A comparative study on energy efficiency of the maritime supply chains for liquefied hydrogen, ammonia, methanol and natural gas

Abstract

To cope with climate change, emerging fuels- hydrogen, ammonia and methanol- have been proposed as promising energy carriers that will replace part of the liquefied natural gas (LNG) in future maritime scenarios. Energy efficiency is an important indicator for evaluating the system, but the maritime supply system for emerging fuels has yet to be revealed. In this study, the energy efficiency of the maritime supply chain of hydrogen, ammonia, methanol, and natural gas is investigated, considering processes including production, storage, loading, transport and unloading. A sensitivity analysis of parameters such as ambient temperature, storage time, pipeline length and sailing time is also carried out. The results show that hydrogen (2.366%) has the highest daily boil-off gas (BOG) rate and wastes more energy than LNG (0.413%), with ammonia and methanol both being lower than LNG. The recycling of BOG is of great importance to the hydrogen supply chain. When produced from renewable energy sources, methanol (98.02%) is the most energy efficient, followed by ammonia, with hydrogen being the least (89.10%). This assessment shows from an energy efficiency perspective that ammonia and methanol have the potential to replace LNG as the energy carrier of the future and that hydrogen requires efficient BOG handling systems to increase competitiveness. This study provides some inspirations for the design of global maritime supply systems for emerging fuels.