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Understanding Fuel Cells

By: Dr Gareth Evans - Updated: 22 Apr 2010 | comments*Discuss
 
Fuel Cell Hydrogen Oxygen Water Clean

Say the words “fuel cell” to most people and they’ll probably instantly conjure up an image of a modern and revolutionary high-tech device that holds the promise of exactly the sort of clean energy we so desperately need. While their potential for virtually emission-less power is undoubtedly true, surprisingly the technology behind fuel cells themselves is much older than you might imagine and understanding them requires a lot less technical know-how than you’d first think.

Victorian Innovation

The story begins back in the early part of the nineteenth century, when scientists had discovered that passing electricity through water splits it into its two chemical constituents – oxygen and hydrogen. The idea intrigued the young William – later to be “Sir” William – Grove and it set him pondering the possibility of doing the same thing, only the other way round. Was there a way to bring oxygen and hydrogen together to create water, but this time get electricity out of the process?

A lot of thinking and a few attempts later, he produced the first truly practical version – which he named a gas voltaic battery – in 1839. It didn’t, however, prove to be the catchiest of names, and it wasn’t until Charles Langer and Ludwig Mond coined the description of ‘fuel cell’ that Grove’s device was to have a name to really remember.

Simple Science

The underlying principle is surprisingly simple – and the clue’s in the name that Grove originally gave his invention – it’s basically a battery! Unlike the familiar household version, however, fuel cells don’t contain all the chemicals that they need to function inside their own little casings; they need to be provided with constant external supplies to work, but the upshot of this is that, unlike torch batteries, they don’t gradually run down and die. So long as hydrogen and oxygen flow in, then the cell keeps running and electricity continues to be generated.

Technically this is known as electro-chemical energy conversion and although building your own fuel cell isn’t exactly a quick weekend DIY project, the general process is not that hard to understanding. There are a number of different kinds of fuel cell, but the way they work is essentially the same. A supply of hydrogen, or alternatively a hydrogen-rich fuel, is fed over one of two electrodes fitted within the cell, while oxygen is passed over the other.

Electrons, which are by nature slightly negatively charged, separate from the hydrogen and are attracted to the oxygen on the other side of the fuel cell, rather like the south pole of one magnet is drawn to the north pole of another. The way the fuel cell is constructed stops the electrons from simply hopping across to the other side, forcing them to travel along an electric circuit instead and so producing the cell’s electric current.

Big Benefits

There are some big benefits to be had from fuel cells, not least of these being the much heralded promise of clean energy. A fuel cell, fed pure hydrogen yields only two by-products of its electrical generation, namely water – most usually in the form of steam – and heat, while even those using high-hydrogen fuels such as ethanol produce very little in the way of harmful emissions. Moreover, the way they work and the simplicity of the idea makes them ideal for a range of applications at all sorts of scales – from a full-size power station, to a domestic generator unit or even under the bonnet of a family car.

It may be some time before we routinely see hydrogen powered vehicles on our roads; it seems that the first cars aren’t expected to be in the showrooms until 2020 at the earliest. Elsewhere, however, fuel cells are already making important contributions to reducing conventional energy demand – and some of these innovative applications would be worthy of the technology’s Victorian pioneers themselves. One Californian wine company, for instance, is using naturally occurring electrochemically active microbes to turn its winery wastewater into hydrogen, which is then fed into an on-site fuel cell. Strange to think that such a modern process – microbial electrolysis was only invented in 2003 – should fit so easily beside the invention of a man born in Swansea nearly 200 years earlier.

Now that might just have amused even Queen Victoria herself!

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