Rotor Sail Wind Propulsion Design Gains Approval for MR Tankers Maritime Activity Reports, Inc. June 9, 2026 The completed MR tanker concept showing the two Anemoi 5x35m EX-rated Rotor Sails in the folded position (Credit: Anemoi Marine Technologies) Anemoi Marine Technologies and its partners have completed a joint development project aimed at simplifying the integration of Rotor Sail wind propulsion systems on medium-range (MR) tankers, with classification society DNV granting Approval in Principle (AiP) for the design. The project was developed in collaboration with Guangzhou Shipyard International (GSI) and tanker operator Hafnia and focused on integrating two folding, explosion-rated Rotor Sails into an MR tanker design. The approval provides shipowners with a verified design basis for installing wind-assisted propulsion systems on product tankers, a vessel segment where deck space, cargo handling requirements and safety considerations can complicate deployment. The concept incorporates Anemoi's 5 by 35-meter folding Rotor Sails, designed to meet explosion safety requirements for hazardous areas on tanker decks. The project also developed a lightweight deck seat that avoids the need for underdeck strengthening while allowing inspection and maintenance access. DNV reviewed the design package, including the treatment of the Rotor Sails under the International Maritime Organization's Energy Efficiency Design Index (EEDI) and Energy Efficiency Existing Ship Index (EEXI) frameworks, before issuing the AiP. The project is said to have demonstrated potential energy-efficiency benefits while providing a practical pathway for wind-assisted propulsion adoption in the MR tanker sector. “Completing this project is a significant step for wind-assisted propulsion in the tanker sector. Demonstrating that our EX-rated Rotor Sail can be integrated efficiently, safely and with minimal structural impact on MR tankers gives owners a clear, verified pathway to adoption,” said Nick