Whether green, blue or grey, hydrogen needs to be transported. There are several ways to do this: the simplest solution at present is to fill large cylinders or tanks and transport them to their destination by road, rail or sea. This approach requires hydrogen to be kept at high pressures, meaning high compression costs.

But since hydrogen occurs naturally as a gas, it can be transported through pipelines. This solves one problem, as a network of pipes can carry hydrogen at low pressures: the hydrogen pipeline network is, unsurprisingly, expanding continuously worldwide. There are currently 1,500 kilometres of hydrogen pipelines in Europe and 900 in the United States.

History of hydrogen pipelines

Historical sources cite the hydrogen pipeline at Verrés, in the Aosta Valley, as the first experiment in transporting this valuable gas: it was 1934, and these pipelines carried 42,000 cubic metres of hydrogen in 24 hours. Their use was linked to the production chain for fertilisers based on pyrite extracted from the nearby Champdepraz mine. Today, however, the facility has been converted into a technical institute and the pipes that carried hydrogen are no longer in operation.

Then there is another hydrogen pipeline, also built in the 1930s (in 1938, to be precise) that is still in operation. It is the one serving the Rhine-Ruhr metropolitan area in Germany: today, hydrogen in the Ruhr is produced mainly through the steam reforming of gas and water vapour (meaning we are talking about grey hydrogen, derived from a fossil fuel), but several companies in the basin are converting to green hydrogen, using hydroelectric and wind energy. Most notably, there are 230 kilometres of pipelines that partly move hydrogen for the district's industrial uses and partly transfer it by vehicle to other destinations.

The hydrogen pipeline network has expanded over the years into France, the Netherlands, Belgium and England (while outside Europe there is a substantial network of hydrogen pipelines in the United States and, to a lesser extent, in South Africa, Brazil, Thailand and Indonesia). And now that the European Union has identified hydrogen as an opportunity to achieve the goal of net zero greenhouse gas emissions by 2050, strategies for transporting this gas have multiplied.

Among the strategies under way is the one defined by European Hydrogen Backbone, a project bringing together the largest natural gas companies in Europe. The idea is to convert existing gas pipelines to carry hydrogen. According to the companies involved in the project, by 2040, hydrogen could rely on a network of 40,000 kilometres, 69 per cent of which would be made up of converted existing gas pipelines, connecting 21 European countries. Among the objectives is also that of reducing transport costs: from the current 10 cents per kilogram per 1,000 kilometres, costs could fall by 25 per cent. And, as a result, the final cost to the consumer would decrease.

Hydrogen pipelines in Italy

As of 2018, the national gas pipeline network in Italy stretched for more than 30,000 kilometres. This pipeline system is managed by Snam, the national gas pipeline company. For the first time, in 2019, Snam injected a mixture of 5 per cent hydrogen by volume and natural gas into the Italian gas pipeline network. The experiment, the first of its kind in Europe, took place in Contursi Terme, in the province of Salerno, and involved supplying a mixture of hydrogen and gas to two industrial companies in the area — a pasta factory and a mineral water bottling company. The following year, the hydrogen content in the mixture rose to 10 per cent.

In its 2020–2024 plan, worth 7.4 billion euros, Snam will invest 150 million euros in the hydrogen sector, and among the activities will be the modernisation of the gas network with a view to making it "hydrogen ready". The network has also recently been certified as compatible with the transport of hydrogen by Rina, a certification body operating worldwide in the infrastructure sector. While the announced replacements concern 1,200 km of pipelines, Snam explains that more than 70 per cent of the gas pipeline tubes are already ready to carry hydrogen. Among Snam's investments, there is also space for hydrogen compression plants: following the trial of the first hybrid gas turbine with 10 per cent hydrogen by volume, to be installed in 2021 at the Istrana station, new tests are under way to determine the maximum quantity of hydrogen that can be fed into turbines and compressors.

Snam @snam

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European Hydrogen Backbone to grow to 40,000 km, covering 21 countries, by 2040!
23 gas infrastructure companies, including Snam, now backing plans presented today.
#EUgreendeal
➡️snam.it/en/Media/news_…

♥ 22 13 apr 2021 · Apri su X →

According to Stefano Mauro, a professor in the Department of Mechanical and Aerospace Engineering at the Politecnico di Torino, the idea of using natural gas transport networks appears to be a winning one: devices based on selective membranes are being studied that would allow, when necessary, the hydrogen to be separated from the natural gas once it reaches its point of use (an alternative is to use the natural gas and hydrogen mixture directly as a fuel). However, achieving 100 per cent hydrogen in pipelines designed to carry gas will not be straightforward.

"Particular attention must be paid to what can happen when hydrogen interacts with steel," writes Stefano Mauro. "It is known that hydrogen can have certain effects on the material, in some cases altering its performance, particularly its ductility and toughness." This is a phenomenon known as "embrittlement", whereby the steel from which gas pipeline tubes are made becomes more brittle upon contact with hydrogen, risking fracture. According to the professor, transporting a mixture with 10 per cent hydrogen will not introduce any effects on existing pipelines: this means that, since the transport of methane gas in Italy amounts to 47 billion kilograms, injecting 10 per cent hydrogen would make it possible to transport 4.7 billion kilograms of hydrogen, with an energy content of approximately 187 terawatts. Since energy consumption in Italy is around 320 terawatts (of which approximately 60 are produced from renewable sources), the 10 per cent limit nonetheless gives "ample scope to provide a storage option for renewable energy production plants that will be installed in the coming years," the professor concludes.

Similar experiments are also under way elsewhere in Europe. The draft Strategic, Research & Innovation Agenda (Sria), a document prepared in response to a request for an institutional public-private partnership dedicated to developing hydrogen technologies in the European Union, cites the case of Leeds (England) as a demonstration of the feasibility of converting the gas network to 100 per cent hydrogen: following a five-year feasibility study, the United Kingdom funded a gas network conversion project with an investment of 60 million euros. Work could begin in 2025.

Hydrogen transport and the Pnrr

There is another school of thought, according to which it is more useful to produce and use hydrogen locally, avoiding long-distance transport, as is the case with gas pipelines. This solution entails the construction of a large number of small plants and dedicated hydrogen pipelines. A pioneer in this regard was the hydrogen pipeline inaugurated in 2008 in Arezzo: it consists of 3.5 km of urban network, created to bring hydrogen to the area's goldsmithing district.

Among future developments, the Arezzo project envisages the possibility of extending the network for residential use. This is confirmed by Emiliano Cecchini, a physicist and former councillor for innovation at the Tuscan municipality at the time of the inauguration. "At the moment, most of the hydrogen fed into the pipeline comes from steam reforming of methane and is transported by cylinder truck," says Cecchini, who is a member of the energy cooperative La fabbrica del sole. "But we also have a solar-powered electrolyser that produces 300 litres of hydrogen per hour. On certain days that can be considered a decent amount." Through its hydrolab, La fabbrica del sole is planning to bring hydrogen to every home, starting with the San Zeno district of Arezzo.

The National Recovery and Resilience Plan (Pnrr) just submitted to the European Commission puts its weight behind both solutions, whether hydrogen is transported to industrial customers or to refuelling stations by tanker truck, or through pipelines mixed with methane. But the Pnrr also dedicates 160 million euros to technical and scientific research on hydrogen, and among the main areas of intervention is precisely the "development of technologies for the storage and transport of hydrogen and improvement of the resilience of current infrastructure in the event of wider hydrogen uptake," as the document states.