Hydrogen seeps into nooks and crannies

Could hydrogen replace natural gas in the future? Aside from the question of whether this would always be the best choice for specific applications, the infrastructure that we are now using to store and transport natural gas is not readily usable for hydrogen. Because hydrogen is a much smaller molecule than natural gas, it can easily leak. Even worse, despite its small size, hydrogen can affect larger materials and make them as brittle as glass.

FSE Science Newsroom | Text Charlotte Vlek | Images Leoni von Ristok

Suppose we have managed to produce green hydrogen, with high efficiency and for various applications. If we want to use hydrogen as a ‘green battery’ for storing variable wind and solar power, however, we must be able to store hydrogen for an extended period of time.

In the ground

For natural gas, temporary storage is already quite common: a surplus in summer is stored for winter, sometimes in existing gas fields or salt caverns underground. ‘For example, this is already being done in Zuidwending, in the province of Groningen,’ explains geologist Johannes Miocic, who is investigating whether something similar is possible for hydrogen. He quickly adds, ‘But that will not be stored in the Groningen gas field! That’s much too sensitive politically, given the earthquakes that have occurred here as a result of gas extraction.’

The ground below Groningen does provide Miocic with his research materials, given its easy accessibility due to the gas-extraction facilities. Because the entire area of the Netherlands, including under the sea, has a similar subsurface composition, however, hydrogen could conceivably be stored somewhere in an empty offshore gas field.  

Miocic focuses on two main questions: how subsurface rocks will hold up in various circumstances and how much leakage is to be expected. To this end, Miocic will take natural samples — rock fragments from below Groningen — and subject them to tests in the lab. More specifically, he will measure both the composition and strength of the rock, as well as how these characteristics might be affected by the presence of hydrogen. By entering his findings from the lab into computer models, he will be able to make predictions about subsidence and other relevant aspects.

How steel embrittles

The research subjects of the materials scientists Bart Kooi and Francesco Maresca are not provided by the ground in Groningen, but by the Gasunie. Kooi and Maresca’s goal is to find out how the steel pipes that are currently used for natural gas would hold up if hydrogen were to be pumped through them. Leakage is one potential problem, but Kooi and Maresca are focusing their investigation on a different phenomenon: embrittlement.

It has been known for about 150 years that metal breaks much more easily in the presence of hydrogen. Maresca explains, ‘Imagine a metal spoon. With hydrogen around, the spoon suddenly behaves like a precious piece of porcelain that breaks into pieces when it falls and hits the ground.’

‘Hydrogen will move through pipelines at variable pressure. This varying pressure in particular will strain the material,’ notes Kooi. In that case, even a tiny crack can be fatal. The exact reason that hydrogen makes materials brittle is not known, but various theories exist. Maresca and Kooi will put several of these theories to the test in their work

The Hydrogen Valley Campus Europe is located in the Northern Netherlands. It is the place where green energy comes ashore (from wind turbines on the North Sea), where years of working with natural gas has led to a wealth of experience, and where universities and vocational institutions will work on new research and the education of the next generation of engineers for the hydrogen economy of the future. This is episode 3 of a series on hydrogen research at the Faculty of Science and Engineering at the University of Groningen.

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