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In a world exceedingly concerned about climate change, everyone is getting excited about hydrogen.
Experts claim that it could be "the fuel of the future" because it's clean (the only waste-product is water), plentiful (one of the most abundant elements in the universe) and can be used in a wide range of engines and fuel-cells.
In an attempt to prove this, we're seeing major car manufacturers such as BMW rolling out concept vehicles fueled by hydrogen, and public transport fleets have been partly converted to this "fuel" to promote the clean, green alternative.
Hydrogen can even be burnt in conventional internal combustion engines with little modification. The addition of a tank, a demand-regulator and some plumbing is enough to perform a basic hydrogen-fuel conversion.
When used in a fuel-cell, hydrogen can generate electricity without the need for any moving parts. By directly reacting inside the fuel cell, the hydrogen bonds with oxygen and (in the process) creates significant amounts of electrical energy.
The only thing, we're told, stopping hydrogen from taking over from fossil fuels is the lack of a suitable distribution infrastructure.
But is that really true?
Well no it's not.
The hydrogen economy is just a myth being hyped up by the media and a few self-interested parties, often looking for investment money.
Let's dispel some of the untruths:
Hydrogen is a fuel
Hydrogen is no more a fuel than electricity is a fuel.
Unless we can find a source of hydrogen gas that requires little energy to extract, package and transport, hydrogen does not qualify as a fuel.
As it stands, there are no untapped reservoirs of hydrogen gas on the earth, simply because this gas escapes very easily and tends to float off towards space due to its very low weight.
All current methods of producing hydrogen gas are extremely energy intensive, so when we use hydrogen as a fuel, we're simply recovering *some* of the energy that was expended to create the hydrogen in the first place.
In this regard, you can think of hydrogen not as a fuel but as a form of battery -- soaking up energy at one end and releasing it at the other.
Hydrogen is abundant
Yes, hydrogen is the most abundant element in the universe (74% of all the mass) and there is a huge resource in our oceans, lakes, rivers and streams for a start. That's because fresh water is 11% hydrogen by mass.
Unfortunately, that hydrogen is bound strongly to oxygen in the form of water molecules. To extract the hydrogen from oxygen we need to use a lot of energy by way of the electrolysis process. There are no free lunches.
Another way of creating hydrogen gas is to "crack" a more complex molecule such as oil. This cracking process is currently one of the most common methods for producing hydrogen gas -- but it is reliant on fossil fuel reserves so can hardly be considered a "green alternative" to gasoline.
Hydrogen is clean and green
When you take into consideration the significant amounts of energy and/or fossil fuel required to create each kilogram of hydrogen gas, you realise that hydrogen is far from environmentally friendly.
The power or oil required to make the hydrogen has to come from somewhere and that's likely to be electricity generated by coal, gas, oil or nuclear power stations. While hydrogen my burn cleanly in a vehicle or fuel-cell, all you're really doing is moving the environmental damage from the point of use to the point of production.
Other problems with hydrogen
The hydrogen molecule is an escape-artist.
Being incredibly small (due to its simple atomic structure), hydrogen has little trouble finding its way between the molecules of heavier materials such as steel and aluminum.
That means it's very hard to store any significant amount of hydrogen for any length of time. If you fill a steel pressure tank with hydrogen, it will immediately start forcing its way through the matrix of iron molecules then dissipating into the atmosphere.
Although this rate of dissipation isn't so fast that you'd see your fuel gauge moving, it does occur, and over time much gas is lost -- which means wasted energy.
This ability to work its way into and through the molecular matrix of metals also produces another phenomenon known as hydrogen embritlement. When hydrogen atoms force their way into steel, they effectively weaken the bonds between the molecules that make up that steel. Embritled metals the fracture far more easily, making the design of pressure vessels even more complex.
One method of storing hydrogen that shows promise but is not yet practical is to use metal hydrides. By allowing the hydrogen to combine with specially chosen metals, useful volumes of hydrogen can be stored in relatively small volumes without generating a lot of pressure. Unfortunately it requires significant heat to then release that hydrogen and there are a number of safety issues to be resolved.
So are we being misled with all this talk of hydrogen as a viable fuel?
Yes we are.
Right now, and for at least the next decade or so, hydrogen is simply an energy transportation mechanism, and not a very practical one at that.
Even if all the world's vehicles were converted to hydrogen tomorrow we would not seem much (if any) reduction in green-house gas emissions. That's because the energy would still have to come from somewhere and the vast majority of the world's electricity (required to make the hydrogen) is sourced from non-renewable resources.
What of the future
Some promising work is being done with other ways of producing hydrogen gas.
These include the use of bacteria and algae to generate hydrogen from biomass and experimentation with various catalysts that allows sunlight to directly split the bonds in a water molecule.
However, as we all know, there's usually a significant lead-time between when "success" is announced in such research and when we actually see the benefits of such breakthroughs. So don't hold your breath.
If you'd like to discuss the hydrogen fuel issue, please do so in The Aardvark Forums.