How do fuel cells work?

A while back I wrote about fuel cell cars that run on hydrogen rather than ye olde fossil fuels. But I wanted to know how these fuel cells actually work? The hydrogen, presumably, isn’t being “burned” in the normal sense, so what’s going on?

Let’s take a look at that most common of electrical sources, the battery.  Batteries usually consist of two metal “poles”, with an acid or salt solution sandwiched between them. The chemical reaction of these components makes electrons collect on the negative (-) terminal of the battery and, when an electrical item is attached to the battery, these electrons are used for power. At the same time, though, the chemical reaction within the battery is continuing, which eventually reduces the difference in charge between the positive (cathode) and negative (anode) poles… and the battery stops producing power.

How about a fuel cell? There are a number of different types of fuel cell, but we’ll look at hydrogen cells here. Fuel cells still work by transferring electrons, but the source of those electrons is different: the electrons are stripped from the hydrogen fuel itself. The fuel cell consists of two catalyst-coated electrodes, separated by a membrane which only allows charged particles to pass through. The two electrodes are also connected to an electrical load, such as a car’s motor. Hydrogen is fed into the cell at one end, where the catalyst prompts the Hydrogen to become positively charged H+. The dropped electron from the Hydrogen is picked up by the electrode (which becomes the negative anode), and used to power the load (i.e. the car). Meanwhile, the positively charged H+ passes through the membrane to the other electrode (the cathode), where it is combined with oxygen from the air, and the returning electrons, to become water.

Fuel Cell DiagramFuel-cell flow diagram – click on the image to enlarge

I did wonder what happens when the catalysts are used up, but then I remembered that catalysts, while playing a part in aiding chemical reactions, are not actually used up in them. So the catalysts just sit there, merrily helping to convert the hydrogen to H+, and then into water.

What amazes me about this setup is how none of the components of the fuel cell are used up in the reaction – as long new fuel is fed in, the cell will never go flat!

This type of fuel cell produces a small amount of Direct Current, so several fuel cells are stacked together to get enough power to run something like a car. It obviously works, with the Honda FCX boasting a generating capacity of 100kw.

So the technology works, and it actually seems very elegant. It is much more efficient than combustion, and much better for the environment. Hydrogen is the most abundant element in the universe, and even if we did somehow run out, we could always find a way to extract more from water or hydrocarbons. Not bad, really.

Scan to Donate Bitcoin
Like this? Donate Bitcoin to at:
Bitcoin 37jTGtDxbNyYznXA19LzQMfobgGuKJSs3f
Donate

Join us on Facebook

Facebook icon

Declare your geekdom for the world to see... well, the part of the world that's on Facebook anyway.

Visit our Facebook page to keep up to date with the latest Geek-Speak posts right in your Facebook stream, as well as hearing about discounts and offers before they're posted on the site.

What are you waiting for? Head on over and "like" us.

Facebook icon used under CC license

Comments

  1. Hi

    Thanks for your useful info. This is all incredibly helpful.

    Dzo

  2. Thanks for the comment – glad you found it useful.

    Chris

  3. Tyrone says:

    The problem with hydrogen as a fuel is that you don’t find pure hydrogen in nature. To produce hydrogen, energy has to be used to break the natural bonds it forms with other elements. It’s like turning water into hydrogen and oxygen and then back into water. This link, while I haven’t read all of it, looks to have a pretty good explanation of a “hydrogen future”: http://www.woodgas.com/hydrogen_economy.pdf. Hydrogen therefore, isn’t a source of clean energy, merely a potential carrier for it.

  4. Thanks Tyrone – I’ll have a look at that.

    I see Honda are trialling a solar hydrogen refuelling station in California, which might go some way to at least producing the hydrogen cleanly… but it remains to be seen whether it’ll produce enough to keep a family car fuelled. And I wonder whether it would get enough power to do its job in somewhere like the UK.

    For this to really be the “environmental” choice – the fuel would need to be produced cleanly via solar, tidal or wind power. What do you think?

  5. Very interesting Tyrone – I’ve heard of laptops running on methanol; do you think that could be expanded to larger-scale power generation?

  6. Tyrone says:

    I really do not know very much about methanol as a conventional fuel replacement, however, after a quick search, it seems that methanol has been seriously considered as a viable fuel alternative. The main issue, is again, the emission of CO2 when burned, because Methanol is an alcohol. http://en.wikipedia.org/wiki/Methanol_economy

    Also, I don’t think I mentioned in my first post, the original article was very nice.

  7. There would be one big advantage to methanol, though: it’s something to use when the oil runs out :)

    Thanks for the remark about the post too, by the way. It’s always good to get some discussion going!

  8. Tyrone says:

    The problem with hydrogen as a fuel is that you don't find pure hydrogen in nature. To produce hydrogen, energy has to be used to break the natural bonds it forms with other elements. It's like turning water into hydrogen and oxygen and then back into water. This link, while I haven't read all of it, looks to have a pretty good explanation of a “hydrogen future”: http://www.woodgas.com/hydrogen_economy.pdf. Hydrogen therefore, isn't a source of clean energy, merely a potential carrier for it.

Comment are closed: Sorry, comments are closed on this article. We automatically close comments on older articles to try and cut down on the amount of spam comments being submitted to the site.

If you want to tell us what you think about this article, why not visit our Facebook Page or Subreddit and leave a comment there instead?