Hydrogen-Powered Aircraft

Hydrogen-Powered Aircraft: A few numbers

In 2006, Ulf Bossel, founder of the European Fuel Cell Forum, published an excellent article about the hydrogen economy [1]. The paper contains simple fundamental analyses of the challenges of a hydrogen economy in a form that would be understood by a first year undergraduate engineer. I would strongly recommended this paper for anyone who wants to delve into the technical challenges of a hydrogen economy. In the paper, Bossel provides an interesting case study about the implications of fuelling aircraft with hydrogen. It is based on the laws of thermodynamics, which haven’t changed recently, so Bossel’s analysis is still acceptably accurate…

“About 50 jumbo jets leave Frankfurt Airport every day, each loaded with 130 tons of kerosene. If replaced on a 1:1 energy base by 50 tons of liquid hydrogen, the daily needs would be 2500 tons or 36 000 m³ of the cryogenic liquid, enough to fill 18 Olympic-size swimming pools. Every day 22 500 tons of water would have to be electrolyzed. The continuous output of eight 1-GW power plants would be required for electrolysis, liquefaction, and transport of hydrogen. If all 550 planes leaving the airport were converted to hydrogen, the entire water consumption of Frankfurt (650 000 inhabitants) and the output of 25 full-size power plants would be needed to meet the hydrogen demand of air planes leaving just one airport in Germany.

For hydrogen derived from fossil hydrocarbons, the availability of water and the safe sequestration of CO₂ may pose serious problems, not because of inadequate technology, but with respect to logistics, infrastructure, costs, safety, and energy consumption. To fuel the 50 jumbo jets with hydrogen, about 7500 tons of coal and 11 250 tons of water are needed daily and 27 500 tons of CO₂ carbon dioxide must be liquefied for transport, shipped to a suitable disposal site (perhaps in the deep waters of the mid-Atlantic) and safely deposited. The significant energy needs for hydrogen liquefaction and transport are the same for any source of hydrogen. Fuelling the 50 jumbo jets at Frankfurt airport is only an insignificant part of a hydrogen economy. Has the magnitude of the task been recognized?”

Of course, in 2020, Blue Hydrogen is more likely to be manufactured from natural gas than coal, but the numbers are not too different.

It is interesting to consider the recent announcement by Airbus, of three Hydrogen-powered aircraft concepts which “could enter service by 2035” [2]. Has Airbus run these basic numbers about hydrogen as a fuel?

Given that the average commercial aircraft is in-service for 30 years, waiting until 2035 to introduce low-carbon aircraft seems a little late. If a full-scale aircraft replacement programme doesn’t start until 2035, at most half of the fleet will be replaced by 2050. The other half will still be generating Carbon emissions at approximately 2020 levels in 2050. This is not a plan that gets the civil aviation sector to net zero by 2050!

Perhaps Airbus would be better focussing on drop-in replacement biofuels that could be used in existing aircraft engines? … and do something about the problem immediately instead of waiting until it is too late to discover that the numbers don’t work. (See interesting article on this topic by Toby McCann.)