Functional principle

Flettner propulsion uses the wind to generate additional thrust for the ship’s propulsion: A Flettner rotor is a tall cylinder that stands vertically on a ship and rotates around its own axis. It is powered by an electric motor. The interaction between the rotor surface and the wind flow creates a lifting force, giving the ship extra thrust. This not only saves fuel, but also reduces emissions.

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The Magnus Effect

The Magnus effect, named after Heinrich Gustav Magnus, is a phenomenon in fluid mechanics that describes the force experienced by a rotating circular body in a flow.

In the case of a Flettner rotor, this refers specifically to a rotating cylinder around which the wind flows. Durch die Rotation entsteht dabei eine Kraft, die quer zur Windrichtung wirkt.

Drive by underpressure

When the wind blows against a rotating cylinder, the air flow is increased on the side where the wind direction and the direction of rotation are the same. On the other side, the direction of rotation is reversed and the air is slowed down.

This creates negative pressure (faster flow) and positive pressure (slower flow) on the cylinder, resulting in a force acting on the cylinder. In summary, the Flettner rotor is both pulled and pushed forward. This force is transverse to the direction of the wind and produces the propulsion of the ship.

This much is saved

The Flettner rotor is an old concept that is constantly being improved with modern technology and materials. The aim is to reduce emissions from shipping and take a big step towards protecting the environment and the climate. The results are excellent.

The efficiency of the rotors is highly dependent on the strength and direction of the wind and the ship’s route. However, independent analyses have shown that the use of Flettner rotors can save up to 25 per cent of fuel.

How it all began

The first rotor ship was designed and built by Flettner as early as 1924: the “Rotorschiff Buckau” had two 13-metre high Flettner rotors. However, the rotors failed to catch on and lost out to steam and diesel engines in the years after 1930.

Nowadays, Flettner rotors are installed in ships as an auxiliary drive to form an energy-saving hybrid propulsion system.


Not only saving fuel, but also emissions.

The first ECO-FLETTNER rotor was installed for initial operation on the coastal freighter “Fehn Pollux”, where it was examined in an ongoing endurance test and data was generated.

Insights have been gained into fuel savings, operational safety and reliability, service life and the possibility of integrating wind propulsion systems into existing ship concepts.

The impact on ship operations and cargo handling, the handling of the steering system and the behaviour of the rotor in heavy weather conditions, as well as optimised route planning were investigated and evaluated.

Fuel and emission savings of 15% – 20% were realised for the Fehn Pollux, depending on the sailing area.


Further Information

„Flettner – rotor reduces cost of fuel (German) “


Sören Berg


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