Nature

449, 272-273

September 20, 2007

http://www.nature.com/nature/journal/v449/n7160/full/449272a.html

The shipping forecast

Although cargo vessels are currently spared emissions restrictions, the industry is planning ahead. Kurt Kleiner looks at the ideas being floated to improve energy efficiency on the high seas.

By Kurt Kleiner

When the ship MV Beluga SkySails weighs anchor later this year it will do something unusual for a modern cargo ship: it will hoist a sail. The 140-metre vessel is being equipped with a kite-like sail that will fly from its bow, offering it extra propulsion and potentially cutting the amount of fuel needed for its voyage by up to 35%.

The sail is just one example of the ways in which the shipping industry is trying to tackle the question of energy efficiency. Partly motivated by rising costs of fuel oil, ship designers and operators are also hoping to pre-empt the inevitable clampdown on the greenhouse gases their vessels emit.

When it comes to transporting freight around the world, ships move by far the greatest amount - about four times more than lorries, six times more than rail and 400 times the weight carried by planes each year. But shipping has so far been

exempt from emissions restrictions. It is, in fact, comparatively efficient, as it uses 25-50% as much fuel as lorries to move a tonne of cargo a given distance.

James Corbett, an engineer at the University of Delaware in Newark who studies transportation and pollution, estimates that cargo ships emit some 2.7% of the global total of greenhouse gases. This equates to 800 million tonnes of emissions

per year - a figure that could double by 2030 as global trade increases, Corbett warns.

The International Maritime Organization (IMO), which regulates the shipping industry, is compiling a survey of greenhouse-gas emissions from cargo vessels, as the first step in deciding whether to impose limits. The results are expected early in 2008.

Meanwhile, the European Commission is considering

whether to include shipping in a future

cap-and-trade system for greenhouse-gas

emissions. Shipping and aviation are not included

in the European carbon market, and both

industries face similar challenges: their

emissions are likely to be regulated in the

future, and they want to be seen doing something

about the problem now (see Nature 448, 120-121;

2007).

"There is pressure on all industries not only

from regulators, but also from the general

public, to reduce emissions of greenhouse gases,"

says Alfons Guinier, secretary-general of the

European Community Shipowners' Associations,

which is based in Brussels.

One of the easiest ways to make shipping more

efficient would be to slow the ships down. Fuel

consumption increases rapidly with speed:

doubling a ship's speed means using eight times

as much fuel. With the amount of freight to be

shipped on the rise, and shippers demanding quick

transit times, ship owners are under pressure to

accelerate their vessels.

So engineers and designers are looking for ways

to squeeze more efficiency out of traditional

ship designs. "Until two years ago very few in

the shipping industry were interested in this,"

says Per Brinchmann, a naval architect with

Wallenius Wilhelmsen Logistics in Lysaker,

Norway. "Now everybody is talking about it."

The IMO has set out a number of options for

improving energy efficiency. These range from

engine optimization to better hull and propeller

designs. Improving hull design, for example,

could increase energy efficiency by an average of

15%, the IMO says.

Some designers are proposing more radical

solutions: the sail being tested on the Beluga

SkySails, for instance. These sails have been

dreamt up by SkySails, a small firm based in

Hamburg, Germany, and set up in 2001 by an

economic engineer and a naval architect. Attached

to the hull with carbon-fibre rope, the kite-like

sails have an area of up to 5,000 square metres

and can be steered to provide pull even when the

ship is travelling at a steep angle into the

wind. They act like parafoils - wing-like

structures that fill with air and generate lift.

SkySails says the kite can provide propulsion

equivalent to a 5,000-kilowatt (6700 horsepower)

engine, saving 10-30% in fuel costs. Such

savings, the company says, would recoup the cost

of the kites - between euro dollar 500,000

(US$700,000) and euro dollar 2 million - in three

to five years.

Bremen-based Beluga Shipping, which owns the

Beluga SkySails, plans to test the system over

the next year. "We'll collect data and

experiment," says Verena Frank, a spokeswoman for

the company. "Most probably we will equip another

ship."

Turning the tide

A company in the Netherlands, meanwhile, is

planning to harness the power of air in a

different way - by pumping it under the ship's

hull to reduce friction with the water.

Jørn Winkler, founder of the Rotterdam company DK

Group, has developed a design that uses some of

the ship's power to pump air into cavities built

into the bottom of the vessel. This means that a

good portion of the hull floats on a cushion of

air, rather than coming into contact with water.

"On a standard tanker, we have 8,000 square

metres of wetted surface that we can actually

remove from the equation," says Winkler. "That's

a standard football field."

The DK Group is rebuilding a 2,500-tonne vessel

to demonstrate the system. Preliminary tests

suggest that it will reduce fuel use by 15%,

while consuming only about 1% of the ship's

power. The system would cost roughly 2-3% of the

total cost of the vessel, Winkler says.

Another possible way to reduce greenhouse-gas

emissions would be to switch to alternative fuels

such as natural gas, which emits much less carbon

dioxide than the fuel oil burned by most cargo

ships.

Per Magne Einang, a research director at the

Norwegian Marine Technology Research Institute in

Trondheim, is studying whether

natural-gas-burning combustion engines could

efficiently power short-haul ships. Natural gas

would be an affordable fuel, he says, especially

as regulations against emissions of sulphur and

nitrogen oxides become stiffer. Unfortunately,

natural gas is only a little better than fuel oil

when it comes to greenhouse-gas emissions -

although it emits much less CO2, not all of the

methane gets burned and this, when emitted, is a

much more potent greenhouse gas than CO2.

A way around this might be to put the natural gas

in fuel cells, says Tomas Tronstad, a project

manager at DNV Research and Innovation in Oslo.

DNV is fitting a 100-metre supply ship with a

fuel cell made by the Munich company CFC

Solutions that can run directly on natural gas.

Tronstad says that this will result in 50% fewer

greenhouse-gas emissions than a diesel engine.

The fuel cell will be an auxiliary engine,

complementing a conventional natural-gas

combustion engine that drives an electric motor.

But Tronstad says that eventually, similar fuel

cells might be able to power a ship's engine

completely.

Brinchmann says that such green innovations

probably aren't affordable at the moment. But if

fuel prices continue to rise as expected, he

thinks the new designs may start looking much

more attractive.

And with the possibility of emissions

restrictions on the horizon, even more explosions

in innovation may be coming, says Brinchmann:

"We're still waiting for the big bang in this."

--

"Many people, however, are concluding on the

basis of mounting and reasonably objective

evidence that the length of life of the biosphere

as an inhabitable region for organisms is to be

measure in decades rather than in hundreds of

millions of years."

G. Evelyn Hutchinson. "The Biosphere." Scientific American, Sept., 1970

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