Anemoi Marine Technology’s rotor sails earn DNV type approval certification

The UK-based wind-assisted propulsion provider Anemoi Marine Technologies has been awarded a type approval design certificate by Norway-based classification society DNV for its rotor sail design measuring 5 meters in diameter and 35 in height.

Anemoi Marine Technologies received the certificate during a special ceremony at trade fair SMM in Hamburg, Germany, last week, confirming that Anemoi Marine Technologies’ 5x35m rotor sail design complies with DNV’s technical standard (ST-0511) for wind assisted propulsion systems (WAPS).

Hasso Hoffmeister, Senior Principal Engineer at DNV, emphasized that WAPS technologies have been on an upward trajectory over the past several years, stating that, the number of installations has ‘trippled’—as confirmed by a recent report from the International Windship Association (IWSA)

“This growth has been built on innovation, safety, and trusted expertise. We are very pleased to build on the excellent collaboration with Anemoi with the presentation of this certificate. Together we are continuing to develop the technical standards and class notations that will enable the momentum behind WAPS to continue to build and enhance shipping’s drive to greater sustainability,” he said.

Reflecting on the recent milestone, Anemoi CEO Kim Diederichsen expressed his enthusiasm regarding the type approval from DNV, calling it a ‘testament’ to the ‘rigorous’ design and engineering work conducted at Anemoi.

“This certification provides shipowners and operators with the assurance they need to invest in our 5x35m Rotor Sail solution, which has already been selected for upcoming installations on several vessels,” he said.

In May this year, Anemoi’s 5×35 rotor sail was installed on the 388,000 dwt DNV-classed bulk carrier Berge Neblina, owned by Singapore-based dry bulk shipowner Berge Bulk, marking the ‘first’ commercial deployment of this product size.

Previously, the company had obtained a full Statement of Design Appraisal for the rotor sail, with additional installations—including the Sohar Max, a 400,000 dwt very large ore carrier (VLOC) operated by Brazilian mining heavyweight Vale—planned for later this year and into 2025.

Otherwise known as ‘flettner rotors’, rotor sails are vertical cylinders that harness renewable power of the wind to propel ships. They capitalize on an aerodynamic phenomenon known as the Magnus Effect to provide additional thrust.

More precisely, the Magnus Effect occurs right when the cylinders start to rotate. As they spin, they interact with wind and create a pressure difference on either side of the cylinder. This pressure generates lift, which acts as thrust, propelling the vessel forward.

According to Anemoi, this kind of technology could allow Berge Neblina to enjoy increased efficiency through the reduction of the power needed from the main engine. This would allow the vessel to cut down on fuel consumption substantially and lead to much lower greenhouse gas emissions.

Ship owners, particularly in the bulker and tanker sectors, have increasingly been embracing rotor sails. They have become a preferred technology not only for improving vessels’ energy performance but also for helping companies achieve their net-zero targets.

In addition, as a form of compact technology, rotor sails offer a large thrust force combined with a minimal impact on visibility, stability and port operations, helping them comply with crucial international emissions reduction frameworks, such as the Carbon Intensity Indicator (CII) and EEDI/EEXI.