Auxiliary wind propulsion system developer Norsepower Oy Ltd. has installed five tilting rotor sails on board a new-build very large ore carrier (VLOC) chartered by Vale, a Brazilian mining company.

The five 24 m high and 4 m diameter rotor sails fitted on the 325,000 dwt VLOC can be tilted by using hydraulic cylinders to enable efficient cargo operations and management. The wind energy-harnessing equipment is expected to reduce fuel consumption and is projected to deliver an efficiency gain of up to Source: Vale8% and a consequent reduction of up to 3,400 tons of carbon dioxide emissions annually.

The rotor sail solution is a modernized version of the Flettner rotor, which uses a spinning cylinder to convert the force of the wind into thrust to help propel the ship. Propulsion is attributed to the Magnus effect, wherein a revolving body moving relative to air is subjected not only to drag, but also to lift. As the speed of the cylinder — spinning at right angles to the flow — increases, the pressure decreases on the side of the cylinder where the natural flow and the spin-induce flow combine. The decrease in pressure generates lift, and the lift increases as the surface velocity increases.

The Magnus effect can generate more lift per unit of projected area than typical airfoil forms. The fully automated system detects whenever the wind is strong enough to deliver fuel and emission savings, at which point the rotor sails are activated.