As large-scale hydrogen import becomes increasingly important for low-carbon energy systems, efficient unloading of liquid hydrogen at receiving terminals is a key operational issue. Conventional unloading commonly relies on submerged cryogenic pumps, but these systems can increase maintenance burden and operating cost because of reliability issues, cavitation risk, and difficult maintenance inside cargo tanks. This study evaluates a compressor-assisted unloading concept in which make-up boil-off gas from the receiving terminal is compressed and injected into the carrier tank to transfer liquid hydrogen without a submerged pump.

An integrated dynamic simulation model was developed for the unloading and depressurization process, including the carrier tank, transfer line, terminal tank, and make-up boil-off gas compressor. The base case considered a 15,000 m3 liquid hydrogen carrier unloading over 48 h. The proposed concept was compared with conventional pump-assisted unloading using three indicators: boil-off mass fraction, boil-off gas quantity, and energy consumption. Additional scenarios examined increased make-up gas injection and thermal stratification in the carrier tank.

The results show that the compressor-assisted concept can achieve a boil-off mass fraction and total boil-off gas quantity comparable to those of conventional pump-assisted unloading under the base condition. When thermal stratification in the carrier tank was considered, the proposed system performed more favorably: the boil-off mass fraction decreased by about 50% and the total boil-off gas by 38%, mainly because subcooled liquid hydrogen transfer and interfacial condensation suppressed vapor generation. Energy consumption was also significantly lower. Compared with the pump-assisted case, the compressor-assisted system reduced energy demand by 68–76% in representative cases, although the benefit decreased to 11% when make-up gas injection was substantially increased.

Overall, the results demonstrate that compressor-assisted unloading is a technically feasible and energy-efficient alternative to pump-assisted unloading for liquid hydrogen cargo transfer, especially when low carrier-tank pressure and thermal stratification are maintained.