In the segment 'A Look Around Innovation,' we introduce research and development (R&D) sites that have led to social implementation. In the 26th installment of this series, JST News interviewed Principal Researcher Hideki Kawashima of the National Maritime Research Institute, National Institute of Maritime, Port and Aviation Technology. He is engaged in research and development that combines an advanced air lubrication system that reduces frictional resistance between ships and water with the IoT to improve energy-saving effects. This technology has been put into practical use, and the first ship entered service in January 2025.
30 years of research and experiments in a giant tank — Selected for cross-ministry commercialization program
JST News visited the National Maritime Research Institute, located about 10 minutes by bus from Mitaka Station in an area with abundant greenery, including Jindai Botanical Park. The institute has numerous testing facilities on a vast site spanning Mitaka City and Chofu City in Tokyo Prefecture. Most notable is the giant experimental tank measuring 400 meters in length (Figure 1). Using ship models, verification experiments can be conducted in conditions close to actual navigation. Kawashima has been working on air lubrication research since 1995, when the institute was still the Ship Research Institute under the Ministry of Transport.
Blowing air from the bottom of a ship improves fuel efficiency. This is called "air lubrication." Generally, as the proportion of small air bubbles in water increases, frictional resistance decreases. In experiments, frictional resistance can be reduced by nearly 100 percent, but in actual ships, the reduction is around 30 to 40 percent. The reduction in frictional resistance also varies depending on ship speed and waves. Furthermore, frictional resistance can also be reduced by blowing air periodically rather than continuously. According to Senior Researcher Daijiro Arakawa of the institute, "We are verifying the effects of frictional resistance reduction by air bubbles under various conditions using numerical simulation" (Figure 2).
Research toward the commercialization of the Advanced Air Lubrication Method (AdAM), which aims to improve energy-saving effects by periodically blowing air and controlling it through monitoring, was selected for the cross-ministry SBIR (Small/Startup Business Innovation Research) program led by the Cabinet Office, and was carried out in two phases. Phase 1 was implemented with JST's Program for Creating Start-ups from Advanced Research and Technology (START) Project Promotion Type SBIR Phase 1 Support. A prototype monitoring system utilizing the IoT was built for coastal ships sailing domestically, and control technology for the air lubrication system was developed to respond to hull conditions and sea conditions such as waves and tidal currents. Economic efficiency and energy-saving performance were evaluated through numerical simulations and experiments, assuming installation on a 499-ton cargo ship. The aforementioned giant tank was used for the experiments.
The subsequent Phase 2 was given support for commercialization and development by the Ministry of Land, Infrastructure, Transport and Tourism, and more full-scale technology development was carried out, working toward social implementation. This included simulations for optimal air blowing methods in accordance with ship conditions such as wave-induced rocking, and examination of IoT-based monitoring systems. "When the hull is rocking, air escapes from the bottom of the ship and the effect is reduced, so we are searching for the optimal way to blow air," said Kawashima.
In the system they have developed, the IoT collects various data such as ship speed, rocking, engine, and air lubrication system equipment information, and sends it to data servers on land. By analyzing this data and controlling the equipment installed on the ship in an optimal manner, energy savings can be achieved without adding additional work for the crew.
Coastal cargo ship "Churasan" enters service: Attracting inquiries from home and abroad
Kawashima's partner for the social implementation of AdAM is Nakashima Propeller (Okayama City), which is world-renowned for ship propeller manufacturing. The company has achieved high performance in ships, primarily through propellers, and has worked on energy saving, fuel consumption reduction, and greenhouse gas emission reduction. Since 2021, they have conducted research and development with Dr. Kawashima and others, and commercialized the new air lubrication system "ZERO." The first ship to adopt "ZERO" was the coastal cargo ship "Churasan," which is approximately 76 meters in length and 499 tons in weight, and entered service in January 2025 (Figure 3). "Churasan" is currently in the stage of acquiring data while operating and analyzing energy-saving effects. Analysis is not easy because waves, tidal currents, and cargo volume vary from day to day. Nevertheless, results showing energy-saving effects from the method of blowing air have emerged. Analysis of operational data showed that periodic blowing produces greater energy-saving effects than continuous blowing, proving the effectiveness of AdAM.
Manager Keita Fujii at Nakashima Propeller said, "Once we have a track record of people adopting the system, it builds momentum. We've actually started receiving inquiries from Japan and other countries." An official from the Ministry of Land, Infrastructure, Transport and Tourism who has worked with them to find solutions to challenges facing the system's social implementation commented, "This is the result of the collaboration between SBIR Phase 1 and Phase 2 leading to social implementation. I believe this system will bring new light to the coastal shipping industry, which faces challenges such as crew shortages and low carbon/decarbonization, and will help solve these problems." With such support, AdAM is likely to play an active role on the world stage from now on.
A key factor in climate change countermeasures — Working in tandem to refine technology
Alternative fuels such as biofuels and synthetic fuels are being considered for use in ships as climate change countermeasures, but their prices are higher than conventional heavy oil fuel. Therefore, the economic benefits of energy saving become even greater. Furthermore, as a modal shift from trucks to cargo ships is expected to reduce greenhouse gas emissions, energy saving for ships will become even more vital than before. For this purpose, it is necessary to optimize air lubrication systems.
Looking back on his 30 years of research, Kawashima recalled, "Research is linked to social conditions, so there were times with tailwinds and times with headwinds. But it's important not to give up and to keep going." And meeting and holding discussions with people from outside the world of researchers through the two support phases of SBIR, especially through JST's Phase 1, broadened his perspective and encouraged him. "I want to continue working in tandem with Nakashima Propeller to brush up on the technology and implement it on ships around the world," he said.
(Article: Keiichi Motohashi, Photography: Erika Shimamoto)