Learnings

Outcomes

The work on this project has identified a need for both the upstream and downstream sectors of the gas industry to work collaboratively to determine the minimum energy requirements of end users to ensure adequate volumes of hydrogen are delivered for the customer’s future energy requirements at times of peak demand.

This project has outlined several mitigation measures that need to be explored further to establish the most cost effective and least disruptive solution to the issues raised in relation to the domestic service population. An option to mitigate the effects of the increased flow rate with 100% hydrogen would be to operate the LP network at elevated pressures (within the existing upper boundary of LP pressure limit). 

This project demonstrated that increasing the network operating pressures, for example to 50mbar, it is possible to ensure the minimum 19mb is supplied at the extremity (ECV) for all services to deliver 64kW/scmh. However, the next phase of work needs to establish if this current level of energy consumption is a reasonable assumption as well as determining the wider impact of elevating pressures on the networks.   

Within the GDNs it is already common practice to evaluate the network operating pressures, as networks are renewed and become more leak tight, increasing the operating pressure to maximise system capacity. It should therefore be achievable to increase network operating pressures, in line with current network procedures, to mitigate the vast majority of service supply issues caused by conversion to 100% hydrogen.

This project has reviewed the impact on domestic low-pressure services if the networks were to be converted to 100% hydrogen. The research undertaken has determined that large numbers of services may experience low supply issues so the following recommendations have been made:

• Across-industry engagement is required for consistency in industry standards to meet the future needs of the networks consumers. Currently the GDNs have their own working procedures based on recognised UK industry standards. For example, IGEM have instigated the low-pressure working group, and a similar group could be formed between the GDNs to review the future service supply issues for hydrogen, the mitigations required, and the necessary updates to GDN policies and standards.
• A review of the existing velocity limit of 15 m/s should be undertaken to ascertain if this can be increased without detriment to network safety or reliability to reduce the amount of service upgrades required
• The impact of increasing minimum operating pressure on network models, network reinforcement and shrinkage should be researched further to determine the impact on cost and disruption to the wider network upstream of the services.
• The sizing of services, either for new or during current replacement works (IMRRP) are sized to be hydrogen ready which is based on an agreed reasonable domestic consumer energy consumption.
• The project found increased pressure differential across service lengths and included standard fittings, when flowing hydrogen. Further testing should be undertaken on individual fittings including excess flow valves to assess their individual contribution to the increase in pressure differential and included for in any revised new installation guidance tables. 
• If a decision is made to upgrade services, accurate service population data is required and could be facilitated during pre-conversion household surveys.
• Further work on testing of downstream pipework pressure drop and velocity increase should be undertaken as the pressure differential across downstream pipework is likely to be higher than currently designed for as is the case for services.

Lessons Learnt

The project proved to be complex due to the scale and variability of the subject matter, an allowance for further flexibility in testing should be made in future projects of this type as data and learning is generated. The internal effort required was also underestimated which led to the appointment of a further external project partner being appointed to support the production of the final report as discussed. This also provided additional benefit to the project in allowing an independent review of the testing parameters and data which shall be considered in future projects. 

The data generated and recommendations derived from the project has stimulated significant stakeholder interest and in the interests of closing the remaining evidence gaps out in a timelier manner, consideration shall be given to including the next steps in the original scope in future.