Innovative energy-saving and simplified hydrogen liquefaction system using LNG cold energy

Using cold energy can reduce electricity consumption of the hydrogen liquefaction process, and liquefied natural gas (LNG) receiving stations can provide abundant and low-cost cold energy. From this perspective, an innovative hydrogen liquefaction system using LNG cold energy was proposed. The novelty lay in using LNG cold energy to pre-cool both hydrogen and helium, which was different from the conventional system that only utilizes LNG cold energy for hydrogen pre-cooling. This design enabled helium compression at cryogenic temperatures, simplifying the refrigeration system and effectively reducing electricity consumption. Meanwhile, energy, exergy, and economic analysis were performed for the proposed system. The results showed that the specific energy consumption, coefficient of performance, and exergy efficiency were 3.65 kWh/kg, 0.333, and 39.51 %. The LNG receiving station in Yantai, China, and the hydrogen production data were used to perform a case study. When the price of liquid hydrogen was 5.2, 5.3, and 5.4 $/kg, the dynamic payback periods of the system were 9.4 years, 4.2 years, and 2.8 years. Overall, the proposed new system could offer technical advantages of reducing energy consumption and simplifying hydrogen liquefaction process, as well as favorable economic advantages over conventional systems.