob
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