Hawaii
Energy Policy Forum > 2003
Articles
Arctic town to get offbeat tidal energy
By Alister Doyle
Reuters
Thursday, November 07, 2002
OSLO, Norway - In a novel use of clean energy, the world's
most northerly
town will soon be the first to get electricity from a sub-sea
power station
run on tidal currents tugged by the moon.
Gigantic forces
in the oceans - waves, currents, and tides - have often
proved too costly or awkward to harness, compared to wind
or solar power, in global efforts to cut reliance on nuclear
power or on fossil fuels blamed
for global warming.
Starting in late November or early December,
however, a tidal current will
start turning the blades of a windmill-like turbine standing
on the seabed
near Kvalsund at the Arctic tip of Norway.
"
We will be the first in the world to use tidal currents to
generate
electricity to be fed into the local grid," said Harald
Johansen, managing
director of Hammerfest Stroem.
Other unorthodox sub-sea experiments
to generate power from tidal currents from Australia to Britain
have not gotten to the stage of selling power. All the technologies
mark a shift in traditional methods of exploiting the tide.
Tides
have previously been tapped for use in power plants in France,
Canada, and Russia by building barrages to trap water in
artificial lagoons at high tide. When the tide goes out,
gravity sucks the water through turbines to generate electricity.
But
giant damming projects are out of fashion because they can
damage the
ecology of rivers and coastlines. Seabed turbines, by contrast,
are silent
and invisible, and fish can swim around them without getting
sliced up.
" Of all the renewable energy technologies, ocean energy is
probably the one in the earliest stages," said Mark
Hammonds at the International Energy Agency (IEA) in Paris. "Many
projects have proved to be too costly."
Tidal power exploits
the gravitational pull of the moon, and to a lesser
extent the sun, on the oceans as the Earth spins. The seas
rise and fall in
a cycle of 12 hours and 25 minutes and can cause sweeping
currents along the seabed at the same time, like the ones
seen off the north Norway coast.
LIGHTS FOR 1,000 HOMES
The Norwegian sub-sea turbine will have a tiny capacity of
300 killowatts
and is due to expand to 20 mills from 2004, giving enough
power for perhaps 1,000 homes.
Hammerfest, with 11,000 inhabitants,
calls itself the world's northernmost
town. Johansen reckons the project there has cost 50 million
Norwegian
crowns (US$6.7 million) so far and will cost 100 million
by completion in
2004.
High oil prices and pledges to curb emissions of greenhouse
gases as part of
the Kyoto pact to limit global warming, blamed on emissions
from burning
coal or oil, are helping make green technologies like tidal
power more
attractive despite their drawbacks.
Other systems to tap the
oceans range from giant snakelike tubes that
generate power when rocked by waves to machines that extract
power from the contrast between warm surface waters and chill
temperatures at ocean depths.
But experts are uncertain about
the potential, especially because of sub-sea
maintenance costs. Storms have wrecked many experimental
ocean power
stations.
" We need to harness all low-impact renewables we can
develop. But offshore wind is more competitive and solar
has more potential," said
Greenpeace spokesman Truls Gulowsen.
The biggest tidal power
plant in the world is a barrage across the La Rance
river in northern France, in place since the 1960s. It has
a 240-megawatt
capacity, but Electricite de France has no plans to build
new ones.
Canada's Bay of Fundy in Nova Scotia has the highest tides
in the world, at about 39 feet. Nova Scotia Power's 20 megawatt
plant at Annapolis Royal, built in 1984, is the only one
in North America, but the company is now focusing more on
wind. "There are ecological objections
to building more tidal plants along the coast," said
Margaret Murphy, spokeswoman for Nova Scotia Power.
All the
plants are tiny. Western-style nuclear generators typically
have a
capacity of 500 to 1,000 megawatts and can be counted on
for reliable power generation, unlike many renewable energy
sources.
QUIXOTIC POWER?
In Norway, Hammerfest Stroem reckons that building tidal
turbines could
become a business worth hundreds of millions of dollars.
It notes many
experts used to dismiss windmill parks, now widespread in
countries like
Denmark, as quixotic.
In Kvalsund, the water flows at about
8.2 feet per second apart from a pause at high and low tides.
By contrast, windmills are useless in calm weather and have
to be built to withstand hurricane force winds.
Solar power
is a non-starter in winter in Hammerfest, where the sun sets
for
about two months in mid-winter. The town was the first in
Europe to get
street lighting almost 100 years ago.
But costs of the electricity
are initially likely to be three times that of
typical hydro-generated electricity in Norway. Tidal power
will be added to
the mix of electricity in the local grid and consumers will
be obliged to
swallow the cost.
The tidal turbines weigh about 200 tons
including the base and are well
below the keels of passing ships. They turn to face the tide
when the
currents change direction. The turbines are designed to be
maintenance-free for three years, but divers can go down
if needed.
British-based Marine Current Turbines, which plans
to test a similar tidal
current system off Devon in southern England next year, says
that
maintenance could be a problem for Hammerfest. "When
you have strong enough currents for tidal energy generation,
there are few slack tides when divers can work," said
Peter Fraenkel, the group's technical director.
Marine Current Turbines' design, which sticks above the water,
allows the
turbines to be winched up to the surface. "The size
of this resource is not
understood," he said. He said that a British study a
decade ago estimated
that the eight most promising sites off the British coast
alone could
generate one-fifth of Britain's electricity.
http://www.enn.com/news/wire-stories/2002/11/11072002/reu_48896.asp
|
