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At a time when ‘green ships’ are going to become a must according to IMO requirements and new rules against pollution at sea entering into force in coming years, energy saving solutions are recommended. Reduction of emissions from ships is expected from applied research in different fields: hull form design and propulsion, hybrid engine technology and fuel cells. This paper is totally devoted to the reduction of resistance and powering obtained via hydrodynamic solution.

Based on the results of the latest investigations carried out at KSRC, analysis of pros and cons of the Air Cavity System Technology (ACST) aimed to improve ship propulsion efficiency is carried out.

The paper discusses the steps to be undertaken in order to optimize the performance of the ACST through an ad-hoc design in relation to the type of vessel and exploitation conditions of it. It also analyzes the types of vessels and hull shapes as object for the implementation of the Air Cavity System, mainly in terms of the preferable ranges of block coefficient and Taylor quotient.

Lastly, a practical implementation of the ACST is demonstrated through its application on a typical large container ship designed at conceptual level, whose hull shape has been re-designed (lower C_B) to optimize the performances of the system.

The two design solutions, that is, the ‘conventional ship’’ and the ‘ACS-fitted ship’, are then compared according to criteria such as powering performance, fuel consumption and shipping economics. Finally, advantages of ACS technology are discussed on the basis of simulation of a round-voyage route.