Hydrogen Cars Failed to Deliver. Investors Hope Planes Are Different.
Does the hydrogen hype that once surrounded cars have better prospects with planes? Yes, but probably not in time to meet the aviation industry’s emissions targets.
The past year has brought some vindication to those who see hydrogen as aviation’s passport to a cleaner future. Last fall, European plane maker Airbus unveiled three hydrogen-powered aircraft concepts for 2035. More recently, U.K. startup ZeroAvia got backing from British Airways as part of a $24 million funding round. Likewise, Universal Hydrogen, led by former Airbus executive Paul Eremenko, has just raised $21 million from heavyweights such as the venture-capital subsidiaries of JetBlue and Toyota.
For decades, hydrogen was a promising future power source for passenger cars. Now most light vehicle makers favor batteries, and hydrogen is looking for a better home in trains and trucks, as championed by startups such as Nikola.
The aviation industry has set itself a target of halving emissions by 2050, which would be roughly in line with the 2016 Paris Agreement to limit climate change. Only a third of the reduction is expected to come from improvements in turbofans and airframes. Sustainable fuels can play a role, but production capacity is limited, and the most affordable ones remain pollutive.
Aviation’s initial interest in the electric-vehicle revolution faded as executives realized that carrying heavy batteries more than very small ranges through the air is unfeasible. Rechargeable lithium-ion batteries only deliver 0.9 megajoules per kilogram of weight, compared with 40 MJ/Kg for jet fuel.
Hydrogen, on the other hand, packs an impressive 140 MJ/Kg. Encouragingly, it is a relatively mature technology. Fuel cells, which are being used by Universal Hydrogen and ZeroAvia to convert light and regional aircraft, cost $40 per kilowatt, 68% less than in 2006, Bernstein Research estimates. That is expensive for a car but not a plane.
“We don’t need any fundamental scientific improvements: It’s an engineering problem,” said Val Miftakhov, founder and chief executive officer of ZeroAvia. He successfully tested a six-seat aircraft last year, and hopes to refit a 100-seater by the 2030s.
Hydrogen isn’t an environmental no-brainer yet. Turning electricity into hydrogen and then back into electricity is inefficient: Only about 45% of the energy ends up being used, compared with 90% for batteries, the World Energy Council estimates. Furthermore, only 0.1% of global hydrogen production is currently carbon-free; most comes from natural gas and coal.
Still, many analysts expect “green” hydrogen to become price-competitive relative to jet fuel in the next five years, making it a commercial option for airlines.
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That still leaves many engineering challenges. Not all the energy in today’s prototypes comes from hydrogen: ZeroAvia’s aircraft needs a battery to provide additional power during takeoff, at least for now. Universal Hydrogen also employs a battery, but says it would play a smaller role. Also, hydrogen is energy-efficient in terms of mass but not volume: It requires big tanks that would make planes heavier and less aerodynamic, since fuel couldn’t simply be stored in the wings as it is now.
The wider problem is that decarbonizing regional jets won’t make a big dent in the industry’s carbon footprint. They make up 29% of flights but only 7% of emissions, according to the International Council on Clean Transportation.
The reason why Universal Hydrogen is spending $100 million to get a re-engined regional aircraft certified by 2025 is not just the plane itself, but rather the need to accelerate investments in hydrogen storage, distribution and refuelling, which are big hurdles to the technology’s wider adoption. The company has devised pill-shaped pods that can be easily stacked and transported, and serve both as storage containers and gas tanks.
Showing this infrastructure in action with regional airlines could convince Airbus and Boeing to develop hydrogen-fueled replacements for the 160-seat A320neo and 737 MAX, which are the backbone of the global fleet, Mr. Eremenko said. “They are very risk averse, but having proof of passengers flying could tip the balance,” he added.
While Boeing CEO David Calhoun has been publicly skeptical about hydrogen playing a part in the next generation of narrow-body jets, his counterpart at Airbus, Guillaume Faury, championed the technology during his spell at French car maker Peugeot and has taken up the cause again.
Yet the fuel cells currently being tested won’t be of use to Airbus or Boeing, because they would need to be prohibitively heavy to move bigger planes. The A320 replacement pitched by Airbus last year would mostly rely on a traditional engine to burn hydrogen directly. This basic technology has been around since the 1950s, but has many drawbacks, such as the emission of nitrogen oxide—also a greenhouse gas.
There are also reasons to doubt Airbus’ conviction in its own timeline for the rollout of hydrogen technology. It presented two other concepts at the same time: a regional aircraft that would be an unambitious goal for 2035; and a “blended wing” futuristic plane that would be far too ambitious.
Hydrogen seems like a useful power source to eventually decarbonize aviation. Thinking it can be deployed in time to meet the industry’s 2050 emissions targets, however, requires a lot of optimism.
Write to Jon Sindreu at email@example.com
Corrections & Amplifications
Rechargeable lithium-ion batteries deliver 0.9 megajoules per kilogram of weight. An earlier version of this article incorrectly said they deliver 9 megajoules per kilogram of weight. (Corrected on May 18)
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Published at Wed, 19 May 2021 01:39:00 +0000