Mitsui O.S.K. Lines (MOL) has obtained approval in principle from Lloyd's Register for two new designs of 174,000 cbm LNG carriers equipped with four Wind Challenger hard sail wind-assisted propulsion systems.

The Japanese shipping company said the designs were developed jointly with HD Hyundai Heavy Industries and Samsung Heavy Industries. The Marshall Islands has approved the HHI design, while Liberia has approved the SHI design.

According to MOL, the new vessel designs position the bridge toward the bow to accommodate four Wind Challenger units and optimise their placement. This configuration is claimed to maximise fuel efficiency gains compared to previous designs that incorporated two units.

MOL said preliminary calculations suggest fuel savings could reach up to 30% per voyage, with average annual savings of 15-20% on the North America-Europe route. The company noted that outcomes may vary depending on route conditions, ship speed, and weather patterns.

The approval follows comprehensive risk assessments conducted with the shipyards, classification society, and flag states. These assessments covered sail arrangement, visibility impact, emergency operation procedures, and other safety measures.

Last year, MOL obtained approval to install two Wind Challenger units on a conventional LNG carrier design. Detailed design work for the new four-unit vessels is currently underway.

MOL plans to exhibit the new vessel design at the Gastech Exhibition & Conference 2025 in Milan from September 9-12. The company will hold a commemorative ceremony for the approval in principle award in collaboration with the shipyards, classification society, and flag states.

The Wind Challenger system features rigid sails capable of automatic extension, retraction, and rotation. MOL has set a target to install Wind Challengers on 25 vessels by 2030 and on 80 vessels by 2035. To date, two vessels have been delivered with the system, and installation has been confirmed for an additional nine vessels.

The development forms part of MOL's environmental vision to achieve net zero greenhouse gas emissions by 2050.