Hamburg  - Six months after the first freighter put to sea drawn by a giant kite, a German company said Thursday that the invention could "realistically" reduce a ship's fuel use by 15 per cent.

Enthusiastic proponents say that the computerized SkySails system could usher in a new age of wind power in commercial shipping, although the main power still comes from the ship's engine. Because of high oil prices, even small savings are valuable to ship-owners.

A 90-metre coastal freighter, the Michael A, was retro-fitted with one of the kites at the end of last year and a purpose-built kite vessel, the Beluga SkySails, set off in March on a two-month maiden voyage to Venezuela, the United States and Norway.

The Hamburg-based SkySails company said its forecast of at least a 15-per-cent reduction in annual fuel costs applied for European coastal waters including many regions with moderate winds.

It compared the Michael A to 13 similar conventional ships at sea at the same time.

Germany's Wessels shipping company based in Haren, owner of the Michael A, has now ordered the Skysails system for three new ships.

The 160-square-metre kite has a pull of eight tons in a stiff breeze, almost as much as a single engine on an Airbus A318 plane and reducing fuel use at such moments by half, Skysails said.

Flying higher, the kite had more pull than a sail on a mast.

The tests on the Michael A showed the owner could choose between fuel-saving or greater speed, with the sail forecast to raise average speed during the year from 10 to
11.6 knots. Testing is to continue till next year before the system is commercialized.

"The emphasis in the second pilot phase will be on extending the flight periods of the kite and optimizing its performance," said Stephan Wrage, 35, inventor of the system and founder of the firm. He hopes to make it pull evenly when the ship pitches in a swell.

He said 60,000 of the 100,000 freighters in the world could be retro-fitted with such a kite, though his system was not suitable for very large container vessels. (dpa)