f Hydrogen Risk Mitigations – GDN risk mitigations selection proposal

Hydrogen is being proposed as a suitable low carbon alternative to natural gas. It has the potential to reduce green-house gas emissions across Great Britain’s industrial landscape but also for heating buildings. The Department of Energy Security and Net Zero (DESNZ) statistics show domestic heating currently accounts for 37% of the country’s CO2 emissions. Hydrogen also helps reduce fatalities associated with carbon monoxide. Discussions with the Health & Safety Executive (HSE) on incident statistics suggest that by 2032 there will still be 1.5 fatalities per year attributed to carbon monoxide poisoning as a direct result of using methane based natural gas for heating and cooking.
Hydrogen and natural gas are very similar when compared with other fuel sources. They are both gaseous at distribution operating pressures, they can both be burned to release energy, and they are both non-corrosives. This means that a piped distribution system and combustion appliances can be used to exploit their captured energy. They also differ from one another in that hydrogen has a broader range of flammability and lower ignition energy but is also much more buoyant and has higher diffusivity than natural gas; hydrogen also releases no carbon when burnt. The differences mean that to transition from one gas to the other, with the intention of utilising the same piped distribution system and end-utilisation, requires due diligence, assessment, and where necessary, updates to the system – be that to the assets themselves or the way they are operated.
A strategic Government decision on the role of hydrogen in decarbonising heat is due in 2025. Ahead of this, DESNZ has commissioned the Health and Safety Executive to carry out a Comprehensive Formal Assessment (CFA) of all safety and technical evidence on hydrogen, due in mid-2025. The deadline to have all evidence to be assessed with the HSE is September 2024 (albeit work will continue after this date but not be part of the CFA). One of the safety demonstration requirements is an assessment of the change in risk posed by a transition to hydrogen. Whilst other projects focus on the risks related to transmission assets, the emphasis of this piece of work has been on below 7 bar distribution assets and its end-users, excluding industrial users and storage, who would require bespoke risk assessments for their processes.
Several projects have been undertaken or contributed to hydrogen distribution and end-use risk assessments. DESNZ’s Hy4Heat Programme included a safety assessment in 2021. NGN’s H21 project, and concurrent development of the Hydrogen Village Trial submissions, helped progress the risk assessments in 2022 and 2023. They included the development of quantitative risk assessments (QRA), being carried out using the DNV modelling tool, CONIFER, which was developed specifically to differentiate between natural gas and hydrogen distribution systems.
Recognising the influx of additional safety and technical evidence throughout 2023 and 2024, leading up to the CFA deadline of September 2024, a final risk assessment was commissioned to cover all of Great Britain. It is the most thorough risk assessment the gas industry has ever carried out. All the Gas Distribution Networks (GDNs) and some of the Independent Gas Transporters (IGTs) have contributed to the study.
This report was submitted to HSE for their assessment of the safety evidence for 100% hydrogen heating, which can be found at Hydrogen heating: HSE assessment of the safety evidence - GOV.UK.
Queries should be directed to DESNZ: https://www.gov.uk/guidance/contact-desnz.