The hydrogen bubble...

The ultimate 'Green' high?

Frequently these days one hears talk of using hydrogen as an energy source. Manufacturers of large, expensive luxury cars have almost without exception shown off their miracles of R&D; cars that run on either straight hydrogen or hybrids that are fuelled by conventional fossil fuels with the added feature of being able to run on hydrogen in high-density urban conditions.

Hydrogen is clean burning, which in these times of Global Warming and Ozone depletion is a benefit hard to mark as insignificant. In essence, from the exhaust of an engine burning pure hydrogen come only heat and water. Hydrogen is all around us in many forms and seems logically be easily isolated for fuel use by electrolytically seperating it from oxygen in water molecules. Water covers 70% of the earth. The ultimate idea of fuelling our machinery by simply pouring water into the tank is alluring, especially when coupled to the idea that nothing but water is exhausted – how very close to energy Nirvana can we get; water in, water out? The apparent pinnacle of 'green', the idea attracts like perpetual motion.

Unfortunately, and surely because of this allure, the notion of a hydrogen-fuelled economy is given considerable attention. It seems many are misinformed and view hydrogen as the fuel of the future, the saviour of mankind and his insatiable appetite for more and more of everything.
The hope that our technological mastery will solve yet another of our problems has sprung forth, resulting in the belief that high science and hydrogen will combine to ensure that life as we know it will continue and all will live happily ever after.

The reality of hydrogen as a fuel source is far removed from this Utopian ideal.

What it is and where we get it.
Primarily, hydrogen is an energy carrier, not an energy source.
Something like a battery, it needs to be created, charged and then not expected to deliver anything like the same quantity of energy as went into it. This kind of energy sinkhole can best be described as a nett loss, from start to finish and everywhere inbetween.

Close to 95% of all the suitably pure hydrogen available to us today is made from fossil fuels. Crude oil, natural gas and coal are however the self-same compounds that we will soon have to live without. In large measure, it is our over-utilisation of those same compounds that first prompted us to look at hydrogen as fuel.
The processes that are employed to isolate hydrogen atoms from fossil fuels average out at a efficiency of somewhere around 70%, implying that some 30% of the energy contained within the fossil fuel source was wasted in the hydrogen extraction process, excluding the energy it took to extract and transport the fossil fuel to refinery.

Only about 5% of available hydrogen is extracted from water by electrolysis, for applications where the hydrogen is required to be extremely pure. The reason that so little of the world's available hydrogen is created by this means is because it is a very energy intensive way of extracting hydrogen. Most of the electricity we use is generated in oil, gas or coal fired power plants that are at best around 50% efficient. Additionally, the process of electrolysis is only around 70% energy efficient, so in total the extraction of hydrogen from water by electrolysis is only about 35% energy efficient.

At the same time, though hydrogen is clean burning, the processes used in its manufacture certainly are not.
Coal releases large amounts of the number 1 greenhouse gas carbon dioxide into the atmosphere in the process of hydrogen extraction, so the low-carbon benefits from burning hydrogen are more than offset by the high-carbon cost in creating the same hydrogen from coal.
Extraction of hydrogen from crude oil will never be feasible because of the greater value that oil has as a fuel on its own. Similarly, the additional value of fossil fuels as sources of fertilizers and plastics will forever make them more valuable for other purposes than simply as a source of hydrogen.
So the actual source of hydrogen as a viable fuel is as yet undetermined. Fossil fuels are simply too valuable to waste both as feedstock in the production of hydrogen and as fuel to power the process of electrolysis.

Additionally, hydrogen is the lowest energy dense fuel on earth. This means that in its natural state at room temperature and pressure, it would require about 3000 litres of hydrogen to return the same amount of energy as a litre of petrol. So in order to gain some measurable benefit from using hydrogen as a fuel in a motor car, we are required to compress hydrogen by means of a multi-stage compression process that costs another 10% to 15% of its ultimate energy yield.
Alternatively we can, at a cost of some 30% of ultimate energy yield, liquefy the hydrogen. The problem with this option is keeping the liquid at approximately minus 200 degrees Centigrade. In a car this is not easy, as it can at times be difficult simply keeping the interior at a comfortable 20 degrees Centigrade!

At this stage hydrogen has already lost much of its initial appeal as the ultimate 'green' fuel.

Keeping and storing it.
An interesting formula looks like this.
A realistic consumption figure for a hydrogen vehicle is something like 90 km per kg of hydrogen.
A 3kg tank, with attendant insulation, cooling and able to withstand the required pressures will weigh in the region of half a ton. With this the car will be able to cover some 270 km.
Imagine a half ton pick-up, loaded to its suspension stops with gear and fuel – and unable to travel from Johannesburg to Nelspruit.

Greater compression of the fuel in order to cram more into the tank implies higher pressures, implying in turn greater weight and cost.

Fuel cells are exorbitantly expensive, as well as being heavy. A metal hydride fuel cell system yielding 5 kg of hydrogen would still weigh over 300 kg and cost over a million dollars! It would have a working life of about 1000 hours only and still offer a very limited range.

Low temperatures, high pressures and the lowest ignition point of any fuel makes the transportation and storage of bulk hydrogen extemely difficult. A leak can be ignited by an electrical storm miles away, and low temperatures and pressures make for brittle, crack-prone pipes and seals; altogether an engineers nightmare.

A forty ton hydrogen delivery vehicle would typically carry some half a ton of hydrogen, enough for less than two hundred cars to refuel.The energy required to power this truck on a delivery of about 250 km would be in the order of 20% of the usable hydrogen it carries.
Again, because of the low temperatures and high pressures involved, transportation by pipeline would require a pipeline prohibitively expensive to build and maintain.


Bursting the bubble.
The fundamental problem with hydrogen thus is its energy expense of extraction, storage and utilisation, in return for a relatively low energy yield.
As an alternative fuel it represents an energy nett loss in that it costs significantly more energy to use than it releases.
The notion of a hydrogen-based economy really only serves to illustrate in greater detail the intricacies of our addiction to petroleum and its attributes, making the overcoming of our petro-dependance all the more daunting a task.

Physics will always show the hydrogen economy to be nothing less than a bottomless black hole of diminishing return upon increasing input. Pursuit of a hydrogen fuelled economy is misleading our attention away from what remains the most important challenge facing us as a species; the drastic reduction of our dependence upon and consumption of fossil fuels. This is the real challenge that will soon have to be taken up by every single inhabitant of this planet, as prices of fossil fuels continue to climb to levels unimaginable ten years ago.

There remains on earth arguably insufficient available fossil fuel energy to finance the luxury of making sizeable disbursements in time, money and energy on erroneous and ill-informed approaches to solving the energy problems that will soon beset us.
Collective efforts and energies would be better spent on finding other, more innovative ways to help us move away from a hydrocarbon based economy.