D7.1 Inventory of relevant aspects for conversion of gas distribution networks to hydrogen

A model conversion plan is being developed in work package 7 of HyDelta 2 “Conversion of a natural gas distribution network to hydrogen” for large-scale conversion of gas distribution networks to hydrogen. This is done considering distribution networks from practice as case studies. The conversion plans for these practical case studies will be drafted based on the existing knowledge in and experience with converting distribution networks to hydrogen. This report is an inventory of the knowledge and experience that will be used when drafting the plans for the case studies. This report also provides an overview of the relevant aspects to be considered when drawing up a model conversion plan.

Projects and studies

Based on literature, an overview of hydrogen projects and conversion studies has been made. The overview includes 11 projects (mainly field tests and pilots) and 8 studies. Out of these 19 projects and studies, 14 are from the Netherlands, 3 from Germany and 2 from the United Kingdom.

Regulation

Similar to the natural gas market, regulation will apply to the hydrogen market. This regulation is still under development. The European Commission intends to amend the Gas Regulation and the Gas Directive for this purpose. In the proposed new regulation, among other things, a hydrogen distribution network will require a separate network operator, separate from the network management of the natural gas distribution network. If the natural gas distribution network is to be used for hydrogen, those assets must be transferred to the operator of the hydrogen distribution network.

In the absence of a specific legal framework (the current framework prohibits network operators from playing a role in hydrogen pilots), ACM has drawn up a Temporary Framework for Hydrogen Pilots for the next 5 years. A pilot must relate to the built environment and have a specific learning objective. Grid operators are allowed to distribute hydrogen through the grid, but have no role in the production, trade and supply of hydrogen.

Materials, components and technical knowledge and skills

Based on the available literature, an overview of components and materials present in the current gas distribution network and end-use installations, indicating whether they are suitable for hydrogen, or whether they need to be replaced or require adjustments has been made. In this overview for some components it is indicated that the suitability for hydrogen is not yet sufficiently known and that further research is required. An inventory was also made of the required technical skills and knowledge for the conversion.

Supply areas for hydrogen

Before plans can be made for the actual conversion of gas distribution networks to hydrogen, municipalities will draw up plans in consultation with property owners, residents and network operators (DSO and TSO) to determine which customers will continue to be supplied with gas or which will switch to another form of heat supply. In the areas where the gas supply is maintained, a choice is made for the type of sustainable gas: green gas or hydrogen.

For the built environment, the most cost-effective sustainable heat supply can be determined per neighbourhood, such as green gas or hydrogen supply. A similar consideration can be made for business customers (business parks, horticulture greenhouses). In the case of hydrogen, the basic principle is that the existing gas network of DSOs and TSO is used, because this is cost-effective and accelerates implementation. A distribution network of a DSO consisting of a medium and low pressure network behind a city gate station (GOS) comprises several tens of thousands of customers. A low-pressure system just behind a district station provides about 250 to 500 home connections.  There are major differences between distribution networks of a DSO in urban areas, rural areas and business parks. If the hydrogen supply is provided from the regional transport pipeline network of a TSO (RTL), other distribution networks and industry connected to this RTL network must be taken into account.

Hydrogen supply

Five situations can be distinguished for hydrogen supply, of which 4 relate to the supply of (almost) pure hydrogen. Delivery from a GOS that is connected to the high-pressure transmission line (HTL) hydrogen backbone via a regional transmission line (RTL) seems to be the most attractive in the long term, considering cost effectiveness and security of supply. Hydrogen supply areas behind a GOS can have a size of several tens of thousands of customers. Smaller hydrogen projects with several tens to hundreds customers, which will probably be the first to be developed, can be supplied with hydrogen via tube trailers and/or hydrogen produced locally with electrolysers. These projects can be scaled up at a later stage and connected to a GOS that supplies hydrogen from the RTL network connected to the hydrogen backbone. This will improve security of supply and reduce the need to store hydrogen locally. Hydrogen distribution networks that are fed from the hydrogen backbone will be the first to arise in the vicinity of this backbone and where RTL pipelines are converted to hydrogen transport, for example for supplying hydrogen to industrial customers.

Step-by-step plans

In some of the conversion projects and studies that were analysed, a step-by-step plan has been developed for the conversion of natural gas distribution networks to hydrogen. These step-by-step plans relate to the preparation and the actual implementation.  Although the step-by-step plans are quite different and therefore difficult to compare with each other, they offer different starting points for developing a model conversion plan in the remainder of the study.