Hydrogen Compression Technologies for Decentralized Green Hydrogen Infrastructure: A Review from Mechanical Compressors to Near-Isothermal Liquid-Piston and Electrochemical Systems

Hydrogen compression is a critical interface between production, storage and end use in decentralized green hydrogen infrastructure, where fluctuating electrolyzer output and intermittent demand require operation over variable pressure and flow conditions. This review provides a cross-technology and application-oriented assessment of conventional mechanical, liquid-piston, electrochemical, metal-hydride and hybrid compression systems using common criteria including pressure ratio, specific energy consumption, thermal behavior, hydrogen purity, dynamic flexibility, reliability, scalability and technology readiness. The comparison shows that mechanical compressors remain the reference choice when high pressure, high throughput and commercial maturity dominate. Liquid-piston systems may offer advantages where thermal management and near-isothermal operation are priorities, but their performance depends on working-fluid properties, interface stability, chamber scaling and hydraulic efficiency. Electrochemical compressors are attractive for compact, high-purity and moderate-flow applications, although membrane durability, hydrogen crossover and water management remain key barriers. Metal-hydride systems are most relevant where low-grade or waste heat is available, while hybrid systems can distribute complementary compression functions between stages. Overall, no single technology is optimal; selection should consider the complete operating envelope and integration with electrolyzer operation, buffer storage and downstream demand. Future development requires standardized reporting, long-term cyclic validation, and realistic lifetime and cost data.