The spotlight is on hydrogen. Politicians and the industry vastly invest in green hydrogen as a sustainable fuel and energy carrier. Infrastructures are being developed worldwide to enable the large-scale distribution of this promising gas.
However, to use hydrogen worldwide, massive transportation is needed. This blog explains why this transport is so important and the pros and cons of three energy carriers: ammonia, LOHC (liquid organic hydrogen carrier), and liquified hydrogen.
Why international hydrogen transportation?
While the demand for hydrogen is exceptionally high in specific parts of the world, these regions cannot always accommodate the required large-scale production. Producing green hydrogen requires large amounts of renewable energy and advanced electrolysis infrastructures, and these prerequisites need specific conditions and ample space.
An excellent example of an area with high demand for green hydrogen, but where large-scale production is complex, is Europe. In fact, according to a Roland Berger report, the demand for green hydrogen in Europe will rise sharply enough to require much more green hydrogen in 2050 than can be expected to be produced locally. Sufficient opportunities for renewable energy production do simply not exist in Europe.
Some examples of very suitable areas for producing renewable energy are Chile, Australia, and the Middle East. In some of these areas, large-scale experiments are also being conducted with converting electricity into green hydrogen using electrolysis.
The uneven worldwide distribution of renewable energy and electrolyzers makes the international transportation of hydrogen inevitable if a global green hydrogen economy is to be realized.
Hydrogen pipelines and trucks are the best solutions for transport over smaller distances. However, when quantities or distances become greater, other techniques are needed. Three energy carriers that can make this transport possible are ammonia, LOHCs, and liquid hydrogen. All three of these methods are currently under extensive investigation, and all three methods have both pros and cons.
Hydrogen transportation using ammonia
The first option of enabling large-scale hydrogen transportation is ammonia. Ammonia is a chemical that, in addition to being used as a raw material for fertilizer, can also be used to store and transport hydrogen.
How it works.
Ammonia as an energy carrier for hydrogen is produced through ammonia synthesis. This chemical process allows hydrogen and nitrogen to react, creating liquid ammonia. This liquid is stored in tanks which makes it easy to transport.
When the ammonia reaches its destination, it is broken down (“cracked”) into its components, releasing hydrogen and nitrogen. After the hydrogen is purified, it is ready for use.
The pros and cons
Hydrogen transportation using ammonia has several advantages. For example, ammonia has been used in various industries for a long time, and the infrastructures for ammonia synthesis are abundant. Also, ammonia can be stored in slightly refrigerated tanks at -33 °C or at ambient temperatures under a pressure of 8-10 bar. This makes storing and transporting ammonia relatively straightforward and affordable.
Unfortunately, ammonia also has disadvantages. Although the infrastructures for producing ammonia are in place, the process of cracking it is still relatively new and not energy efficient. Moreover, after cracking, additional steps are required to purify the hydrogen for use.
Lastly, ammonia is a toxic substance that, if it leaks, may have a negative impact on the air, soil, and water quality as well as the health of people living in the vicinity. Because of the potentially dire consequences, it is questionable to what extent the storage and transport of ammonia is a justifiable option.
Hydrogen transportation using a LOHC
A Liquid Organic Hydrogen Carrier (LOHC) is a liquid capable of absorbing and releasing hydrogen through a chemical reaction.
How it works.
The LOHC is brought into contact with hydrogen through a hydrogenation reaction to absorb hydrogen. This chemical reaction occurs under increased pressure and temperature and with a catalyst present. The LOHC, even when merged with hydrogen, can simply be stored or transported in atmospheric conditions.
If the hydrogen is needed again after some time or has arrived at its destination, the LOHC is dehydrogenated. This process also requires an increased temperature and a catalyst.
Several agents can be used as LOHC. A good example is dibenzyl toluene. This ‘carrier’ can absorb large amounts of hydrogen using the technique described above. As much as 56 kg of hydrogen can be stored in 1 m3 of LOHC.
The pros and cons
Hydrogen transportation using a LOHC also has its pros and cons. A well-known advantage is that the process is relatively inexpensive and safe. In addition, the LOHC is a diesel-like substance, which can be transported under atmospheric pressure and temperature with regular vehicles for gasoline or diesel.
Unfortunately, this method also has disadvantages. First, dehydrogenation requires much heat and thus energy. In large-scale use, the costs can therefore mount up considerably. Additionally, the production of LOHC causes extra CO2 emissions. Exactly how much depends on how long the LOHC lasts and how often it can be reused.
Hydrogen transportation in the form of liquid hydrogen
The last option to efficiently transport hydrogen is to transform it into liquid hydrogen. As previously described in our blog on the energy density of hydrogen, the density of liquid hydrogen is significantly higher than that of gaseous hydrogen. This means that much more liquid hydrogen than gaseous hydrogen can be transported within the same storage volume.
How it works.
To transform gaseous hydrogen into liquid hydrogen, the gas is cooled to a temperature of -252.9 °C . It can then be transported and stored in its liquid form, provided it is very well insulated. It loses its liquid form and becomes gaseous again when it warms up.
After transportation or temporary storage, liquid hydrogen is made gaseous again with an evaporator.
The pros and cons
A significant advantage of liquid hydrogen as a mode of transportation over ammonia or a LOHC is that the hydrogen is not merged with any other substance. Hydrogen in liquid form is still hydrogen; it just changes its appearance. Chemical reactions and additional purification steps are consequently not necessary; thus, the hydrogen retains its optimal quality.
Unfortunately, liquid hydrogen also has some drawbacks as an energy carrier. For example, extreme cooling takes a lot of energy, and superior quality insulation is required to maintain the extremely low temperature. In addition, a small amount of boil-off gas cannot be prevented over time.
Do you want to know more?
Demaco already has 30 years of experience designing and manufacturing vacuum insulated liquid hydrogen infrastructures. If you have questions about our products and services, don’t hesitate to get in touch with us or browse through our products and projects for more information.