The New Age Of Sail
jlrogers±³©
'The coming of steam sent the world's great sailing fleets into decline. The
internal combustion engine finally finished them off. So it would be a
strange twist of fate if the age of sail was resurrected by what amounts to
a child's toy.
'For several weeks last summer, a team of German engineers sailed back and
forth across the Baltic Sea playing with a large inflatable kite. The
engineers, from the Hamburg company SkySails, were testing the potential of
high-tech kites to pull a ship across the ocean by hitching a ride on winds
high above the waves.
The idea isn't to propel a ship by wind alone - a conventional diesel engine
will help it along on days when the wind is blowing from the wrong
direction, is too strong or dies away entirely. But since the kite reduces
the need to use engines, the team at SkySails believes it can halve the
amount of fuel a ship burns.
This is just one of the ways in which sail power is being revived - and it's
not the first. In tests more than 20 years ago, Japanese engineers equipped
several ships, including a bulk carrier and a tanker, with masts and sails.
The projects were eventually shelved, but this time round there are sound
reasons why wind could win through.
For nine years a team of naval architects in Copenhagen, Denmark, has been
working on a completely new design: a 50,000-tonne cargo ship whose diesel
engine will be augmented by a set of high-tech sails set on six masts.
Canvas is definitely out. Aerofoils are in.
Denmark is already a world leader in developing wind turbines for power
generation and is keen to capitalise on this expertise to develop wind
propulsion for ships. In 1995 the Danish Environmental Protection Agency
began financing a major research project into windships. Led by the naval
architects Knud E. Hansen, the research not only produced a new design of
ship but also looked at how the ship could make the most of wind power and
the cargoes it would be best suited to carrying. Now the team is about to
embark on full-scale trials.
Though wind power has obvious commercial advantages - wind is free, after
all - traditional sailing ships were never cheap to run. They needed a large
crew to operate the rigging, the sails themselves had to be replaced and
repaired regularly, the canvas had to be stored somewhere on board, which
reduced the space for cargo, and the variability of the winds made schedules
unreliable. On top of that, the economics of sail were steadily undermined
in the 20th century by the rising cost of labour and a decline in the real
price of oil. Engines won out, and even hybrid wind-assisted ships never
became widely used, says Brian Lavery of the UK's National Maritime Museum
in Greenwich. "They didn't go in for multi-skilling in those days," he says.
"You would need one crew to operate the rigging and then stokers to run the
engines."
So why should modern hybrid sailing ships fare any better? Part of the
answer is that the economies of running a ship have changed again. The small
crew needed on a modern ship, combined with the low wages they are paid,
means that the cost of fuel as a proportion of total running costs rose from
10 per cent in 1900 to between 25 and 60 per cent by 2000.
Modern windships can also take advantage of new technologies and materials
that weren't available in the days of sail. Wind tunnel tests on different
types of rigging and sails quickly showed the Danish team how poorly
traditional sails perform. A sail is more than a simple sheet of fabric. To
propel a ship it needs to take up an aerofoil shape, and that only happens
when the wind fills it. If the wind is too light, or it keeps changing
direction, the canvas flaps uselessly and generates drag rather than
propulsion.
So the Danish team came up with an alternative that exploits materials
borrowed from the aerospace industry. Using high-performance steel for the
masts does away with the need for stays to hold them upright. The sail
itself is made of fibreglass, with a profile like an aircraft wing (see
Diagram). Flaps on the sail's trailing edge generate extra thrust when
extended, but can be retracted to minimise aerodynamic drag - important when
using engine power alone.
Wind-tunnel tests showed this design to be twice as efficient as the sails
on a traditional windjammer. Even more importantly, the sail generates
thrust when the ship is sailing close to the wind. Simulations suggest that
the vessel will be able to make progress under sail even when the wind is
blowing as little as 40 degrees off the bow, which is an excellent
performance for a large sailing vessel. With a fresh breeze of 9 metres per
second at 100 degrees - blowing only slightly from behind - the sails alone
can propel the ship at 13 knots (25 kilometres per hour.
