Design and retrofit towards zero-emission ships: Decarbonization solutions for sustainable shipping

The maritime transport sector is undergoing significant development to meet the stringent targets set by the International Maritime Organization and national regulations. An informed decision-making process is essential during the design of new ships or the refurbishment of existing ones, especially when selecting new technologies or implementing alternative fuels. This paper presents an approach based on dynamic simulation and multi-objective optimization aimed at identifying the technologies and strategies to be implemented on board. The methodology combines physics-based and data-driven modelling to enhance the performance and consumption assessment of ships under real-world conditions, using tools such as Autodesk Revit for 3D modelling, MatLab and Python for weather data customization, and TRNSYS for simulating the onboard energy system. Specifically, the analysis focuses on optimizing an existing cruise ship and integrating cutting-edge technologies, using measured ship operational data through a calibrated and validated model. Technologies such as single and double absorption chiller, wet steam screw expander and fuel cell are investigated to define a roadmap to their implementation towards energy and emission efficiency. The proposed methodology shows that significant reductions in pollutant emissions can be achieved by their optimization and implementation. Indeed, the use of bio-liquified natural gas to power fuel cells can lead to non-renewable primary energy savings of up to 16.8 %. The study also highlights the importance of future incentive policies for the development of cost-effective green fuels. This research underscores the necessity of innovative solutions to be properly optimized and designed to achieve substantial reductions in greenhouse gas emissions in the shipping sector.