Leveraging a long history in hydrogen compression to drive an evolving sector
Compressing 99.99% pure hydrogen sounds like a straightforward task, but it poses unique challenges compared to handling other industrial gases. Because hydrogen is extremely light and has a very low molecular weight, it does not build pressure easily. This requires compressors to run at very high speeds or use multiple stages, which significantly increases energy consumption per unit of gas.
Hydrogen molecules are the smallest of all gases, allowing them to escape through microscopic gaps in seals and joints. This constant leakage is an economic loss and a major safety hazard due to hydrogen's wide flammability range of 4% to 75% in air and its very low ignition energy.
Material integrity is another critical concern. Hydrogen can weaken metals through hydrogen embrittlement, leading to unexpected failures in compressor parts — such as impellers and shafts — unless special materials, including austenitic stainless steels, are used.
Maintaining the 99.99% purity level is equally difficult because oil-lubricated compressors risk contaminating the gas. While oil-free designs are preferred, they are often more complex and expensive. Additionally, hydrogen's thermodynamic properties lead to rapid temperature rises during compression, creating an overheating risk that necessitates intercooling between stages.
Because no single technology perfectly handles high flow, high pressure, and ultra-purity simultaneously, the industry generally selects equipment based on specific application needs:
- Integrally geared centrifugal compressors are excellent for large-flow volumes and provide an oil-free path, making them ideal for bulk handling in green hydrogen plants.
- Barrel centrifugal compressors are similarly robust for large-scale infrastructure and pipeline networks. For applications requiring very high pressures — such as storage or mobility — oil-free reciprocating piston compressors are the traditional choice, although maintenance-intensive.
- Diaphragm compressors serve as "purity champions" for speciality applications such as fuel cells, offering zero risk of oil contamination and minimal leakage, despite their limited flow capacity.
In many real-world green hydrogen plants, a hybrid system — using centrifugal compressors for high-flow initial stages and reciprocating compressors for final pressure boosting — is the most practical way to balance efficiency and cost.
Ebara Elliott Energy (EEE) supports this evolving industry by leveraging a long track record in hydrogen-rich compression dating back to the 1950s. Our deep domain expertise allows us to build tailor-made solutions that account for hydrogen’s low molecular weight and high stage requirements.
To ensure the long-term reliability essential for global supply chains, EEE and Ebara are constructing a new, full-scale commercial testing and development centre in Futtsu City, Chiba Prefecture, Japan. This facility is the first of its kind, equipped with actual fluid test capabilities for liquid hydrogen pumps at scale, reinforcing EEE’s position as a trusted solution provider.
EEE’s centrifugal compressor portfolio also includes both horizontally and vertically split designs that can be customised for everything from electrolyser bulk compression to large-scale transport. These systems are designed to support electric motor drives with variable frequency drives (VFDs), which lower onsite emissions and integrate seamlessly with renewable power grids.
Beyond providing hardware that complies with stringent API norms and ensures oil-free operation, EEE offers comprehensive lifecycle support through its global service network, including installation, maintenance, and reliability upgrades. This end-to-end support ensures high uptime for the demanding duty cycles of the hydrogen energy value chain.
