How new technologies could clean up air travel

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

Batteries have the advantage of being a widely used technology today in electric vehicles, and they have improved a lot during their decades of development. But batteries will need to continue to improve dramatically for electric planes to carry significant numbers of people a significant distance. (Check out my story from last year on electric planes for more.)

Hydrogen could be a versatile fuel for aviation in the future. Planes could use hydrogen in two different ways. It could be burned in combustion engines, similar to how jet fuel is used today. Alternatively, hydrogen could be used in fuel cells, where chemical reactions generate electricity. We like to have options.

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

In both cases, hydrogen has a major advantage: it contains a lot of energy without being too heavy (unlike batteries). When a vehicle has to drag its power source 30,000 feet in the air, that power source better be really light – and hydrogen, as the lightest element on the periodic table, matches perfectly to this invoice.

The problem is that while hydrogen is light, it also takes up a lot of space. In order to put it into a volume small enough to carry on an airplane, the hydrogen will likely need to be cooled to cryogenic temperatures (below -250°C). Designing these systems and getting them on planes will be difficult. The same will apply to the supply and distribution of large quantities of hydrogen produced from renewable energies. And there’s the small fact that while there have been some experiments with hydrogen-powered flying planes over the years, the technology still needs work. It’s hard to remake an industry, so SAFs, the alternative, are likely the most likely to be adopted in the near future, when hydrogen will take decades to break through.

But there has been an exciting movement on the use of hydrogen for aviation over the past couple of years, with big players like Airbus entering the game and announcing planned test flights.

And last week, startup ZeroAvia made headlines again, announcing that it had performed a test flight of a 19-seat Dornier 228, the largest aircraft flown partly on hydrogen fuel cells. Prior to this test, the company had tested a smaller nine-seat aircraft.