Reducing the environmental impact of large cruise ships by the adoption of complex cogenerative/trigenerative energy systems

The International Maritime Organization (IMO) has developed new and stricter rules about environmental impact of big vessels. Those rules are going to widen significantly the so called Emission Controlled Areas (ECA) and to generally gain more control over pollution levels over the seas. The solution that most ship-owners are going to prefer is most likely to be the implementation of pollutant emissions reducing systems, such as Scrubbers and Selective Catalytic Reactor Systems, to dampen emissions produced by the present propulsion systems, based on Internal Combustion Engine (ICE) which burns the cheap but polluting Heavy Fuel Oil (HFO). An alternative solution, based on the adoption of Gas Turbines (GT) in the propulsion system, fuelled by Marine Gas Oil (MGO), can be taken into account, allowing considerable savings in weight and space occupied and lover NOx as well as SOx emissions than those of ICEs, even if with a loss in the engine efficiency (Armellini et al., 2018). In this paper, the possibility of using simultaneously ICEs and GTs as well as the use of trigeneration system is analyzed, with the aim of exploiting the positive feature of both the engine systems. The paper provides a quantitative comparison among different hybrid engines configurations (ICEs and GTs working together) making reference to a large cruise ship as a real case. Considering a cruise ship rather than a cargo ship implies an important and time-dependent thermal energy demand, so that an onboard trigeneration system may result a convenient solution.