Hydrogen Storage in Liquid Cryogenic Form

The Linde cycle is a simple cryogenic process based on Joule-Thompson effect. It is composed of different steps the gas is first compressed, then preliminarily cooled in a heat exchanger using liquid nitrogen, finally it passes through a lamination throttle valve to exploit the benefits of Joule-Thomson expansion. Some liquid is produced, and the vapour is separated from the liquid phase and returns back to the compressor through the heat exchanger. A simplified scheme of the overall process is reported in Fig. 2.9. 

The process is rather expensive because of high electricity costs for compression and the low Joule-Thomson inversion temperature of hydrogen (203 K), that involves high energy consumption necessary to maintain the hydrogen continuously cooled (about 30% of its LHV) [114], 

The materials used in the different size vessels are based on stainless steel or aluminium alloys, but also on polymeric materials, such as Teflon. The sphere form is ideal for the minimization of vapour release, due to its minimum surface to volume ratio with respect to all other possible geometries, and for the limitation of stress and uniformity of strain distribution. On the other hand, the manufacturing costs for spheres are too high, in compared with cylindrical shape which is the most economical solution. 

Recently, a new liquefaction approach based on the magnetocaloric effect has been proposed [115]. The method is based on the characteristics of some magnetic materials that heat up when placed in a magnetic held and cool down when removed from it. The magnetic refrigeration can develop its potentialities in terms of overall efficiency for liquefaction process, as it is theoretically able to exploit 

---