Zero-emission propulsion system featuring, Flettner rotors, batteries and fuel cells, for a merchant ship

To meet the International Maritime Organization's (IMO) goal of decarbonising the shipping sector by 2050, zero-emission ship propulsion systems should be developed to replace conventional fossil fuel-based ones. In this study, we propose a zero-emission hybrid hydrogen-wind-powered propulsion system to be retrofitted to a benchmark merchant ship with a conventional propulsion system. The ship and its propulsion systems are modelled using an in-house platform. We analyse power and energy requirements for the ship over a realistic route and one-year schedule, factoring in actual sea and weather conditions. Initially, we examine the battery-powered propulsion system, which proves impractical even with a reduction in the ship's speed and the addition of a charging station. This retrofitted battery-powered propulsion system will occupy a significant portion of the existing ship's deadweight due to its substantial weight, consequently reducing the ship's cargo capacity. To address this, we evaluate integrating a hydrogen-powered fuel cell system with power equal to the non-propulsive constant load in the ship. We demonstrate that under these conditions, and with four Flettner rotors and the charging station positioned mid-port on the ship's route, the size of the zero-emission propulsion system can be approximately 20% of the deadweight, rendering such a system feasible.