[ aviation ]
Universal Hydrogen storage tank . Image © Universal Hydrogen
hydrogen storage solution for aviation . Also of deep importance is that in addition to having a higher gravimetric energy density , the energy input requirement to densify VERNE ’ s cryocompressed hydrogen is approximately half the electrical power required to produce liquid hydrogen . As hydrogen aviation scales up , this energy saving for cryo-compressed hydrogen could equate to many MWh of avoided power usage .
Help from helium
Achieving high energy efficiency in the hydrogen supply chain is imperative . This message has clearly been understood by the US company GenH2 . Their concept is to use a little power to save a lot of energy .
GenH2 technology relies on helium being cooled in a Brayton refrigeration cycle to a temperature about 10 ° C colder than -253 ° C , the temperature at which hydrogen liquefies at atmospheric pressure . This helium sub-cools liquid hydrogen over a heat exchanger to make sLH 2
. There is a
power penalty involved in operating the helium compressor in the Brayton refrigeration cycle ; however , the boil-off losses of hydrogen in the supply chain are reduced .
When cryogenic liquid hydrogen sits in a storage container for more than a few hours , a tiny amount of ambient heat begins to ‘ leak ’ through the storage vessel insulation and vaporise the hydrogen . Over a long duration , the pressure in the tank can build up to the point where safety devices fitted on the tank release the pressure .
When hydrogen is vented , not only does this represent a loss of cold energy that was required to liquefy the hydrogen , but it also represents a loss of the energy that was required to produce the hydrogen itself . So , avoiding boil-off venting can justify some additional amount of power for sub-cooling liquid hydrogen .
Sub-cooled hydrogen has not yet been used in aviation , but for several years it has been considered the fuel of choice for hydrogen storage
38 Hydrogen Tech World | Issue 17 | August 2024