Current gas turbines are not equipped to operate on hydrogen, as revealed by researchers from Germany, China, and France in their recent study published in Nature Materials. Hydrogen fuel is generating significant interest as a sustainable energy source. However, for it to be completely emissions-free, it needs to be extracted from water using renewable energy sources.
Presently, the majority of the world’s hydrogen is produced from natural gas, a fossil fuel, which results in substantial carbon dioxide emissions. Beyond this, a key challenge in the hydrogen economy is its infrastructure, an issue not widely recognized.
Hydrogen molecules are the smallest, even tinier than methane, the principal component of natural gas. It is already known that hydrogen can affect metal pipes and tanks, even at normal temperatures, a challenge that has been encountered in transporting it across the United States. These minute hydrogen molecules can penetrate small spaces in steel pipes, causing the alloy to become brittle.
Emre Gençer, an energy scientist at MIT, stated in 2023, “The bottom line: it is not as straightforward as just pushing through hydrogen in existing infrastructure.” Gençer referred to the challenges of hydrogen transport and storage, but the new research reveals these are not the only infrastructure components needing replacement in a hydrogen economy.
Inside a gas turbine, at high and fluctuating temperatures, hydrogen’s capacity to embrittle machinery is intensified. Through mechanical testing in high-temperature and pressure environments, researchers examined hydrogen gas-powered turbines made from the industry-standard nickel-base superalloy (IN718) as they neared temperatures of 600°C (1,112°F). The introduction of heat caused hydrogen to double the damage to the alloys compared to ambient temperatures, posing a risk of catastrophic failure.
This indicates that existing infrastructure cannot accommodate hydrogen as a fuel source, necessitating a complete revamp and new alloys. Hydrogen’s impact on the alloy varied with temperature, with most issues occurring as temperatures rose, particularly between 400°C and just under 600°C, where turbine ductility decreased by up to 30 percent.
Xizhen Dong from the Max Planck Institute for Sustainable Materials explains, “When hydrogen enters a nickel-base superalloy at ambient temperatures, it is usually trapped at interfaces and dislocations. 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.”
Carbides are meant to strengthen alloys, crucial for metals that must contain high-pressure gases and endure the forces within turbines. However, the study suggests carbide-strengthened alloys are unsuitable for hydrogen-based technology. Conversely, alloys resistant to hydrogen embrittlement tend to be too soft, which is also problematic.
Researchers are actively seeking more appropriate materials for hydrogen transport and storage. One team achieved progress by combining scandium with an aluminum-magnesium alloy, enhancing the material’s strength by 40 percent and its resistance to hydrogen embrittlement nearly fivefold.
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For the high-temperature, rotating parts of turbines, much more research is needed, and the discovery of new alloys remains critical. According to the journal’s editors, “These findings may serve as important considerations for material design in the pursuit of hydrogen-fueled gas turbines and aircraft engines.”
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.
