f MOBs Phase 3: Decarbonisation of Multi-occupancy Buildings Feasibility Study - Hydrogen in MOBs, GDN Aligned Summary Report

This feasibility study has investigated the potential of repurposing existing gas installations for hydrogen use in Multi-Occupancy Buildings (MOBs). MOBs is a broad term extending from a single floor of flats over a shop to large tower blocks. For this study a MOB is defined as a building having at least one meter point, and which meets one of these two criteria:
• The building contains at least three domestic dwellings
• The building contains a mixture of domestic dwellings and commercial units, with there being at least three dwellings and units in total.
Due to the diverse nature of MOBs and the assets, meter positions and appliances used in them it is necessary to sub-divide the population into archetypes and separately assess the risk posed in each category. Customers should only be exposed to Broadly Acceptable risk, as defined as an individual risk of fatality of no more than 1 in 1 million per year in the HSE guidance document Reducing Risk Protecting People [1]. Due to the potential for multiple fatalities in MOBs it is important to understand how each building might respond to an incident and reduce risk to As Low As Reasonably Practicable (ALARP).
It is also reasonable to suggest that a customer’s risk after conversion to hydrogen should be comparable to that which currently exists for natural gas. Therefore, risk to individuals within a building once converted to hydrogen should be no worse than either the risk faced by them prior to conversion or the average risk for that building height prior to conversion.
Based on SGN’s data, the analysis has shown that with universally applied risk mitigation measures and up to two additional mitigations where required, around 99% of MOBs can converted to hydrogen using repurposed assets. Detail can be located in Table 7 on page 12 of this report.
There are around 1% of MOBs where it is likely that existing natural gas installations cannot be repurposed for hydrogen use at an economic cost. The following options are available for this small proportion of buildings:
1. Accept a small individual risk increase in a small minority of building types.
2. Implement additional risk mitigation measures that would reduce those individual risks, but at a disproportionate cost.
3. Remove gas supplies to these buildings and install an alternative energy source.
Based on the results, the following recommendations are given:
• All MOBs to be divided into archetypes and subdivided by installation type prior to a pre-conversion site survey to identify the most practicable and cost-effective energy solution
• The survey will assess all the existing equipment, which includes gas pipelines, meter locations, installation pipes and appliance locations against Gas Industry Standards
• Non-compliant installations will require further analysis and risk assessment on a case-by-case basis to determine their suitability for conversion to hydrogen
• It is proposed that where significant work will be required to re-purpose the existing installation to the required level of safety an economic assessment will be undertaken to determine the optimum solution for customers
• Further work should continue to develop and refine the risk assessment of hydrogen in MOBs. This will support the development of strategic decisions related to conversion. The risks associated with decommissioning gas installations in MOBs could also be assessed in future iterations
• Further work is required to assess Great Britain’s populations of MOBs and gas installation configurations
• Further work is required to provide a detailed cost benefit analysis across the Great Britain distribution networks to ensure that any proposals appropriately address societal expectations of risk versus investment and legal obligations
• Further work is required to define duty holders’ roles, responsibilities and interoperability to convert MOBs to hydrogen
• The project has demonstrated that, in most cases, it is feasible to convert MOBs to hydrogen. The next steps include scoping of resource and operational strategies for conversion
• The additional MOB safety evidence recommendations detailed in Work Pack 3 - Task 12 of Appendix D should also be addressed.
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.