Hydrogen electric aircraft developer ZeroAvia completed a test flight this week of what it said is the world’s largest ever aircraft powered by the zero-emission fuel.
A Dornier 228 twin-engine aircraft, retrofitted with a prototype hydrogen-electric powertrain on one wing, flew for a 10-minute circuit between take-off and landing at the company’s research facility at Cotswold Airport in Gloucestershire, in the west of England.
The startup, which has received investment from Shell, United Airlines and American Airlines, said the flight performed as expected with what was its largest hydrogen engine tested to date, having flown many tests of a six-seat prototype over the past few years.
As the technology does not produce any carbon emissions during flight, the Anglo-US company says it is potentially a greener alternative to current fossil-fuelled planes, as well as producing much fewer emissions than sustainable aviation fuels and potentially being less affected by weight problems than solely electric battery-powered aircraft.
The announcement follows a test firing by Rolls-Royce and easyJet of a hydrogen-powered jet engine late last year, with Airbus following up with news that its own hydrogen-powered wide-body jumbo jet being developed along with ArianeGroup is expected to be ready for testing within a few years.
A hydrogen-powered engine could potentially power a zero-emissions aircraft that Airbus plans to test in the coming years, with the A380 MSN1 flight test aircraft for new hydrogen technologies currently being modified to carry liquid hydrogen tanks and their associated distribution systems.
Backed by a petrol stock engine on its right wing, under the 19-seater’s left wing was a ZeroAvia hydrogen-electric powertrain employing two fuel cell stacks, with lithium-ion battery packs providing peak power support during take-off and adding additional redundancy for safe testing.
For its tests, which are part of a full flight permit with the UK Civil Aviation Authority, hydrogen tanks and fuel cell power generation systems were housed inside the cabin, but the company’s commercial plans would incorporate external storage.
ZeroAvia said it is aiming for a certifiable configuration to be finalised and submitted for certification this year, with a larger powertrain in development to drive a 90-seater aircraft that it aims to deliver for commercial routes by 2025.
It is initially targeting a 300-mile range for aircraft of nine to 19 seats by 2025, building up to 700-mile range in 40–80 seat aircraft by 2027.
Pre-orders have been received for 1,500 engines, the company said, including from American Airlines and United Airlines. It also has partnership agreements with seven aircraft manufacturers, a number of green hydrogen producers and airports including Rotterdam in the Netherlands and Edmonton International in Canada.
Founder and chief executive Val Miftakhov said the test flight was “a major moment, not just for ZeroAvia, but for the aviation industry as a whole, as it shows that true zero-emission commercial flight is only a few years away”.
He said the flight also showed “just how scalable our technology is and highlights the rapid progress of zero-emission propulsion”.
Hydrogen gas for the powertrain was produced at the airport by an electrolyzer operated by the European Marine Energy Centre (EMEC).
Is hydrogen practical for flights?
While the production of hydrogen gas is a relatively simple process, but there are potentially sizeable hurdles for the air industry.
In order to be used in aircraft it would likely have to be liquified, which requires an energy-intense process of cooling it to almost -253C.
Clean energy expert Michael Liebreich outlined that liquifying 7,500 tonnes of hydrogen per day to meet Heathrow’s fuel needs would require roughly 2.8GW of electricity, “similar to the output of Hinkley Point C.”
Hydrogen’s potential biggest downside is to do with weight.
While Airbus outlined that by stacking hydrogen fuel cells “the megawatt levels of power – which are needed for an electric aircraft – are achievable,” experts tend to disagree, suggesting the amount of the green fuel needed for aircraft would be excessive.
Hydrogen, while being “one of the hottest items in the long-term pursuit of renewables,” requires about four-times the volume of conventional jet fuel for the same amount of power, according to geopolitical analyst Irina Tsukerman.
But this could lead to future aircraft might requiring a redesign to allow for the space issue and safe transportation, she said.
Liebreich added: “The difficult bit is that even for short haul, one third of your fuselage is liquid hydrogen at take off.”
“Longhaul is completely out,” he warned.