Beluga Group has become the first shipping firm worldwide to sign a contract to furnish a modern diesel freighter with sail power--in this case Sky Sail: a super-sized kite which pulls the ship across the seas. The idea has been around for a while, and poo-pahed just about as long (see the comments even after Sky Sails won the Aichi World Expo Eco-tech award, as reported in Treehugger Sky Sails Promise). But now it will become reality.Sail power in the modern age has been simply unable to compete with diesel engines. The manpower required to manage traditional sails makes the system uncompetitive. But worse, the force of the wind in the sails causes a masted ship to "heel" or tip at an angle--a real danger for a ship packed to the sky with containers. The Sky Sails system overcomes the disadvantages by setting a football field sized kite on a cable over the ship. This takes advantage of the even more forceful winds present at higher elevations. A computerized systems steers the kite cable and plans the most efficient route taking account of weather forecasts and other factors. The kite contains cells which can be filled with helium to help launch the kite or stiffened with compressed air.
The Sky Sail cannot replace diesel entirely, since the sail is not capable of powering the ship in or out of port, cannot be used in narrow or crowded seaways and cannot go upwind (an angle of 50 degrees is maximal, with 70 degrees being the limit of efficiency in reality). But if the Sky Sail is used alone in optimal conditions and an assist whenever possible, at least half of the usual fuel demand can be spared. An estimated 289 million tons of fuel per year industry-wide is at stake. The Sky Sail will be installed on a 140 m multi-purpose heavy duty freighter, the MS Beluga SkySails due to take its maiden voyage in 2007.