As the UK heating sector continues to explore greener alternatives to natural gas, Paul Harmer, lead technical consultant at the Chartered Institute of Plumbing and Heating Engineering (CIPHE), considers the role hydrogen has to play in decarbonising the grid.
As part of the 2008 Climate Change Act, the UK has committed to cutting greenhouse gas emissions in order to mitigate the potential consequences of global warming.
By the year 2050, emissions need to be net-zero, but reducing emissions to such an extent is not an easy task. Natural gas (methane) is supplied to around 85% of households through a vast underground network of pipes.
It is worth noting that gas is not necessarily ineffective, and the existing infrastructure enables it to be efficiently delivered to homes. But, even as a reasonably low emitter of CO2, it still produces around 180gm/kWh CO2. Given that research and testing is in its early stages, it is important to be aware that a range of options remains on the table – from hydrogen gas boilers to the electrification of heat.
One option that may help improve the situation would be to decarbonise the gas going into the grid. Studies into the use of hydrogen as a replacement for natural gas have gained considerable traction in recent years.
Research reports carried out for BEIS, such as the Frazer Nash reports, highlighted the pros and cons of converting the existing natural gas network to hydrogen, and the technology challenges both in the consumers property and within the boiler design itself.
Encouragingly, BEIS also recently formed a hydrogen economy team and allocated £25m to advance industry studies via a project called ‘Hy4Heat’.
Investment in innovation and testing must be ongoing, so that challenges and obstacles surrounding the introduction of 100% hydrogen can be resolved before it enters customers’ properties.
It is worth bearing in mind that the efficiency and cost of hydrogen creation is a hotly debated subject. Steam methane reformation (SMR) is currently the only commercially utilised process in operation for splitting hydrogen, which as the name suggests, uses methane as part of this method.
Questions remain over the sustainability of this process, and there is a question over how the inherent CO2 emissions are going to be negated. Clearly, advancements in carbon capture and storage (CCS) will be critical to achieving a greener gas.
Another pioneering energy project is HyDeploy, which is trialling the feasibility of blending hydrogen with the existing natural gas supply. Forming a composition of 20% hydrogen and 80% natural gas, for example, could be an easy way to reduce CO2 emissions from home cooking and heating, without potentially changing customer appliances.
It is conceivable that if this project can demonstrate the viability of a blended gas supply, the percentage of hydrogen could be increased incrementally.
On this note, it is worth highlighting the technology readiness level (TRL) process, which was first introduced by NASA in the 1970s. This is where individual components, such as those within a boiler, are given a TRL number of 1-9: with nine being ready and one indicating that new scientific research and advancement is required. Assessments on boilers has already started, highlighting that the existing pre-aerated burner and ionisation flame detection devices in natural gas boilers cannot be used for hydrogen. This might necessitate hydrogen boilers equipped with two burners, one for natural gas and one for hydrogen.
In theory, switching to hydrogen would still allow homeowners to use a gas hob. The only difference would be the colourless flame – although research is required to find a suitable odorant and colourant that will be acceptable for food hygiene. The prospect of converting the country’s entire gas supply is a familiar concept too. For example, in the late 1960s, the UK made a switchover from town gas to natural gas, but further research is required to ascertain the extent to which pipes in consumers’ homes will need altering. Considering that hydrogen fuel will require three times the volume to deliver the same energy as natural gas, it may mean that existing gas carcasses within properties need to be revisited.
There is every possibility that hydrogen could be one of the fuels of the future, but the step cannot be taken until the appropriate research has been done. Both the purity of the hydrogen deployed throughout the UK’s gas infrastructure, as well as the requirement for artificial colourants in hydrogen, are potential issues currently under review. Having a colourless, odourless flame is a particularly big concern, given its presence at the heart of people’s homes. Safety must be a top priority.