Francesco Mauro (Universita' di Trieste, University of Rijeka)
The compressed natural gas (CNG) transport is becoming nowadays an attractive solution not only for stranded gas shipping where current technologies like liquefied natural gas (LNG) and pipe lines are not economically competitive, but also for long-enough distance transport of large volumes of natural gas, where LNG still represents the most economical solution. In fact, recent studies on pressure vessels (PV) materials allow to slightly reduce the displacement (PV Type 4) leading to design completely different hull forms, compared to existing prototypes (PV Type 1, 2 and 3). Since CNG vessel design is a new research field for Naval Architecture, the concept design phase assumes an even higher importance compared to conventional projects, not only for the main parameters determination and performances assessment, but also for the study of completely different solutions for some subsystems. To this purpose, the present study is presenting the comparison between two different kinds of propulsion systems: conventional diesel drive propulsion with propellers and a complete diesel electric solution with pods. The differences between the two solutions are influencing both internal layout and ship dimensions, leading to two completely different ship concepts. The two solution have been compared in such a way to determine the most cost effective solution not only for the single CNG ship but mostly for the fleet composition in a given transport scenario.