Digging into the weeds of the EEDI is a whole ‘nother kettle of fish, so let’s just take Lloyd’s word on that double-digit improvement. As cited by Anomie, Lloyd’s has “validated that the newbuild Newcastlemax would have its EEDI score reduced from 1.92 to 1.37 (29% reduction) by installing six 5x30m Rail Rotor Sails and 1.47 (23% reduction) by installing four 5x35m Folding Rotor Sails.”
As for how it works, that’s easy. “The Rotor Sails are driven to rotate by a motor,” Anemoi explains. “When a wind flow meets the spinning Rotor Sails, a pressure differential is created. This causes a thrust force which provides auxiliary propulsion to the vessel and can be used to increase the vessel speed or reduce the consumption of the main power unit.”
See Lloyd’s Register Gets Behind Wind Power For Cargo Ships
Only a handful of cargo ships use wind power today, but Lloyd's Register has stamped its seal of approval on new rotor sail technology that improves energy efficiency and reduces carbon emissions.