KIEL, Germany - What its makers say is the world's biggest boat powered by the sun has been unveiled in Germany ahead of its planned circumnavigation of the globe next year - the first under solar power.

"This is a unique feeling to see in front of me today a boat which I so often dreamed about," Raphael Domjan, the boat's future skipper and initiator of the project, said on Thursday.

'PlanerSolar', which makers say is the world's biggest boat powered by the sun.

The sleek, 31 metre by 15 metre catamaran PlanetSolar, 35 metres by 23 metres when flaps at the stern and the sides are included, will be "silent and clean", say its makers, also called PlanetSolar.

The vessel will be able to achieve a top speed of about 15 knots, equivalent to 25 km/h, and can accommodate 50 people on its round-the-world voyage, its Swiss-based makers say.