Unlike traditional sails, these fibreglass wings will not need a large crew
to operate them, the designers say. They can be controlled hydraulically
from the bridge, and because they never need to be lowered there is no need
for storage space that would eat into the cargo capacity. The downside is
that in light winds, with the ship under diesel power, they exert
aerodynamic drag - even with flaps retracted - which negates some of the
fuel savings from having them there in the first place.
The SkySails kite suffers no such handicap. The idea is to harness the winds
higher above the ocean with an inflatable aerofoil - a kite designed to fly
at a height of 100 to 500 metres, towing the ship on a cable fastened to the
hull.
At 500 metres, winds are often stronger and less variable than at sea level,
and can differ in direction from those immediately above the waves by 10 to
15 degrees, according to Barry Gromett of the UK's Met Office in Exeter.
"Although these differences are not huge they could be really useful," he
says.
SkySail's aerofoil is designed to maximise thrust whatever the wind
conditions. It uses a computer autopilot and patented wind sensors coupled
to the ship's steering system to calculate the kite's optimum position. Then
the autopilot manoeuvres the kite using motors in a control unit suspended
beneath it to change the trim of the aerofoil by adjusting the tension in
its control lines. The kite can move along a rail around the hull to
maximise its towing efficiency and a winch on the ship adjusts the length of
the kite's main line to fly it where the wind speed and direction are most
favourable.
“By 2010 cargo vessels will account for three-quarters of Europe's sulphur
dioxide emissions”
Last year's trials in the Baltic, aboard an 8-metre model of a cargo vessel,
were mostly carried out in unfavourable conditions of weak and variable
winds. Nevertheless, they showed that the SkySails kite can generate 1 to
1.15 kilowatts for every square metre of aerofoil. "In favourable winds it
would generate a lot more thrust," says Stephan Wrage, founder of the
company. The kite is designed to be retrofitted to ships of almost any size,
but SkySail's largest version, with an area of 2000 to 5000 square metres,
will generate propulsive power equivalent to a large ship's engine, he says.
Since the kite is controlled by an autopilot, Wrage says it will not need
many extra crew to handle it. Compressed air will be used to blow it up when
it is deployed and when not in use it is deflated, so storing it should not
be a problem either. But as any kite flyer will tell you, launch and
recovery are likely to be a little more complicated. SkySails says it will
be an automated process, but won't reveal details until its engineers fit
their first system to a ship next year.
Selecting a course that maximises the benefits from the wind is an important
part of any successful voyage under sail. Here modern windships have another
key advantage over their predecessors: they will have access to far more
accurate weather forecasts to help get the best from the wind.
In the old days of sail, a ship left port if the wind was in the right
quarter. The course of a voyage was largely a matter of luck, the ship
changing course to use whatever winds there were. Nowadays the UK Met Office
and its counterparts elsewhere provide shipping companies with route
forecasts - principally to avoid bad weather. It would need only a small
extension to the service to provide forecasts of the best winds, says
Gromett.
The Danes have already looked at different strategies for setting a course.
By studying records of winds and weather forecasts during the 1990s, they
calculated how much power the wind would contribute during a voyage. One of
the least successful of the strategies they modelled was to calculate the
best course given the weather forecast at the start of the voyage, and then
stick to it. Following this inflexible approach meant changes in the wind
during the voyage robbed the ship of almost all the advantages of wind
power. In fact, it was little better than ignoring the wind direction and
simply sailing the most direct course to the destination. Far better, they
found, was to re-plan the course every 24 hours based on the latest
forecast.
