Advancing liquid hydrogen storage : thermal performance and safety enhancements for cryogenic systems

The rapid expansion of industries has intensified concerns about global warming, primarily due to increasing CO₂ emissions. To mitigate these environmental impacts, the transition to sustainable energy sources with zero emissions is required. Hydrogen, one of the most abundant elements on Earth, has emerged as a promising energy carrier due to its unique properties, enabling a sustainable and emission-free alternative to conventional fuels. Notably, hydrogen possesses a dual-function capability, allowing energy to be converted into hydrogen and vice versa. Hydrogen can be produced using both renewable and non-renewable energy sources, meaning its carbon footprint varies depending on the production method. To achieve a truly sustainable hydrogen economy and minimize CO₂ emissions, electrolysis powered by renewable energy is the preferred production method. However, beyond the energy source, cost remains a critical factor in making hydrogen a viable alternative to fossil fuels. To establish a competitive hydrogen market, large-scale production is necessary, which in turn demands the development of appropriate storage and transportation infrastructure. While advancements in renewable energy production continue to progress, efficient storage solutions remain a significant challenge. Efficient hydrogen storage is essential to the hydrogen economy. Any storage system must not only optimize energy density but also ensure safety to gain public acceptance. Hydrogen’s inherently low volumetric energy density necessitates compression to high pressures (e.g., 700 bar) to enhance its energy content within a confined volume. Alternatively, liquid hydrogen (LH₂) offers significantly higher energy density which makes it more suitable for large-scale storage and transportation. State-of-the-art cryogenic storage systems utilize double-walled tanks with a vacuum-insulated interstitial space, often supplemented with low-conductivity materials such as multi-layer insulation (MLI) to minimize heat transfer. These super-insulating materials are essential for reducing heat ingress particularly at normal operating conditions, defined as the temperature gradient between cryogenic temperatures and ambient room temperature. Even with safety valves designed to prevent over-pressurization, cryogenic tanks, especially those used in mobile applications, are not immune to failure if the pressure management system malfunctions. In such situations, insulation becomes a critical safeguard, helping to limit heat absorption and prevent the tank from rapid overheating and building up dangerous pressure. While these types of accidents are rare, when they do occur, the consequences can be severe. There are limited studies that investigate the behavior of insulation materials under extreme heat loads, particularly in the event of fire-related accidents. Furthermore, no existing studies comprehensively analyze the transient response of cryogenic storage tanks under such conditions. This PhD thesis aims to address these knowledge gaps through a combination of fundamental experimental investigations and detailed numerical modeling. By studying the behavior of insulation materials under high thermal loads, this research will provide critical insights into heat transfer mechanisms and enhance the efficiency as well as safety of LH₂ storage systems.