Estimating energy demand for decarbonising the aviation and maritime fleets of Germany: An agent-based technology diffusion approach considering investment behaviour

As hard-to-abate transport sectors, aviation and maritime are major CO2 emitters for which decarbonisation is particularly difficult to achieve. Meaningful emission cuts depend on the uptake of emerging low-carbon propulsion technologies. Therefore, understanding their diffusion and the associated energy demand is vital for achieving long-term climate goals. This study estimates the future propulsion fuel demand for German-registered aviation fleets and the bunkering fuel demand for maritime fleets by simulating the adoption of emerging technologies within a data-driven, agent-based diffusion model. The analysis considered fleet age, technology readiness, infrastructure availability, and regulatory measures. The decision-making framework for technology adoption was modelled using utility maximisation, where both economic and environmental utilities contributed to an overall utility score. This study examined two future scenarios for technology adoption. In the first scenario, investment decisions were primarily driven by economic utility, whereas in the second, an accelerated scenario emphasised on environmental considerations. Both scenarios were evaluated against a baseline scenario of continued use of existing technologies. Under Scenario 2, CO2 emissions in aviation reduced by 82%, and by 15% in maritime by 2050, relative to the baseline. However, these reductions demanded significantly higher electricity, primarily due to the production of fuels like hydrogen and synthetic fuels. By 2050, electricity demand for decarbonising the fleet portfolio is projected to rise to 80 TWh, while maritime demand remains stable at approximately 35 TWh.