In Italy there is a large fleet of passenger ferries, this fleet always operates in a very special “scenario”: no matters if we talk about internal waters such as the lakes or the Venetian lagoon or the coasts of the islands in Gulf of Naples or the Sicilian ones, all those ferries must deal with port structures, often of historical interest, and environmental situations extremely particular and requiring attention. The ferries operating in those areas have the need to offer great manouvrability, silent running, low emissions or no emissions at all. For all those aspects the hybrid propulsion, combining the use of diesel electric generators and batteries, offers the possibility to adopt efficient systems for manouvrability and propulsion, such as azimuthal or azipodal propellers and battery packs to ensure silent approaching to the mooring facilities, the possibility to stay at night in a port without generators working during the nocturnal stop, using a ship that can operate with almost complete silence and no pollution near the areas of interest.
All those advantages have an impact on the general layout of the project, considering the necessity to respect the limitations in term of stability, with special attention to the damaged stability conditions.
The disposition and the subdivision must be conformed to the navigation requests, not only according to the range calculation performed, but also considering the results of tank tests and the evaluation of the size batteries.
Furthermore the hybrid propulsion, as well known, can be more “space demanding” in terms of installation, due to the need to install not only the diesel engine, but also several components for the management of the propulsion system, and this has an impact on subdivision.
In conclusion the subject of the work is the case study of two projects for ferries, different in size and typology, with hybrid propulsion, examining the fact that the request of maintaining the stability criteria and a emergency propulsion in some situations requires choices of project and obliges the naval architect to a careful disposition of the subdivision. This work aims at underlining those aspects.