Research of Cryogenic Compressed Hydrogen Storage System Based on Multistage Ortho-para Hydrogen Conversion

Cryogenic-compressed hydrogen storage technology is a high-density hydrogen storage method that combines the advantages of high-pressure hydrogen storage and cryogenic liquid hydrogen storage. However, existing research has mainly focused on the development of storage devices for cryogenic-compressed hydrogen, with limited research on the cooling process. To address the challenges associated with low density in high-pressure gaseous hydrogen storage and the significant evaporation of low-temperature liquid hydrogen storage, this paper proposes a novel low-temperature compression hydrogen storage system based on multistage ortho-para-hydrogen conversion. The HYSYS software is utilized to simulate and optimize the system's process. For optimization, nine key parameters, including the helium pressure, outlet temperature of helium from the heat exchanger, mass flow of helium and liquid nitrogen, etc. are selected. With unit energy consumption as the target parameter, a genetic algorithm is employed for the global optimization. The exergy analysis of the energy consumption and heat transfer analysis, as well as the evaluation of processing technology are conducted, showing that the exergy losses of the heat exchanger and water coolers are the greatest. The results demonstrate that the hydrogen density within the storage system can reach up to 90% of the density of liquid hydrogen, effectively mitigating the issue of substantial liquid hydrogen evaporation. Moreover, compared to the conventional hydrogen liquefaction processes, the optimized system boasts a unit energy consumption of 6.872 kW∙h∙kg⁻¹ and an exergy efficiency of 42.42%, showcasing significant advantages. According to the results of the heat transfer analysis, the heat exchanger （HEX1） exhibits the largest temperature difference within the system, resulting in the exergy losses of 105.98 kW, accounting for 26.75% of total exergy losses. This highlights that enhancing heat transfer efficiency is crucial for optimization. In summary, this study not only presents an innovative solution to improve hydrogen storage density and reduce evaporation but also offers insights into optimizing system efficiency through modeling and exergy analysis.