[backwoods-engineer]

How does it work? Okay, did you ever do the experiment where you make hydrogen by reacting a metal with acid, and then burn the hydrogen in a test tube, which makes a little "pop" or whistle? The energy of producing water with hydrogen and oxygen were converted to mechanical energy (the "pop") and heat energy.

In a fuel cell, the energy from making water from hydrogen and oxygen is converted instead into an electrical current, through an ion exchange. This exchange is made possible by the use of a catalyst, usually involving one or more metals in the platinum series on the periodic chart.

Here's why I say hydrogen is an energy-storage medium, not a fuel. There's ain't large deposits of hydrogen underground, like there are hydrocarbons. Since it takes energy to release hydrogen (reducing an acid with a metal isn't useful for the large amounts you need for powering cars), you're really just storing the energy used to release the hydrogen, and then releasing it later in the fuel cell as electricity.

[woodbutcher1963]

OK, so how many of these fuel cells does it take to power a 4 door passenger car with the equivalent of a 4 cylinder 150 HP gas/diesel engine?