(205d) Hydrogen Liquefaction: An Overview of the Fundamental Physics, Engineering Practice, Economic Viability, and Future Opportunities

Hydrogen is emerging as one of the most promising energy carriers for a decarbonized global energy system. Transportation and storage of hydrogen are critical to its large-scale adoption and to these ends liquid hydrogen is being widely considered. The liquefaction and storage processes must, however, be both safe and efficient for liquid hydrogen to be viable as such an energy carrier. Identifying the most promising liquefaction processes and associated transport and storage technologies is therefore crucial; these need to be considered in terms of a range of interconnected parameters ranging from energy consumption and appropriate materials usage to considerations of unique liquid hydrogen physics (in the form of ortho-para hydrogen conversion) and boil-off gas handling. This study presents the current state of liquid hydrogen technology across the entire value chain whilst detailing both the relevant underpinning science (e.g. the quantum behaviour of hydrogen at cryogenic temperatures) and current liquefaction process routes including relevant unit operation design and efficiency. Cognisant of the challenges associated with a projected hydrogen liquefaction plant capacity scale-up from the current 32 tonnes per day to greater than 100 tonnes per day to meet projected hydrogen demand, this study also reflects on the next-generation liquid-hydrogen technologies and the scientific research and development priorities needed to enable them. Specific examples of the research on liquid hydrogen currently conducted in Australia will be presented. This study also provides a comprehensive techno-economic assessment demonstrating the viability of a conceptual Australia-Japan liquid hydrogen supply chain. Viability for this specific scenario can be used to indicate broader viability for both Asia-Pacific hydrogen supply chains and potentially hydrogen supply chains globally.

Furthermore, this work will present the design, construction and comissioning of a unique laboratory capability at the University of Western Australia (UWA) that has been recently developed (named LH2Facility) and consists of two major sections: Ortho-para (O-P) hydrogen conversion and hydrogen liquefier and LH2 boil-off monitoring. A single-stage cryocooler is deployed to enable ortho-para measurements at various amounts of catalyst, temperatures ranging between (350 and 30) K, and pressure up to 5 MPa, where ortho-para ratio is monitored by in-situ Raman spectroscopy using in-line fibre optic probe. A dual-stage cryocooler is used to liquefy hydrogen (at around 20 K and 1 bar), which is then transferred to a BOG test cell, where temperature stratification and boil-off rates is studied at different amounts of heat ingress, liquid level, and system pressure. The BOG testing rig has been fabricated, which includes vacuum shields (aluminum and copper cans) and LH2 stainless steel cell. Detailed thermal analyses were performed to minimize heat ingress into the hydrogen liquefier and BOG testing cell. The results were directly applied to the material selection, vacuum considerations, cooling capacity, instrumentation, and the dimension of every component. Overall, the LH2Facility design temperature is 20-350 K with the maximum pressure and volume of 5 MPa and 7 ml for (i) o-p conversion cell; and (ii) 1 MPa and 7 L for the boil-off testing cell. The design, engineering drawings, HAZOP, safety review, SOP, and construction of the LH2Facility have been finalized, and the apparatus is currently being commissioned and tested with liquid nitrogen and liquid neon.