Ways to Store Hydrogen
It’s possible to make hydrogen using only electricity and water. This gives is great potential as a low-carbon fuel. For this reason, the European Union has big plans for renewable hydrogen. However, storing hydrogen can be difficult. Overcoming the challenge of storage could be key to the success or failure of hydrogen in our energy mix. So let’s consider some options for hydrogen storage.
Compressed Hydrogen Tanks
One way to store hydrogen is in a high-pressure tank. This method comes with the advantage of portability, making it ideal for hydrogen vehicles. However, high-pressure hydrogen tanks are expensive. Two main factors contribute to the high price. Firstly, the tanks must be strong enough to withstand very high pressure. Secondly, they must be made of composite materials. This is because steel or aluminium would fail due a problem called hydrogen embrittlement. Another disadvantage of high-pressure hydrogen storage is the cost to compress the gas.
Compressed Hydrogen Underground
Underground storage reduces cost by doing away with the high-pressure tanks. Instead, the hydrogen is stored in underground salt caverns and depleted natural gas wells. This makes it ideal for storing large volumes of hydrogen over long periods of time. In particular, underground hydrogen storage could be ideal for balancing out variable renewable energy.
You can turn hydrogen into a liquid by cooling it to -253 degrees C. Unfortunately though, cooling hydrogen to such a low temperature takes a lot of energy. Despite the high energy requirement, liquefied hydrogen could still be an attractive option in some cases. Sea transport is one of these cases. In fact, Japan recently launched the world’s first liquid hydrogen carrier ship.
Metal hydrides can store hydrogen at room temperature and moderate pressure. Unfortunately though, they’re pretty expensive. More research might help bring the cost of metal hydrides down.
An obvious way to store hydrogen is to simply hold it in a large container. The main drawback of this method is the space requirement. On the other hand, it’s extremely simple and energy-efficient.
What’s the best container for hydrogen? One option is a “gasometer”. These tower-shaped gas containers rise towards the sky as they fill with gas. Other gas containers, like baloons and bags, are popular in the biogas industry. Big containers are more suited to short-term, rather than long-term, hydrogen storage.
Addition to the Natural Gas Grid
Most countries already have a natural gas network. Blending hydrogen into this network could be a cost-effective way to store it for later use. However, there are some challenges with this approach.
Firstly, not all natural gas pipelines are suitable for transporting hydrogen, due the risk of hydrogen embrittlement. However, most pipelines can handle at least some hydrogen. This second issue is that hydrogen burns differently to natural gas. Therefore, standard natural gas appliance won’t work with hydrogen. The solution here is to mix some other gas with the hydrogen to create a blend that burns like natural gas. Propane is a popular option.
There are many ways to store hydrogen. Figuring out the best one could be key to the energy transition. In particular, cost-effectiveness is a key consideration.