Skai revises targets for its liquid-hydrogen, long-range eVTOL
Comment of the Day

July 10 2020

Commentary by Eoin Treacy

Skai revises targets for its liquid-hydrogen, long-range eVTOL

This article by Loz Blain for NewAtlas may be of interest to subscribers. Here is a section:

One challenge for anyone who wants to work with liquid hydrogen is that you need to keep it extremely cold to keep it in its liquid state. At atmospheric pressure levels, we're talking just 20.28 kelvins above absolute zero (−252.87 °C, or −423.17 °F).

That temperature can rise a little if you're willing to pressurize as well as cool (using a cryogenic system running between 250 and 700 bar of pressure), but Gunter says that's not part of Skai's plans, as "even a moderately pressurized system has significant weight penalties."

So, super-cooling it'll be, and while that entails extra energy losses in the liquefaction stage, the cooling equipment, the conversion back into gas for use in the fuel cell and in boil-off in the tank itself, the net result will still be a much longer range aircraft than anyone dealing with gaseous hydrogen – or certainly lithium batteries – will be able to deliver.

It'll be interesting to see how Skai gets the job done, as really you've got to look to NASA and other space programs to find liquid hydrogen being used in serious volumes.

"The good thing in all of this," says Gunter, "is the notable developments that occur in this space on an increasing basis. The efficiencies we’ve seen in fuel cells and the same the industry is seeing regarding H2 production all point to increasing effectiveness of any form of H2 as a future focused solution."

"There's a number of naysayers about what we're doing with hydrogen," says Hanvey, "but we believe we've gone from the question to the possible, and it's now the probable. We know we can fly with hydrogen, and the question is just how quickly we can get it to the market. And based on our experience, we think we can get there a lot quicker than perhaps the market will give us credit for."

Eoin Treacy's view

Hydrogen’s energy density is orders of magnitude greater than any other fuel currently used in the global economy. The only reason we don’t already use it is because of the technological difficulty of containing what is a highly combustible material. The whole world knows about the Hindenburg accident 83 year ago, which put an end to transatlantic zeppelin travel. It did to the hydrogen industry what the Fukushima accident did to nuclear.

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