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Global shipping contributes (2.8%) to greenhouse gas emissions and needs to find future fuels which will allow the International Maritime organisation's 2050 net zero targets to be met. There is much uncertainty as to which fuels should be used between hydrogen, ammonia or methanol as future costs are uncertain. We propose and evaluate a Wind-to-Wake ratio that provides an objective measure based on the amount of renewable energy required to propel a ship. Time domain voyage energy demand profiles are used to simulate the fuel used and emissions for a cruise ship, a research survey vessel, a container ship and a large multi-fuel Liquefied Natural Gas carrier. Alternative ship power systems are investigated using various carbon-based fuels, ammonia and hydrogen either using conventional engines or fuel cells. For all voyage and fuel scenarios the combination of hydrogen and fuel cells uses 30% less renewable energy than ammonia and 26% less than methanol. Hydrogen only emits steam whereas the other fuel scenarios still emit significant amounts of greenhouse gasses. [Display omitted] • Wind to wake ratio provides an objective measure for comparing future fuels • Time-domain energy demand allows for 4 vessel types and 12 power systems. • Quantitative comparison of methanol, ammonia and hydrogen as future marine fuels. • Hydrogen through fuel cells requires the least amount of renewable energy investment. • Methanol and ammonia combustion scenarios yield a carbon footprint and other air emissions. [ABSTRACT FROM AUTHOR]

Recent targets have increased pressure for the maritime sector to accelerate the uptake of clean fuels. A potential future fuel for shipping is hydrogen, however there is a common perception that the volume requirements for this fuel are too large for deep sea shipping. This study has developed a range of techniques to accurately simulate the fuel requirements of hydrogen for a case study vessel. Hydrogen can use fuel cells, which achieve higher efficiencies than combustion methods, but may require a battery hybrid system to meet changes in demand. A series of novel models for different fuel cell types and other technologies have been developed. The models have been used to run dynamic simulations for different energy system setups. Simulations tested against power profiles from real-world shipping data to establish the minimum viable setup capable of meeting all the power demand for the case study vessel, to a higher degree of accuracy than previously achieved. Results showed that the minimum viable setup for hydrogen was with liquid storage, a 105.6 MW PEM fuel cell stack and 6.9 MWh of batteries, resulting in a total system size of 8934 m3. Volume requirement results could then be compared to other concepts such as systems using ammonia and methanol, 8970 m3 and 6033 m3 respectively. • Mathematical models developed for fuel cells and batteries. • Dynamic simulations ran against real-world shipping data. • Accurate volume requirements determined for alternative fuel energy systems. • Liquefied hydrogen volume requirements compared to batteries, ammonia, methanol, & compressed hydrogen. [ABSTRACT FROM AUTHOR]