Technology

Norsepower Rotor Sails are modernized versions of Flettner Rotors. The Rotor Sail technology is based on the Magnus effect.

Norsepower Rotor Sail

Norsepower’s Rotor Sail Solution harnesses wind to maximise ship fuel efficiency.   When wind conditions are favourable, the Rotor Sails allow the main engines to be throttled back, saving fuel and reducing emissions while providing the power needed to maintain speed and voyage time. A variable electric drive system, which is powered by the ship's low voltage network, is used for rotating the Rotor Sail.   The Norsepower Rotor Sail technology 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.  

The technology, whose basic concept 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 had a limited degree of sophistication, but Norsepower has created various new improvements for which several patents have been granted.   The optimal number and size of Norsepower Rotor Sails are based on the size, speed, and operating profile of the target vessel.   Norsepower Rotor Sails are available in five sizes with Rotor Sail heights of 18, 24, 28, 30 or 35 metres. The essential parts of the Rotor Sail Solution are:  

  • Norsepower Rotor Sails, which deliver the forward thrust
  • A control panel, which gives the captain full control of the operation and performance of the Norsepower Rotor Sail Solution
  • A fully automatic control system, which optimises the forward thrust of the Rotor Sails
  • A low-voltage electrical power supply to each Rotor Sail.

Magnus effect

Norsepower Rotor Sails are modernized versions of Flettner Rotors. The Rotor Sail technology is based on 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 change in the speed of air flow results in a pressure difference, which creates a lift force that is perpendicular to the wind flow direction. The same principle applies to all rotating spheres and cylinders. This can also be observed for example in golf, tennis, or football, where spinning balls curve in flight.