Liquid hydrogen: Potential, problems, and a proposed research program

Abstract

Hydrogen may be stored in gaseous, liquid, slush and solid forms (metal hydrides). Every mode of storage has its advantages and disadvantages in terms of cost, stability, convenience of usage, and energy density. Liquid hydrogen has several advantages over other storage modes, especially in terms of energy density and convenience of utilization. However, several problems stand in the way of its large-scale production and long-term storage. This includes problems associated with energy consumed in liquefaction as well as boil-off losses during storage and handling. Boil-off losses occur due to a variety of mechanisms such as ortho-para conversion, thermal stratification and self pressurization, heat leaks, sloshing, and flashing. This paper will review some of the aforementioned problems and discuss some of the prospects of large-scale liquid hydrogen production and utilization. The paper will also outline a research program that can address some of the areas where knowledge is a little deficient.