The Rebirth of Sustainable Shipping
By EV World
For thousands of years ships were powered by the wind and trade was subject to its whims. The advent of the coal-powered steam engine allowed captains to weigh anchor without a second thought to time or tides.
By the beginning of the twentieth century, cheap, dirty bunker fuel had replaced coal. As the slideshow below demonstrates, 90 percent of the 100,000 ships over 100 gross registered tonnes plying the world's oceans continue to burn this highly polluting fuel, contributing an estimated 813 million tons of carbon dioxide annually. Conservatively, that represents three percent of all man-made CO2 emissions; some experts estimate the total emissions as high as 5 percent.
Tellingly, the world's maritime fleet is currently exempt from the Kyoto Accords. Projections see that fleet increasing by 75 percent by 2020.
Aware of the environmental damage being done by commercial shipping, the maritime community has agreed that by 2020 its ships will have to burn cleaner diesel fuels with a sulfur content of 0.5%, compared to the 4.5% of today's bunker fuels. It is taking other steps to literally clean up its act, including improvements in hull design, installation of expensive after-treatment catalysts, special propeller coatings... and the use of sails.
But not the kind you'd associate with sail boats and clipper ships. SkySails are more akin to gigantic kites than traditional sails. Flown from the bow of cargo ships and trawlers, these giant airfoils can produce an amazing amount of tractive force, effectively allowing the ship to idle its diesel engines, depending on available wind.
SkySails estimates that when flown in winds between 3 and 8 on the Beaufort scale (8-46 mph), a 600 m2 Beluga would exert 8 tons of motive force in a 25 knot wind (12.8 m/s). That's equivalent to a 600-1000 kW diesel engine.
The beauty of the Beluga Skysail is that it can be flown between 100 and 300 meters in height where the wind is stronger and less subject to sea level frictional forces. The wind at 150 meters is 25% stronger than at 10 meters and since the power of the wind increases logarithmically with its speed, the higher the crew flies the wing, the more power it can exert.
The SkySail can be deployed as near as 50 degrees to either side of the direction of the wind. That means it can be used in 310 degrees of the compass. Since most ships are at sea an average of 210 days a year, the company estimates the sail could be deployed between 30-50% of the time. Careful voyage planning using advanced weather forecasts can take advantage of favorable winds and seas.
The SkySail is controlled from the bridge. It can be retracted and stowed in a telephone booth-sized container on the bow in 20 minutes time.
Thanks to Eduardo Souza for his photos and bringing this situation to our attention.
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