[ aviation ]
Plug Power Georgia liquid hydrogen production plant . Image © Plug Power
Onboard NASA ’ s rockets , ultra-lightweight composite tanks have been used . The advantage of this type of construction is that a gravimetric efficiency of between 75 and 85 % can be achieved . On the other hand , tanks of this type can be used only once .
For commercial aviation , the idea of a single-use tank would not be realistic . However , multipleuse composite tanks to store liquid hydrogen are under development . This technology may offer the prospect of achieving a gravimetric efficiency of more than 50 % in a reusable tank .
1 litre contains 16 grams of hydrogen . At double the pressure , the same container holds 27 grams , almost twice as much .
When hydrogen is cooled to a cryogenic liquid , its density reaches 36 grams of hydrogen per litre . Beyond the gaseous and liquid phases of matter , there is an additional fourth phase known as a ‘ super-critical fluid ’. In this phase , when hydrogen is both cold and compressed , its density is greater than normal atmospheric pressure liquid hydrogen . At 300 bar , a 1-litre storage tank of cryocompressed hydrogen would contain 40 grams .
The fourth phase of matter
Working on the materials of construction for the tank is one lever that can improve the gravimetric efficiency of liquid hydrogen storage . Exploiting the thermodynamic and physical properties of hydrogen is an alternative .
In many applications , the advantage of cryocompressed hydrogen may not justify the additional complexity of this medium . However , in aviation , the gravimetric energy density is so critical that cryo-compressed hydrogen may be applied in this niche .
As hydrogen is compressed , its density progressively increases . For example , at 350 bar , a compressed gas cylinder with a volume of
Zero Avia , based in the UK , and the US startup VERNE announced their collaboration to explore the use VERNE ’ s cryo-compressed
Hydrogen Tech World | Issue 17 | August 2024 37