Existing gas turbines aren't ready to run on hydrogen, according to researchers from Germany, China, and France, who just published a study in Nature Materials.
There's a lot of excitement about hydrogen fuel as a sustainable energy solution, though to be truly emissions-free, it must be harvested from water using renewable energy.
Currently, most of the world's hydrogen is made from natural gas, a fossil fuel, in a process that emits large amounts of carbon dioxide into the atmosphere.
But another great challenge facing the hydrogen economy is lesser-known: its infrastructure.
Hydrogen is the smallest of all molecules, much smaller than methane (the main component of natural gas).
We already knew hydrogen could impact the metal pipes and tanks it moves through, even at ambient temperatures: it's a problem companies have already faced in transporting it across the United States.
The tiny molecules of hydrogen can easily creep into nooks and crannies in steel pipes, for instance, making the alloy brittle.
"The bottom line: it is not as straightforward as just pushing through hydrogen in existing infrastructure," said MIT energy scientist Emre Gençer, back in 2023.
Gençer was referring to problems facing hydrogen transport and storage, but the new research reveals these aren't the only pieces of infrastructure that would need replacing in a hydrogen economy.
At the high and variable temperatures inside a gas turbine, hydrogen's ability to 'embrittle' the machinery is sent into overdrive.
By mechanical testing in high-temperature and -pressure environments, the researchers closely examined what went on inside hydrogen gas-powered turbines – made from the industry-standard nickel-base superalloy (IN718) – as they approached temperatures up to 600°C (1,112 Fahrenheit).
With the addition of heat, hydrogen did twice as much damage to the alloys than it does at ambient temperatures, in what could amount to catastrophic failure.
This suggests existing infrastructure won't cope with hydrogen as a fuel source: it's going to require a total overhaul, and entirely new alloys.
The way hydrogen degraded the alloy changed depending on temperature, and most of the problems actually occurred en route to the higher temperatures, between 400°C but below 600°C.
At 400°C, turbine ductility dropped by up to 30 percent.
"When hydrogen enters a nickel-base superalloy at ambient temperatures, it is usually trapped at interfaces and dislocations," explains Xizhen Dong, of Max Planck Institute for Sustainable Materials.
"At elevated temperatures, hydrogen atoms migrate to carbon vacancies within carbides, causing their partial decomposition. Moreover, hydrogen and carbon atoms react and form methane. This highly pressurized methane exerts a high local internal pressure that weakens the interfaces, and promotes damage."
The purpose of carbides in an alloy is to provide strength, which is important when a metal's job is to contain high-pressure gases, and withstand the forces a turbine is exposed to.
But carbide-strengthened alloys, the study suggests, are not suitable for hydrogen-based technology.
On the flip side, existing alloys that can resist hydrogen embrittlement tend to be quite soft, which is not ideal either.
Scientists are already working on finding more suitable materials for hydrogen transport and storage.
One research team found success by mixing scandium with an aluminum-magnesium alloy, to improve the material's strength by 40 percent and their resistance to hydrogen embrittlement by almost five times.
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But when it comes to the hot, spinning parts of the turbine, there's far more work that needs to be done – and new alloys that need to be discovered.
"These findings may serve as important considerations for material design in the pursuit of hydrogen-fueled gas turbines and aircraft engines," the journal's editors add.
The research was published in Nature Materials.
This article was fact-checked by Fiona MacDonald and edited by Fiona MacDonald. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.