Measuring Atmospheric Hydrogen Ahead of the Anticipated Hydrogen Economy

The continuous population and economy growth demands more energy, currently provided predominantly by burning of fossil fuels. However, the depletion of fossil fuel resources and the detrimental environmental impacts of burning fossil fuels are driving the public opinion and governments towards renewable energy (RE) sources. Solar and wind power are the most promising, but its reliability is shadowed by their weather dependence. Hydrogen is considered as a very promising energy carrier which can overcome the limitations of the existing RE sources. Producing hydrogen at the solar panel fields or incorporating water electrolysers within wind turbines will smooth the energy supply, and even reduce the energy transport. If the hydrogen economy takes effect as anticipated, then the hydrogen impact on the climate needs to be re-assessed. In order to simulate future hydrogen concentrations, it is necessary to build a model which can simulate present day hydrogen emissions and sinks, and resultant atmospheric concentrations, which are currently infrequently measured. Building a history of hydrogen measurements opens up possibilities in the future to determine background and pre-existing hydrogen sources, and gives a baseline before the switch to a hydrogen economy.

Historically, Reduction Gas Analysers (RGA) were the workhorse in the laboratory and field, where reductive gasses like hydrogen or carbon monoxide release mercury gas by passing along a heated solid mercuric oxide bed, which in turn is analysed by ultraviolet (UV) absorption. The method is well established but lacks linear response and stability. CSIRO is working on novel methods for more accurate and precise hydrogen measurement. The Pulsed Discharge Helium Ionization Detector, or simply PDD, is an alternative to the RGA. CSIRO has been operating a PDD for hydrogen at Cape Grim (along with the classic RGA) for 7.5 years using shared calibration tanks. The mean difference between them (50,000+ matched data points, when pollution events are removed) is just 0.02 ppb, proving PDD’s incredible compatibility with the established RGA technique. The PDD also has a demonstrated superior precision and linearity compared to the RGA. Another two PDD systems are operational at Aspendale measuring urban hydrogen since 2019 and 2021. The later one is to be deployed at the CSIRO Clayton site, where Aspendale will relocate to in 2025. Another PDD system is in a development stage, able to measure not just hydrogen, but many other atmospheric gases (CH4, CO2, N2O, Kr, Xe). The inability of optical instruments to measure hydrogen (homonuclear diatomic molecule) will mean that there will be an increased demand for RGA or PDD measurements of hydrogen in the future.