The 10,000-tonne MS Beluga SkySails set off on its maiden voyage from Bremen with the newly developed kite attached to the bows.

"Only the tough conditions imposed on a ship during a long voyage of this kind can show whether the SkySail is effective and whether the materials can stand up to the stresses and strains it will undergo," said Stephan Wrage, managing director of shipbuilder SkySails.

"During the next few months we will finally be able to prove that our technology works in practice and significantly reduces fuel consumption and emissions."

"We aim to prove it pays to protect the environment."

"Showing that ecology and economics are not contradictions motivates us all."

The 160-square-metre kite could reduce fuel consumption by 35 percent -- dependent on prevailing wind conditions.

But SkySails acknowledge that the experimental sail may not be sufficiently strong for general commercial use at the moment.

"It is particularly important to raise the manageability and robustness of the system to the level demanded by our customers," said Stephan Brabeck, technical manager at SkySails.

But shipping companies are keenly aware that energy costs are increasing and are anxious to test the effectiveness of the sail.

Germany's Beluga Shipping has two more vessels on order and SkySails have a total of five ships on their order book at present.