Rubber 'Snake' Could Help Wave Power Get A Bite Of The Energy Market
ScienceDaily (July 7, 2008) — A device consisting of a giant rubber
tube may hold the key to producing affordable electricity from the
energy in sea waves. Invented in the UK, the 'Anaconda' is a totally
innovative wave energy concept. Its ultra-simple design means it
would be cheap to manufacture and maintain, enabling it to produce
clean electricity at lower cost than other types of wave energy
converter. Cost has been a key barrier to deployment of such
converters to date.
Named after the snake of the same name because of its long thin
shape, the Anaconda is closed at both ends and filled completely with
water. It is designed to be anchored just below the sea's surface,
with one end facing the oncoming waves.
A wave hitting the end squeezes it and causes a 'bulge wave'* to form
inside the tube. As the bulge wave runs through the tube, the initial
sea wave that caused it runs along the outside of the tube at the
same speed, squeezing the tube more and more and causing the bulge
wave to get bigger and bigger. The bulge wave then turns a turbine
fitted at the far end of the device and the power produced is fed to
shore via a cable.
Because it is made of rubber, the Anaconda is much lighter than other
wave energy devices (which are primarily made of metal) and dispenses
with the need for hydraulic rams, hinges and articulated joints. This
reduces capital and maintenance costs and scope for breakdowns.
The Anaconda is, however, still at an early stage of development. The
concept has only been proven at very small laboratory-scale, so
important questions about its potential performance still need to be
answered. Funded by the Engineering and Physical Sciences Research
Council (EPSRC), and in collaboration with the Anaconda's inventors
and with its developer (Checkmate SeaEnergy), engineers at the
University of Southampton are now embarking on a programme of larger-
scale laboratory experiments and novel mathematical studies designed
to do just that.
Using tubes with diameters of 0.25 and 0.5 metres, the experiments
will assess the Anaconda's behaviour in regular, irregular and
extreme waves. Parameters measured will include internal pressures,
changes in tube shape and the forces that mooring cables would be
subjected to. As well as providing insights into the device's
hydrodynamic behaviour, the data will form the basis of a
mathematical model that can estimate exactly how much power a full-
scale Anaconda would produce.
When built, each full-scale Anaconda device would be 200 metres long
and 7 metres in diameter, and deployed in water depths of between 40
and 100 metres. Initial assessments indicate that the Anaconda would
be rated at a power output of 1MW (roughly the electricity
consumption of 2000 houses) and might be able to generate power at a
cost of 6p per kWh or less. Although around twice as much as the cost
of electricity generated from traditional coal-fired power stations,
this compares very favourably with generation costs for other leading
wave energy concepts.
"The Anaconda could make a valuable contribution to environmental
protection by encouraging the use of wave power," says Professor John
Chaplin, who is leading the EPSRC-funded project. "A one-third scale
model of the Anaconda could be built next year for sea testing and we
could see the first full-size device deployed off the UK coast in
around five years' time."
The Anaconda was invented by Francis Farley (an experimental
physicist) and Rod Rainey (of Atkins Oil and Gas). There may be
advantages in making part of the tube inelastic, but this is still
under assessment.
Wave-generated electricity is carbon-free and so can help the fight
against global warming. Together with tidal energy, it is estimated
that wave power could supply up to 20% of the UK's current
electricity demand.
The two-year project 'The Hydrodynamics of a Distensible Wave Energy
Converter' is receiving EPSRC funding of just over £430,000.
*A bulge wave is a wave of pressure produced when a fluid oscillates
forwards and backwards inside a tube.
posted to ClimateConcern by Lily Anselm
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