By Chris Davey
I was tempted to talk about the new government and its climate policies; but there is more than enough chatter on that to be had elsewhere. Instead I am going to keep things “light” and talk about hydrogen, H2.
Some time back I was in touch with a distant friend, by which I mean not one who lives miles away, but one that you go ages without seeing or hearing from. Then several WhatsApps came in, and in the end I replied at some length with my “news” from the past few years, including the good news that I’d made the change to electric driving and wished I’d done so years ago. The reply was a bit of a surprise to me; he was “disappointed” that I’d fallen for the electric-car thing and it was pretty evident that they were not as great as cracked up to be, but maybe hydrogen would have a role in the future. Well, as the time machine is broken, I can’t pop forward a century and see if that was a good prediction. It might well be, but from here in 2024, it’s not looking likely. There are broadly two ways of using hydrogen for transport – burning it in an internal combustion engine, ICE, or using it in fuel cells to generate electricity for motive power. But let’s pause there for a (brief, honestly!) science lesson.
Hydrogen is the simplest of all the elements, consisting only of one proton and one electron. In a natural state, two hydrogen atoms join to form one molecule, written as H2. So the molecules are very small and very light, which accounts for the way it tries to escape upwards, and if not captured will end up in space. Other basic facts: hydrogen is highly flammable, and the fun chemistry experiment is to fill a test tube or flask with it, then hold it near a flame, whereupon it will instantly combust with what is commonly called a squeaky pop. An easy way to form H2, as in the video, is to react magnesium with hydrochloric acid; but you can also electrolyse water, which as we all know, is H2O, two hydrogen atoms and one oxygen atom forming a water molecule, which electrolysis splits into its components. Lastly, H2 is an odourless, colourless gas. But it also has many colours…
Colours are used to describe how the H2 is obtained. Green hydrogen is of course the best, but some folks like the idea of blue. Black is generally a no-no, and grey is not great either. The National Grid website has a handy guide, but briefly, green hydrogen is made by splitting water, using renewable electricity; blue is derived from the fossil fuel natural gas, aka methane, also liberating carbon dioxide, which is then captured and stored. If we need it at all, we need green.
And the best way to use it would be in a fuel cell, which takes hydrogen as an energy source, and from it generates electricity. This is a slightly roundabout way of using electricity as a motive power, and it does so less efficiently than a battery electric vehicle (BEV), losing about 40%. The advantage is that refuelling takes about as long as with diesel or petrol, so much faster at the time of writing than charging a BEV. The main disadvantages are that hydrogen can be rather tricky to store and contain – remember that tiny molecule – and also that there are just six hydrogen fuelling stations open to the public in the UK (2023 figure), most of which are in the south east of England. Across Europe, there are 265 according to electrodrive.com, of which 105 are in Germany, 51 in France, 22 in Holland and 17 in Switzerland. So they have rather more than we do, but still tiny numbers compared with petrol/diesel stations. A further comparison: according to ChargeUK, at the end of June 2024 there were approximately 930,000 EV charging points in the UK.
I remember seeing a hydrogen-fuelled experimental ICE car in the 70s, probably this one at UCLA, showing the exhaust pipe dripping with clean clear water, the only combustion product. It was converted by engineering students, one of whom collected some of the water in a beaker, and drank it, to show it was water. (Hmm… not sure I’d have done that – the engine will have been lubricated by mineral oil, and so there would probably have been traces of polycyclic hydrocarbons in that water). So the only exhaust product of the hydrogen-fuelled engine is water. But, hydrogen burns at ∼1,300C, and that converts some of the nitrogen in the air to NOx, a powerful greenhouse gas, which is released into the air.
Hydrogen has been seen as a useful fuel for larger vehicles, which up to now have been more difficult to design as BEVs than cars, as huge and heavy batteries have been needed to give decent range. But like any new tech, advances have been made. There is a growing range of battery heavy goods vehicles available, for example, these by Mercedes as driven by Robert Llewellyn on Fully Charged.
So where does that leave us? Well, it seems to me that future transport will be largely electric – it isn’t really clear whether it will also be somewhat hydrogenated.
