Improved hydrogen metering
Hydrogen fuel is one of very few genuinely practical clean energy options. One factor limiting widespread adoption is the difficulty of commercially metering the fuel’s usage. The EU-funded HYAC (HyAC – High measurement accuracy of hydrogen refueling) project provided new information about the operating environment of 70 MPa mass flow meters. The devices are used in hydrogen refuelling stations (HRSs), and the operating information was intended to benefit flow meter suppliers. The team also studied the optimisation of such meters, and developed equipment for testing accuracy. The developments allow verification of HRS meters. Researchers conducted a total of 16 fuelling tests and accuracy measurements on the flow meter. The testing was intended to assess the project-developed testing equipment. The accuracy testing method used a precise weighing device to measure the weight of storage tanks before and after fuelling. Thus, the team was able to exactly measure the mass of consumed hydrogen. Tests confirmed that today’s equipment and methodology are reasonably accurate. Measured accuracy error is in the range of – 5.3 to + 0.65 %. Measurement errors were typically negative, meaning that customers would be undercharged for a given usage. Such results were outside the Californian target requirements for 2018, and every year the requirements will become increasingly strict. Testing accuracy subsequently became more stable using the optimised mass flow meter developed in HYAC. However, the team recommended that future research and development address peak deviation. Researchers also offered several theories explaining the result, plus recommendations for further testing and development. For instance, investigators suggested that reducing the weight of testing equipment would enable more precise measurement. Weight had not been a design consideration, and therefore there is great scope for future weight reduction. Project staff also recommended that future designs enable faster change of the mass flow meter in the testing set-up. The present design requires partial disassembly to effect changes. More rapid change could reduce the cost of testing. HYAC’s findings and recommendations will inform future advocacy about the accuracy of hydrogen metering and help in the development of new guidelines.
Keywords
Hydrogen, mass flow meters, HYAC, hydrogen refuelling,