Hydrogen Field Test Standard: Laboratory and Field Performance.

Area of Science:

• Metrology
• Fuel Dispensing Technology
• Gas Metrology

Background:

• Accurate verification of retail hydrogen dispensers is crucial for consumer protection and fair trade.
• Current methods for testing gasoline dispensers provide a model for hydrogen dispenser verification.
• The National Institute of Standards and Technology (NIST) has developed a prototype field test standard (FTS) to address this need.

Purpose of the Study:

• To evaluate the accuracy and feasibility of three field test methods for retail hydrogen dispensers: gravimetric, Pressure Volume Temperature (PVT), and master meter.
• To compare the performance of these methods in laboratory and field settings.
• To identify critical factors affecting measurement uncertainty in field testing.

Main Methods:

• The study employed a prototype Field Test Standard (FTS) incorporating gravimetric, PVT, and master meter test methods.
• Testing was conducted using helium gas in NIST's Transient Flow Facility and hydrogen gas at a field dispenser.
• Data analysis focused on method agreement, testing time, and sources of measurement uncertainty.

Main Results:

• All three methods demonstrated good agreement, within 0.57% (helium, lab) and 1.53% (hydrogen, field).
• Laboratory tests highlighted the importance of thermal equilibrium for PVT and master meter methods, and buoyancy corrections for gravimetric measurements.
• Field tests revealed sensor drift as a significant uncertainty source (up to 1.7% for pressure sensors), necessitating robust sensor selection and calibration.

Conclusions:

• The gravimetric, PVT, and master meter methods are viable for field verification of hydrogen dispensers.
• Achieving desired measurement uncertainty requires careful attention to thermal equilibrium and sensor calibration.
• Improved sensor technology and pre-field calibration protocols are essential for reliable field testing of hydrogen dispensers.