The next 20 years and your SUV Part I

Noticed how no one is talking about the hydrogen economy anymore?  A couple of years ago we were told that within the next few decades we'd be topping up the SUV with environmentally loveable hydrogen without having to worry about destroying our planet or the rapacious foreign oil companies.  Why is it that things have gone all quiet on the hydrogen front?  I'll tell you why: because it was a damn stupid idea in the first place.

Let's start from the top.  It is perfectly possible for an internal combustion engine to run on hydrogen.  It'll combust just nicely with oxygen inside a cylinder producing the desired power output and (mostly) water vapour.  No problems there.  I'll tell you from experience that if you ask an engineer to do something (i.e. build a car that runs on hydrogen) he or she will go ahead and do it (assuming, of course, it doesn't violate any of the laws of physics).  Ask an engineer to build a car that runs on human faeces and he'll churn something out given enough time and sufficient resources.  This doesn't mean we should propose a shit-based economy though.

Hydrogen has basically killed itself off because the overall hydrogen economy system doesn't add up.  The problem is that hydrogen isn't an energy source, it's just an energy storage medium (and, as we shall see, not a very good one).  It's just like a battery - a way of holding energy.  You can't dig hydrogen out of the ground, grow it in a field or otherwise make it magically materialise, you've got to produce it.  There are two options here.  The first is that you can separate it from a hydrocarbon (i.e. methane gas or coal which you CAN find in the ground), but why not just burn the hydrocarbon in the first place?  The second option is to produce it by separating the hydrogen from the oxygen in good old fashioned water.  That sounds promising!  Water is readily available and pretty harmless, right?  The problem is it takes energy to extract the hydrogen from the water and, thanks to the inconvenient (and immutable) laws of thermodynamics, it takes more energy to do this than you'll get out of the hydrogen when you burn it (in fact thermodynamics burns us twice here: internal combustion engines are only about 20% efficient so most of the energy in the hydrogen you produced at great energy expense gets lost anyway, and as much as you might try you'll never get an engine which is even close to 100% efficient - look up "Carnot efficiency" if you're curious).  And where do we get this energy from?  Chances are you'll be burning some coal.

The other inconvenient truth about hydrogen is that it remains a gas unless it is cooled to very low temperatures and held at very high pressures.  Not only does cooling and pressurising stuff take a lot of energy, it also makes it something you don't really want to strap underneath your toddler and newborn on your way to plunket.  Also, I beg of you to note hydrogen's position on the periodic table.  You will observe that it is the smallest of the elements and thus, I think you'll find, it is rather difficult to contain.  Try transporting your flour around in a sieve and you'll get an idea of what is going to happen.  Note also a phenomenon one learns about in Materials Science 101 in any good engineering course: hydrogen embrittlement.  Hydrogen has the nasty side-effect of causing steel to become brittle.  Boom.

When all is said and done, the hydrogen-economy just doesn't make sense.  You're not likely to be seeing hydrogen replace good old-fashioned oil any time soon.  Or ever.

The thing is, before we jump on a particular future transportation bandwagon we have to actually look at the whole system to see if it works, not just whether a particular component is technically possible.  The system is all important.  In my next rant, I promise to talk about some of the other proposed alternatives to oil, why they don't work as systems and to introduce the rather disturbing concept that maybe, just maybe, we might have to abandon the idea that in 20 years time we'll be all whizzing around in cars running on a magical elixir other than oil-derivatives.