How new technologies could make air travel cleaner

Batteries could power planes, at least for short distances. Some companies have attempted test flights of electric aircraft powered in this way, mostly small eVTOL (electric vertical take-off and landing) aircraft that can only carry a few people. Unlike combustion-powered aircraft, electric aircraft would cause no pollution and could achieve zero emissions if charged with renewable energy.

Batteries have the advantage of being a technology that’s widely used in electric vehicles today, and they’ve gotten a lot better over their decades of development. But batteries must continue to improve dramatically in order for electric planes to be able to carry significant numbers of people a significant distance. (See my story from last year on electric airplanes for more info.)

Hydrogen could be a versatile fuel for aviation in the future. Airplanes can use hydrogen in two different ways. It could be burned in internal combustion engines, much like jet fuel is used today. Alternatively, hydrogen could be used in fuel cells, where chemical reactions generate electricity. We love options.

The environmental impact and feasibility of hydrogen will depend on how it is used. Combustion will result in some tailpipe emissions, although these would be mostly water. Hydrogen-electric planes, like battery-powered planes, could be pollution-free, depending on how the hydrogen is produced.

In any case, hydrogen has one thing to offer: it contains a lot of energy without being too heavy (unlike batteries). When a vehicle has to tow its power source 30,000 feet in the air, it’s better if that power source is really light—and hydrogen, as the lightest element on the periodic table, fits that bill perfectly.

The problem: Although hydrogen is light, it also takes up a lot of space. In order to pack it into a small enough volume to carry on board an airplane, hydrogen will likely need to be cooled to cryogenic temperatures (below -250 °C). It will be difficult to design and get these systems on planes. This also applies to the procurement and distribution of large quantities of hydrogen from renewable energy. And there’s the small fact that while there’s been some experimentation with flying hydrogen-powered airplanes over the years, the technology still needs work. Reshaping an industry is difficult, which is why SAFs, the drop-in solution, are likely to be the ones most likely to be used in the near future, while hydrogen will take decades to catch on.

But in recent years there have been some exciting moves towards using hydrogen for aviation, with big players like Airbus stepping in and announcing planned test flights.

And last week, startup ZeroAvia was in the news again, announcing that it had completed a test flight in a 19-seat Dornier 228, the largest aircraft partially flown on hydrogen fuel cells. Prior to this test, the company had tested a smaller nine-seat aircraft.

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