A hydrogen combustion engine has been tested at sea aboard a Japanese vessel, giving the technology a real-world marine propulsion trial.
The test took place on 25 September when Kikou Maru sailed for about two hours in Osaka Bay, covering roughly 33 km.
The 4,500-gross-tonne vessel was fitted with an engine developed by Yanmar Power Solutions. The system uses pilot ignition and runs on hydrogen as its main fuel.
The Nippon Foundation, which supported the project, described the trial as the first demonstration voyage of a vessel fitted with a hydrogen-only engine, based on research as of September 2026.
Ueno TransTech, the vessel’s owner and operator, handled the conversion and crew training for hydrogen operations.
The demonstration was estimated to have avoided around 1.2 tonnes of CO₂ emissions compared with conventional fossil-fuel operation.
The trial is part of the Nippon Foundation’s Zero Emission Ship Project, which is developing hydrogen-powered vessels for Japan’s domestic fleet.
The project began in 2022 and involves three consortia. A separate vessel, HANARIA, demonstrated zero-emission operation using hydrogen fuel cells in April 2024, while trials involving the other two consortia are planned by the end of fiscal 2026.
