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several hundred kilowatts delivered by
a free-flow turbine. The sole drawback:
the turbines only work efficiently when
the tidal difference is at least 5 metres.
So there is just a handful of suitable
locations in the world. ‘And man-made
sites aren't an option either.’
Location, location, location
Swansea is an ideal place for a tidal
power plant because of the large
difference between high and low tide. A
breakwater about fifty to one hundred
metres wide and almost ten kilometres
long will create a lagoon with space for
sixteen turbines that generate power
when the water rises or falls.
This is the first tidal lagoon on this
scale and so the project could be a
public attraction. The lagoon will be
located exactly between two ports in
order not to interfere with shipping.
Only a small part of the breakwater
can be seen above the water and the
idea is that it will be open to the public.
The Tidal Lagoon website says that the
lagoon will also generate opportunities
for local employment, water sports and
other leisure activities. Anton explains:
‘The turbines can also pump water.
That means that the water level can be
controlled accurately to keep the local
impact to a minimum.’
Scale model
Deltares developed numerical and
physical models to calculate the
optimal conditions for the turbines.
‘During the process, we discovered that
energy production fell when the water
didn't flow straight into the turbine.
A skewed flow can reduce turbine
efficiency by up to ten percent.’
Deltares has devised several solutions
for this problem. They include placing
breakwaters in smart locations or
changes to the structure to improve
the flow to the turbines. Tidal Lagoon
PLC is now looking at the solutions to
determine which are the most practical.
There are also ongoing negotiations
with the British government about a
fixed price per kWh. Building will not
start until those negotiations have
been completed. The price guarantee
is essential because development
costs are high. The price tag is 1 billion
euros. But once the plant is up and
running – the planned date is 2020 –
it is expected to continue producing
electricity for about 120 years. The
lagoon can produce enough power
annually for 155,000 households,
which is almost the entire city of
Swansea.
More information:
anton.defockert@deltares.nlPOWER FROM
TIDES IN
SWANSEA BAY
DELTARES, September 2016
DOSSIER
STUDY
Impression of the breakwater surrounding the lagoon