(Berlin) - “The fastest and cheapest way to establish a Europe-wide hydrogen network is to convert existing natural gas pipelines, supported by the targeted construction of fewer hydrogen pipelines.” Because existing pipelines are “fundamentally suitable for the safe transport of hydrogen and can be converted from natural gas to hydrogen.” . This is the conclusion reached in a paper on the transport options and conditions for hydrogen that the National Hydrogen Council (NWR) recently approved.
The conversion of a natural gas pipeline in the southwest of the Netherlands has already been demonstrated. Individual components that were not suitable for use in hydrogen networks - such as measuring and control systems or compressors - were replaced and the line to be converted was checked for suitability. “More extensive technical measures, such as attaching an inner lining, are not necessary for the transport application.” Established solutions are already available for the components to be replaced, especially the compressors, and are being continuously developed.
Higher flow speed enables almost identical energy transport capacity
Hydrogen has a lower calorific value based on volume than natural gas. However, due to the lower density of hydrogen, higher flow speeds are possible in the long-distance pipelines, so that a natural gas transport pipeline converted to hydrogen can ensure 80 to 90 percent of the original energy transport capacity, all other things being equal. “Hydrogen pipelines can therefore achieve the high energy transport capacity known from natural gas transport of around eight to ten times the energy transport capacity of a power line.”
Underground hydrogen storage facilities connected to the supra-regional transport network flank the system as seasonal storage facilities and enable the temporal decoupling of production and consumption. There are currently 51 underground natural gas storage facilities in Germany, in which around 230 percent of Germany's current annual natural gas consumption can be stored with 30 terawatt hours. Additional suitable geological formations such as salt caverns for hydrogen storage existed in various locations in Germany.
Smaller quantities can be transported by truck
Smaller quantities of hydrogen could be transported flexibly via truck trailers, larger quantities by long-distance pipeline or ship. In the European environment, transporting hydrogen even in newly built pipelines is the most economical option for distances of up to around 10.000 kilometers. For such a line-bound transport, the study on the “European Hydrogen Backbone” (EHB) determined specific transport prices of around 0,16 euros per kilogram per 1.000 kilometers of transport route with long-distance lines almost fully utilized.
As reported, the EHB initiative only presented an updated version of their plans for hydrogen transport infrastructure across Europe in April. The group, consisting of network operators, proposes to build a hydrogen network with a total length of 39.700 kilometers by 2040. The network would then connect 21 European countries. The previous version from July 2020 described a network of 23.000 kilometers for ten countries. 
The transport prices determined in the EHB study were based on a significant proportion of converted natural gas pipelines in the planned system. Since these lines already exist, their use reduces system costs, accelerates implementation, avoids corresponding environmental interventions and thus increases social acceptance, according to the NWR paper.
Natural gas distribution networks at local level are largely suitable for transporting a natural gas-hydrogen mixture or pure hydrogen. The line materials used in the distribution network (low-alloy steels, plastics such as PE and PVC) generally have the appropriate material compatibility. Other network components such as fittings would have to be evaluated according to the rules of technology for the specific use. “The quality of hydrogen is fundamentally guaranteed when transported in converted natural gas pipelines,” says the National Hydrogen Council.
As an alternative to transporting compressed hydrogen, it could be liquefied to further increase the energy density. The conversion of hydrogen into ammonia is also possible. The recently developed transport medium LOHC (Liquid Organic Hydrogen Carrier), which absorbs hydrogen while releasing heat and releases it again when heat is added, is also suitable. The carrier medium is then brought back to the place of origin hydrogen-free. In addition, methanol offers “numerous possible uses” as a transport medium for hydrogen and even has advantages over ammonia. It is in liquid form at atmospheric pressure and has a significantly lower toxicity. “Transportation is almost problem-free – even in pipelines.”
Scientists are investigating the problem of steel embrittlement
The NWR generally does not want to follow fears that the brittleness caused by hydrogen in the steels commonly used in gas pipelines would impair transport. Analyzes have shown “that the steels used in natural gas pipelines and systems are fundamentally suitable for use with hydrogen and that the dimensioning and design of the pipeline for use with hydrogen can be confirmed”.
Furthermore, research in this area is very active. As reported, scientists at the... Max Planck Institute for Iron Research GmbH (MPIE) and their colleagues from Tsinghua University China and the Norwegian University of Science and Technology published a paper on this topic in the journal “Nature”. Accordingly, the researchers have found a way to blunt cracks and thus stop crack propagation by implementing manganese-rich sections into the microstructure of the steel
The National Hydrogen Council paper is available free of charge as a PDF (ten pages) at
https://www.wasserstoffrat.de/fileadmin/wasserstoffrat/media/Dokumente/NWR_Wasserstofftransport_WEB-Bf.pdf
Photo above
Welders working on a new long-distance gas pipeline in Lausitz © Ontras Gastransport GmbH
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Plan of a European H2 backbone for 2040 / © Guidehouse
