Hydrogen boilers could cause four times as many explosions as gas
Safety fears as government-backed assessment finds the alternative fuel could spark as many as 39 blasts a year
So declared the headline to a Telegraph article on 4th August, and it was far from being alone in headlining with the “four times as many explosions as gas” theme. But was it justified? And what was behind it?
In 2017 the Department for Business Energy & Industrial Strategy (BEIS) appointed Ove Arup & Partners to be the programme managers for the Hydrogen for Heat Programme. As is now standard in the ongoing infantilisation of debate and dumbing-down of standards everywhere, it is to be known as Hy4Heat. The task of the programme managers was:
to establish if it is technically possible, safe and convenient to replace natural gas (methane) with hydrogen in residential and commercial buildings and gas appliances, to enable the government to determine whether to proceed to community trial.
In fairness, the programme managers have not produced a dumbed-down piece of work. The reporti appears to have been published on (at least it bears that date) 1st May 2021, but (short-lived) interest in it in the mainstream media seems to have been limited to the last few days. It runs to 144 pages, and a detailed analysis is beyond the scope of a short article here.
Wisely, the decision seems to have been taken to make the safety assessment on the basis of:
a two storey, masonry-built, terraced house with a basement and a loft conversion. This type of property has been selected because it comprises the single largest proportion of houses in the domestic housing stock in Great Britain, and is considered to be one of the most susceptible forms of construction in relation to gas explosion risks in domestic properties. This is because they are, in general terms, the least robust, due to historic or non-existent building regulations being used in the design and construction. They are often of unknown quality and could include substantial owner/occupier modification. They are also the type of home where historically the majority of deaths and injuries have occurred and where the differences in properties between methane and hydrogen indicate that the risks from hydrogen by comparison with methane are likely to be exacerbated.
The report considers the risks from fires and explosions, and doesn’t consider the risk from carbon monoxide (CO) poisoning, since CO is not a waste product of hydrogen. This is one area where hydrogen is safer than natural gas (though the report does point out that the last CO fatality in the UK was in 2015).
The report estimates an average, for the entire British population, of nine explosions (it calls them “ignited events”) per annum from natural gas, excluding any incidents which might be expected to arise from misuse of appliances (such as leaving a gas hob on but unlit).
By alarming contrast, it estimates, for the same population, an average of 39 “ignited events” per annum. They point out that they predict a greater number of very large explosions than observed in practice from historical incident reporting. The number of injuries predicted from hydrogen gas explosions are “considerably higher” than those predicted from natural gas.
This is because of the more serious consequences predicted by the Warwick model for the higher concentration hydrogen explosions.
Only one mitigation measure that might be adopted is then considered, but it makes quite a difference.
Excess flow valves – they might substantially reduce the expected number of injuries so as to be more in line with those associated with natural gas, by reducing the frequency of large and very large leaks, which would lead to the worst-case explosions. There is, however, a caveat:
[F]urther work may be needed to determine whether there is a requirement for regular long-term maintenance strategies in order to ensure these valves are performing as expected.
Unfortunately, even very small hydrogen ignitions can be disproportionately noisy, this may need to be addressed in consumer literature at an appropriate time.
Hydrogen meters should be installed outside the property for safety reasons (many leaks are apparently associated with meters).
Ventilation – very important.
Competence and training:
Existing competent Gas Safe engineers must be upskilled for facilitation of the community trial, including installation, testing and commissioning, having undertaken an appropriate training course (and subsequent assessment) for working with hydrogen gas.
A key assumption of this assessment is that hydrogen would not cause accelerated material degradation compared to natural gas in a domestic setting. And, therefore, there is no change in the likelihood of an initiating leak between the two gases. This is considered a reasonable assumption based on theory. However, there is limited published evidence regarding the use of hydrogen in low pressure networks to reference.
Headlines in newspapers such as the Telegraph, Daily Mail and the Mirror, to the effect that hydrogen boilers could cause four times as many explosions as would be the case with natural gas are justified only in terms of the effect of widespread installation of hydrogen boilers without the mitigation measures urged in the report. The clickbait picture associated with this article isn’t really justified, but at least I’m learning about clickbait from the BBC and the Guardian. And if I can’t trust those headlines, why should I trust the headlines associated with climate change?
Nevertheless, there are several caveats; also some irritating details (I for one don’t fancy a “disproportionately noisy” system, even if it is relatively safe); and potentially significant costs associated with the process. Where is the hydrogen to come from? As I understand it, it is going to be produced by electrolysis, so energy has to be used to generate a different energy source. I’m not sure that’s such a great idea.
And finally, what is the by-product of burning hydrogen? Water vapour. Isn’t that a greenhouse gas?
Well, the next stage is a Government trial of hydrogen gas. More taxpayers’ money will be spent in search of a magic solution to a problem that the UK on its own can’t begin to solve. All this despite the fact that we have an existing infrastructure and an efficient and relatively cheap source of heating our homes already. Natural gas, even after recent wholesale price rises, is still only around 20% of the cost to consumers of electricity, and electricity costs are only going to rise as inefficient, expensive and unreliable renewables become an increasing part of the mix.