We’re stood at the far end of Hall One on the second day of the Farnborough International Air Show. Temperatures outside the hall are reaching around 38 degrees celsius — it feels even hotter inside.
“Customers say that they see how we’re advancing technology,” says James Peck, the Vice President for Business Development at ZeroAvia, a company working on hydrogen-powered aviation.
“But, you take the [Boeing] 777-9 flying out there, there’s a long way to go.”
However, ZeroAvia thinks its retrofit, line-fit, and upcoming purpose-built hydrogen-powered planes will prove an enticing and enduring solution for airlines around the world. We spoke to Peck and his colleague Rudolf Coertze, CTO Hydrogen, to find out why ZeroAvia is leading the charge.
Hydrogen and Batteries
“At ZeroAvia, we are focusing on developing what we’re calling a zero-emission, hydrogen-electric powerplant for aircraft,” says Coertze.
“So for us, it’s really important to reduce the emissions of aviation or aviation contribution to CO2 and greenhouse gas emissions. So we decided to focus on hydrogen, but not on hydrogen combustion, specifically on hydrogen that is electrochemically generated by using hydrogen and oxygen from the air in fuel cells, and then driving electric propulsion systems to actually drive the aircraft.”
ZeroAvia’s fuel cell-based approach is far from novel but, as Coertze explains, its application in the aviation industry is.
“Fuel cells and hydrogen fuel cells per se, are of course, not brand new. There is already a large body of knowledge and also a large industry active already in the automotive space and trucking and in the bus space with regards to fuel cells and hydrogen.
“What we do at ZeroAvia is we are taking fuel cell technology to the next level to actually apply it in aviation. But we also understand that there is already a significant amount of technology maturity in fuel cell technology available that we can get to certifiable products and to market with its existing state of the art fuel cell technology already relatively quickly.”
ZeroAvia wasn’t alone in demonstrating its alternative propulsion systems at Farnborough last week. Lilium, for example, had a gigantic stand with a scale model of its four- or six-seat battery-powered eVTOL aircraft.
However, for Coertze and Peck, batteries simply do not offer the range, flexibility, or scalability needed for the larger 10-19- and 70-80-seat aircraft ZeroAvia is targeting.
“Batteries have limitations because their energy density is much less than hydrogen,” explained Peck.
“So, therefore, you’ve got a big battery that’s very heavy and the batteries also have a cyclic life. So if you’ve driven an electric car, batteries have to be replaced is 100,000 miles, for example.
“On an aircraft, if you equate that to flights and cycles in terms of charge, discharge, charge, discharge, you’re replacing the batteries in the aircraft, in some cases in less than a year. That’s a major maintenance event and very expensive. So you’ve got that issue, and then you’ve got the fact that you’ve got to charge them.”
Hydrogen power, as a result, does away with most of the issues surrounding battery-powered flight at a stroke. However, hydrogen power is not completely perfect.
“Fuel cells are already very mature, but what you do find is that you need we need to increase the power density of the fuel cells for aircraft because, in many automotive applications, the biggest driver has not been weight, it has been cost. The automotive industry is very cost-sensitive, but in aircraft and aerospace weight is an extremely large driver,” explained Coertze.
“Similarly, technological challenges for storing hydrogen, and hydrogen storage technologies do exist both in gaseous form and in the cryogenic liquid hydrogen form.”
Storing hydrogen for use in aircraft is far from straightforward and poses different challenges to both battery- and kerosene-powered flight.
“Hydrogen has got a much higher energy density than typical kerosene,” continued Coertze, “usually three times the energy density.”
“However, in gaseous form, you cannot store that much, you have to really compress it to high pressure. So, for gaseous storage, there is always the challenge that the tank weight is going to be quite significant for the amount of hydrogen that you can store.”
For its 10-19 seat aircraft, ZeroAvia is looking at gaseous hydrogen storage. However, for its 70-80 seat aircraft, the company is employing cold storage techniques.
“We are definitely looking at cryogenic liquid hydrogen storage, which of course has its own specific benefits but also challenges,” said Coertze.
“So, first of all, it’s the cryogenic temperatures. Hydrogen is a liquid at around -250 degrees celsius. These technologies exist and have been used in space and in other industrial applications. But they need to get to the point where all the necessary storage, refuelling, and distribution on board the aircraft are developed and certified to be able to operate effectively and safely for reasonably cost-effective lifetimes.”
Unsurprisingly, keeping hydrogen that cold on a plane requires some space-age solutions.
“With insulation, you can keep it cool,” said Coertze.
“So you need to use vacuum insulation with advanced thermal insulation materials, of which a good number have been developed since the early Space Shuttle days, and they were typical foams. But nowadays, you have much more advanced installation materials available like aerogels, and all kinds of different materials that are being used already, as well vacuum and double wall tank installation.”
Building the Future
For many sustainable transport companies, the switch to alternative propulsion systems is an excuse to rip up the rulebook when designing their vehicles.
ZeroAvia, however, is taking a different approach — at least initially.
“We are focusing on fixed-wing aircraft at the moment and we’re also targeting retrofits,” explained Coertze.
“Then we also target what we call line fit. Line fits are also existing aircraft but, if they are newly manufactured, when they come off the production line, instead of getting a traditional powerplant and fuel storage, they will get our hydrogen-electric powerplant and hydrogen storage.”
This might seem like a relatively unexotic business plan — taking existing aircraft and swapping out the motors. But, according to Peck, it is precisely because the model is familiar that ZeroAvia is seeing success.
“It’s less about the business opportunity than it is about the speed to market, developing the technology, getting maturity in the engine.
“By retrofitting,” Peck continued, “we can get a decent fleet built up more quickly, start to get that maturity, and start to get that development done, whilst also commercially generating revenue that helps us fund the development as well.”
“So the Retrofit is, strategically, the best way to do it. Line fit is very attractive because when someone takes a new aircraft, they’re generally going to operate it for a long time. So, if you’re somebody that is going to fly an aircraft for 20 years, our opportunities to make revenue through the life of the product are very good.”
ZeroAvia also has a unique way of providing ongoing service to its customers. Rather than simply manufacturing the engines, retrofitting them to existing aircraft, and then providing routine and emergency maintenance, the company is also supplying the hydrogen needed to fly the planes.
“So for us, we’ve got a whole separate division focused on infrastructure,” continued Peck.
“We have infrastructure partners, such as Shell, which invested in us to work with infrastructure. So from a B2B perspective, we sit down with an operator, we lay out their whole route network, we work out how much fuel they would be using, how much hydrogen they would need on every route network, and we put together a whole plan for delivery and infrastructure.
“We’re taking responsibility for the delivery of fuel and we’re offering a $1 per flying hour rate, which no one has ever done before. Normally, that just covers maintenance but ours is maintenance and fuel.”
ZeroAvia’s approach might not be particularly headline-grabbing but, with its reliance on existing technology, affordable flying rates, and clients including United Airlines, you’re very likely to see a hydrogen plane overhead ver