Part 10: The Scope of the Domestic Hydrogen QRA
Part 10: The Scope of the Domestic Hydrogen QRA
Series 1, previously published on LinkedIn, January 10, 2023
The focus of Part 10 is to discuss the scope of the ARUP+ QRA study, i.e. the types of residence that were considered, why they were chosen and whether or not it provides a good representation of roll-out risk. This will be in conjunction with an examination of how the implications have been interpreted by the Hydrogen Insight article, ‘Is it safe to burn hydrogen in the home? Let’s look at the evidence’ by Tom Baxter.
Before that it is perhaps useful to briefly outline the physical boundaries within these dwellings.
The QRA specifically considers areas of existing pipework from the outlet of the ECV up to and including the appliance isolation valve. This boundary has been highlighted in Figure 3 [See below].
Safety Assessment Conclusions Report incorporating Quantitative Risk Assessment, Hy4Heat Workpack 7, ARUP+
From Mr Baxter’s Hydrogen Insight article:
The Royal Academy of Engineering’s recent report, The Role of Hydrogen in a Net Zero System, cites Hy4Heat and comments: “There are limitations of the Hy4Heat assessment that future projects and demonstrations will need to address, such as flats and multi-occupancy buildings, housing that lacks natural ventilation, and the safety of supply through gas networks to homes.”
‘Is it safe to burn hydrogen in the home? Let’s look at the evidence’ Hydrogen Insight, Tom Baxter
The Royal Academy of Engineering are only reiterating what was stated in the QRA about study boundaries, which is the document Mr Baxter is principally reviewing, so why is he citing this rather than the original source? Is he trying to imply that they had uncovered an oversight to lend credence to Mr Baxter’s assertion that the report is flawed?
Instead of that innocuous citation, why did he not instead try to make something out of the following paragraph, within the same Royal Academy report?
Safety: Hydrogen is a highly explosive molecule. It poses many health and safety challenges that must be resolved before approving its widespread use. According to the Hy4Heat safety assessment conducted on behalf of the government and covering detached, semi-detached, and terraced houses, using hydrogen in homes could be up to four times more dangerous than natural gas, but risk can be reduced to a similar level as natural gas by installing two excess flow valves in a property. This assessment therefore concluded that, with this measure and for the properties covered, use of 100% hydrogen could be made as safe as natural gas.
The Role of Hydrogen in a Net Zero System, The Royal Academy of Engineering
I think I know why. From this passage there is no doubt that the Royal Academy are aware of the risks Mr Baxter identifies, but despite that, they are receptive to the conclusion that ARUP+ have reached about the feasibility of risk reduction. This does not fit into Mr Baxter’s narrative that he is identifying risks that have not been properly considered.
So what does the ARUP+ report actually say about it’s own scope boundaries?
The safety assessment is based on 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.
Safety Assessment Conclusions Report incorporating Quantitative Risk Assessment, Hy4Heat Workpack 7, ARUP+
So it is designed to cover the largest proportion of UK housing stock with the greatest risk of explosion. But why are these at greatest risk?
… 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.
Safety Assessment Conclusions Report incorporating Quantitative Risk Assessment, Hy4Heat Workpack 7, ARUP+
Since the study maps structural damage to the probability of occupant injuries, construction becomes an important factor in determining safety. So is there any other corroboration offered for this assumption?
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.
Safety Assessment Conclusions Report incorporating Quantitative Risk Assessment, Hy4Heat Workpack 7, ARUP+
OK there is empirical evidence that such dwellings are the biggest cause of casualties, plus this is precisely the types of buildings where the differential risks of hydrogen would be exposed, or as ARUP+ state:
For the reasons set out above, the basis of the QRA (being a two-storey terraced house), is considered to be conservative relative to the risks in the other applicable housing typologies. Extension of the findings from the QRA to these other housing typologies is therefore considered to be conservative.
This assessment does not include the following building types and so these should not be included in community trials until further risk assessment work has been undertaken:
− Industrial facilities.
− Commercial properties with gas usage significantly greater than domestic environment, i.e.
installed gas usage greater than 100kW (e.g. sports facility with a swimming pool).
− Houses in multiple occupation, for example blocks of flats or other buildings in multiple
occupation.
− Any large or prefabricated buildings.
− Buildings that do not have continuous natural ventilation in excess of the level specified Section 14.
− Buildings that use mechanical (or forced) systems for background ventilation.
