Technology
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Rotor Sail or Flettner Rotor
Technology Overview
Flettner Rotors or Rotor Sails are rotating composite cylinders with a top disc and possibly a bottom disc that are rotated at up to 300 rpm (dependent on size/application) by low power motors and as the wind catches the rig, they use the Magnus effect (difference in air pressure on different sides of a spinning object) to generate thrust. Systems already designed include ones deployed on rail systems, hinged and telescopic versions.
History
The Flettner rotor was named after the German inventor Anton Flettner (1885-1961) and the first experimental rotor vessel named Buckau was built in 1924 with two 15m x 3m sails and after sailing on the North Sea routes in 1926, it was renamed Baden-Baden which sailed to New York via South America. This was followed by the Barbara, a three rotor sail vessel, however unfortunatley the great depression put paid to these new types of wind powered vessels and it was not until 2010 and the new build 130m, 12,968 GT RoLo General Cargo vessel E-ship 1 with four 24m x 4m rotors that this technology really entered the modern era again.
Buchau (1925)
Barbara (1926)
E-ship 1 (2010)
Design
Rotor sails are made from 6 main components and the support systems. These include the ‘Rotor’ itself, which is the cylinder that rotates, on which there is an upper and at times lower ‘Disc’ that helps maintain the wind engagement with the rotor. The internal ‘Tower’ along with a set of upper and lower ‘Bearings’ along with an ‘Electrical Drive’ and this system is set on a ‘Foundation’.
The rotor is full automated and connected to the control system on the bridge and in early installations this has been a standalone system which will be more fully integrated into the ships operational systems.
Materials
The rotor cylinder is generally made from a lightweight composite material and the foundation and tower construction is fabricated from steel. The and the Tower is a steel column structure.
We use these materials to ensure maximum performance of our Rotor Sails and to withstand all weather conditions. Choosing lightweight materials also means our systems are typically less than 0.1% of vessel deadweight.
Operations
Rotor Sails are fully automated and rotated by the low power electric motor at up to 300 rpm (dependent on size/application) and as the wind catches the rig this generates thrust. They perform well with ‘side’ or ‘beam’ winds and the weather station and wind sensors on board help the control system to automatically adjust rotation speed.
The control system for the rotors is informed by data received from the wind sensors onboard and could be further monitored via sensor arrays on the rotor and other working elements to monitor performance, adjust or optimise operations or in facilitating predictive maintenance.
The rotor systems already in operation vary from 1m diameter x 18m height to 5m diameter to 35m height.
Training requirements for the crew are minimal for day-to-day operations as the system is highly automated, however safe operations, maintenance and emergency procedures do require familiarisation.
