2009-09-08 04:04:58
By Jorn Madslien
Business reporter, BBC News, Stavanger, Norway
Heading offshore in the Rygercruise catamaran, it is a journey into uncharted
territory.
Not in terms of sea charts - the Norwegian energy giant StatoilHydro knows
these waters well, having spent the past 30 years drilling for oil and gas here
- but in terms of technology.
Statoil has constructed the world's first full-scale floating wind turbine a
couple of hours by catamaran from the oil town Stavanger, in the hope that one
day vast wind farms could be constructed far offshore in water depths of up to
700m.
Standing firm as the catamaran rolls in the waves, Sjur Bratland is optimistic
with regards to the technology's potential.
Yet, having spent the past two years listening to a whispering crowd of
nay-sayers, he wants proof. He wants to see for himself that the turbine can
cope with winter storms that whip the North Sea into a froth and winds that rip
roofs off houses.
And he wants to be sure that the supply industries can deliver the right
turbines, supply ships and so on.
Fortunately, Mr Bratland is in charge of the Hywind project, and he has been
given some 400m Norwegian kroner ($66m; 35m) to play with by Statoil, with the
government injecting a further 59m kroner.
Trouble shooting
As the turbine slowly emerges through the mist, the first impression is how
stable it is.
As the catamaran moves closer, the turbine stands as firm as if it was pinned
to the seabed, the way conventional offshore turbines are, its 65m tubular
carbon steel tower and slowly rotating 80m diameter blades, together stretching
100m above the sea.
The most interesting aspects of the turbine can be found in the depths of the
sea, where a 100m long steel cylinder weighing 3,000 tonnes thanks to its
ballast of water and rocks is anchored to the sea-bed with mooring lines that
can hold the structure at depths of up to 700m.
So-called slack anchors are used, allowing the structure to move with the seas.
In fact, in spite of its apparent sturdiness, the 138 tonne turbine is
constantly moving.
Everything below the water line is "known technology from the oil and gas
industry", where StatoilHydro has 30 years of experience from its extensive
offshore operations around the world, Mr Bratland explains.
"Actually, the really tricky thing is to apply this technology in a completely
new setting in a new industry," he says. "That has been a challenge."
Deap seas
The Hywind turbine will be tested over a two-year period, at the end of which
Mr Bratland hopes to have found proof that offshore wind farms can be built,
and that they are economically viable - perhaps even competitive with
conventional offshore wind.
Today's solutions are too costly as the margins are so much slimmer in this
area than in the oil and gas industry
Sjur Bratland, Hywind asset manager, StatoilHydro
Turbines pinned to the sea-bed are relatively cheap in water depths of up to
25m, when the basic monopole foundation can be used. At greater depths of up to
50m, the tubular turbine towers will need gravity bases and stronger steel
structures that push the price up.
Statoil's floating turbine requires the waters to be at least 120m deep, though
beyond that the sea is the limit - literally.
"But first, we'll need to look for smarter solutions that make it commercially
viable," says Mr Bratland.
Better and cheaper turbines
Above sea level, the offshore structure has been bolted together with a
conventional offshore turbine of the sort used for near-shore wind farms that
are bolted to the sea-bed.
Ease of entry for maintenance is a seemingly trivial yet major headache for Mr
Bratland.
Though the seas are relatively calm, the waves are nevertheless too large for a
safe mooring against the base of the structure to enable the BBC team to climb
the 17m steel ladders up to the service deck.
At a more fundamental level, turbine technology must be developed specifically
for far offshore conditions, he insists.
On land, turbines are getting taller all the time to accommodate ever larger
blades, explains Mr Bratland.
For the purposes of floating wind farms, such turbines are not light enough,
they are too tall and the rotor blades are too small, according to Mr
Bratland's early assessments, made even before the 2.3 megawatt turbine has
started delivering electricity through the sea-bed cable that connects it to
the Norwegian national grid.
He wants turbine manufacturers to produce lower turbines, to take advantage of
winds blowing strongly and steadily close to the surface of the sea. Closer to
land, the wind lifts to enter the beaches and climb over the cliffs.
Lower turbines should, together with clever design and material selection, help
reduce the turbines' weight, and thus their need for ballast, which in turn
should reduce sub-sea costs.
At the same time, Mr Bratland wants the power output of each turbine to be
raised to perhaps 6MW, and he wants it all to be cheaper than it is today.
This could be possible as there is tremendous potential for economies of scale,
both in terms of mass production, which reduces the cost of each turbine, and
in terms of the construction and management of vast wind farms offshore where
there are few limits on available acreages.
Moreover, onshore production of floating turbines that are then towed offshore
to be anchored in place should prove cheaper than the weather-restricted and
costly off-shore construction of sea-bed turbines.
Grid cables transporting the power to shore are neither expensive - in the
greater scheme of things - nor technologically complicated to roll out, so this
is a minor part of the project, according to Mr Bratland.
"Still, we have some way to go," says Mr Bratland.
"Today's solutions are too costly as the margins are so much slimmer in this
area than in the oil and gas industry."