Why Don't We Just Run Internal Combustion Engines on Hydrogen?

Hydrogen burns with zero emissions. Couldn't we just use it in place of gasoline? The answer is more complex than you might expect.


We know we need to find a replacement for fossil fuels. Automakers are working hard to find solutions to the dilemma. Most of those solutions seem to involve getting rid of our beloved internal combustion engines. But couldn't we just redesign the typical piston engine to run on something cleaner, like hydrogen?

If only it was that easy. As lays out, you could design a piston engine to run on hydrogen. It just wouldn't be very good.

Hydrogen is a tempting alternative fuel. When burned correctly, its only emission is water vapor. Fenske has been exploring hydrogen's possibilities in multiple videos already this month, both and .

There are two major problems with a hydrogen internal combustion engine. First, hydrogen is not as energy-dense as other fuels, meaning that you need a whole lot of it to do a little bit of work. Couple that with the inherent inefficiency of a piston engine (at best, you're only turning about 30 percent of the fuel's energy into forward motion), and you've got a recipe for disappointment.

The second problem? When you combust hydrogen, you get other emissions besides water vapor. Mainly, you get NOx, the toxic emission at the heart of the Volkswagen diesel emissions cheating scandal. If you're looking for a clean alternative to gasoline, hydrogen's NOx emissions take it out of the running.

The answer? Use hydrogen in a fuel cell to generate electricity. Fuel cells are far more efficient than internal combustion engines, and a hydrogen fuel cell has cleaner emissions than an internal-combustion hydrogen engine. To learn more, check out Fenske's full video below.

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