Identification of sustainable technology and energy vector combinations for future inter-continental passenger aircraft

Aviation contributes to negative environmental impacts. The future aviation demand is expected to double in the next two decades. Thus, the associated environmental impacts are expected to further increase. This growing aviation demand would result in more rigorous aviation policies for mitigating the impacts of aviation. The use of advanced aircraft technology and low-carbon alternative fuels are important strategies of the International Air Transport Association that have the potential to significantly reduce aviation’s climate-change impacts. The aim of this research is to evaluate low-carbon technology and energy vector combinations for future inter-continental passenger aircraft, especially in the long-term. Firstly, in this research a comparative assessment of the performance characteristics of the six alternative fuels is conducted using the standard Breguet range equation and viable alternative fuel(s) for inter-continental travel are identified. It is observed that liquid hydrogen and 100% synthetic paraffin kerosene are the alternative fuels found to be feasible for intercontinental travel. Secondly, an advanced and/or novel aircraft and engine technology of the future is used for conducting a more precise performance analysis of these identified alternative fuels. The aircraft engine design and optimization is conducted in a commercial software by using a standard conceptual design scheme for the use of the conventional jet fuel and identified alternative fuels. The engine analysis includes engine performance simulation at on-design and off-design points for conventional jet fuel and identified alternative fuels. Thereafter, the aircraft energy consumption is modelled using standard aircraft weight sizing process/methodology for the conventional jet fuel and identified alternative fuels, where the engine performance parameters evaluated separately are inputs to the aircraft weight sizing process. It is found that liquid hydrogen fuel offers highest energy efficiency benefits in the future aircraft concept as compared to Jet-A case. Lastly, when considering low-carbon alternative fuels in the conventional aviation sense would mean low or zero carbon emissions in the use phase of the aircraft. However, there will always be some form of embodied emissions associated with any fuel. Therefore, it is also important to consider the life-cycle perspective for the alternative fuels under consideration, so that there are no unintended impacts of using the said fuel. This research compares different feedstocks and/or pathways of manufacturing different identified alternative fuels where the conventional jet fuel case is the reference case. This study evaluates all alternative fuel (manufacturing) feedstocks and/or pathways based on their performance, in future aircraft technology considering primarily greenhouse gas emissions. Such a holistic life-cycle integrated research can potentially guide researchers and decision makers in technology development, and policy makers, in making more informed decisions for the future. Particularly, this research will enable more research-development activities of low-carbon aircraft technology and feedstocks for alternative fuel production. This includes the impact on fuel production capacities, fuel costs and market penetration. Additionally, a systems-level interpretation of this study for global aviation would enable drafting of greener aviation policies.