Will hydrogen power the future?

We’ve designed RoboPlant to feature an electrolyser, powered by solar cells, which splits water into oxygen and rocket fuel. Wait, what?

rocket 2That is correct – pure hydrogen is a fuel, and has been suggested as the energy medium of the future due to its high energy density, abundance (it’s the most abundant element in the universe) and the fact that it produces only water as a by-product when burned. Indeed, it has been used as a powerful rocket fuel for NASA’s space shuttles, also supplying the crew with drinking water. But could hydrogen fuel really be utilised beyond such niche applications, and be the fuel of a sustainable, emissions-free future? This week I wanted to know if there’s any warrant for all the hype about hydrogen, and if a proposed ‘hydrogen economy’ could really be achieved, so I hit the net and endeavoured to find out.

The idea of a future world powered by hydrogen is not a recent one. In his 1874 novel The Mysterious Island, the French author Jules Verne – as much a pioneer of modern science as a brilliant storyteller – had one of his characters, Harding, explain the idea when asked what mankind would do once coal reserves run out:

“But what will they burn instead of coal?” asked Pencroft
“Water,” replied Harding.
“Water!” cried Pencroft, “water as fuel for steamers and engines! water to heat water!”
“Yes, but water decomposed into its primitive elements,” replied Cyrus Harding, “and decomposed doubtless, by electricity, which will then have become a powerful and manageable force…Yes, my friends, I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable. Someday the coalrooms of steamers and the tenders of locomotives will, instead of coal, be stored with these two condensed gases, which will burn in the furnaces with enormous calorific power… Water will be the coal of the future.”

(Abridged from The Mysterious Island by Jules Verne, 1874)

Leave the mysterious island and jump forward to 2013, and after nearly 140 years, there are genuine signs that Verne’s vision may finally be becoming a reality. The “inexhaustible source of heat and light” refers to the energy that is released when hydrogen is reacted with oxygen in the air. Hydrogen gas, when mixed with oxygen and ignited with a spark, causes a powerful exothermic reaction (a reaction which releases energy – an explosion, in other words), which also forms water. Technologies have been developed to harness the energy of this reaction, almost exactly as Verne prophesised. In rocket engines, the powerful explosion resulting from the combination of liquid hydrogen with compressed oxygen is enough to propel the rocket into space. In hydrogen fuel cells, energy is released when stored hydrogen reacts with oxygen in the air, and this reaction energy generates an electric current. Hydrogen powered cars are propelled by electricity from fuel cells in this way. They have already been developed and many car companies are already looking to bring them to the masses. Hydrogen cars may well be the first step to realising a hydrogen-powered transport infrastructure.

The Honda FCX Clarity is one of the first commercial cars to be powered by a hydrogen fuel cell. Unike conventional cars which run on fossil fuels, this car emits only water from its exhaust.

The Honda FCX Clarity is one of the first commercial cars to be powered by a hydrogen fuel cell. Unike conventional cars which run on fossil fuels, this car emits only water from its exhaust.

However, Verne was slightly off in that hydrogen is not so much a ‘source’ of energy as a ‘carrier’. Hydrogen is highly abundant in the universe, but not so on Earth, as it is so light that it simply rises up and floats into space. On Earth it is locked up inside compounds such as sugars, water and methane, and energy is required to break these compounds apart. Therefore, whether it is ‘inexhaustible’ depends on where this energy comes from. Electrolysis of water is the obvious method, but this requires electricity, and most of our current electricity comes from fossil fuels. There would be little point in using oil-derived electricity to obtain hydrogen, because that oil may as well just go straight into the car. Ideally therefore, the power plants of the future would use renewable energy sources such as wind, solar and hydro-electric to electrolyse water, and then store the hydrogen so it can be used when needed. The problem with renewables such as wind and solar is that they are intermittent, which means they are not always reliably available. These forms of energy also cannot be stored (you cannot store direct sunlight, wind, or constantly flowing water). Electricity generated by these energy sources can be stored to an extent within batteries, but the chemicals used by batteries to store charge make them unsuitable for large scale use (batteries go ‘flat’ over time). Storing hydrogen as a fuel could potentially solve the problem – provided it can be done safely.

Hydrogen transport doesn’t exactly have a pristine record, however. The 1937 Hindenburg disaster, which killed 36 people, is believed to have resulted when the hydrogen-air mixture within the airship was ignited, setting fire to the outer canvas and sending it plummeting to the ground in flames. In reality however, such hydrogen-air mixtures are no more flammable than petrol, and the fate of the Hindenburg was as much thanks to the use of flammable acetate and aluminium powder covering the airship as it was thanks to hydrogen. Nevertheless, storing large quantities of hydrogen in small spaces so it can be transported and kept safely for use in, say, hydrogen-powered cars, is a technological challenge. There are numerous safety issues with some of the currently suggested techniques, including storage as compressed gas in highly pressurised tanks or as liquid in super-cooled tanks. These tanks may be liable to explode on impact or if they are exposed to too much heat, unless they are built from a very strong material. Current hydrogen cars use highly pressurised tanks, which are made out of steel to make them strong enough to be safe. However, these tanks are heavy and bulky and leave much to be desired. Another, safer method that has been suggested is solid state storage – in which hydrogen atoms are absorbed and retained within a lattice of other atoms such as titanium and aluminium. Hydrogen can be released by applying heat. However, this technology is still in the early stages of development.

Consider health and safety

Consider health and safety

For the time being, let us assume that these hurdles will be overcome in the future, and we do find a safe and efficient way to store hydrogen fuel and power zero-emission fuel cell vehicles. What then? The vehicles on their own are little use if they cannot get the fuel they need, and this is why an extensive supply and distribution network – a hydrogen infrastructure – would need to be built. Hydrogen produced at power stations would need to be delivered to a series of fuel pumps which can be accessed by vehicles. The fuel could be delivered via massive road tankers and trains, but a more convenient and efficient solution would be to construct pipelines. The latter would be a mammoth financial undertaking, which leads us straight into a catch-22: currently, hydrogen vehicles are not popular enough to warrant the construction of a distribution network, but the lack of a distribution network is one of the main reasons hydrogen fuel is unpopular! Fossil fuels therefore, may still have the monopoly for some years to come, as a global infrastructure of refineries, pipelines, storage facilities and pumps make oil far too convenient to simply switch to something else.

A basic schematic of a hydrogen economy

A basic schematic of hydrogen economy

Nevertheless, the ‘switch’ will need to occur sooner or later, as fossil fuels will not last forever. The concept of a hydrogen economy may not become realised in our lifetime, and there are some who argue that it may never happen at all. Crucially, however, what hydrogen offers is a means of storing the energy from intermittent renewables, and may be invaluable in helping countries achieve targets for renewable energy consumption (the UK aims to have 15% of its energy consumption derived from renewable sources by 2020, for example). Perhaps, rather than considering a ‘switch’ to hydrogen, a gradual transition is more realistic. Trial schemes which involve establishing small-scale hydrogen networks are already underway, with the state of California already having its own ‘hydrogen highway’, and countries such as the UK, Japan, and Denmark now looking to implement similar small-scale schemes. Perhaps taking things in small steps is the way to go, and then in time we may eventually see a sparkling future, with whirring fuel cell cars topping up at hydrogen fuel stations a normal site in urban life. Time and technological innovation will tell!

My name is John Kimble, and I love my [hydrogen] car

My name is John Kimble, and I love my [hydrogen] car

Watch the video below in which the Top Gear crew discuss the implications of hydrogen fuel cell technology.

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One response to “Will hydrogen power the future?

  1. Pingback: A Vision of a Solar Powered Future | RoboPlant·

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