A consortium consisting of Anemoi, Hafnia, Guangzhou Shipyard International, and DNV has successfully secured an Approval in Principle (AiP) for integrating folding, explosion-proof Rotor Sails onto medium-range (MR) tankers. Unveiled at Posidonia 2026, the joint development project overcomes critical hazardous-area safety and deck-space constraints through an innovative, lightweight deck design that requires no underdeck structural strengthening. This independent verification by DNV establishes a scalable, “Rotor Sail-ready” technical blueprint, offering tanker owners a verified pathway to cut fuel consumption and meet tightening international emissions mandates.
Athens | June 9, 2026 – The commercial viability of wind-assisted propulsion systems (WAPS) on product tankers has received a major boost. Marine engineering firm Anemoi Marine Technologies, alongside a high-profile consortium of industry heavyweights, has successfully navigated the complex technical, structural, and hazardous-area regulatory hurdles that have historically slowed down the adoption of rotor sails on medium-range (MR) tankers.
Announced and celebrated at a ceremony during the Posidonia 2026 exhibition in Athens, classification society DNV has officially issued an Approval in Principle (AiP) for a joint development project (JDP) featuring two of Anemoi’s 5×35-meter folding, explosion-proof (EX-rated) Rotor Sails integrated onto an MR tanker design.
The project brings together an elite tier of maritime stakeholders: Anemoi as the technology provider, leading tanker owner and operator Hafnia, and premier Chinese shipbuilder Guangzhou Shipyard International (GSI).
Overcoming the Tanker Conundrum: Deck Space and Explosion Safety
While wind-assisted propulsion has gained rapid traction in the bulk carrier and VLOC (Very Large Crude Carrier) segments, the MR tanker segment has long been a tougher nut to crack. Tight constraints around deck space, complex cargo-handling operations, and strict explosion-safety regulations in hazardous zones have previously limited the feasibility of large-scale mechanical sails.
The JDP directly confronted these limitations by deploying an EX-rated version of Anemoi’s folding Rotor Sail. The EX rating ensures that the electrical and mechanical components meet the stringent safety requirements for operating in volatile, hazardous areas on a product tanker’s deck.
Furthermore, the design addresses the operational reality of port calls and cargo loading. The folding mechanism allows the 35-meter towers to be lowered, ensuring they do not interfere with shoreside loading arms, overhead obstructions, or complex port maneuvers.
Key Technical Achievements of the JDP:
- EX-Rated Hardware: Fully compliant with explosion safety protocols for hazardous product tanker decks.
- Innovative Foundation: GSI and Anemoi engineered a proprietary, lightweight deck seat. Crucially, this design eliminates the need for extensive underdeck structural strengthening, a major cost and weight factor in retrofits and newbuilds.
- Simplified Maintenance: The deck seat architecture allows for straightforward, long-term inspection and maintenance access without disrupting internal ship structures.
Regulatory and Performance Verification
A critical component of DNV’s independent assessment was verifying how the mechanical sails interact with both the vessel’s hydrodynamics and international regulatory frameworks. DNV reviewed the entire design package, explicitly evaluating how the Rotor Sails would be treated under the International Maritime Organization’s (IMO) Energy Efficiency Design Index (EEDI) and Energy Efficiency Existing Ship Index (EEXI) frameworks.
The assessment factored in potential aerodynamic interactions between the sails, ultimately confirming a verified baseline for significant energy efficiency gains and fuel burn reductions.
Typically, an Anemoi Rotor Sail deployment of this scale can save roughly one tonne of fuel per day and approximately three tonnes of CO2 emissions per sail, offering an immediate toolkit for compliance with tightening global carbon intensity indicators (CII).
“Rotor Sail-Ready” Standard Newbuilds
The successful completion of the JDP signals a shift from bespoke, speculative engineering to standardized, scalable deployment for the tanker sector.
“Completing this project is a significant step for wind-assisted propulsion in the tanker sector,” said Nick Contopoulos, Chief Production and Partnerships Officer at Anemoi. “Demonrading 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.”
For shipowners, the verified design arrives at a time of escalating regulatory pressure from the EU Emissions Trading System (EU ETS) and the impending FuelEU Maritime mandates.
“Identifying practical, scalable efficiency measures for the MR tanker segment is a priority for Hafnia as we navigate increasing energy efficiency and emissions reduction demands from both charterers and regulators,” noted Jesper Kristiansen, General Manager Technical at Hafnia. “The work undertaken with Anemoi, GSI, and DNV gives us a credible technical foundation from which to assess deployment of wind-assisted propulsion across this fleet.”
From a shipbuilding perspective, the collaboration positions GSI at the forefront of the next generation of eco-tankers. Huang Jun, Deputy Chief Engineer at Guangzhou Shipyard International, confirmed that the yard is now prepared to commercialize the technology immediately “This project not only deepens industry understanding around wind-assisted propulsion integration but also solves very practical issues to deploying solutions on MR tankers. The result is that we are now in a position to offer Rotor Sail–ready MR tanker designs to owners worldwide.”
Evaluating the regulatory milestone, Aakash Dua, Regional Business Development Manager at DNV, emphasized the importance of independent vetting to de-risk new clean-tech options “The technical challenges of integrating new on-deck efficiency solutions for MR tankers make having an independent verification of new designs essential. At DNV, we are continually working to have our WAPS rules and guidelines evolve as innovations hit the market. this AiP means we have a new technical reference point for WAPS in this important ship segment.”
With the commercial and technical blueprint now validated by DNV, the maritime industry will likely watch closely to see which owners move first to turn this “Rotor Sail-ready” design into physical steel on the water.
About Anemoi Marine Technologies
Founded in 2015, Anemoi Marine Technologies Ltd is a UK-based maritime engineering company that designs and installs Flettner Rotor Sails on large commercial vessels. Its cutting-edge wind-propulsion technology harnesses one of the world’s most abundant renewable energy sources to slash fuel consumption and emissions, driving global shipping toward a cleaner, more efficient future. Anemoi typically deploys three to five 35-meter Rotor Sails per vessel, with each unit saving approximately one tonne of fuel and three tonnes of CO2 emissions daily.
Source: Anemoi