2,647 km per kilogram of hydrogen are no coincidence

Shell Eco-marathon | Hydrogen Prototype “Hydraix II”

At the Shell Eco-marathon 2025, the Ecogenium team achieved a specific range of 2,647 km/kg H₂ with its hydrogen prototype vehicle Hydraix II, securing second place worldwide. Achieving this level of efficiency required the exact, reproducible, and dynamically stable measurement of the hydrogen mass flow throughout the entire driving cycle.

Real-time hydrogen flow measurement

The red-y smart series mass flow meter from Vögtlin Instruments was integrated into the vehicle’s hydrogen supply system to continuously measure the mass flow directly in the supply line. Measurement data were transmitted in real time to the control system and used both for consumption monitoring and for subsequent analysis to optimize control strategy and driving profile.

Due to the limited installation space in the vehicle, the measuring device had to be compact and allow seamless mechanical and electrical integration into the existing system. At the same time, high measurement stability was required to deliver valid, low-noise signals even at very low flow rates.

Technical challenges

Precision under extreme conditions

Competitive operation placed high demands on the measurement technology. The objective was to maintain a hydrogen mass flow that was as constant as possible, ensuring stable supply to the fuel cell, which feeds its energy into capacitors to minimize efficiency losses caused by load peaks.

During driving, so-called purge events occur at regular intervals. These involve briefly opening valves to release nitrogen accumulations from the fuel cell. Such events are accompanied by short-term increases in hydrogen mass flow and must be reliably captured by the measurement system.

In addition, elevated ambient temperatures exceeding 30 °C, as well as mechanical influences from vehicle operation, affected the overall system. Under these conditions, a drift-free, temperature-stable, and fast-responding flow measurement was essential to obtain reliable data for system optimization.

Technical solution with the red-y smart series

Stable data at minimal flow rates

The red-y smart series met these requirements thanks to its high measurement accuracy at very low gas flow rates and its fast sensor response to transient operating conditions. The stable and reproducible measurement of hydrogen mass flow enabled precise quantification of energy usage throughout the entire driving cycle.

In addition, the mass flow meter was extensively used in stationary test setups to determine hydrogen consumption and the optimal operating point of the fuel cell at various power levels. The digital availability of measurement data proved to be a decisive advantage both during development and in competition.

The compact design facilitated vehicle integration, while the high data quality provided a reliable basis for software adjustments and performance analyses between individual runs. As a result, the red-y smart series made a measurable contribution to improving overall system efficiency.

Results and benefits

A measurable competitive advantage

By using the red-y smart series mass flow meter, hydrogen consumption could be precisely monitored and systematically optimized. The high data quality and measurement stability played a key role in achieving a range of 2,647 km/kg H₂ and securing second place worldwide at the Shell Eco-marathon.

This application clearly demonstrates how precise mass flow measurement in hydrogen systems contributes to maximizing efficiency and reproducibility—even under real-world, dynamic operating conditions.