Die Klimawirkung der Wasserstoffleckagen im Verkekehrssektor einer zukünftigen Wasserstoffenergiewirtschaft

Abstract

To limit global warming and decarbonize the current energy system, especially the global transport sector needs broadly low-carbon fuels instead of the fossil-fuel-based ones as well as alternative propulsion technologies such as fuel cells. The transport sector was worldwide still growing by 65% within the last 30 years starting in 1990 (JointResearchCenter, 2023) and approximately one quarter of all anthropogenic energy-related greenhouse gas emissions are caused by the transport sector (Plötz, 2022). For example the greenhouse gases emitted by aviation especially in Asia are the fastest rising (Lee u. a., 2021). Hydrogen is one fuel discussed for major challenges such as hardly to electrify transport modes like road heavy duty transport, long-distance shipping and aviation. The properties of the hydrogen molecule lead to losses into the atmosphere, this hydrogen leakages occur on small scales through venting, purging and diffusion. The impact of hydrogen leakages throughout the entire future hydrogen energy system along the value chain of production, transport, storage and end use can be essential on large scale hydrogen application. The indirect climate impact of these hydrogen leakages is quantified with available literature in this work. This thesis focuses upon the future year 2050, especially for the projected hydrogen demand. A higher atmospheric hydrogen concentration, which is possible in a large scale hydrogen economy results in increases of the potent greenhouse gases methane, ozone and stratospheric water vapour. In this work, the transport sector approach is to use the percentage of the entire hydrogen demand (in 2050, scenario dependent hydrogen in transport sector divided by total hydrogen usage is 20 % to 65 % and 90 % (IEA, 2021) ) and assume it as the share of the total climate impact of the complete hydrogen energy economy. To this end, this thesis presents ranges for the hydrogen demand in 2050, the measured and assumed hydrogen leakage rates along the entire value chain or parts of it and the climate impact of hydrogen, mainly as Global Warming Potential (GWP) which almost doubled in the latest studies and needs further reduction of its uncertainties. However, the low volume of data available for hydrogen's leakage rates especially in the transport sector show the requirement of further measurements and studies to ensure a hydrogen climate benefit also in the near term after the technology switch. Nevertheless, uncertainties remain in the annual hydrogen demand, the leakage ratesand its radiative forcingpublications). Moreover, the lifetime of hydrogen with 1.4 - 2.3 years depends on the highly uncertain ground sink and it's unclear how a higher atmospheric hydrogen concentration influences the atmospheric aerosol.