Several methods exist for storing hydrogen. These include mechanical approaches such as using high pressures and low temperatures, or employing chemical compounds that release H2 upon demand. While large amounts of hydrogen are produced by various industries, it is mostly consumed at the site of production, notably for the synthesis of ammonia. For many years hydrogen has been stored as compressed gas or cryogenic liquid, and transported as such in cylinders, tubes, and cryogenic tanks for use in industry or as propellant in space programs. The overarching challenge is the very low boiling point of H2: it boils around 20.268 K (−252.882 °C or −423.188 °F). Achieving such low temperatures requires expending significant energy.
Net storage density of hydrogen
'Available storage technologies, their capacity and discharge time.'
Liquid hydrogen (H2(l)) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.
Liquid hydrogen
The global headquarters of Air Products in Trexlertown, Pennsylvania, a leading global supplier of liquid hydrogen
Liquid hydrogen bubbles forming in two glass flasks at the Bevatron laboratory in 1955
A large hydrogen tank in a vacuum chamber at the Glenn Research Center in Brook Park, Ohio, in 1967