Development of Instrumentation for Mobile Measurements of Hydrogen Emissions

In the coming decades, hydrogen infrastructure is expected to expand significantly as our energy supply moves towards net-zero carbon emissions in response to anthropogenic climate change. However, whilst hydrogen itself is not a greenhouse gas, it causes indirect warming. It reacts with other trace gases in the atmosphere, resulting in increased concentrations of tropospheric methane and ozone, and stratospheric water.

This project aims to quantify parts per billion (ppb) level concentration variations in mobile measurements of atmospheric hydrogen in the UK, enabling small leaks to be detected. Molecular hydrogen can be difficult to contain due to its small size and tendency to leak from storage.  Reducing gas analysers require frequent calibration and are generally not portable. Furthermore, hydrogen is not IR active, and therefore cannot be measured using the same techniques as other mobile analysers. 

We are redeveloping an off-the-shelf cavity ring-down spectroscopy (CRDS) analyser to be used for mobile measurements. The instrument contains a catalyst which converts molecular hydrogen within sample gases into water vapour that is measured using CRDS. Due to this measurement method, gases in the analyser must be dried prior to injection. The instrument is regularly flushed with dry nitrogen (N2), and ambient air and calibration standards are passed through a drying inlet that we have designed to reduce moisture within the sample gas. This inlet consists of a flow meter followed by a Nafion dryer, Drierite and magnesium perchlorate; the sample passes through a moisture detector before injection. The air is dried further by an internal drier within the instrument.

Local data will be compared to both continuous and flask measurements taken with the gas chromatography and reducing gas photometer instrument in our laboratory. After this, we will conduct field campaigns at industrial sites across the UK that are likely to be emitting molecular hydrogen. 

A precise, accurate mobile analyser allows for accurate measurements of fugitive emissions from the industrial sector and better constraint of models and hydrogen’s source inventory. The analyser also allows for measurements in remote locations, and could be extremely beneficial in the search for natural hydrogen. This project allows for improvement in our understanding of hydrogen’s impact on the climate and energy sector.