Hydrogen is difficult to store and transport
There’s no question this is true. Hydrogen has a very high energy density per weight, but very low energy density per volume.
In order to store enough hydrogen to fuel a car for a 300-mile journey—around 5kg—you’d need a 150-200 litre fuel tank!
If it is to be stored as a liquid, it would need to be cooled to -250° Celsius—which would take a huge amount of energy.
But that doesn’t mean it can’t be stored and transported. While we’re already starting to see shipments of liquid hydrogen (they can be controversial!), the answer is probably more likely to lie in hydrogen derivatives like ammonia.
The advantage of shipping hydrogen as ammonia is that there is already a mature, global supply chain.
So how are we going to overcome the problem of storage and transport?
We posed this question to Francois Aguey-Zinsou, Professor of Chemistry at the University of Sydney. He is a leading expert in hydrogen technologies and holds a number of roles, including Director of the Australian Association for Hydrogen Energy, and Co-director of the ARC Training Centre for the Hydrogen Economy (GlobH2E)
"There are certainly challenges. As you mentioned earlier, when you store hydrogen as a gas, it needs to be stored at pressure and can still only achieve fairly low energy densities and, when you store it as a liquid, it needs plenty of energy to keep it at a very low temperature.
But it’s worth noting that these challenges are not insurmountable. Recently, a trial shipment of liquid hydrogen set sail, in a purpose-built Japanese vessel, from Australia to Japan. It was controversial because the hydrogen wasn’t renewable—but we have to start somewhere! If we’re to learn the best ways to ship hydrogen, we need the hydrogen to put inside it. Right now, we’d struggle to fill a ship with green hydrogen."
"However, liquid hydrogen isn’t the only answer. We can also use liquid organic hydrogen carriers (LOHC), in which hydrogen molecules are bound to hydrocarbons and then released at the other end when heat is applied.
Another emerging and exciting way of shipping hydrogen is through its derivatives, like green ammonia, methane and methanol."
Green hydrogen and its derivatives
Ref: Australian REZ conference_Amal.pdf
"As a fuel, green ammonia has a similar energy density to fossil fuels and is seen by the International Maritime Organisation as the future fuel of shipping.
A ship transporting ammonia could literally use its cargo to power its voyage. This ammonia can then be used at the other end in its existing form or be converted to hydrogen.
What’s exciting about this is that there is already a mature global supply chain in place for ammonia. Other hydrogen derivatives, like green methanol and green methane, are also potential ways of storing and transporting hydrogen using well-proven and established technologies."