A team of researchers has developed a pioneering methodology to replace diesel engines on ferry boats with pneumatic propellers, offering a cleaner, quieter, and potentially more cost-effective alternative for maritime transport.
The study, published in Energy Conversion and Management, outlines a system in which two air motors, each generating 250 kW, successfully powered a ferry along a fixed route in Finland’s maritime transport system. The experimental system demonstrated that pneumatic propulsion could meet the same performance standards as traditional diesel engines, but with significantly reduced environmental impact.
The research aimed to assess both the technical and economic feasibility of implementing pneumatic propulsion on existing vessels. “It is demonstrated that pneumatic propulsion, while unconventional, holds promise as a sustainable and energy-efficient alternative to conventional marine engines, particularly for short-distance ferry operations,” the authors wrote.
Diesel engines, while currently unmatched in power density and reliability, are associated with high fuel consumption, noise, and environmental pollution. In contrast, pneumatic engines offer a quieter, cleaner option. Compressed air can be stored within the ferry’s body or in auxiliary tanks, which also contribute to the vessel’s buoyancy.
Lead author Professor Abdul Hai Alami, from the University of Sharjah, explained, “Replacing these engines with pneumatic ones is a cleaner and more effective option. The simplicity and modularity of the design also make it adaptable to a variety of ferry types—even under challenging operational conditions.”
The system uses compressed air stored in high-pressure tanks, which is then released into vane air motors coupled to naval impellers to generate propulsion. The research used polytropic relations to model the air’s behavior from compression to discharge, ensuring accurate energy calculations and performance projections.
Kaj Jansson, co-author and Finnish ferry expert from K. J Marineconsulting Ab, managed the retrofit and testing of the converted ferry. “Pneumatic propulsion is the future of sailing on fixed maritime routes,” said Jansson. “Ferries operate on predictable schedules and loads, making them ideal candidates for replacing polluting diesel engines with air-powered alternatives.”
The study presents a comprehensive techno-environmental and life-cycle assessment. According to the findings, the pneumatic system offers a lower operational cost and reduced maintenance requirements. Economically, it promises substantial savings—approximately USD 73,000 over its lifecycle—with an estimated payback period of eight years.
The innovation’s uniqueness lies in its application to an existing diesel-powered ferry, originally built in 1985, thereby highlighting the retrofitting potential of the system for older vessels.
Professor Alami emphasized the broader implications of the work: “The development of vane air motors using advanced materials will make pneumatic engines even stronger. Our findings suggest that the conservative estimate of an eight-year payback could be improved under more favorable conditions.”
The researchers hope their methodology will pave the way for wider adoption of pneumatic propulsion in the maritime sector, particularly for ferries operating on short and consistent routes.
By Impact Lab
