Why Electrolyzer Stacks Need a New Approach

All electrolyzer stacks face a common challenge: managing the complex, two-phase interaction between liquid water and evolving gas under pressure. Whether the environment is alkaline (with circulating lye) or PEM (with ultrapure water), the physical mechanisms are similar:

• Water must remain available across the active surface of the electrodes.
• Gas must be evacuated efficiently to avoid blockage or flooding.
• Heat must be removed quickly to prevent hot spots.
• Current must distribute evenly to avoid localized membrane stress.
• Internal pressure must remain stable across every cell.
  
  

In both technologies, conventional stack architectures struggle with the same problems:

• Channel flooding or dry-out.
• Non-uniform flow distribution.
• Uneven temperature profiles.
• Accelerated degradation of electrodes or membranes.
• Instability when operated at higher pressures.

Because industries increasingly demand reliability, efficiency, and predictable operating costs, a more stable internal environment is essential. HIFI™ Technology provides this stability.

HIFI™ Technology: The R&D Journey Behind the Innovation

Rather than making incremental updates, this engineering initiative emerged from a long, multi-disciplinary effort at Exion Hydrogen’s Belgian and Polish technology centers, where the team rebuilt internal flow and heat management from first principles. This extensive work ultimately led to HIFI™ Technology, developed through a fundamental reassessment of legacy stack architectures and shaped by a comprehensive ground-up redesign.

The supporting research included:

• High-fidelity CFD modelling of two-phase flow.
• Thermal simulations across full active-area surfaces.
• Mechanics-of-materials analysis for compression and sealing.
• Pressure behavior simulations under industrial conditions.
• Prototype validation under 30 barg.
• Iterative stack testing in real industrial environments.

This research revealed a clear conclusion: achieving stable operation and long lifetime in pressurized cell stacks requires a deliberate redesign of flow geometry, internal spacing, and pressure balance.

A Cross-Platform Framework for Flow and Thermal Optimization

HIFI™ Technology is a comprehensive engineering framework that optimizes how water, gas, heat, and electrochemical reactions behave inside a pressurized cell stack.

It combines several coordinated innovations:

• Advanced Flow Geometry
  Reshaping the internal flow paths to enable stable, predictable two-phase behavior. Wider, optimized flow fields allow water and gas to travel more uniformly across the entire electrode surface.
  
  

• Uniform Gas–Liquid Distribution
  The design yields a defining advantage: a 2–5× higher water–gas ratio inside the cells, ensuring consistent hydration, smoother gas evacuation, and far less risk of flooding or dry-out.
  
  

• Enhanced Thermal Balance
  Optimized channel architecture and improved coolant pathways deliver about 20% more efficient heat evacuation. This keeps temperature gradients low — a critical factor in reducing long-term degradation.
  
  

• Equalized Electrochemical Activity
  Uniform flow and temperature translate directly into uniform current density, preventing localized hot spots or stress zones that shorten the usable life of stack components.
  
  

• Pressure-Balanced Operation at Scale
  The design maintains stable hydraulic and mechanical conditions at 30 barg, benefiting both PEM and alkaline stacks, and supporting their long-term reliability.

Together, these features create an internal environment where the electrochemical process can operate at its full potential, with fewer disturbances and longer system lifetime.

Stabilizing Two-Phase Flow Across Technologies

Two-phase flow — the simultaneous movement of liquid water and generated gas — is the dominant physical challenge inside any electrolyzer stack. The liquid medium may differ (ultrapure water in PEM, lye in alkaline), but the physics remain consistent:

• Gas bubbles form directly at catalyst surfaces.
• They must escape without blocking water access.
• Water must remain evenly distributed at all times.
• Heat must be carried away continuously.

In both alkaline and PEM stacks, conventional fuel-cell-derived architectures often lead to:

• Gas pockets and uneven void fractions.
• Water starvation in parts of the active area.
• Flow stagnation or channel blockage.
• Rapid temperature swings.
• Accelerated degradation of catalysts, membranes, or diaphragms.

As a result, HIFI™ Technology creates a more stable and predictable two-phase environment. Gas evacuation becomes smoother, water coverage stays consistent, and temperature remains balanced across the entire cell. 

This reflects in:

• Higher efficiency.
• Lower operating voltage rise over time.
• Better durability of electrodes, catalysts, membranes, and separators.
• More stable performance under dynamic loads.

These advantages reduce total cost of ownership in industrial environments.

Optimized for Pressurized Operation – A Universal Advantage

Operating under pressure unlocks major system-level benefits:

• Reduced downstream hydrogen compression.
• Better gas–liquid separation.
• Higher hydrogen purity.
• More compact system layouts.
• Faster installation and commissioning.
• Improved integration with pipelines, tanks, or fueling systems.

Exion Hydrogen designs and optimizes its stacks for operation at 30 barg—a pressure level that balances performance, safety, and cost efficiency—and HIFI™ Technology is explicitly engineered to stabilize internal stack behavior at this operating point.

This enables:

• Consistent cell hydration.
• Equalized pressure distribution.
• Stable membrane or diaphragm loading.
• Reduced mechanical fatigue.
• High gas purity directly at the stack outlet.

In practice, this turns pressurized operation into a long-term advantage rather than a constraint.

Zero-Compromise Materials and Mechanical Engineering

To help ensure longevity, Exion Hydrogen pairs its flow and thermal innovations with robust materials and precise mechanical engineering. Although alkaline and PEM platforms use different specific materials, the same core principles apply:

• Precision-controlled stack compression.
• Corrosion-resistant, high-conductivity internal components.
• Robust plates, separators, and diffusion layers.
• Protective coatings for durability
• High-purity water or electrolyte management.
• Stable sealing and gasket behavior under pressure.

This combined approach ensures that the internal improvements translate into measurable durability gains.

A Technology-Agnostic Platform for All Exion Hydrogen Cell Stacks

Although this technology made its commercial debut in the PEM stack integrated into the HyGGe™ 500P, it was designed from the start as a core Exion Hydrogen platform innovation with applicability across:

• Pressurized PEM stacks.
• Pressurized alkaline stacks.
• Future hybrid or next-generation cell designs.

Its hydraulic, thermal, and electrochemical benefits apply naturally across technologies. By deploying one framework across multiple platforms, Exion Hydrogen gains:

• Shared design principles.
• Common manufacturing learnings.
• Consistent reliability improvements.
• Faster development times.
• Higher confidence for industrial users and investors.

This approach establishes a strong foundation for future stack design.