Japan’s 4,800-ton hydrogen tanker: How its engine, batteries and motors work

Japan has demonstrated a coastal tanker using a hydrogen-fired, four-stroke, high-speed engine in what the project describes as a world first. The 4,800-dwt vessel sailed approximately 20 miles in Osaka Bay during a roughly two-hour demonstration on September 25. The Nippon Foundation reported that the voyage reduced carbon dioxide emissions by approximately 1.2 tons compared with conventional fossil fuels. The demonstration forms part of a foundation-sponsored research program supporting the decarbonization of shipping. The tanker combines a hydrogen engine, electric propulsion motors and lithium-ion batteries. How the tanker’s propulsion system works The tanker uses electricity generated by a hydrogen engine housed in a container mounted on deck which powers two electric propulsion motors connected to two shafts. The vessel also carries a hybrid generator and lithium-ion batteries. The batteries smooth the load and help optimize fuel consumption. In this configuration, the hydrogen engine generates electrical power rather than driving the propeller shafts directly. The electric motors provide propulsion through the vessel’s two shafts. Yanmar Power Solutions designed the engine used in the project. Its first bench tests were completed in October 2024, when it successfully operated at a rated output of approximately 500 kilowatts. During those initial tests, the engine used a small amount of diesel oil as a pilot ignition source to burn a premixed combination of hydrogen and air. Subsequent testing worked toward using hydrotreated vegetable oil, known as HVO, for pilot ignition. The supplied account does not identify which pilot ignition fuel was used during the September demonstration. The project called for a tanker specifically designed for hydrogen propulsion. Fukuoka Shipbuilding, a member of the project coalition, launched the vessel at its Nagasaki yard on February 14, 2025. Measuring approximately 344 feet (105 m), the tanker was delivered to Uyeno TransTec in October 2025. What the demonstration covered The September 25 voyage tested the tanker’s hydrogen-fired engine while sailing in Osaka Bay. The Nippon Foundation described it as a carbon-neutral demonstration and estimated the carbon dioxide reduction at about 1.2 tons compared with conventional fossil fuels. Beyond the engine, the project’s scope included developing the fuel supply system and hull design to obtain Approval in Principle from the classification society ClassNK. The team also developed training and an operating manual for hydrogen-fueled vessels. According to the foundation and the operator, the demonstration produced experience and knowledge to support hydrogen adoption in domestic coastal shipping. The project’s stated goal is to develop a model and pathway for that adoption. “This demonstration represents a significant step towards the practical application of hydrogen-fueled zero-emission ships and is expected to contribute to the promotion of decarbonization in Japan’s shipping sector,” said Kazuma Kashiwagi, Director of the Environmental Bureau for Kobe City. Japan has committed to achieving carbon neutrality in its domestic shipping sector by 2050. The wider hydrogen vessel program The Nippon Foundation launched the project in 2022. In June 2023, it assigned three consortia to develop separate demonstrations under its Zero Emission Ship 2050 program. Alongside the tanker, one team focused on demonstrating a hydrogen fuel cell aboard an offshore wind turbine work vessel. Another worked on a hydrogen-fueled engine for the tugboat “Ten-Oh.” The program’s first hydrogen fuel-cell demonstration took place in April 2024 aboard the 238-gross-ton passenger vessel Hanaria. Additional demonstrations were scheduled for 2026, alongside work on hydrogen stations to supply fuel. Other hydrogen shipping projects include Norway’s liquid-hydrogen-fueled ferry MF Hydra and inland barges in Europe. Cruise operators have also begun testing fuel cells and hydrogen systems to supply electricity for hotel operations and reduce emissions in port.Get the latest in engineering, tech, space & science - delivered daily to your inbox.Atharva is a full-time content writer with a post-graduate degree in media & amp; entertainment and a graduate degree in electronics & telecommunications. He has written in the sports and technology domains respectively. In his leisure time, Atharva loves learning about digital marketing and watching soccer matches. His main goal behind joining Interesting Engineering is to learn more about how the recent technological advancements are helping human beings on both societal and individual levels in their daily lives.