Are Wind-Assisted Ships in Our Future?

By Roland Piquepaille

Several companies around the world are experimenting with wind-assisted ships, which would reduce fuel consumption at a time where fuel can represent up to 60 percent of the running costs of operating a ship. But another goal is to reduce pollution: the toxic emission volume of the world trade fleet is roughly equivalent to the U.S. one today. In "The new age of sail," New Scientist describes a ship that will be partially pulled by a high-tech kite flying at an altitude of up to 500 meters where winds are more stable than at sea level. The German designers, who tested a prototype last year, estimate that such a hybrid sailing ship would see a 50 percent reduction of its fuel consumption. Danish and Japanese companies are also designing wind-assisted ships. Read more...

So let's look at this ship -- partially -- pulled by a kite.

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.

	Here is a rendering of the SkySails wind-assisted ship (Credit: SkySails GmbH).
	And here is a diagram of its components (Credit: SkySails GmbH).

But will such a ship be more efficient than today's ships?

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.

And of course, this will contribute to reduce fuel operating costs.

As shown in this chart, "cargo vessels can increase their speed by a minimum of 10% -- in the example given speed is increased yet by 2.25 bends, equaling 15%. Alternatively by using the SkySails propulsion fuel savings of up to 50% can be implemented." (Credit: SkySails GmbH).

For its part, the Danish company of naval architects Knud E. Hansen started another kind of wind-assisted ship back in 1995. You'll find more details by reading the "Modern Windship Phase II" section on this page.

Here is a rendering of the proposed Windship (Credit: Knud E. Hansen).

The company confirms the SkySails's findings about fuel savings.

Where the weather/wind conditions are reasonable - e.g. on Atlantic routes - fuel savings of about 27% can be achieved. On routes where the superior internal volume capacity of the WindShip can be properly utilised, 50% fuel savings are possible.

And here is what New Scientist adds about the Danish effort.

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."

Will these wind-assisted ships be part of the future of sea commerce? I really don't know. What do you think about these projects?

Sources: Mick Hamer, New Scientist Print Edition, February 26, 2005; and various websites

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• Energy
  
• Environment
  
• Future
  
• Technology
  
• Transportation