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.

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.

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.