A separate safety assessment would be required for such properties.
Safety Assessment Conclusions Report incorporating Quantitative Risk Assessment, Hy4Heat Workpack 7, ARUP+
There are obviously property types that are beyond the scope of this ARUP+ assessment but the fact that they have been identified is not a weakness. It shows awareness of the report limitations and identifies where further study and risk assessment will be necessary.
Referring to the report by the Royal Academy, Tom Baxter writes:
It adds: "The [UK] Health and Safety Executive [HSE] independently reviewed the evidence and was satisfied that the assessment provides an adequate basis for gas network operators to design and risk-assess future hydrogen trials.”
‘Is it safe to burn hydrogen in the home? Let’s look at the evidence’
So this seems to be quite clear. Yet the limitations of housing construction is not solely a problem for hydrogen heating, because the Royal Academy report includes an extensive section on features that make buildings unsuitable for heat pumps, before commenting:
Therefore, hydrogen boilers could play a role in homes where heat pumps are not suitable and that have existing gas grid connections – although zero-carbon district heating may also be part of the solution for these types of homes
The Role of Hydrogen in a Net Zero System, The Royal Academy of Engineering
That heat pumps are not suitable for all buildings is a fact that many hydrogen opponents would rather ignore. So the Royal Academy does acknowledge the limitations of the ARUP+ QRA study, viz.
… there are limitations of the Hy4Heat assessment that future projects and demonstrations will need to address, such as flats and multi-occupancy buildings, housing that lacks natural ventilation, and the safety of supply through gas networks to homes.
The Role of Hydrogen in a Net Zero System, The Royal Academy of Engineering
Yet the Royal Academy also appear to accept the HSE interpretation of the case made by ARUP+:
The Health and Safety Executive independently reviewed the evidence and was satisfied that the assessment provides an adequate basis for gas network operators to design and risk assess future hydrogen trials.
The Role of Hydrogen in a Net Zero System, The Royal Academy of Engineering
And even Mr Baxter notes:
In a letter of assistance to the UK government's energy department, the HSE refers to the Hy4Heat programme and states: “... [The] HSE is satisfied that this provides an adequate basis, if applied appropriately by the relevant dutyholder, for: Designing the scope of future hydrogen trials, Assessment of the risks arising from those trials, and Management of those risks in accordance with a suitable and sufficient risk assessment for those trials.”
‘Is it safe to burn hydrogen in the home? Let’s look at the evidence’ Hydrogen Insight, Tom Baxter
So to be clear the QRA is deemed by the HSE to be sufficiently robust for trial design which, like absolutely every project you might think of, must have a bespoke risk assessment. Had the HSE concluded that no further risk assessment was necessary beyond this generic case-maker, I too would be objecting.
While I am labouring this to exasperation, Tom Baxter is able to interpret this differently, by simply disregarding everything he reads:
In other words, the HSE is clearly not in a position to recommend that hydrogen can be made safe in a domestic setting. Much more work is needed.
‘Is it safe to burn hydrogen in the home? Let’s look at the evidence’ Hydrogen Insight, Tom Baxter
The ‘other words’ he refers to are his own and not, as might be led to believe, a rephrasing of what the Health and Safety Executive (HSE) said or concluded. This is dogma.
The HSE could not possibly ‘recommend’ hydrogen for all domestic situations. What they do say is that it can be made safe, subject to all necessary provisions including case by case risk assessments, being in place. It is bizarre to suggest the HSE could have drawn a more positive conclusion without a massive overreach of their remit. Of course, no such inhibitions existed for them to state that hydrogen could not be ‘made safe’, so it is important to notice that they didn’t do that.
If I have not made this clear then consider this. Locating a gas meter indoors will require a risk assessment, that being the case, the best the HSE could possibly say is that gas meters are safe in principle subject to compliance with regulation and best practice. From such a statement would we conclude that the HSE to be non-committal on the safety of meters?
Mr Baxter wraps up these thoughts with:
I, however, am unequivocal — there is sufficient knowledge and evidence available now to dismiss hydrogen for domestic heat.
‘Is it safe to burn hydrogen in the home? Let’s look at the evidence’ Hydrogen Insight, Tom Baxter
Make no mistake, this is a view that is not supported by the citations, because despite mining the opinions of the Heath and Safety Executive (HSE) and The Royal Society of Engineers, he has found nothing. To be ‘unequivocal’ under such circumstances is not suggestive of a good appreciation of the issues.