alt.energy.renewable

Ending a dammed nuisance
Feb 19th 2008
From Economist.com

A new generation of free-standing turbines will liberate hydroelectricity
from its dependence on dams

IN TODAY'S green world, hydroelectric dams are often unwelcome. Though their
power is renewable and, on the face of it, carbon-free, there are lots of
bad things about them, too. Blocking a river with a dam also blocks the
movement of fish upstream to spawn and the movement of silt downstream to
fertilise fields. The vegetation overwhelmed by the rising waters decays to
form methane-a far worse greenhouse gas than carbon dioxide. The capital
cost is huge. And, not least, people are often displaced to make way for the
new lake. The question, therefore, is whether there is a way to get the
advantages without suffering the disadvantages. And the answer is that there
may be.

The purpose of a dam is twofold. To house the turbines that create the
electricity and to provide a sufficient head of water pressure to drive them
efficiently. If it were possible to develop a turbine that did not need such
a water-head to operate, and that could sit in the riverbed, then a dam
would be unnecessary. Such turbines could also be put in places that could
not be dammed-the bottom of the sea, for example. And that is just what is
starting to happen, with the deployment of free-standing underwater
turbines.

The big disadvantage of free-standing turbines is that they are less
efficient in transforming the mechanical energy of water into electrical
energy than turbines in dams are. They are also subject to more wear and
tear than turbines protected by huge amounts of concrete. They can be hard
to get at to repair and maintain. And the generators they run, being
electrical machines, need to be protected from the water that surrounds the
rest of the turbine.

A discouraging list. But in the past three decades computing power has
become cheaper, helping developers to simulate the behaviour of water and
turbine blades-something that is hard to do with paper, pen and formulas.
Moreover, prototypes can be built directly from the computer model. All this
has helped scientists and industry to solve the weaknesses inherent in
free-standing turbines.

The first new design was by Alexander Gorlov, a Russian civil engineer who
worked on the Aswan High Dam in Egypt. He later moved to America where, with
the financial assistance of the Department of Energy, he produced the first
prototype of a turbine that could extract power from free-flowing currents
"without building any dam". The Gorlov Helical Turbine as it is known,
allows you to use any stream, whatever the direction of its flow. The
vertical helical structure, which gives the device its name, provides a
stability that previous designs lacked. It increases the amount of energy
extracted from a stream from 20% to 35%. In addition, as the shaft is
vertical the electric generator can be installed on one end above the
water-without any need of waterproof boxes.

In 2001 Mr Gorlov won the Edison patent award for his invention, and the
turbines have now been commercialised by Lucid Energy Technologies, an
American company, and are being tested in pilot projects in South Korea and
North America.

A second design is by Philippe Vauthier, another immigrant to America (he
was originally a Swiss jeweller). The turbines made by his company, UEK, are
anchored to a submerged platform. They are able to align themselves in the
current like windsocks at an aerodrome so that they find the best position
for power generation. As they are easy to install and maintain, they are
being used in remote areas of developing countries, as well.

Finally, a design by OpenHydro, an Irish company, is not just a new kind of
turbine but also a new design of underwater electric generator. Generators
(roughly speaking) consist of magnets moving relative to coils. Why not have
the magnets encapsulated in the external, fast moving part of a turbine? The
turbine is then installed in an external housing, containing the coils. The
result looks like an open-centre turbine contained within a tube. OpenHydro's
generators do not need lubricant, which considerably reduces the need for
maintenance, and are said to be safer for marine life.

These new designs, combined with the fashion for extracting energy from the
environment by windmills and solar cells, means money that previously shied
away from the field is now becoming available. According to New Energy
Finance, a specialist consultancy, investments in companies proposing to
make or deploy free-standing turbines have risen from $13m in 2004 to $156m
in 2007. Projects already underway include the installation by American
Verdant Power of a tidal-turbine in New York's East River and pilot projects
in Nova Scotia with UEK, OpenHydro and Canadian Clean Current.

And that, optimists hope, is just the beginning. Soon, many more investors
will be searching for treasures buried in the ocean sea beds-or, rather,
flowing above them.


http://www.economist.com/research/articlesBySubject/displayStory.cfm?story_id=10715508&subjectID=348924&fsrc=nwl


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