The hydrogen revolution hinges on efficiency and, above all, safety. While the sheer power of an H₂ vehicle comes from its fuel cell or engine, the real engineering challenge lies upstream: managing hydrogen under extreme pressure.
In a recent Hyfindr Tech Talk, host Steven Oji spoke with Waldemar Raskop, Senior Technical Manager at Poppe Potthoff, to dissect the crucial components that bridge the gap between a 700-bar tank and a 5-bar fuel cell. The takeaway? Complexity is out; simplicity is the new standard.
The Hydrogen Supply System: Fewer Components, More Power
Hydrogen is stored in vehicle tanks at pressures up to 700 bar (or 350 bar), yet fuel cells and combustion engines typically operate in the range of 5 to 60 bar. The system that manages this drastic pressure drop is the Hydrogen Supply System (HSS).
Poppe Potthoff's core philosophy is to reduce the number of components and joints, directly enhancing safety and reducing cost. Raskop highlighted three essential elements, starting with the flow from the tanks:
1. High-Pressure Lines (Pipes)
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Material: Poppe Potthoff utilizes their proprietary PPH2 material (chromium-molybdenum based) as a cost-effective alternative to stainless steel.
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Safety: This material has a proven track record in the hydrogen world, with extensive testing to mitigate the risks of hydrogen embrittlement.
2. The Parallel Charging Unit (PCU)
The PCU (or manifold) is a modular component placed between the main inlet and the tanks.
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Function: It divides the hydrogen stream to fill multiple storage tanks simultaneously, enabling faster fueling times.
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Design: It’s a key piece of the modular system, offering flexibility to integrate elements like pressure sensors, temperature sensors, and check valves.
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Movement Compensation: Crucially, the joints feature a sphere-in-cone interface allowing up to three degrees of movement. This design, adapted from high-performance diesel technology, compensates for manufacturing tolerances and vehicle vibrations, preventing stress-induced cracks in the joints.
3. The High-Pressure Regulator Unit (HPRU): The Star Component
The High-Pressure Regulator Unit (HPRU) is where Poppe Potthoff delivers the biggest impact on system simplification. This component integrates several functions that typically require multiple standalone parts into a single, compact unit.
From 700 Bar to "Vroom Vroom"
The HPRU manages the entire pressure reduction process via an electronically controlled proportional valve. It takes the tank's high pressure and delivers a stable, precise outlet pressure directly to the consumer.
| Consumer Type | Target Pressure Range | Flow Demand |
| Fuel Cell | ≈5 to 15 bar | Static (steady flow) |
| H₂ Combustion | ≈15 to 60 bar | Dynamic (rapid response) |
Raskop demonstrated that the HPRU can regulate pressure across this entire spectrum with phenomenal accuracy, boasting a control deviation of less than 1%. This performance is vital for combustion engines, which demand rapid, dynamic flow changes (the "vroom vroom") for acceleration.
Integrated Safety and Service
The HPRU is designed to replace complex dual-stage reduction systems with one robust unit, and it bundles all necessary safety features:
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Built-in Filter: A 10-micron filter manages particle contamination, a persistent issue in hydrogen systems.
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Pressure Relief Valve (PRV): Essential on the low-pressure side. Since H₂ systems are never perfectly tight, pressure can slowly build up on the low-pressure side. The PRV opens to release this pressure, protecting the sensitive fuel cell from damage, and then closes again.
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Burst Disc: This is the absolute worst-case scenario failsafe. As Raskop noted, it is expected to never activate, but it provides a mechanical safety backup required for functional safety (ASIL) standards, avoiding the complexity of solely relying on software solutions.
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Service Interface: This allows for maintenance, such as depressurizing the system or cleaning the low-pressure area.
Proving Durability: The Endurance Test
The HPRU was subjected to an endurance test simulating 15–20 years of real-world use under extreme conditions. The component performed for 100 hours in a worst-case scenario, rapidly cycling between 0% and 100% performance level while operating in a climate chamber from −40°C to 120°C.
The test results showed the component's pressure output accurately and consistently followed the optimum line, even after 100 hours of stress, proving its readiness for the road.
Poppe Potthoff’s work in reducing a truck’s system architecture from 41 components to just 25 by integrating their PCU and HPRU is a significant stride toward making hydrogen mobility less complex, more affordable, and inherently safer. Watch the full video here.
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