Rolls-Royce Patent Could Retrofit Aircraft with Hydrogen Engines

Hydrogen faces a number of hurdles before it can be considered a suitable alternative to jet fuel – namely, cost.

Photo of a Rolls-Royce patent
Photo via U.S. Patent and Trademark Office

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Rolls-Royce may want to give traditional airplanes a hydrogen makeover.

The British aerospace and defense firm filed a patent application for a “cryogenic fueled aircraft.” The patent details a way to complement a plane’s typical engine with one fueled by hydrogen. 

“In order to limit emissions of carbon dioxide, use of hydrogen as an alternative to hydrocarbon fuel in gas turbine engines has historically only been practical in land-based installations,” Rolls-Royce said in the filing. 

Notably, Rolls-Royce claims this design can be retrofitted to existing aircraft, allowing operators to switch between using hydrogen and traditional jet fuel. 

Because hydrogen has a very low density in its gaseous form (and thereby takes up a lot of space), this patent pitches storing hydrogen cryogenically, or at extremely low temperatures in its liquid form. 

The filing also suggests safety improvements by keeping the hydrogen fuel tanks external to the fuselage, reducing the risk to passengers in the event of a leak or fire. The fuel tanks themselves are also separate from one another, with each tank containing multiple hydrogen containers. That creates failsafes if one goes haywire. 

Flying isn’t exactly great for the environment. Aviation accounted for roughly 2% of global carbon emissions in 2022, according to the International Energy Agency. But much of the industry recognizes this problem, with members of the International Air Transport Association — which includes airlines such as United, Delta, and American — committing to reaching net zero emissions by 2050. The Federal Aviation Administration has made similar goals

Rolls-Royce has been testing the waters with hydrogen as an alternative for several years now. The company has partnered with discount airline easyJet to build and test hydrogen-powered engines, and launched the Hydrogen in Aviation alliance in partnership with easyJet and Airbus last September. 

However, hydrogen as a power source faces some large barriers in many use cases. As the patent seeks to address, hydrogen needs to be kept at extremely low temperatures and high pressures due to its low energy density. The transportation, storage, and dispensing of this fuel would require significant and costly changes to infrastructure

Plus, the cost of producing green hydrogen is prohibitive, with a Harvard University study published this week reporting that notoriously expensive carbon capture may be a more cost-effective way of cutting emissions. 

And despite the company’s continued research in the area, Rolls-Royce CEO Tufan Erginbilgic told media in November that hydrogen has a long way to go before it could be considered a legitimate alternative.