Neither coal, nor gas, but hydrogen

Greenhouse gases from UK buildings must be virtually eliminated for the UK to meet its legally binding climate change targets, says the Committee on Climate Change. Natural gas is currently used to heat around 24 million UK homes, but for the UK to achieve net zero by 2050, natural gas will need to be phased out completely.

One option is to replace natural gas with hydrogen and this is the goal of the government-funded, industry-led Hy4Heat programme. When hydrogen is burned, it produces water and heat, but no carbon. Hy4Heat aims to establish whether it is technically possible and safe to replace natural gas with hydrogen in both residential and commercial settings, in a way that is acceptable to consumers.

Researchers at the University of Leeds are central to one project within Hy4Heat, looking at using hydrogen in coal-effect domestic gas fires, the most popular type of gas fire in the UK.

Combustion expertise

Professor Gordon Andrews has been using his combustion expertise and facilities in the University’s hydrogen lab to develop new types of burners that can work with hydrogen, producing similar or greater amounts of heat than possible with natural gas. But although burning hydrogen does not produce CO2, it can create polluting nitrogen oxides (NOx) when burned at a high temperature.

Professor Andrews explains: “One of the main arguments used against hydrogen as an alternative to natural gas is that it produces NOx, but we’ve been able to solve this problem in coal effect fires by using the interaction between the flame and the ceramic ‘coals’ to control the flame temperature. Our designs now actually produce lower levels of NOx than methane burners.”

The original brief given to Professor Andrews and his team was to design replacement burners and ignition systems for both open and glass-fronted coal-effect fires, but they’ve actually gone a step further. The systems they are designing are dual-fuel, able to run on both natural gas and hydrogen to smooth the transition, should it take place.

This is key, according to James Maxfield from Clean Burner Systems, which oversees the project: “The advantage of appliances than run better on natural gas than existing ones, but are also hydrogen-ready, is that they could be marketed straight away, before the switch to hydrogen happens. This makes them commercially viable to manufacture, but will also mean substantial savings for consumers – and the government – in conversion costs, by not requiring millions of appliances to be changed all at once.”

Stunning innovation

Professor Andrews has also been given an additional brief to design an ‘innovative fire’ – one that doesn’t attempt to copy the look of coal, but can exploit the visual and aesthetic opportunities that burning hydrogen can provide.

“For this fire, we’re using reverse flow combustion, so that the flames burn in their own products which reduces NOx without the presence of ceramic ‘coals’,” says Professor Andrews. “The flames radiate up a ceramic wall instead and look stunning. Hopefully stunning enough to entice consumers away from a look alike traditional fire.”

The project, which involves four industry partners, has been reliant on the University’s expertise and facilities for the progress made, according to James Maxfield.

“The University of Leeds has really been pushing the frontiers on these kind of burners – we couldn’t have done it without them,” he says.  “We’re making the hardware on the basis of the University’s designs and then they are testing for performance and safety.”

The ultimate goal is to pilot the fires in a field trial in which a section of the gas grid serving a local village or area would be converted to hydrogen, but this is still a work in progress.

Read more about our hydrogen research theme