There’s a lot to like about hydrogen. It’s light; it’s abundant (at least atomically - water and hydrocarbons contain plenty of hydrogen atoms); it’s clean burning.
But its advantages are not always easily accessed. It’s light – but in its gaseous form, it is so light it escapes the Earth’s atmosphere. It’s abundant – but it needs to be extracted before it can be used.
Many of the advantages of hydrogen come about because it reacts with oxygen to produce water. This makes its potential application as a fuel source in a low-carbon environment wide-ranging and very exciting, especially in transport and manufacturing. As an alternative energy carrier it could transform the way our world operates.
Yet while the goal of a “hydrogen economy” has been pursued for many decades it has not yet been reached. The vision of a hydrogen economy continues to spur innovation around the world.
There are still some major hurdles to be overcome. This blog will look at just one of them: hydrogen storage.
The storage issue
The Future of Sustainability report, recently published by Abu Dhabi’s “future energy company” Masdar, argues that for a successful energy transition to hydrogen, innovations in storage must be achieved.
Whilst it is possible to store hydrogen for extended periods of time and in large quantities, it is not without its challenges. While burning cleanly, it also burns easily, as anyone old enough to recognise the name “Hindenburg” will know. At normal pressures, as a gas, it also has a low energy density by volume, meaning that a relatively large amount of it as a fuel is needed. A kilogram of hydrogen gas might drive a car as far as three kilograms of petrol but, under normal pressure, would necessitate a fuel tank the size of the car itself.
That naturally low energy density by volume means larger or higher pressure storage, and all the disadvantages associated with those. Liquefying hydrogen is incredibly difficult because of the very low temperature needed.
Furthermore we have to think about what happens during use. Because of its energy density, a useful container or storage tank for hydrogen must be able to withstand a significant change of internal pressure during use. Because of the potentially explosive nature of hydrogen, conduit security is also vital.
So innovation is needed – and researchers, entrepreneurs and corporations around the world are doing just that.
This can be inferred from the intellectual property activity around the technology. It is fair to say that there are a lot of patents and applications relating to hydrogen. In the US, European and Japanese Patent Offices it is one of the highest amongst ‘sustainable’ energy sources. A few years ago, Toyota made the decision to make available, royalty free, licences for some 5680 patents: and that is just the very tip of their patent iceberg. Just recently that number has risen to around 8000 patents relating to fuel cells, royalty free, until 2030.
A large proportion of those patents relate to fuel cell technology, but of course to have the cell you need the fuel. So hydrogen storage is still a key subject for development, as highlighted by the Masdar report mentioned above.
There are a few approaches that can be taken to improve the storability of hydrogen. One can consider new ways of reinforcing, lining or sealing containers, and even entirely new storage tank materials. Carbon fiber has shown promise in this area, being renowned for its high strength combined with low weight.
We can also think about the many technologies being developed to store hydrogen by absorption, adsorption or otherwise incorporation in some more stable or secure matrix. This itself can alleviate some of the pressure-change concerns, and even mollify reactivity concerns too.
For example, Researchers at the University of Bath are looking at how microporous materials can be used to store hydrogen within their structure. If pores can act as “microtanks” they can absorb hydrogen for storage, potentially each at a higher pressure than could be safely achieved in a bulk storage solution.
Another option is to bind or adsorb the hydrogen, releasably, onto a carrier material. The carrier material can be engineered to be easier to handle, transport or use than raw hydrogen. In Germany, the Erlangen-based Hydrogenious Technologies has developed its LOHC (Liquid Organic Hydrogen Carrier) which binds hydrogen to a non-explosive and non-toxic carrier liquid from which the hydrogen can subsequently be released. The catalytic reactions needed at each end of the process mean that storage and release can be performed at will, and the bound hydrogen transported and distributed using non-specialized channels.
Similarly, GKN Powder Metallurgy is developing a hydrogen storage system for residential homes using solid state metal hydrides; by using storage tanks loaded with a metal powder, hydrogen reacts and forms the metal hydride storage product. This can then be stored at a volume less than half that of a high pressure gas, and a pressure ten times lower.
These are of course just a few of the innovations being made to bring the “hydrogen economy” to life, and hydrogen as a fuel into our homes. What’s next? There is currently no overwhelming ‘favourite’ technology, so it will probably be some time until standards are created and implemented. In the meantime, hydrogen fuel cells continue to gradually progress into conventional products. Soon those readers fancying a trip to Orkney will be able to experience the world’s first seagoing car and passenger ferry fueled by hydrogen!
Interested in hydrogen?
Read about hydrogen fuel cell vehicles here.