Another factor affecting the overall viability of a wind-assisted ship is
that its performance will vary from ocean to ocean. In the North Atlantic
the average wind speed is 8 metres per second. On routes such as Rotterdam
to New York the ship would save up to 27 per cent of the normal fuel bill at
its design speed of 13 knots, the Danish team calculate. But in the Indian
Ocean, winds are far lighter. On routes such as that from the Ras Tanura oil
terminal in Saudi Arabia to Mumbai in India or Singapore, there is not
enough wind to maintain a speed of 13 knots without using the engine on full
power. The usually light winds combined with the aerodynamic drag of the
sails when sailing under power would mean fuel bills were actually higher
than with a conventional ship. Even under more favourable conditions, they
found that over its lifetime, the windship would be about 10 per cent more
expensive to run than a conventional ship when the extra cost of
construction is included.
Wind of change
These results proved a major setback and work on the project stopped in
2000. But since then the cost of marine diesel, which closely follows crude
oil prices, has soared to nearly three times its 1999 levels, and now the
project could be moving again, with backing from Scandinavian governments
and the European Union. And this time, environmental benefits are being
factored into the equation too.
In the last couple of years it has become clear that marine diesel engines
are having a greater environmental impact than many experts had believed.
These engines release pollutants such as sulphur, nitrogen oxides and PM10
particles. In particular, marine diesel oil contains 2.7 per cent sulphur -
more than 500 times what is allowed by the EU for diesel sold for cars and
trucks. By 2010 it is estimated that cargo ships will account for
three-quarters of all Europe's emissions of sulphur dioxide. In the US, the
Environmental Protection Agency is stepping in with new regulations to help
improve air quality around large ports.
Could this signal a sea change for sail? "It will now be profitable both
environmentally and economically to build the windship," says Anders
Carlberg of Knud E. Hansen. Other new sailing ship projects are already in
the works, one in Germany and one in Japan. Carlberg and his team estimate
that full-scale trials of their design will start within three years.
It is not just the oil price that has moved in the windships' favour. The
Danish team is confident that it will be able to design a more efficient
vessel. Jesper Kanstrup, Knud E. Hansen's senior naval architect, says that
the original designs concentrated on minimising the amount of space the
engine and sails took up to maximise cargo space. "They weren't designed for
fuel economy."
Reducing the design speed of the windship from 13 to 11 knots, for example,
would cut fuel bills by a third on both the North Atlantic and the Indian
Ocean routes because the engine wouldn't have to work so hard. Ships this
slow would only be suitable for non time-critical cargoes, typically bulk
goods such as grain, timber and bauxite, which together account for only 20
per cent of cargoes worldwide. Though this would restrict the use of
wind-assisted ships, there should still be a big enough market to establish
the technology commercially. However, the shipping industry is conservative,
Kanstrup warns, and it will need a lot of convincing before it adopts sails.
SkySails has its eye on a rather different market. "One surprising result
from the trials was the vessel's stability in heavy seas," Wrage says.
Unlike conventional sails, the kite tends to stabilise the ship instead of
making it heel over. This is partly because it is tethered to a rail close
to the vessel's centre of gravity, and partly because the horizontal tug of
the kite is counterbalanced by the vertical pull it generates, which tends
to hold the vessel upright. "The sail acts like a damper so the ship moves
smoothly, which will prevent passengers being sick." This is significant
because Wrage sees cruise liners, and the growing number of cargo ships that
carry passengers, as important markets for the technology.
For Wrage the next step is to move from a model to a full-size craft and he
thinks the system's superior seakeeping will be attractive to the owners of
large and expensive motor yachts. After all, the last thing any modern
sailor wants is to spill their gin and tonic.
--
jlrogers±³©
Beaten by George W. Bush! Now that's funny!
Scott Vernon
sail it. The boat with masts/sails looks like they would be too high.
Some ships barely get under some bridges now.
SV
"jlrogersąłŠ" <u...@ftc.gov> wrote in message
news:0SCVd.20794$D34....@newssvr12.news.prodigy.com...
Thom Stewart
Also, The economics of speed is being left out of the equation. A ship
traveling at 30 knots can make 5 trips to a ship traveling at 6 knots. 5
times the profits and cargo carried.
The change will probably be to Aircraft.