| dc.description.abstract | Net Zero Emissions 2050 (NZE 2050) outlines an ambitious goal of complete reduction of net CO₂ emissions to zero in the next two decades. This is aimed to be achieved through maximum decarbonization of energy production, transportation, residential and industrial sectors. One of the active strategies for decarbonization is switching from fossil-based energy
sources to renewable energy sources which is expected to contribute approximately 40 % towards net zero. However, analysis of current technology readiness levels of renewable
energy utilization and prediction of future technology development suggest that switching to renewable sources might not be sufficient to reach net zero by 2050. In addition to renewable energy, carbon-free or carbon-neutral fuels are attractive options for replacing fossil-based fuels and accelerating emissions reduction. Hydrogen is the most prominent carbon-free fuel under consideration and hydrogen and its derivatives are expected to have a significant role in the overall CO₂ emissions reduction strategy.
Hydrogen is a high energy density fuel and is currently used in industries such as chemicals production, iron and steel and refineries. NZE 2050 roadmap predicts the expansion of
hydrogen usage to transportation, electricity production, heating by blending in gas grid and many other sectors. However, the current hydrogen infrastructure is not sufficient for
large scale hydrogen utilization and a wide range of improvements in technology development, technology scale-up, economic feasibility analysis and policy development are required. In this regard, this thesis contributes towards low-cost and low-emissions strategies for hydrogen
infrastructure development in three different stages of the hydrogen life cycle: production, storage and transportation.
In the hydrogen production stage, a low-cost spray synthesis process is investigated for the production of mixed metal oxide materials which are potential catalysts that improve
hydrogen production efficiency. Synthesis of mixed metal oxides is highly challenging due to separation of the constituent elements during the product material formation process. In this
section, the evaporation of the spray droplet is visualized to improve understanding of the element separation during the product particle formation. It is shown that addition of just 2
wt % urea to the precursor spray solution causes violent bubbling and mixing of elements in the droplet at 150 °C. This strategy can be used to mitigate the element separation and form uniform product particles as desired.
In the hydrogen storage stage, the development of highly sensitive hydrogen leak detection sensors to improve operational safety is discussed. Storage and transportation of hydrogen is dangerous due to low ignition energy and high flame speeds. Chemiresistive metal oxide sensors are suitable leak detection devices with a simple design, minimal energy requirement and capability of detecting sub-ppm level of hydrogen. The response of these sensors to low
concentrations of hydrogen leaks is known to be dependent on the structure of the sensing metal oxide film. However, the effect of sensing film structural features such as film porosity, constituent particle size and packing density on the sensor response is not yet well understood.
In this section, an attempt is made to elucidate this structure-response relationship in sensors by preparing varied sensing film structures following established methods and evaluating
sensor response for ppm level hydrogen exposure. The results show that including only structural features that accelerate surface reactions in the sensing mechanism may not be
sufficient to get a good sensor response and a more holistic approach considering all stages of the sensing mechanism is required to design high performing sensors.
For the hydrogen transportation stage, Techno-economic analysis (TEA) and Life cycle analysis (LCA) methods are used to estimate the costs and emissions of using hydrogen carriers
as means of long-distance hydrogen transportation. With increasing hydrogen demand in various sectors in accordance with NZE 2050, development of a global hydrogen supply chain
is essential to ensure uniform usage. Pipeline transportation of gaseous hydrogen becomes too complicated and expensive for distances above 1800 km. A strategy to overcome this challenge
is converting hydrogen to higher density liquid materials called hydrogen carriers which can be easily transported globally using tanker ships. This section discusses the estimation of eco-
nomic feasibility and emissions reduction potential for long-distance hydrogen transportation from Australia to Japan via four hydrogen carriers methanol, methane, ammonia and liquid
hydrogen using TEA and LCA methodologies. The analysis shows that when the end-use for the hydrogen carriers is fixed as 20% cofiring in natural gas power plants, ammonia is the
cheapest hydrogen carrier with a delivered cost of $40/GJ-LHV and adds $50/MWh to the produced electricity cost.
The thesis outlines implementable and economically and environmentally feasible strategies for improvements in efficiency of hydrogen production, safe operation through leak detection and long-distance transportation. The thesis contributes towards accelerating the development of hydrogen infrastructure to achieve the CO₂ emissions reduction goals set by NZE 2050. | |
