Despite the significant challenges posed by the need to reduce quickly aviation’s greenhouse emissions, engine and systems providers are confident that genuine progress can be made – provided the whole industry works together.

credit Thongchai Siriporn Shutterstock

Source: Thongchai Siriporn Shutterstock

Batteries, hydrogen and SAF are three of the technologies that might help aviation reduce its carbon footprint

That was the message from panelists on a Farnborough Connect webinar today – Sustainability: engineering the propulsion of the future – which addressed the hurdles the industry faces.

In the short-term, while the “technological roadmaps are pretty clear”, says Rob Watson, director of Rolls-Royce Electrical, the aerospace sector must be able to prove the safety, reliability and redundancy of the novel powertrains it is developing.

“The challenge is to get [a system] through certification and into service,” he says. “It’s less about demonstrating a revolutionary new technology – you have to turn that research project into a revenue product.”

Rolls-Royce sees “really early opportunities for greater electrification” of the industry, notably in the general aviation, urban air mobility (UAM), and regional aviation segments.

And while there are still “significant challenges” around certification, Watson believes the strong relationship between industry and aviation safety regulators is enabling “great engagement to find a path through this”.

Michael Winter, senior research fellow for advanced technology at Pratt & Whitney, stresses that the research projects it is working on “hand in glove” with the US Federal Aviation Administration and NASA are helping the engine manufacturer to “understand in advance where those challenges and barriers [to certification] are”.

But Winter points out that where certain issues are outside the industry’s control – for example, ensuring sustainable aviation fuel (SAF) or hydrogen are available at scale – it should not see a problem but an opportunity. Instead it must use the time available to improve the efficiency of its engines or mature hybrid-or full-electric powertrains, he argues.

Nonetheless, the panelists agreed that boosting availability of SAF and bringing its price down to an affordable level will be key to cutting aviation’s greenhouse gas emissions, particularly for long-haul flights where the efficiency of gas turbine engines will still be required “to move hundreds of people thousands of miles”, says Watson.

For long-haul “clearly SAF is the technical solution that will help, but it requires SAF at volume,” says Russ Dunn, chief technology officer at GKN Aerospace, which it turn will help to bring the price that is “sustainable in the long term”.

Dunn says that dynamic also applies to hydrogen, where cost and the sustainability of its production will be key considerations. However, he notes that aviation will “not be the full driver in needing to create green hydrogen in significant global volumes”.

Manish Dalal, vice-president of advanced technology at GE Aviation, says that slashing the cost of green hydrogen will be vital to offset the likely reduction in passenger loads of up to 30% on larger aircraft required to accommodate larger and heavier hydrogen fuel tanks.

Dalal does not believe battery technology will have improved sufficiently even over the next 30 years to power widebody or even narrowbody aircraft, but they will “have an important role to play” in helping to hybridise large commercial jets.

And, says Winter, the 1MW-size powertrains currently being developed for UAM operations could easily be transferred across to provide some of the power for commercial aircraft, whether that be for a 2MW-output regional turboprop, or for a narrowbody jet where each engine is producing around 18MW at take-off.

“You could provide 3-5% just with today’s equipment,” he says, “and that will get better as batteries improve.”