Towards High-Efficiency Modular Hydrogen Liquefaction: System Design and Experimental Validation

Abstract

Conventional hydrogen liquefaction capacity is typically increased by scaling up a single process train, resulting in large, capital-intensive plants with limited flexibility. This study investigates an alternative number-up strategy based on high-efficiency modular Modified Collins Cycle units using electronically controlled floating-piston expanders. Combined production capacity could therefore be increased by replicating standardized modules rather than enlarging individual machinery. A transient two-stage model predicted a specific energy consumption of 10.1 kWh.kgH2−1 using helium as the working fluid, decreasing to 7.5 of kWh.kgH2−1 with a 20:80 He–H₂ mixture. An FPGA-controlled room-temperature prototype was developed and evaluated through 16 experimental tests using air, nitrogen, argon, and helium. Stable operation was demonstrated with all gases, including a continuous 12.2 h test comprising 25,170 cycles without stalling or system failure. These results establish the feasibility of the expander architecture and support its development toward modular cryogenic liquefaction systems that can be numbered up for larger capacities or deployed in distributed, portable and zero-boil-off applications.