Russo, Roberta (2025) DEVELOPMENT OF MODELS FOR OPTIMISING THE ENERGY PERFORMANCE OF PASSENGER SHIPS WITH NEW LOW ENVIRONMENTAL IMPACT TECHNOLOGIES. [Tesi di dottorato]

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Abstract

This doctoral thesis presents an in-depth investigation into the integration of alternative fuels and advanced green technologies to enhance the energy performance and sustainability of passenger ships. The study explores hydrogen, methanol, ammonia, and LNG as key alternative fuels and evaluates innovative technologies such as Proton Exchange Membranes fuel cell (PEM), High-Temperature PEM (HT-PEM), and Solid Oxide Fuel Cell (SOFC) with a focus on coupling these technologies with both conventional energy power systems and energy storage systems. Employing advanced modeling, simulations, and experimental analyses, the research identifies viable strategies to significantly reduce the environmental footprint of maritime transportation while maintaining or improving operational efficiency. A detailed case study of a hydrogen-fuelled PEM powertrain, applied to a high-speed passenger catamaran and a megayacht, demonstrates hydrogen’s potential as a clean alternative to conventional fuels. For the catamaran, simulations conducted on the Salerno–Capri Island route revealed a hydrogen consumption rate of 3.5 kgH2 per nautical mile and a storage requirement of 250 kg for a round trip, utilizing nine Type IV hydrogen tanks. For the megayacht, with an average speed of 8 knots over a 12-hour journey, hydrogen consumption totalled 49.7 kg (1.5 kgH2/nm), supported by a PEM system delivering a steady 140 kW output. These systems showcased robust performance, emphasizing the role of energy storage systems (Li-ion based batteries) in handling load variations. Additionally, thermal and pressure management emerged as critical factors for ensuring efficiency and durability in hydrogen fuel cell systems. A methanol-fuelled HT-PEM to be installed on board a small sailboat has been investigated. This study is based on the results of a 5 kW HT-PEM system experimental apparatus. The system’s feasibility has been demonstrated. It resulted in an average specific methanol consumption of about 540 g/kWh. The system achieved greater stability and autonomy by integrating battery storage, leveraging methanol’s high gravimetric density. Green methanol was identified as a pathway to attaining zero-emission sailing, highlighting its potential for sustainable marine applications. Ammonia was evaluated as a hydrogen carrier in a PEM fuel cell system retrofitted to a megayacht. While the bulky ammonia processing system for generating high hydrogen flow rates presented installation challenges, the study demonstrated the viability of using ammonia for compliance with Emission Control Area (ECA) regulations. The analysis also noted that increasing storage capacity would require significant vessel modifications but could extend operational autonomy. In another case study, an LNG-fuelled SOFC system was integrated with a heat recovery system (HRS) on board a cruise ship. This configuration not only reduced global emissions but also achieved LNG savings of up to 14.4%. Partial water recovery from SOFC exhaust further optimized onboard resource usage, enhancing the sustainability of large-scale passenger ships. The methodology and results obtained in this thesis research provide critical insights into the application of alternative fuels and green technologies in maritime propulsion. This research establishes a foundation for the maritime sector's transition toward carbon-neutral shipping, addressing key challenges such as fuel handling and storage, system efficiency, and regulatory compliance. By aligning maritime practices with global climate goals, this research supports the development of sustainable transportation and commerce for the future.

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