H21- Strategic Modelling Major Urban Centres

This report summarises the results of an independent audit carried out by DNV GL on the model conversions from natural gas to hydrogen for the models being used as a benchmark for the wider UK proposed hydrogen conversion of the natural gas network. The detailed model conversion process was derived from the H21 modelling meetings and the detailed notes were put together by NGN as a basic guide which has been included in Appendix A and is summarised as follows:

• Current 5 year planning model is updated and then used to generate a Replacement Expenditure (REPEX) natural gas model which would remove metallic pipes from the networks by insertion where possible,
• Merging models together to form larger networks where required,
• Preparation for conversion to hydrogen which would include the District Governor (DG) capacity increases to run the additional model flows,
• Conversion of the models to hydrogen by changing demands to thermal and the gas characteristics to those of hydrogen,
• Applying reinforcement to remove pressure failures.