30% of the natural gas fueling UK homes and businesses could be replaced by hydrogen without requiring any changes to the nation’s boilers and ovens, a study by Swansea University researchers has shown. Over time the move could cut UK carbon dioxide emissions by up to 18%. The open-access study is published in the RSC journal Sustainable Energy & Fuels.
The difference between the two percentages—30% hydrogen enrichment and a potential 18% drop in carbon emissions—arises from the fact that hydrogen-enrichment lowers the calorific content of the fuel, necessitating a higher volume of gas for a given energy output. . . .
Domestic gas usage accounts for 9% of UK emissions. In an effort to reduce annual carbon emissions, there is presently a concerted effort from researchers worldwide to offset the usage of natural gas. Enriching natural gas with hydrogen (HENG) is one option. Experiments have shown that modern-day gas appliances work safely and reliably with hydrogen-enriched natural gas as the fuel. It is already used in parts of Germany and the Netherlands. A £600-million (US$805-million) government-backed trial is taking place in the UK this year.
Natural gas naturally contains a small quantity of hydrogen, although current UK legislation restricts the allowed proportion to 0.1%. The question the Swansea team investigated was how far they could increase the percentage of hydrogen in natural gas, before it became unsuitable as a fuel, for example because the flames became unstable. . . .
- Through consideration of the Wobbe Index, we discuss the relationship between molar hydrogen percentage and annual carbon dioxide output, as well as the predicted effect of hydrogen-enrichment on fuel costs. It is further shown that in addition to suppressing both blow-off and yellow-tipping, hydrogen-enrichment of natural gas does not significantly increase the risk of flash-back on ignition for realistic burner setups, while flash-back at extinction is avoided for circular port diameters of less than 3.5 mm unless the proportion of hydrogen exceeds 34.7 mol%. It is thus proposed that up to 30 mol% of the natural gas supply may be replaced in the UK with guaranteed safety and reliability for the domestic end-user, without any modification of the appliance infrastructure.
—Jones et al. . . .