Dynamic energy system modelling to assess viable zero-emission shipping solutions

Abstract

As global warming threatens to be a major environmental crisis, the reduction of global greenhouse gas emissions is necessary. International shipping currently accounts for 2 to 3% of global emissions. A switch to alternative propulsion methods could significantly reduce these emissions. Several concepts may be capable of achieving this, including transitioning to alternative fuels such as hydrogen, ammonia, or methanol. A key technical consideration is their storage requirements, including volume and mass. To assess this a novel bottom-up approach has been developed. Some alternative fuels can use fuel cells, which achieve higher efficiencies than combustion methods, but may require a battery hybrid system to meet changes in demand. In this thesis, a series of 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. Results showed that the minimum viable setup for hydrogen was with liquid storage, a 94.6MWPEM fuel cell stack and 5.8MWhof batteries, resulting in a total system size of 9,088 m3. By comparison, an ammonia SOFC system had a total system size of 9,772 m3, and a methanol high-temperature PEM fuel cell system had a total system size of 6,150 m3. Hydrogen is often dismissed as a shipping fuel due to its perceived low volumetric energy density, however results show that the actual volume requirements are not unrealistic. Data analysis showed that ships tend to have the fuel storage capacity of 1.9 times more than required for any given voyage. The dynamic modelling method for sizing energy systems shows that viability of some systems is considerably higher than using traditional methods. These results will help to demonstrate to the shipping industry that there are some concepts, particularly liquid hydrogen fuel cell concepts, that can viably deliver zero emission shipping. Should the shipping industry begin to reach more of a consensus on the makeup of future propulsion systems, then this will de-risk the transition and help to accelerate the decarbonisation of the sector.

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Identifiers

ORCID for Charlie McKinlay: orcid.org/0000-0002-8345-0271

ORCID for Stephen Turnock: orcid.org/0000-0001-6288-0400

ORCID for Dominic Hudson: orcid.org/0000-0002-2012-6255

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