The science behind fuel cell electric vehicles explained

Ben Stockton of Our Virtual Academy introduces GW readers to fuel cell technology in first of a series of articles

The science behind fuel cell electric vehicles explained

Some would consider what I do to be a technical trainer, but I think of myself more as a professional learner.

I am a script writer for Our Virtual Academy, which is an online technical training portal, where our clients gain access to all the courses we write as part of their subscription.

We choose what videos to create in line with the content requests from our customers, and, one of the requests which came in a few months ago was fuel cell electric vehicles (FCEV’s).

Us being us, we couldn’t wait to get cracking, rolling up our sleeves, and getting to the bottom of this interesting technology.

We found that physically understanding how the fuel cell, or to be specific, how the proton exchange membrane fuel cell works, took a fair bit of fathoming out but finally, with the help of the people who make these vehicles, we got there.

Fuel cell four stroke cycle

As long as you’ve got a decent grasp of a couple of the fundamentals of chemistry, which I’ll make a point of explaining in this article, you’ll find the ‘four stroke cycle’ of a fuel cell is no more complex than the process of combustion in a conventional petrol engine.

The fuel of a hydrogen fuel cell is, unsurprisingly, hydrogen and much like what’s required to understand combustion, you need to look at the fuel up close, and I’m talking at an atomic level.

To understand the fuel cell, we also need to look at what particles are required to make that atom up in the first place.

Electrons and protons

There are two particles which make up the hydrogen atom and these are the electron and the proton.

As an element on the periodic table hydrogen has the atomic number one.

All the atoms in the periodic table are numbered based on the number of protons they contain, and, hydrogen contains just one.

Helium is number two on the table because it’s got two protons.

Lithium has the number three, because it’s got 3 protons.

All elements (the atomic building blocks of everything) have what’s known as a neutral charge and this is because they all have exactly the same number of protons as electrons.

So, in the context of hydrogen, bearing in mind it’s got one proton, it must therefore have one electron.

An electron always has a negative charge and a proton always has a positive charge, and even though the proton is about 1800 times bigger than an electron, these two charges cancel each other out.

This results in the hydrogen atom having a neutral charge.

It also tells us that the charge of an electron is 1800 times more concentrated than the charge of a proton, which is why, electrons, can do the impressive things which they can do.

The proton of a hydrogen atom sits in the middle/nucleus of the atom and the electron orbits around it.

Once again, much like a conventional petrol engine, a fuel cell won’t do much without something else in addition to the fuel, and that is air, or, to be more specific, the oxygen from the air.

So, before we move on, now’s the time to think about oxygen.

Oxygen

Oxygen is number eight on the periodic table and so in line with my earlier logic, that’ll mean that it contains eight protons and eight electrons which brings me on to an important scientific point.

The electrons of an atom orbit the nucleus at different distances.

These orbits are called shells and each shell can only hold so many electrons.

The innermost shell can accommodate two electrons and the second shell can accommodate eight.

If we now think about oxygen with its eight electrons, what happens, is that the innermost shell is filled to capacity (two electrons), and the second shell hosts the remaining six.

For some reason, way above my pay grade, the shells of atoms desire to be filled, and this means that ‘passing’ electrons are most definitely welcome to use those spare ‘seats’.

This is what makes atoms want to react with other atoms, they’re trying to fill those seats.

This means, there’s a second force in addition to the charge force I referred to earlier, and that force is called electronegativity.

So, hydrogen and oxygen in their conventional states have no charge, they are neutral.

They have the same numbers of protons and electrons and they are both electronegative, with hydrogen being electronegative because it’s got a ‘seat’ for another electron in its first shell, and oxygen is electronegative because it’s got 2 ‘seats’ available for electrons in its second shell.

Summary

So, to summarise, there’s two important forces.

The first force is called charge, and that’s governed by the number of electrons and protons in an atom.

The second force is called electronegativity, and that’s governed by the number of seats available for electrons to fill in the outermost shell of the atom.

Those two points are absolutely critical, and if you haven’t nailed them, re-read that bit as it’s essential information.

Ben Stockton will continue his explaining the science behind fuel cell electric vehicles next week in the GW news bulletin.

For further information about Our virtual Academy, select ‘more details’ below.

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