Energy efficiency of ro-ro passenger ships with integrated power systems

The Energy Efficiency Design Index (EEDI) introduced by the International Maritime Organization (IMO) in 2011 had an admirable intent to improve energy efficiency for ships through a set of technical performance standards. Nowadays, after several revisions regarding the EEDI calculation, it is still not clear whether this intent is (or will be) fulfilled. Segments of shipping particularly sensitive to these issues are passenger and ro-ro passenger ships since many of them are promoted by their shipowners as eco-friendly with the aim of attracting more tourists. This is particularly true for ships with integrated power system (IPS). However, the fact is that it is not possible to discuss energy efficiency improvements without a valid methodology to evaluate it. Current methodology to calculate EEDI is not applicable to ships with IPS since it observes only one operating point and only a part of the ship power system. This paper introduces a new methodology to evaluate energy efficiency of ro-ro passenger ships with IPS, based on a holistic approach, evaluates it for the current fleet of ro-ro passenger ships and proposes options to further improve it for new ships.