On Fuel Cells

I assumed, it seems wrongly, that BMW's cars would be combusting H2, the same way pretty much an engine compusts gasoline vapor.

Entropy says I'm all wet, and I believe him, partly because I've just never grokked this whole "fuel cell" dealio. Even when I actually had to teach people about fuel cells for the MCATs. I just sort of vagued it all. Repeated what was in the book. Had no frickin' idea what they were talking about.

Apparently there is a chemical reaction going on -- hence the "fuel part" -- which liberates energy, but it's not actually burning it:

Fuel cells create water by mixing H with O, yes. Absolutely.

But they do not turn use mechanic or kinetic energy. They don't use the expanding (because of heat) H2O to push a piston.

They're actually collecting electric energy from the reaction by forcing the hydrogen to follow a certain path to get to the oxygen, which energizes the circuit the electrons pass through.

It actually has to remain rather cold to work. If it starts blowing up, it will destroy the fuel cell. The water is hot, yes, but the heat is not where the energy is coming from and would be avoided if it could.

Elemental hydrogen is being burned. Somewhat. Yes.

Still, you've got a big tank of H2, yes?

posted by Ace at 07:09 PM

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