The principle on which the Norsepower Rotor Sail operates is known as the Magnus effect. When wind meets the spinning Rotor Sail, the air flow accelerates on one side of the Rotor Sail and decelerates on the opposite side of the Rotor Sail. The difference in the speed of the air flow results into a pressure difference, which creates a lift force that is perpendicular to the wind flow direction. The same principle applies to rotating spheres and cylinders. This can also be observed for example in golf, tennis or football, where spinning balls curve in flight.
Norsepower Rotor Sail
The thrust induced by the Magnus effect can be utilized in ship propulsion by placing a cylinder on the open deck of the vessel and by rotating it around its main, vertical axis. An electric drive system that is powered by the auxiliary electrical network of the vessel is used for rotation of the Rotor Sail.
The Norsepower Rotor Sail Solution is around ten times more efficient than a conventional sail, because more lift is produced with a much smaller sail area. Due to its simplicity, it requires no reefing or crew attention when in operation. It is "push button wind propulsion" from the bridge. This allows the main engines to be throttled back, saving fuel and emissions while providing the power needed to maintain speed and voyage time. The technology, the basic concept of which is known as a Flettner Rotor, was originally invented by Finnish engineer Sigurd Savonius and was later demonstrated by Anton Flettner in an Atlantic crossing that took place in 1926.
The original basic engineering solution has a limited degree of sophistication, but Norsepower has created various new improvements for which several patents have been granted.