Maritime transport routes are vital for Europe as a key player in the global economy. The European Commission is seeking to transform it into a smart, green system, with the European Green Deal strategy targeting a 90% reduction in emissions by 2050 through sustainable alternatives. Ammonia (NH3) as an energy carrier offers the potential for fossil-free ship propulsion systems. However, storage of NH3 for use in the propulsion system is subject to specific operational and design space requirements. Specifically, storage solution must maximize NH3 capacity within limited installation space while ensuring compatibility with existing containerized arrangements for seamless integration into existing vessels, because NH3 requires three times the storage space for same energy output as compared to conventional fuels. Composite fibre-reinforced polymers, with their outstanding mechanical properties, combined with excellent chemical resistance and low density, offer the possibility of designing NH3 lightweight pressure vessels that make optimal use of the available installation space. The methodology involves design space exploration, optimization, and verification through structural analysis of fibre reinforced composite tanks to ensure safety and structural integrity for maximizing storage efficiency. This study promotes sustainable maritime transportation, paving the way for environmentally conscious and commercially viable NH3-fuelled marine propulsion systems.