Comprehensive Evaluation of Renewable Energy Carriers on a Retrofitted Floating Storage and Regasification Unit for Sustainable Maritime Transport

Abstract

Maritime transport underpins global trade but remains heavily dependent on fossil fuels, contributing significantly to greenhouse gas emissions. IMO projections warn of a potential 50–250% increase in maritime emissions by 2050, making decarbonization an urgent priority without sacrificing safety, reliability, or economic viability. Ammonia and hydrogen have emerged as leading renewable energy carriers for the maritime sector, yet their marine deployment demands complex integration of storage, regasification, power generation, and auxiliary systems. This dissertation presents a comprehensive multi-perspective framework for evaluating these carriers and their subsystem integration pathways, using retrofitted LNG Floating Storage and Regasification Units (FSRUs) as modular, relocatable offshore platforms capable of transitioning toward cleaner energy hubs. The methodology integrates six analytical dimensions, namely, systematic literature review, thermodynamic and process modeling, heat transfer and boil-off gas (BOG) assessment for cryogenic storage, life cycle assessment, techno-economic analysis, and structured risk assessment. Key findings reveal that hydrogen imposes significantly stricter storage requirements than ammonia, owing to its much lower boiling point (−253°C vs. −33°C). CFD-based thermal modeling estimated daily BOG rates of approximately 0.15% for LNG, 0.02% for ammonia, and 0.01% for hydrogen. Environmental analysis identified climate change intensities of 1.27 g CO₂/kg for ammonia regasification, 5.68 g CO₂/kg for hydrogen, 16.6 g CO₂/kWh for parabolic dish collectors, and 101.9 g CO₂/kWh for ocean thermal energy conversion. Economically, LNG remains the least capital-intensive option at USD 371.0 million, compared to USD 511.3 million for ammonia and USD 521.8 million for hydrogen. However, hydrogen yields the strongest financial return, with an NPV of USD 1.65 billion, a benefit-cost ratio of 3.6, and a discounted payback period of 2.73 years. Risk assessment identified 45 risks across 9 subsystems, with BOG reliquefication scoring highest at 61. Overall, this dissertation delivers an integrated decision-support framework that balances technical feasibility, environmental performance, economic viability, and operational safety for a sustainable maritime energy transition.

Date of Award	2026
Original language	American English
Awarding Institution	HBKU College of Science and Engineering